Refinery Control Valves
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API RECOMMENDED PRACTICE 553
FIRST EDITION, SEPTEMBER 1998
Copyright American Petroleum Institute
Provided by IHS under license with API
No reproduction or networking permitted without license from IHS
COPYRIGHT 2000 American Petroleum Institute
Information Handling Services, 2000
Not for Resale
API ENVIRONMENTAL, HEALTH AND SAFETY MISSION
AND GUIDING PRINCIPLES
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members pledge to manage our businesses according to the following principles using
sound science to prioritize risks and to implement cost-effective management practices:
●
To recognize and to respond to community concerns about our raw materials, products and operations.
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To operate our plants and facilities, and to handle our raw materials and products in a
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●
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and our development of new products and processes.
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To advise promptly, appropriate ofÞcials, employees, customers and the public of
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and standards to safeguard the community, workplace and environment.
●
To promote these principles and practices by sharing experiences and offering assistance to others who produce, handle, use, transport or dispose of similar raw materials, petroleum products and wastes.
--`,,-`-`,,`,,`,`,,`---
Copyright American Petroleum Institute
Provided by IHS under license with API
No reproduction or networking permitted without license from IHS
Not for Resale
Refinery Control Valves
Manufacturing, Distribution and Marketing Department
API RECOMMENDED PRACTICE 553
FIRST EDITION, SEPTEMBER 1998
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Copyright American Petroleum Institute
Provided by IHS under license with API
No reproduction or networking permitted without license from IHS
Not for Resale
SPECIAL NOTES
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API publications necessarily address problems of a general nature. With respect to particular circumstances, local, state, and federal laws and regulations should be reviewed.
API is not undertaking to meet the duties of employers, manufacturers, or suppliers to
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Copyright © 1998 American Petroleum Institute
Copyright American Petroleum Institute
Provided by IHS under license with API
No reproduction or networking permitted without license from IHS
Not for Resale
FOREWORD
API publications may be used by anyone desiring to do so. Every effort has been made by
the Institute to assure the accuracy and reliability of the data contained in them; however, the
Institute makes no representation, warranty, or guarantee in connection with this publication
and hereby expressly disclaims any liability or responsibility for loss or damage resulting
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Suggested revisions are invited and should be submitted to the Director of the Manufacturing, Distribution and Marketing Department, American Petroleum Institute, 1220 L
Street, N.W., Washington, D.C. 20005.
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iii
Copyright American Petroleum Institute
Provided by IHS under license with API
No reproduction or networking permitted without license from IHS
Not for Resale
--`,,-`-`,,`,,`,`,,`---
Copyright American Petroleum Institute
Provided by IHS under license with API
No reproduction or networking permitted without license from IHS
Not for Resale
CONTENTS
Page
SCOPE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2
REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
3
CONTROL VALVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
3.1
Valve Body . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
3.2
Valve Actuators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.3
Valve Positioner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.4
Handwheels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.5
Switches And Solenoids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.6
Transducers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.7
Booster Relays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4
SPECIFIC CRITERIA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.1
Globe-style Valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.2
Rotary Style Valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5
INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.1
Accessibility. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2
Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.3
Control Valve Manifolds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13
13
14
14
6
REFINERY APPLICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.4
Boiler Feedwater Recirculation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.5
Feedwater to Waste Heat Boiler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.6
Sulfur Recovery Unit Acid Gas Block Valve . . . . . . . . . . . . . . . . . . . . . . . . .
6.7
Sulfur Vapor to Eductor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.8
Liquid Sulfur to Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.9
Hydroßuoric Acid Service. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.10
Cat Cracker Bottoms Slurry Oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.11
Feed to Hydrocracker Fractionator (Flashing) . . . . . . . . . . . . . . . . . . . . . . . .
6.12
Reformer Hot Gas Block/Bypass (Three-Way Butterßy). . . . . . . . . . . . . . . .
6.13
Reactor Letdown with Erosive Solids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.14
KO Drum Vent to Hydrotreater Flare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.15
Antisurge Control Valves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.16
High Volume, Low Pressure Air Blower Anti-Surge Valve . . . . . . . . . . . . . .
6.17
Crude Oil Processing Unit Throttling /Steam to Pre-Heat Exchanger . . . . . .
6.18
Pump Recirculation Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.19
Crude Oil Processing Unit Heavy Bottoms (High Temperature Tar). . . . . . .
6.20
Crude Oil Processing UnitÑThrottling/Wash Oil . . . . . . . . . . . . . . . . . . . . .
6.21
Crude Processing UnitÑThrottling/Hot Oil . . . . . . . . . . . . . . . . . . . . . . . . . .
6.22
Spray Water to Desuperheater (Utilities) . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.23
Exchanger HGO BypassÑFCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.24
Gas Oil RecirculationÑCaustic Hydrotreater (CHD) . . . . . . . . . . . . . . . . . .
6.25
Hot Separator Liquid to Hot Flash Drum (Power Recovery
Turbine Bypass)ÑHydrocracker. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.26
Cold Separator Sour WaterÑHydrocracker . . . . . . . . . . . . . . . . . . . . . . . . . .
14
14
15
15
15
15
16
16
16
16
17
17
17
18
18
18
18
19
19
19
20
20
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1
7
20
21
EMERGENCY BLOCK VALVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
v
Copyright American Petroleum Institute
Provided by IHS under license with API
No reproduction or networking permitted without license from IHS
Not for Resale
Page
7.1
7.2
7.3
7.4
7.5
7.6
Valve Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DeÞnitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Types of EVBs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
EBV General Instillation Guidelines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Actuator Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FireprooÞng . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
21
21
21
22
22
23
8
VAPOR DEPRESSURING VALVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
8.1
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
8.2
Depressuring Valves and Actuator Requirements . . . . . . . . . . . . . . . . . . . . . . 23
9
HYDRAULIC SLIDE VALVE ACTUATORS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.1
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.2
Hydraulic Power Unit (HPU) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.3
Slide Valve Positioner Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.4
Instrumentation Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.5
Performance Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.6
Electrical Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.7
Testing and Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.8
Slide Valve Actuator Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
23
23
23
24
24
25
25
25
25
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Figures
1
Control Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2
Live Loaded . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3
Resilient Seat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4
Inherent Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5A Sliding and Rotary Stem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5B Sliding and Rotary Stem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
6
Pressure Drop Through a Restriction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
7
Cavitation Damage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
8
Typical Plug Damage from Flashing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
9
Multistaged Trim . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
10 Diaphragm Actuator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
11 Double-Acting Spring Return Piston Actuator . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
12 Electrohydraulic Actuator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
13A Handwheels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
13B Handwheels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
14 Limit Switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
15 Butterßy Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
16 Lug Style Butterßy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
vi
Copyright American Petroleum Institute
Provided by IHS under license with API
No reproduction or networking permitted without license from IHS
Not for Resale
Refinery Control Valves
1 Scope
NACE3
Std MR0175-90 SulÞde Stress Cracking Resistant Metallic Materials for OilÞeld Equipment
1.1 This Recommended Practice addresses the special
needs of control valve applications in reÞnery services. The
knowledge and experience of the industry has been captured
to provide proven solutions to well-known problems.
OSHA4
1910.95
1.2 This document provides recommended criteria for the
selection, speciÞcation, and application of piston and diaphragm-actuated control valves. It also outlines control valve
design considerations, and discusses control valve sizing,
noise, and fugitive emissions as well as deÞning types of commonly used control valves and their actuators.
U.S. EPA5
40 CFR Pt. 60
A control valve, as shown in Figure 1, consists of two
major subassemblies: a valve body and an actuator. The valve
body is the portion that actually contains the process ßuid. It
consists of a body, internal trim, bonnet, and sometimes a bottom ßange and/or bonnet ßange. This subassembly must meet
all of the applicable pressure, temperature, and corrosion
requirements of the connecting piping.
The actuator assembly moves the control valve in response
to an actuating signal from an automatic or manual device. It
must develop adequate thrust to overcome the forces within
the body subassembly and at the same time be responsive
enough to position the valve plug accurately during changing
process demands.
2 References
All references shall be the latest edition.
RP 521
Std 556
Std 589
Spec 6FA
Std 607
Std 609
FireprooÞng Practices in Petroleum and
Petrochemical Processing Plants
Guide for Pressure-Relieving and Depressuring Systems
Manual on Installation of Instruments and
Control Systems for Fire Heaters and
Steam Generators
Fire Test for Evaluation of Stem Packing
SpeciÞcation for Fire Test for Valves
Fire Test for Soft-Seated Quarter-Turn
Valves
Butterßy Valves: Double Flanged, Lug-and
Wafer-Type
3.1 VALVE BODY
3.1.1 Process design conditions dictate the ANSI pressure
classiÞcation and materials of construction for control valves,
provided the standard offering meets or exceeds all piping
and process control requirements. The valve end connections
and pressure rating should, as a minimum, conform to the
piping speciÞcation. The valve material shall be suitable for
the process conditions.
3.1.2 Nickel alloy or stainless steel valve metallurgy should
be speciÞed for temperatures below -20¡F. High pressure
steam, ßashing water applications, and boiler feedwater service where differential pressures exceed 200 psi may require
harder, chrome-molybdenum alloys. Sour service valve materials must meet the requirements of NACE MR0175-90. Corrosive and erosive components even in trace quantities may
affect the metallurgical choice of the valve.
ASME 1
B16.34
FCI2
70-2
Boiler and Pressure Vessel Code, Section
VIII, Div. 1, International Society for Measurement and Control Standard S75 Series
of Control Valve Standards
ValvesÑFlanges, Threaded, and Welded
End
3.1.3 Inner valve parts should be the manufacturerÕs standard where acceptable. Hardened trim may be required for
Quality Control Standard for Control Valve
Seat Leakage
3
NACE International, 1440 South Creek Drive, P.O. Box 218340, Houston,
Texas 77218-8340.
Occupational Safety and Health Administration, U.S. Department of Labor,
Washington, D.C. 20402.
5U.S. Environmental Protection Agency, available from the U.S. Government
Printing OfÞce, Washington, D.C. 20402.
4
1
American Society for Mechanical Engineers, 345 East 47th Street, New
York, New York 10017.
2Fluid Controls Institute, P.O. Box 9036, Morristown, New Jersey 07960.
1
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Copyright American Petroleum Institute
Provided by IHS under license with API
No reproduction or networking permitted without license from IHS
Appendix A, Attachment 1: Reference
Method 21. Determination of Volatile
Organic Compound Leaks
3 Control Valves
1.3 Recommendations for emergency block and vent
valves, on/off valves intended for emergency isolation or
venting, and special design valves for reÞnery services, such
as FCCU slide valves and vapor depressuring systems, are
also included in this Recommended Practice.
API
Publ 2218
Occupational Noise Exposure
Not for Resale
2
REFINERY CONTROL VALVES
Adjusting Screw
Gasket
Adjusting Screw
(with Lifting Ring)
Spring Button
Spring
Piston Retaining Nut
Piston Stem O-ring
Actuator Stem Spacer
Cylinder
Actuator Stem Bushing
Piston
Actuator Stem O-ring
Piston O-ring
Cylinder Retaining Ring
Stem Clamp
O
Actuator Stem
Gland Flange
Upper Packing
Stroke Plate
S
Stroke Bellows
Yoke Clamp
Yoke
Packing Spacer
Upper Stem Guide
Bonnet
Upper Stem Guide Liner
Bonnet Flange
Bonnet Flange Bolting
Seat Retainer
Seat Ring
Bonnet Gasket
Seat Ring Gasket
Lower Packing
Lower Stem Guide
Body
Lower Stem Guide Liner
Half Ring
Plug
End Flange
Figure 1—Control Valve
corrosive, erosive, cavitating, or ßashing service, and where
valve differential pressure exceeds 200 psi.
recommended. In addition, high-tensile strength bolting is
required.
3.1.4 Flanges are the preferred end connection for globestyle valves, with butt-weld end connections acceptable for
ANSI classes 900 and above. Threaded valves and valves
with welded end connections are not recommended for
hydrocarbon service and should be speciÞed only with the
ownerÕs prior approval.
3.1.7 Flange Þnish describes the depth of the grooves in the
surface part of a ßange which is available for the sealing gasket. If a special Þnish is required for gaskets, it should be
speciÞed with the valve. The typical standard is 125Ð250
RMS, which provides a good sealing surface for the gasket.
3.1.5 Flanged control valve bodies are available with either
integral ßanges (machined as part of the body casting or forging, or ßanges welded to the body), or separable ßanges (individual removable ßanges that usually lock in place on the
valve body by means of a two-piece retaining ring).
3.1.6 Flangeless valves have no ßange connections as
part of the valve body and are simply bolted or clamped
between the adjoining line ßanges. Long bolts used with
ßangeless valves can expand when exposed to Þre and
cause leakage. A Þre deßection shield and/or insulation is
3.1.8 The installed face-to-face dimension of integral
ßange globe style valves should conform to ANSI/ISA
S75.03. Face-to-face dimensions of ßangeless control
valves should conform to ANSI/ISA S75.04. Face-to-face
dimensions of separable ßanged globe style valves should
conform to ISA S75.20 or ISA S75.03. Butterßy valves are
covered by API 609. Caution should be used to install ßangeless valves so that they will not leak in hydrocarbon service under Þre conditions.
3.1.9 The valve body size should be no less then two
pipe sizes smaller than the line size. Smaller valve sizes
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Copyright American Petroleum Institute
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Not for Resale
API RECOMMENDED PRACTICE 553
3.1.10 Final valve sizing should be reviewed by the valve
manufacturer.
3.1.11 Threaded seat rings should be avoided where possible because corrosion often makes removal difÞcult.
3.1.12 Bonnets
Bonnets should be bolted. Bolting material should comply
with ASTM A193/194/320 and should be compatible with the
valve body and bonnet.
Note: For the temperature range between -50¼F and 1000¼F, bolts and studs
should meet ASTM A193, Grade B7 speciÞcations. For temperatures
between 1000¼F and 1100¼F, bolts should be ASTM A193, Grade B16. For
low temperature applications from -50¼F to -150¼F, bolts should be ASTM
A320, Grade B7. Nuts should be ASTM A194, Grade 2H for the above applications. Stainless steel bodies require stainless steel bolting. Higher grade
valve metallurgy requires 316 SST as the minimum bolting material.
Extended bonnets should be considered for process temperatures below 32¡F or above the temperature limits of the
packing materials shown below in section 3.1.13.
Bonnet gaskets should be fully retained 316 SST spiral
wound, with polytetraßoroethelene or graphite Þller. Flat gaskets made from PTFE sheet stock are acceptable where conditions permit. Insert reinforcements should be 316 SST or
other appropriate alloy, as required.
3.1.13 Packing
a. Packing boxes should be easily accessible for periodic
adjustment. The packing material should (1) be elastic and
easily deformable, (2) be chemically inert, (3) be able to withstand applicable process conditions, (4) provide a degree of
Þre resistance, (5) minimize friction, and (6) reduce fugitive
emissions to meet regulatory requirements. Valve manufacturerÕs packing temperature limits refer to the temperature at
the packing box.
b. PTFE has excellent inertness, good lubricating properties,
and is one of the most popular valve packing materials. It
may be used in solid molded, braided, or turned form (Vrings) or as a lubricant for asbestos-free packing. Its temperature limit with standard packing box construction is 450¡F. If
used to meet fugitive emissions, virgin PTFE should be alternated with carbon-Þlled PTFE or similar minimal coldßowing material and live loaded.
c. Graphite laminated or preformed ring packing is chemically inert except when strong oxidizers are handled. This type
of packing can be used for temperature applications approaching 2000¼F. The biggest difÞculty caused by this type of
packing is very high packing friction, which often requires an
oversized actuator. Performance is often compromised,
because of signiÞcant increases in hysteresis and deadband.
d. Asbestos should not be used.
Copyright American Petroleum Institute
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No reproduction or networking permitted without license from IHS
3.1.14 Fugitive Emissions
The Clean Air Act of 1990 or local requirements have
established strict limits on emission to the atmosphere of certain hazardous substances. These substances are volatile hazardous pollutants listed in the National Emission Standard for
Hazardous Air Pollutants (NESHAP).
Increased emphasis on limiting packing leaks has resulted
in the development of new packing materials and methods.
Individual manufacturers are offering increasingly effective
designs, and vendors should be consulted for speciÞc applications. See Figure 2.
Kalrez¨ also has excellent inertness and good lubricating
properties. It does not cold ßow and therefore does not need
live loading. It is available in V-rings. The temperature limit
with standard packing box construction is 700¼F.
3.1.15 Seat Leakage
a. See ANSI/FCI 70-2 standard for deÞnitions of leakage
classes. Note that these deÞnitions change the way that leakage is deÞned and tested between Classes V and VI. Control
valves should have no less than a Class II leakage rating. For
most services, a Class IV rating is adequate. Class VI ratings
should be considered only for applications requiring minimum possible leakage, and then only with owner approval.
b. Double-ported valves provide a Class II shutoff.
c. Single-seated globe valves with metal-to-metal seating
surfaces meet Class IV. Class V shutoff can be achieved by
providing improved plug to seat ring concentricity or lapping
seating surfaces and/or increasing actuator thrust. Resilient
seats on single seated valves can provide Class VI shutoff.
d. However, before an insert material is selected, it should be
determined that the insert is compatible with the process ßuid,
pressure, and temperature. In addition to normal process
Live-loading
(compressed)
(not compressed)
Carbon-filled
PTFE backups
Virgin PTFE
V-rings
Wiper Rings
Figure 2—Live Loaded
Not for Resale
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must be reviewed to make sure that line mechanical integrity is not violated.
3
4
REFINERY CONTROL VALVES
Insert Retainer
or rotary motion (see Figures 5B and 16). The selection of a
valve for a particular application is primarily a function of the
process requirements for control performance, pressure drop,
temperature, and rangeability.
Insert
Soft Seat Ring
Figure 3—Resilient Seat
100
90
pen
80
r
ea
Lin
en
t
50
ck O
60
Qui
40
rc
Flow, %
70
30
u
Eq
al
Pe
20
10
0
10
20
30
40
50
60
70
80
90 100
Valve Life, %
Figure 4—Inherent Characteristics
condtions, shutdown conditions should be considered in
selecting resilient seats. Steaming through a valve can damage
or ruin a resilient seat. (See Figure 3.)
3.1.16 Control Valve Characteristics
a. Control valve ßow characteristics are determined principally by the design of the valve trim. The three inherent
characteristics available are quick opening, linear, and equal
percentage, as shown in Figure 4. A modiÞed equal percentage characteristics generally falling between linear and equal
percentage characteristics is sometimes available.
b. Positioners may use mechanical cams or be programmed
to provide other desired characteristics.
c. Installed characteristics often differ signiÞcantly from
inherent characteristics if the pressure drop across the control
valve varies with ßow. As a result, equal percentage plugs are
generally used for ßow control applications because most of
the Òsystem pressure dropÓ is not across the control valve.
Linear plugs are commonly used for applications where most
of the Òsystem pressure dropÓ occurs across the control valve.
3.1.17 Control Valve Types
TodayÕs control valves operate by one of two primary
motions: reciprocating (sliding stem) motion (see Figure 5A,)
Copyright American Petroleum Institute
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No reproduction or networking permitted without license from IHS
a. ISA S75.01, Flow Equations for Sizing Control Valves, is
the basic source used. Per ISA 75.02, Control Valve Capacity
Test, the tolerance for control valve Cv testing is ±5% at full
opening; the tolerance for partial openings is not stated. Control valve data is based on water testing with a limited set of
sizes. The calculations become less accurate for ßuids signiÞcantly different from water, for very large or very small sizes,
and for conditions different from laboratory conditions.
b. The primary factors that should be known for accurate sizing are:
1. The upstream and downstream pressures at the ßow
rates being considered.
2. The temperature of the ßuid.
3. The ßuid phase (gas, liquid, slurry) and the density of
the ßuid (speciÞc gravity, speciÞc weight, molecular
weight).
4. The viscosity (liquids).
5. The vapor pressure and critical pressure (liquids).
6. SpeciÞc heat ratio (gas).
7. The compressibility factor (gas).
c. As part of valve selection, the overall system in which the
valve is to be installed should be considered. A typical system
(in addition to the control valves) includes a pump or compressor, which provides energy, and other types of reÞnery
equipment, such as piping, exchangers, furnaces, and hand
valves, which offer resistance to ßow. Note that the differential pressure between the pump head curve and the system
pressure drop curve is the amount of pressure available for
the control valve. If no control valve were used, the ßow
would always be at the rate indicated by the intersection of
the two curves.
d. The presence of reducers upstream and/or downstream of
the valve will usually result in a reduction in capacity because
of the creation of an additional pressure drop in the system by
these enlargements or contractions in series with the valve.
Piping systems where both the inlet and outlet piping are
larger than the valve will result in an increased valve Cv
requirement. Capacity correction factors that can be applied
to calculated Cv values are readily available from most manufacturers for the various styles of valves.
e. In any ßow restriction, a portion of the pressure head of
the incoming ßuid is changed to velocity head, resulting in a
reduction in static pressure at the vena contracta. Refer to Figure 6. As the ßuid leaves the ßow restriction and assumes
downstream velocity, some portion of velocity head is recovered as pressure head. This process is termed pressure
recovery. The degree of pressure recovery is dependent upon
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3.1.18 Sizing
API RECOMMENDED PRACTICE 553
5
Figure 5A and 5B—Sliding and Rotary Stem
These can reduce or prevent cavitation. Some of these
trims are subject to plugging in dirty services and should
be reviewed for suitability in each service.
2. Valves with low-pressure recovery should be used to
minimize or prevent cavitation. In some cases it may be
necessary to use special components, or stage the pressure reduction through the use of two or more valves,
or specially design elements in series.
h. Flashing
1. Flashing occurs where the downstream pressure is
less than the vapor pressure. See Figures 6 and 8.
Flow
P1
Restriction
Vena Contracta
P1
P2 (Cavitating)
Pv
P2 (Flashing)
Pvc
Distance
Figure 6—Pressure Drop Through a Restriction
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P2
Pressure
the internal geometry of the ßow restriction. The pressure
excursion in liquid ßow results in a vena contracta pressure
lower than the downstream pressure. The vena contracta pressure may drop below the vapor pressure of the ßuid. As the
pressure recovers it may stay below the vapor pressure (ßashing) or it may recover above the vapor pressure (cavitation).
Flashing and cavitation are indications of partial or full
choked ßow, which may affect sizing.
f. Choked volumetic ßow occurs in gas or vapor service
when the ßuid velocity reaches the speed of sound at the vena
contracta. With a constant inlet pressure, increasing the pressure drop no longer increases the ßow. This will affect the
valve sizing by limiting the pressure drop available for sizing.
Pressure recovery has the effect of achieving choked ßow at a
pressure drop that is less than would be predicted by the critical pressure ratio. This can become a problem for valves with
high-pressure recovery, such as rotary valves. This necessitates the use of a larger valve or different valve style.
g. Cavitation
1. Cavitation is the generation of bubbles in the lowest
pressure portion of the valve, and then the subsequent collapse of these bubbles. See Figure 6. The bubble collapse
(implosion) releases an intense liquid jet which can
destroy a control valve in a short time. See Figure 7. It is
easily recognized by a characteristic sound Òlike rocks
ßowing through the valve.Ó A single compound such as
water is one of the most damaging ßuids. Hydrocarbon
mixtures can have various vapor pressures for different
components in the mixture, making it very difÞcult to predict the onset or the severity of cavitation. Special
cavitation control trims are offered by manufacturers.
Not for Resale
6
REFINERY CONTROL VALVES
excess capacity at the high end and 10 to 20% below the
minimum required capacity at the low end.
2. A high rangeability is of little signiÞcance if the service conditions for the valves in question do not require it.
The requirement for rangeability is to cover the maximum
and minimum ßow rates at the real ßowing conditions.
j. Manufacturers should analyze all valve speciÞcations for
cavitation, noise, or other detrimental factors, using the data
on the data sheets as a basis. Undesirable operating situations
should be brought to purchaserÕs attention, including noise or
cavitation severity. Manufacturers should propose possible
solutions to these problems within the design limits of the
type of valve covered by the speciÞcation or indicate that a
special design is required.
Figure 7—Cavitation Damage
Flashing, like cavitation, can cause physical damage
and decreased ßow capacity. Velocity is the major concern. The outlet ßow increases velocity due to the ßuid
changing from a liquid to a gaseous state. A larger control valve body size with reduced trim and larger size
outlet piping is usually required to prevent choking and
excessive velocity problems.
2. Flashing damage is usually less severe than the
damage from cavitation. However, restricted piping
conÞgurations at the valve outlet can cause the ßashed
vapor to cavitate and cause piping damage downstream
of the control valve. Manufacturers should be consulted
for recommendations.
3. Outgassing of dissolved gases that have been
absorbed by contacting (such as amine) is similar to
ßashing, but the relative amount of gas released is
much harder to predict. The process engineer should be
consulted to obtain the correct outlet liquid and gas
ßow rates.
i. Rangeability
1. The rangeability of the control valve should be considered during valve selection. Control valves are available
with published Cv rangeability of 50 to 1 and even greater,
at constant pressure drop, a condition that rarely exists in
actual practice. Typically, valves are sized with 10 to 20%
g. In no case should the calculated sound level exceed 115
Copyright American Petroleum Institute
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a. The predicted sound pressure level radiated from a control
valve is a complex determination, and the allowable noise
level in the installed location cannot be stated as one simple
number to be speciÞed in all circumstances. This is particularly true where there are other noise sources in close
proximity, since they have an additive effect. The actual level
depends on a number of factors, such as atmospheric discharge, physical location, proximity of other noise sources and
their magnitude, piping system conÞguration and wall thickness, insulation on piping, presence of reßective sources, etc.
b. Prediction of noise generated by a control valve is an inexact science. Prediction levels for a valve operation at
conditions speciÞed on the speciÞcation sheet can vary
widely using various manufacturersÕ methods.
c. To provide a basis for allowable noise level analysis, control valves calculated to generate excessive noise levels should
have alternate valves proposed that will not exceed 85 dBA at
one meter downstream and one meter out from the pipe. For
atmospheric discharge vent control valves (or system), the
noise level should not exceed 90 dBA at a point four meters
down from the vent exhaust and at a downward angle of 45
degrees. No allowance should be taken for insulation or
increased pipe wall thickness over that speciÞed in making
noise calculation, or in the valve or the noise reduction system.
d. The calculated continuous noise level should not exceed 85
dBA, measured where personnel may be continuously working. This may not be one meter downstream and one meter out
from the pipe. The Occupational Safety and Health Administration decreases the allowable time of exposure as the sound
level increases, and the user is referred to OSHA 1910.95 for
speciÞc guidelines. It is the userÕs responsibility to determine
if the sound level will meet OSHA requirements.
e. Noise levels above 85 dBA may be allowable where personnel are not working continuously.
f. The maximum intermittent sound level should normally
be limited to 110 dBA.
dBA due to possible mechanical failure.
Not for Resale
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3.1.19 Noise
API RECOMMENDED PRACTICE 553
7
Figure 8 — Typical Plug Damage from Flashing
h. Documented procedures and computer programs to estimate control valve noise are available from leading
manufacturers, and they should be used to determine whether
noise is a consideration. However, noise prediction and mitigation is a specialized effort generally requiring the
manufacturer recommendation for an effective design.
i. Valves with noise abatement or cavitation control trim with
small passages tend to plug with debris, particularly during
startup, and should be protected with conical or T-type strainers. See Figure 9.
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3.1.20 Body Integrity
Hydrostatic testing of pressure-containing components is
required per ANSI B16.34. For special services, other nondestructive tests are sometimes speciÞed.
3.1.21 Valve Assembly
The valve, actuator, and associated accessories, regardless of
manufacturer(s), should be assembled, piped, aligned, tested,
and shipped as a unit by the valve manufacturer. Tests may
include hydrostatic, stroke test, leakage, or accessory calibration.
3.1.22 Nameplate
The valve should be supplied with a permanently attached
stainless steel tag, stamped with the manufacturerÕs standard
data, and the tag or item number.
3.2 VALVE ACTUATORS
3.2.1 Pneumatic valve actuators, using air or gas, are preferred for most process control applications. Electric motor or
electrohydraulic operators may be considered for special
applications, particularly when pneumatic power is not available. Electrohydraulic actuators are used where very high
thrust forces are required.
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3.2.2 Actuators are classiÞed as direct acting (an increase
in air loading extends the actuator stem) or reverse acting (an
increase in air loading retracts the actuator stem). Some actuators are Þeld reversible. They can be changed from direct to
reverse acting with no additional parts. Most manufacturers
publish tables that allow selection of actuator size based on
valve size, ßow direction, air action, pressure drop, packing
friction, and available air pressure.
3.2.3 Diaphragm Actuators
a. A spring diaphragm actuator is a single-acting actuator
where pressure is applied against a spring or springs. Upon
loss of air, the spring will move the valve to the desired failure position. Construction of a typical spring diaphragm
actuator is shown in Figure 10.
b. Traditionally, the spring diaphragm actuator stroked over
an input range of 3Ð15 psi. The frequent use of positioners
and the requirements for tight shutoff have led to widespread
use of higher pressures, utilizing the available air supply.
3.2.4 Piston Actuators
a. Piston (or cylinder) pneumatic actuators are used for
control valves where high thrust is required. Single-acting
piston actuators apply air pressure to one side of the piston
against a spring or springs. Upon loss of air the spring will
move the valve to the desired failure position. Double-acting piston actuators are considerably stiffer than singleacting designs and can therefore be used to control higher
pressure drops. Double-acting piston actuators apply air to
both sides of the cylinder. Double-acting piston actuators
without springs require an external volume tank and trip
system to achieve the desired failure position. Springs can
be added to double-acting piston actuators to provide the
air failure mode. See Figure 11.
Not for Resale
8
REFINERY CONTROL VALVES
Figure 9—Multistaged Trim
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Not for Resale
API RECOMMENDED PRACTICE 553
Air
Lifts
Spring
Pushes
Down
9
Upper Travel Stop
Diaphragm Plate
Diaphragm
Loading Pressure
O-Ring Seal
O-Ring Seal
Diaphragm Rod
Spring
Spring Adjuster
Spring Seat
Stem Connector
Travel Indicator
Valve Stem
Indicator Scale
O
Reverse Actuator
Figure 10—Diaphragm Actuator
b. Linear type piston actuators are used for globe style control valves. They are also used for rotary valves with adapter
linkage. Scotch yoke or rack-and-pinion type piston actuators
are normally used for on/off control, but may be used for regulatory control if control degradation is not critical.
S
3.2.5 Electrohydraulic Actuators
A variation of the piston actuator is the electrohydraulic,
actuator which uses an electric motor to drive a pump and
supply hydraulic pressure for the piston. For multiple valve
installations, electrohydraulic actuators may be supplied by a
common electric motor/pump skid. See Figure 12.
Figure 11—Double-Acting Spring Return
Piston Actuator
3.2.6 Actuator Selection
3.2.6.2 Stroking speed requirements should be reviewed
and speciÞed for critical applications, such as compressor
anti-surge control, or where closing speed should be controlled to prevent hydraulic water hammer.
3.2.6.1 Actuator selection guidelines are based on the
assumption that the control valve will be required to operate
against the maximum differential pressure speciÞed. Generally, the worst case is to use the maximum upstream pressure
with the downstream pressure vented to atmosphere. Utilizing this condition for selection of the actuator ensures adequate power for maximum service conditions but can
dramatically affect operator size, particularly on larger valve
sizes. Actuators should be sized for the minimum air supply
pressure available.
3.2.6.3 Valve failure position should be carefully analyzed
in the event that supply pressure or instrument signal is lost.
Generally, the valve should fail in the safe direction on loss of
power or signal.
3.2.6.4 The most reliable fail-safe action is achieved with
an enclosed spring. If capacity tanks are required to provide
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Not for Resale
10
REFINERY CONTROL VALVES
Coil
Force Motor
Input
Signal
Air Bleed
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5 Volt AC
Cycle
Feedback
Spring
Bias
Spring
Cylinder
Shutoff
Valves
Feedback
Cam
Bypass
Valve
1/3 H.P.
Electric
Motor
50 psig (3.4 Bar)
500 psig (34.5 Bar)
Drain Off
Connection
500 psig (34.5 Bar)
3-Section Pump
with Built-In
Relief Valves
Suction Filter
Figure 12— Electrohydraulic Actuator
reserve operating power, they should be sized to stroke the
valve twice. Capacity tanks should be stamped and otherwise
conform to ASME Code guidelines (see Part U-1, Section
VIII, Division 1, ASME Boiler and Pressure Vessel Code).
Capacity tanks should be designed with all necessary accessories to ensure the required valve action and failure position.
teresis should be addressed. The valve, actuator, and positioner should be evaluated as part of the entire loop to
determine loop performance.
3.2.6.5 The actuator case should be rated for the maximum
available pneumatic supply pressure. Filters or Þlter regulators, if required, shall be supplied at the actuator inlet or the
positioner inlet.
3.2.6.9 Sliding stem actuators should be supplied with an
indicator showing valve stem position. Rotary valve actuators
should have a travel indicator attached at the actuator end of
the shaft, graduated in percent or degrees open.
3.2.6.6 The actuator should be sized to meet all control,
shutoff, and valve leakage requirements. Shutoff capabilities should be investigated at conditions of maximum differential pressure.
3.3 VALVE POSITIONER
3.2.6.7 To improve control valve performance, the effects
of low frequency response and excessive deadband and hys-
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No reproduction or networking permitted without license from IHS
3.2.6.8 In general, the actuator materials of construction
should be the manufacturerÕs standard.
3.3.1 Valve positioners should be speciÞed for all applications except on/off service. The valve positioner compares the
valve stem position with the signal generated by the controller.
If the valve stem is incorrectly positioned, the positioner either
increases or decreases the air pressure to the actuator until the
Not for Resale
API RECOMMENDED PRACTICE 553
correct valve stem position is obtained. Pneumatic or electropneumatic positioners are used to improve valve performance.
3.3.2 The following is a list of functions a positioner can
accomplish:
1. Provide for split range operation.
2. Reverse the valve action without changing the ÒfailsafeÓ action of the spring in the actuator. (Note that this
may also be done with a reversing type relay.)
3. Increase the thrust in spring diaphragm actuators.
4. Modify the control valve ßow characteristic.
5. Improve the resolution or sensitivity of the actuator
where high precision valve control is required. Precision
is enhanced by the availability of positioners with adjustable gain.
6. Reduce hysteresis.
11
ented downward. Three-way solenoid valves are used with
spring return actuators and double-acting actuators with positioners. Four-way solenoid valves are used with double-acting actuators with no spring and on/off double-acting spring
return valves. Solenoid valves should be speciÞed so that they
do not require a minimum differential pressure across the
valve to actuate.
3.5.3 Valve trip solenoids should be installed in the actuator inlet tubing. When exhaust rate is critical, the solenoid
valve Cv should be selected accordingly. A quick exhaust
valve, working in concert with a pilot solenoid valve, may be
required if the trip solenoid does not have sufÞcient venting
capacity. Quick exhaust valves have relatively large vent
capacity, with a Cv value at least ten times that of the typical
1/ " solenoid valve.
4
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3.3.3 Positioners should be installed using mounting plates
or bosses provided for that purpose. The positioner should be
mounted by the vendor, completely piped and aligned. The
positioner should be supplied with pressure gauges.
3.5.4 Control valves with solenoids and limit switches
should be speciÞed with 18" connecting leadwires or
prewired to junction boxes. Low voltage and 120-volt wiring
should not be used in the same junction box.
3.3.4 Positioner bypasses should only be speciÞed with
pneumatic positioners having the same or greater input signal
and stroking range. Bypasses are not applicable with electropneumatic positioners or with piston actuators.
3.5.5 DC voltage solenoids should be installed with a transient voltage suppressor or diode mounted in parallel with the
solenoid coil. AC voltage solenoids should have a metal oxide
varistor mounted with the solenoid coil.
3.3.5 Fast loops may require special tuning for best results.
3.6 TRANSDUCERS
3.3.6 Digital positioners further enhance valve performance, provide diagnostic information, and facilitate predictive maintenance programs.
3.4 HANDWHEELS
3.4.1 Manual handwheel operators should be supplied only
on speciÞc request by the owner, or where bypasses are not
installed. Side-mounted, lockable, screw or gear drive manual
operators, continuously connected and operable through an
integral declutching mechanism, are preferred. See Figures
13A and 13B.
3.4.2 Handwheels should be permanently marked to indicate valve open and closed directions
3.6.1 Electropneumatic transducers convert the electrical
output signals from electronic controllers into pneumatic signals that may be used to operate diaphragm actuated control
valves or provide signals to pneumatic positioners. The use of
transducers with control valves is a common practice. Vibration resistant transducers are required when mounted on control valves.
3.6.2
Electropneumatic positioners are available which
convert electronic signals to pneumatic output without a separate transducer. Electropneumatic positioners are widely
accepted in lieu of separate devices.
3.7 BOOSTER RELAYS
3.4.3 When a handwheel is used for piston actuator, a cylinder bypass valve must be included.
Booster relays may be used to increase the speed of
response of the control valve.
3.5 SWITCHES AND SOLENOIDS
4 Specific Criteria
3.5.1 Hermetically-sealed proximity switches are preferred
when independent ÒopenÓ or ÒclosedÓ indication of stem
position is required. See Figure 14.
4.1 GLOBE-STYLE VALVES
3.5.2 Solenoid valves should be rated for continuous duty
with Class H high temperature encapsulated coils and be satisfactory for both NEMA 4 and NEMA 7 installations. The
valve vent port should be equipped with an insect screen ori-
Copyright American Petroleum Institute
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No reproduction or networking permitted without license from IHS
4.1.1 Globe-style valves are preferred for high pressure
drop applications, low ßow applications, or where cavitation,
ßashing, or noise are considerations. However, some rotary
valve models having a characterized ball or eccentric rotary
plug are suitable for these applications.
Not for Resale
12
REFINERY CONTROL VALVES
Figure 13A and 13B—Handwheels
Figure 14—Limit Switches
4.1.2 A globe-style valve that has a cast ßanged body and
that can be serviced while in the line is preferred. Split body
valves are not recommended except in special service, such as
HF acid.
4.1.3 Three-way and angle body valves may be considered
for special applications. Three-way valves can be used for proportioning control of converging or diverging ßow. Angle body
valves should be considered for coking service, where solids
are carried in suspension, for severe ßashing service, and where
the piping design can take advantage of the valve geometry.
4.1.4 The recommended minimum globe body size is one
inch when installed in lines one inch and larger. Valves
installed in lines smaller than one inch should be line sized.
Valve sizes 11/4", 21/2", 31/2", and 5" are not recommended.
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No reproduction or networking permitted without license from IHS
Not for Resale
API RECOMMENDED PRACTICE 553
13
Packing Retainer
Packing
Disk
Taper Pin
Thrust Washer
Shaft
Packing Box Nut
Shaft
Bearing
Gland Flange
Packing Box Stud
Packing Follower
Shaft Bearing
Body
Disk Stop
Thrust Washer
Figure 15—Butterfly Valve
4.1.5 Either integral or separable ßange bodies are acceptable. Valves having integrally cast ßanges are generally used,
but separable ßanged valves are available.
4.1.6 Control valve bodies shall have the ßow direction
permanently marked on the body.
4.1.7 Stem or post-guided, unbalanced trim is preferred for
tight shutoff applications or for ßuids containing suspended
solids. Balanced, cage-guided trim is acceptable for applications in clean, nonslurry service.
4.2 ROTARY STYLE VALVES
4.2.1 Cost considerations and certain process conditions
may favor the rotary style control valve. Eccentric disk
valves (see Figure 15) are recommended in applications
requiring tighter shutoff, and in high ßow, low pressure
drops services. Rotary-segmented ball valves should be
considered for highly viscous services and where greater
ßow turndown ratios are required.
4.2.2 Butterßy valves with lug bodies (see Figure 16) may
have threaded or unthreaded bolt holes. Wafer (unßanged)
valves should have centering holes to ensure proper valve and
gasket alignment. Long pattern valves having longer stud bolts
with greater exposure should be insulated for Þre protection.
4.2.3 Particular attention should be given to clearance
requirements of butterßy disks. Heavy-wall pipe or lined pipe
can interfere with disk rotation.
4.2.4 The valve shaft should normally be oriented in the
horizontal plane. The valve disk or ball should be positively
attached to the valve shaft.
4.2.5 The actuator end of the shaft should be splined to
minimize lost motion.
4.2.6 The shaft bearing should be designed to prevent the
guide bushing from rotating in the body.
4.2.7 Shaft material should be stainless steel for carbon
steel or stainless steel valves. Other trim parts should be stainless steel or better. The bearing material should not cause
galling of the bearing or the shaft.
4.2.8 A shaft retention device should be provided on the
nondriving end.
5 Installation
5.1 ACCESSIBILITY
Figure 16—Lug Style Butterfly
5.1.1 All control valves should be installed so that they are
readily accessible for maintenance purposes and for operation
--`,,-`-`,,`,,`,`,,`---
Copyright American Petroleum Institute
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Not for Resale
REFINERY CONTROL VALVES
of a handwheel, if one is provided. They should generally be
located at grade unless pressure head or other design conditions make such an arrangement impractical. When located
above grade, control valves should be installed so that they
are readily accessible from a permanent platform or walkway
with ample clearances for maintenance purposes. There
should be sufÞcient clearance between the control valve actuator and the bypass line to allow removal of the actuator, bonnet, and plug. Preferred mounting is vertical.
5.2 LOCATION
5.2.1 Where there is a choice of location, it is desirable to
have the control valve installed near the piece of operating
equipment that should be observed while on local manual
control. In these cases, it is also desirable to have indication
of the controlled variable readable from the control valve
handwheel or the bypass valve.
5.2.2 Control valves used in process lines or fuel lines to
Þred heaters should be located on the sides of the heater away
from the burners or at a sufÞcient distance from the heater,
with blocks and bleed valves, so that the line can be drained
and the control valves removed without danger of a ßashback.
An alternate method is to pipe the drain or bleed connection a
safe distance from the heater.
5.2.3 High temperatures can cause premature failure of
actuator or positioner soft goods and electrical or electronic
components. Control valves should not be located adjacent to
hot lines or equipment, or where temperature may be excessive. Consult the manufacturerÕs literature for maximum permissible ambient temperature.
5.2.4 Electrical devices should be approved for use under
the applicable electrical area classiÞcation.
5.3 CONTROL VALVE MANIFOLDS
5.3.1 General
The design of control valve manifolds varies widely. In applications where a process shutdown for the servicing of control
valves cannot be tolerated and the process can be safely operated manually, block and bypass valves should be provided.
5.3.2 Block and Bypass Valves
a. Where the greatest ßexibility is to be provided for future
expansion, the block valves upstream and downstream of the
control valve should be line size. In situations where the control valve is two sizes smaller than line size, the block valves
may be one size smaller than line size.
b. For controllability, the bypass valve capacity should not be
signiÞcantly greater than the control valve capacity. It is not
unusual to make bypass valves smaller than the line size in
such cases.
Copyright American Petroleum Institute
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No reproduction or networking permitted without license from IHS
5.3.3 Manifold Piping Arrangements
a. The manifold piping should be arranged to provide ßexibility for removing control valves, particularly where ring-type
joints are used. Flexibility of piping is also necessary to keep
excessive stresses from being induced in the body of the control valve. Vents and drains should be provided as required to
service the control valve.
b. The piping around control valves should be self-supporting
or should be permanently supported so that when the control
valve or block valve is removed the piping integrity remains.
c. Severe services may require special valve manifold
designs. Design should be reviewed by user and manufacturer.
5.3.4 Swages
a. Where a ßanged or ßangeless control valve smaller than
line size is used, swages are placed adjacent to the control
valve except where additional piping is required to permit
removal of the through bolts. Some users swage outside
the valve manifold to use smaller block valves, but this
reduces the ßexibility of being able to change to a larger
control valve on-line.
6 Refinery Applications
6.1 Following are some speciÞc reÞnery control valve services with application notes and recommendations. The valves
recommended represent the most economical solution to the
given problem. These solutions have been proven in service.
6.2 Materials and packing suggested in these examples may
be modiÞed, based on vendors, suggestions and speciÞc
applications. Special environmental packing may be used
where required.
6.3 The user is cautioned to understand the signiÞcance of
the recommendations and the limitations. It is more likely that
a given problem will resemble an example than actually
match it. Thus, the user must use caution.
6.4 BOILER FEEDWATER RECIRCULATION
6.4.1 Operating Conditions
Flow (#/Hr)
P1(psig)
P2 (psig)
T (¡F)
Fluid
Maximum
100,000
2250
0
160Ð180
Boiler Feedwater
6.4.2 Valve Specification
Special designs are required for this extremely severe
service.
6.4.3 Trim
Cavitation control design, hardened, reduced port. A downstream oriÞce plate, to reduce differential and cavitation, has
Not for Resale
--`,,-`-`,,`,,`,`,,`---
14
API RECOMMENDED PRACTICE 553
been used for some installations. This will only help at higher
valve openings. On/off valve control is sometimes used for
this reason. Soft seats are normally not acceptable. Class V
shutoff rating is required.
15
cally sealed contacts. Stainless steel tubing and Þttings. No
copper or brass components allowed.
6.6.3
Trim
Stainless steel disk and shaft.
6.4.4 Sizing
6.6.4
Conventional, choked ßow.
Sizing
Conventional.
6.4.5 Notes
Consult with knowledgeable manufacturer for proven
designs.
6.5 FEEDWATER TO WASTE HEAT BOILER
6.5.1 Operating Conditions
6.6.5 Notes
This is a safety application and requires NACE materials
(per speciÞcation) and high reliability components.
6.7 SULFUR VAPOR TO EDUCTOR
6.7.1 Operating Conditions
Normal
10000
600
55
228
Boiler Feedwater
Flow (#/Hr)
P1(psig)
P2 (psig)
T (¼F)
Fluid
Flow (SCFH)
P1 (psig)
P2 (psig)
T (¼F)
Fluid
Normal
Shutdown
2000
0
-0.6
0
-0.65
-0.7
300
300
Sweep Air from Sulfur Pit, SG = 1.0
6.5.2 Valve Specification
One-inch carbon steel angle body, special application for
cavitating service, outlet expander with replaceable erosion
insert. Diaphragm actuator with positioner.
6.5.3 Trim
Hardened plug and seat.
6.5.4 Sizing
6.7.2 Valve Specification
Three-inch, line size, block valve, tight shut-off butterßy or
plug valve. Fail closed actuator with solenoid pilot, limit
switches at open and closed positions. Carbon steel body,
steam jacketed on/off service. NACE speciÞcation materials.
No copper or brass components allowed.
6.7.3 Trim
Conventional, choked.
6.5.5 Notes
Tight shut-off required.
6.7.4 Sizing
Mount valve close to boiler with expanded outlet to prevent cavitation damage due to restricted piping.
6.6 SULFUR RECOVERY UNIT ACID GAS BLOCK
VALVE
Conventional.
6.7.5 Notes
Line and valve are steam jacketed with 50 psig steam to
prevent sulfur buildup in valve.
6.6.1 Operating Conditions
6.8 LIQUID SULFUR TO STORAGE
6.6.2 Valve Specification
Ten-inch, line size, high performance butterßy valve, Class
V leakage or better. Carbon steel body, NACE MR01-75 certiÞed materials, double TFE packing required. On/off service,
fail closed on loss of air supply or electric power to solenoid
pilot. Open and closed limit position switches with hermeti-
Copyright American Petroleum Institute
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No reproduction or networking permitted without license from IHS
6.8.1 Operating Conditions
Flow (GPM)
P1(psig)
P2 (psig)
T (¼F)
Fluid
Normal
5
30
20
280
Liquid Sulfur
6.8.2 Valve Specification
Plug type valve with actuator and positioner. Carbon steel
body, restricted trim.
Not for Resale
--`,,-`-`,,`,,`,`,,`---
Flow (SCFH)
P1(psig)
P2 (psig)
T (¡F)
Fluid
Normal
Shutoff
120,000
0
12
14
11.8
0
120
120
Acid Gas, MW = 37.1
16
REFINERY CONTROL VALVES
6.8.3
Trim
Special characterized plug, stainless steel plug and seat.
6.10.3 Sizing
6.8.4 Sizing
Conventional sizing for liquids, allowing for volume of Þnes.
Conventional.
6.10.4 Notes
6.8.5 Notes
Body and ßanges are steam jacketed, 50 psig steam.
6.9 HYDROFLUORIC ACID SERVICE
6.9.1 Operating Conditions
Various ßows, pressures and temperatures.
Hydroßuoric acid (HF), toxic and corrosive.
6.9.2 Valve Specification
Carbon steel body (WCB) for moderate temperature services. Initial corrosion of the surface creates a protective barrier to limit further corrosion. Abrasion or water can remove
this barrier. Use Monel body for high temperature services
above 300¡F (hot acid). Use Monel trim. Monel develops a
protective coating in service. It is necessary to allow adequate
clearances at critical metal interfaces at the plug to guides,
and seat to body, to allow for this buildup.
6.9.3 Quality Control
Because of the toxic nature of HF, the quality of the
foundry and valve manufacturer is important. VeriÞcation of
materials is required. It is important to eliminate any water
from the valve; thus, pressure testing with kerosene is often
speciÞed. Kerosene is less viscous than water and will be
more sensitive in Þnding casting defects and seat leakage.
Leak detecting paint may be speciÞed for ßanges; the orange
paint turns green on exposure to HF. Refer to process licensers for detailed valve requirements.
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6.10 CAT CRACKER BOTTOMS SLURRY OIL
Hydrocarbon/oil slurry with 15% solids.
6.10.1 Operating Conditions
Flow (GPM)
P1(psig)
P2 (psig)
T (¡F)
Line (inch)
Fluid
Normal
2042
60
15
560
6
Oil slurry, 15% catalyst Þnes with
0.010Ðto 0.015-inch particle size.
6.10.2 Valve Specification
Carbon steel body, segmented or eccentric ball design with
shaft upstream and ßow exiting the valve across the seating
Copyright American Petroleum Institute
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No reproduction or networking permitted without license from IHS
area (i.e., backwards). Trim solid alloy 6 plug, seat ring and
retainer, 440C or Alloy 6 bearings, Nitronic 50 shaft.
Catalyst Þnes entrained in the slurry pose a severe erosion
problem and reduced trim life. Consider the impingement
angle of the particles on the trim. For added resistance to erosion, upgrade the body to 316 SS or chrome-moly material
and the ball to ceramic. It may be advisable to purge the bearings with clean oil.
6.11 FEED TO HYDROCRACKER FRACTIONATOR
(FLASHING)
6.11.1 Operating Conditions
Flow (GPM)
P1(psig)
P2 (psig)
T (¼F)
Pv (psia)
Pc (psia)
Line (inch)
Fluid
Normal
1150
586
245
110
593
480
3
Hydrocarbon Liquid
6.11.2 Valve Specification
Angle style globe valve with ßow down over the plug.
6.11.3 Trim
Hardened trim. A hardened liner in the valve outlet can be
replaced when worn.
6.11.4 Sizing
Conventional, ßashing, choked ßow.
6.11.5 Notes
Downstream piping length and restrictions should be minimized. Note that anytime ßashing occurs, it is very possible
that cavitation may occur at any ßow disruption point in the
downstream piping, such as valves, elbows, or thermowells.
6.12 REFORMER HOT GAS BLOCK/BYPASS
(THREE-WAY BUTTERFLY)
6.12.1 Operating Conditions
Flow (MSCFH)
P1(psig)
P2 (psig)
T (¼F)
Fluid
Not for Resale
Minimum
Maximum
800
1600
285 (max)
285 (max)
282 (block)
0 (bypass)
1560
1560
High Temperature Hydrogen
API RECOMMENDED PRACTICE 553
17
6.12.2 Valve Specification
6.13.4 Sizing
Butterßy, combination 20" block, 10" bypass, on tee. 10"
bypass valve has Inconel 800 liner with refractory lining. Piston actuator with high performance positioner. 347 SS body.
There is no analytical method for sizing under these
extreme conditions.
6.12.3 Trim
This valve satisfactorily replaced a globe-style valve with
very short trim life.
Special two-piece bearing for high temperature service,
with tap for steam purge.
6.12.4 Sizing
6.13.5 Notes
6.14 KO DRUM VENT TO HYDROTREATER FLARE
6.14.1 Operating Conditions
Conventional.
6.12.5 Notes
Very special application. Consult with vendor.
6.13 REACTOR LETDOWN WITH EROSIVE SOLIDS
6.13.1 Operating Conditions
Flow (Inlet)
Flow (Outlet)
(GPM/SCFM)
P1(psig)
P2 (psig)
T (¼F)
Fluid
Viscosity
Vapor Press
Crit Press
Solids
H2S
Minimum
595 GPM
Normal
1386 GPM
Flow (SCFH)
P1(psig)
P2 (psig)
T (¼F)
Fluid
Normal
23,760
11.0
10.5
115
Acid Gas
6.14.2 Valve Specification
Maximum
1642 GPM
570/140
1305/290
1580/346
1635
1571
1571
395
395
395
820
820
814
Gas OilÑßuid characteristics outgassing,
ßashing, cavitation, low angle and high angle particle impingement, low pH.
0.24 cp
395 psig
711 psig
3% consisting of clay, catalyst, silica, 90% < 10
microns
3000 ppm
An eccentric butterßy valve with soft seating is the economical choice. Class VI shutoff is required; pressure drop
is low, and required capacity is high. NACE materials with
carbon steel body stress relieved.
6.14.3 Trim
317 SS disk, PTFE seal, PTFE lined 316 SS bearings,
Nitronic 50 shaft.
6.14.4 Sizing
Conventional.
6.14.5 Notes
Materials should conform to NACE requirements (per
speciÞcation), due to acid gas service.
6.15 ANTISURGE CONTROL VALVES
6.13.3 Trim
6.15.1 Centrifugal compressors and blowers may enter a
condition called ÒsurgeÓ at low ßow rates if there is insufÞcient mass ßow to maintain a stable discharge pressure.
Because surge causes sudden changes in the forces on moving parts and bearings, it may damage or destroy the compressor. The most common anti-surge control system directly
or indirectly, measures, the ßow through the compressor and
opens a valve as required to maintain sufÞcient ßow to avoid
an unstable pressure/ßow region. The valve should be sized,
usually for several ßow and pressure conditions, to be sure it
can serve the full range of needs. It must respond quickly and
accurately to prevent a damaging surge in the compressor.
11/2" port, modiÞed parabolic plug, massive plug guiding,
outlet liner. Plug, seat ring, seat ring retainer are mixture of
Inconel 718, TC Grade 701, Inconel 625 with cobalt chrome
hard facing.
6.15.2 These valves typically generate high noise levels
without noise abatement treatment. It is a business decision to
evaluate the frequency and duration that the valve will be
required to open, along with the predicted noise level, before
6.13.2 Valve Specification
ÒAnti-cokingÓ angle valve, 1500# ANSI, 347 SS, 4" x 6"
sweep angle body, expanding venturi outlet, with extended
bonnet, plug/guide purging system, piston actuator with high
performance positioner and valve position switch or transmitter. Heat treatment is required for the valve body.
Quality ControlÑ100 percent radiography of body and bonnet; liquid dye penetrant inspection; mill test reports; hydrostatic test report; Þnal visual inspection; and NACE materials.
--`,,-`-`,,`,,`,`,,`---
Copyright American Petroleum Institute
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Not for Resale
18
REFINERY CONTROL VALVES
specifying the degree of noise control required. An example
application is shown below.
6.16 HIGH VOLUME, LOW PRESSURE AIR
BLOWER ANTI-SURGE VALVE
6.16.1 Operating Conditions
Normal
80000
13
0
270
6.17.4 Sizing
Maximum Shutoff
125000
0
12
16
0
0
270
270
6.16.2 Valve Specification
Four-inch high performance butterßy, for tight shutoff and
wide rangeability. Piston actuator and high performance positioner; specify stroke time based on estimated time constant
of blower with discharge piping. Complete with silencer and
heavy wall pipe between valve and silencer. Vendor should
estimate noise with and without silencer and recommend
installation details. Carbon steel body PTFE packing.
6.16.3 Trim
Carbon steel disk, stainless steel shaft.
6.16.4 Sizing
6.16.5 Notes
This form of anti-surge valve vents to the atmosphere
instead of recycling the discharge to compressor suction. The
butterßy valve provides considerable cost savings over the
low-noise globe style valve. User should specify acceptable
noise level, usually 85 dBA. Stroking speed response is critical for this application.
6.17 CRUDE OIL PROCESSING UNIT THROTTLING /
STEAM TO PRE-HEAT EXCHANGER
6.17.1 Operating Conditions
Normal
250
130
125
356
450
Steam
6.17.2 Valve Specification
Post-guided sliding stem control valve, 2" globe valve ßow
up, ANSI Class 300# WCB carbon steel body with graphite
packing; actuator with positioner.
Copyright American Petroleum Institute
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No reproduction or networking permitted without license from IHS
Conventional. Check for excessive noise.
6.18 PUMP RECIRCULATION VALVE
6.18.1 Operating Conditions
Q gpm (US)
P1 (psig)
dP (psid)
Fluid
SG
Pv (psia)
Vis
Minimum
Normal
1000
3200
422
400
372
350
Crude Oil with 10Ð12% solids.
0.8
0.87
3.00
3.00
3.00
3.00
Maximum
7000
306
256
0.87
3.00
3.00
6.18.2 Valve Specifications
Globe-style control valve with ANSI Class 300# 8 x 6 inch
WCC carbon steel body, Teßon packing, actuator, and positioner for throttling service.
6.18.3 Trim
Conventional, choked.
Qs lb/h
P1 psig
dP psid
T Satur (¼F )
T (¼F)
Fluid
Unbalanced 1.875-inch port, 316 SST plug with CoCr-A
on the plug seat and guide. Post guiding, with 17-4PH stainless steel bushing, 316 SST seat ring with CoCr-A seat, and
17-4PH seat ring retainer. ANSI Class IV shutoff.
Stem-guided 7-inch port, unbalanced construction, 416
stainless steel valve plug, and 410 stainless steel seat ring are
selections with high hardness to combat erosive ßow; precipitation hardened 17-4PH cage. ANSI Class IV shutoff.
6.18.4 Sizing
Standard liquid sizing is adequate here for an initial evaluation. However, special procedures may be required to account
for solids present in ßowstream; beware of underestimating
ßow coefÞcient with standard liquid sizing equations. Sizing
should consider the erosive nature of the solids present in the
ßow stream; the equal percentage characteristic is preferred
to position the operating conditions at an intermediate travel
to avoid the high velocity ßow of low travel conditions. The
equal percentage characteristic will also provide relatively
uniform control loop stability over the expected range of
operating conditions, compensating for the installed gain
effects of the pump curve. The 8 x 6 globe valve has the outlet
area required and pressure recovery characteristics that may
avoid choked conditions in a conventional ball valve while
maintaining the ability to operate at higher travels.
6.19 CRUDE OIL PROCESSING UNIT HEAVY
BOTTOMS (HIGH TEMPERATURE TAR)
6.19.1 Operating Conditions
Not for Resale
--`,,-`-`,,`,,`,`,,`---
Minimum
Flow (SCFH)15000
P1(psig)
16
P2 (psig)
0
T (¼F)
270
Fluid
Air
6.17.3 Trim
API RECOMMENDED PRACTICE 553
Q gpm (US)
P1 (psig)
dP (psid)
T(¡F)
Fluid
1000 (¡F)
SG
Pv (psia)
19
self ßushing valve with actuator and positioner for throttling
control.
Normal
Maximum
285
340
250
250
20
25
800
800
Crude unit heavy bottoms; high temperature of
approximately erosive ßow with ÒstickyÓ particulates.
0.762
0.762
0.500
0.500
6.20.3 Trim
Full 3-inch port with unbalanced, post-guided, equal percentage 316 stainless steel plug with CoCr-A plug seat and
guide. 17-4PH stainless steel seat ring retainer and 17-4PH
stainless steel guide bushing. ANSI Class IV shutoff.
6.20.4 Sizing
Conventional.
6.19.2 Valve Specification
Eccentric rotary valve, ANSI Class 300# 3-inch C5 body,
graphite fugitive emission packing, actuator and positioner for
throttling service. C5 chrome-moly body provides enhanced
hardness characteristics with higher ANSI pressure/temperature ratings. Reverse ßow (ßow passes plug, then seal) ball
valve preferred to maximize valve body life and divert high
velocity erosive ßow downstream. ANSI Class IV shutoff.
6.19.3 Trim
Reverse ßow full port trim conÞguration consisting of 174PH stainless steel seat ring retainer, Alloy 6 (Stellite 6) seal,
and Stellite 6 valve plug with equal percentage characteristic.
Reverse ßow conÞgurations will minimize high velocity ßow
across the rotary plug, seal, and inner valve body surfaces,
helping maintain shutoff speciÞed and optimal body life. 174PH shaft and Stellite 6 bearing will provide high temperature strength, as well as desirable corrosion and galling resistance. The 17-4PH/Alloy 6 shaft/bearing combination will
minimize valve friction which would be caused by excessive
ßuid particle buildup in the bearing areas.
6.19.4 Sizing
6.21 CRUDE PROCESSING UNIT—THROTTLING/
HOT OIL
6.21.1 Operating Conditions
Q gpm (US)
P1 (psig)
dP (psid)
T (¡F)
Fluid
SG
Pv (psia)
Normal
Maximum
314
350
85
85
20
20
600
600
Intermediate temperature hot oil
0.85
0.85
3.00
3.00
6.21.2 Valve Specifications
Sliding stem globe style control valve with ANSI Class
300# 4-inch chrome-moly body, graphite packing, and extension bonnet. Flow down restricted port cage-guided balanced
trim with actuator and positioner for throttling control.
6.21.3 Trim
6.20 CRUDE OIL PROCESSING UNIT—
THROTTLING/WASH OIL
Restricted port, balanced, cage-guided trim with 316
stainless steel valve plug with CoCr-A plug seat and guide.
17-4PH stainless steel equal percent cage with Alloy 6
(Stellite 6) seat ring and 316 stainless steel strain-hardened
stem. ANSI Class II leakage.
6.20.1 Operating Conditions
6.21.4 Sizing
Conventional.
Conventional.
Q gpm (US)
P1 (psig)
dP (psid)
T (¡F)
Fluid
SG
Pv (psia)
Normal
Maximum
285
340
25
25
20
20
600
600
Intermediate temperature wash oil
0.762
0.762
0.500
0.500
6.22 SPRAY WATER TO DESUPERHEATER
(UTILITIES)
6.22.1 Operating Conditions
6.20.2 Valve Specifications
Sliding stem globe style control valve with ANSI Class
300# 3-inch chrome-moly body, graphite packing. Flow-up
Flow:gpm
P1(psig)
dp (psid)
Temperature (¡F)
Fluid
SG
--`,,-`-`,,`,,`,`,,`---
Copyright American Petroleum Institute
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No reproduction or networking permitted without license from IHS
Not for Resale
Normal
0.37
400
183
200
Water
0.96
Maximum
0.75
400
133
200
0.96
20
REFINERY CONTROL VALVES
6.22.2 Valve Specification
One-inch globe style top-guided single port unbalanced
ßow up design valve. Body construction WCB 300 RF
with actuator and positioner for throttling control.
6.22.3 Trim
close action, pneumatic positioner, and electro-pneumatic
transducer with small-volume and self-operated regulator.
6.24.3 Trim
17-4PH cage, 416 SST seat ring, 316 SST stem.
6.24.4
Trim 316 SST seat and stem with 316 SST Alloy 6-plug
tip.
Sizing
Conventional.
6.25 HOT SEPARATOR LIQUID TO HOT FLASH
DRUM (POWER RECOVERY TURBINE
BYPASS)—HYDROCRACKER
6.22.4 Sizing
Conventional.
6.23 EXCHANGER HGO BYPASS—FCC
6.25.1 Operating Conditions
6.23.1 Operating Conditions
Normal
20,000
140
5.00
650
Heavy Gas Oil
0.73
3.00
Q (barrel/day)
P1 (psig)
dP (psid)
T (¼F)
Fluid
SG
Pv (psia)
Maximum
20,000
140
1.00
650
0.73
3.00
6.23.2 Valve Specification
Eight-inch three-way globe valve with diverging ßow
and throttling applications. Carbon steel body. Actuator
with fail down option and pneumatic positioner.
6.23.3 Trim
Stainless steel seat ring, plug, and strain-hardened stem.
6.23.4 Sizing
6.24 GAS OIL RECIRCULATION—CAUSTIC
HYDROTREATER (CHD)
6.24.1 Operating Conditions
--`,,-`-`,,`,,`,`,,`---
Minimum
25,000
1050
1000
400
Gas Oil
3.00
0.85
Normal
45,000
1050
1000
400
Maximum
70,000
1050
1000
400
3.00
0.85
3.00
0.85
6.24.2 Valve Specification
Four-inch globe valve with ßow down and tight shut-off.
Carbon steel body, double TFE packing. Actuator with fail
Copyright American Petroleum Institute
Provided by IHS under license with API
No reproduction or networking permitted without license from IHS
Normal
2008
1645
6250
2435
360
550
545
2449.7
286.0
0.538
0.627
23.580
Hydrogen Liquid with trace H2S
6.25.2 Valve Specification
3" x 4", 1500 RF, angle-style axial ßow multi-step valve. 21/4
percent Cr, 1 percent Mo body, NACE conformance body and
trim. Class V shutoff required.
6.25.3 Trim
Conventional.
Q (bpd)
P1 (psig)
dP (psid)
T (¡F)
Fluid
Pv (psia)
SG
Flow-Inlet (gpm)
Flow-Outlet (gpm)
Flow-Outlet (scfm)
P1 (psig)
P2 (psig)
T-Inlet (¡F)
T-Outlet (¡F)
Pv (psia)
Pc (psia)-(pseudo)
SG (liquid Inlet)
SG (liquid Outlet)
Mol Wt (Vapor)
Fluid
Expanding labyrinth plug with top and bottom balanced
piston guide. Hardened trim.
6.25.4 Sizing
The calculated Cv for this ßashing service is determined by
adding the calculated Cv for liquid and the vapor at the outlet
conditions of the valve. Process simulation is required to calculate the amount of vapor ßashed. The ISA sizing equations
are inaccurate for this ßashing application. ManufacturersÕ
control valve sizing programs which calculate ßashing only
on the basis of single compound streams cannot be used for
this sizing calculation.
6.25.5 Notes
Inlet piping must be sized to minimize potential of ßashing
at the valve inlet. Outlet piping shall be sized to avoid potential for cavitation occurring downstream of valve. Valve
installation with the body and actuator in the horizontal plane
Not for Resale
API RECOMMENDED PRACTICE 553
simpliÞes piping and equipment layout. Trim style must be
trash tolerant.
6.26 COLD SEPARATOR SOUR WATER—
HYDROCRACKER
6.26.1 Operating Conditions
Flow-Inlet (gpm)
Flow-Outlet (gpm)
Flow-Outlet (scfm)
P1 (psig)
P2 (psig)
T-Inlet (¡F)
T-Outlet(¡F)
Pv (psia)
Pc (psia)-(pseudo)
SG (liquid Inlet)
SG (liquid Outlet)
Mol Wt (Vapor)
Fluid
--`,,-`-`,,`,,`,`,,`---
Normal
86.0
81.5
320
2404
354
122
115
512
1300
0.960
0.973
34.020
Water with 2.36 mole % H2S and
trace hydrocarbon
21
7.1 VALVE TYPE
Valve type is dependent upon the distance from the leak
source. Any valve in the Þre zone should be Þre-safe. A gate
valve, metal-seated ball valve, or high-performance butterßy
valve is considered to be Þre-safe. The valve selected should
have been tested to API Spec 6FA, Fire Test for Valves, or an
equivalent standard test.
7.2 DEFINITIONS
7.2.1 Emergency Block Valves
Emergency block valves are designed to control a hazardous incident. These are valves for emergency isolation and
are designed to stop the uncontrolled release of ßammable or
toxic materials. These valves should be Þre-safe rated valves
if they are within the Þre zone. The valves may be referred to
as Types A, B, C, and D.
7.2.2 Determination of Fire Zone
11/2", 1500 RF, angle-style high resistance multi-step axial
ßow valve. Carbon steel body, NACE conformance body and
trim. Class V shutoff required.
This is the area which is unsafe to enter during an emergency situation. Distances are included as example only
refer to plant standards for actual distances. The area is
considered to be within a 25-foot radius minimum surrounding the leak source.
6.26.3 Trim
7.3 TYPES OF EVBs
Series of equal capacity stages with last stage expansion.
Relatively large ßow passages and trim shearing action allow
long service life and reduced potential for clogging which can
occur with other multistage trim styles. Hardened trim.
7.3.1 Type A Valve
6.26.2 Valve Specification
A manually operated Þre-safe block valve installed at the
equipment. This type of valve is installed when, in the event
of a leak, ignition is not expected
6.26.4 Sizing
The calculated Cv for this ßashing service is determined by
adding the calculated Cv for liquid and the vapor at the outlet
conditions of the valve. Process simulation is required to calculate the amount of H2S ßashed. ManufacturersÕ control
valve sizing programs which calculate ßashing only on the
basis of single compound streams cannot be used for this sizing calculation.
6.26.5 Notes
Outlet piping shall be sized to avoid potential for cavitation
occurring downstream of valve. Valve installation with the
body and actuator in the horizontal plane simpliÞes piping
and equipment layout. Trim style must be trash tolerant.
7 Emergency Block Valves
An emergency block valve (EBV) is used as a means of
isolating ßammable or toxic substances in the event of a leak
or Þre.
Copyright American Petroleum Institute
Provided by IHS under license with API
No reproduction or networking permitted without license from IHS
7.3.2 Type B Valve
This Þre-safe block valve should be installed at a minimum
of 25 feet from the leak source when ignition is expected. The
Type B valve is manually operated and is limited to sizes up
to and including 8 inches, and pressure classes through 300#.
For reasons of access, the valve should be accessible via a
platform with stairways or not be installed higher than 15 feet
above grade.
7.3.3 Type C Valve
The Type C valve is a power-operated Type B valve. The
valve must be power-operated if larger than 8 inches or
because a pressure class higher than 300# is required. The
valve should be installed a minimum of 25 feet (outside of the
power zone) from the leak source and no higher than 15 feet
above grade. The controls should be at the valve in an accessible location.
Not for Resale
22
REFINERY CONTROL VALVES
7.3.4 Type D Valve
7.5 ACTUATOR SELECTION
This is an EBV with remote controls. There is no restriction as to where the valve may be located, but the controls
should be a minimum of 40 feet from the leak source and
should be out of the Þre zone. An EBV installed at an elevation greater than 15 feet above grade will also come under
this category. Both the actuator and that portion of the control
cable and tubing which is in the Þre zone should be Þreproofed or designed to operate without failure during Þre
conditions. Specify that the conduit/tubing/cable supports are
required to be Þreproofed.
7.5.1 Electric Motor Actuator
7.4 EBV GENERAL INSTILLATION GUIDELINES
a. The closing torque switch should be bypassed and the
valve should close to make closed position limit switch.
b. The control circuit fuse should be bypassed.
c. The thermal overloads should be bypassed.
d. Any thermistor in the motor windings should be bypassed.
7.4.1 Compressors
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7.4.1.1 EBVs are typically required for all compressors
200 HP or larger handling ßammable or toxic materials.
7.4.1.2 An EBV is required in all suction and discharge
lines.
7.4.1.3 An EBV is required between stages and interstage
equipment if the interstage equipment holds greater than
1000 gallons of liquid.
7.4.2 Pumps
7.4.2.1 An EBV is typically required for pumps having
seals where the upstream vessel contains greater than 2000
gallons of light ends or hydrocarbons above the auto ignition
point or above 600¡F.
7.4.2.2 An EBV is required where the upstream vessel
contains greater than 4000 gallons of liquid hydrocarbons.
7.4.3 Vessels
7.4.3.1 An EBV is required for vessels containing light
ends or toxic material.
7.4.3.2 An EBV is required for vessels containing liquids
heavier than light ends, but above the ßash point.
7.4.4 Heaters
7.4.4.1 An EBV is required for each fuel gas or oil line to
Þred heaters and boilers. A double block and bleed arrangement with a single or multiple valves is often used. Reopening after a trip requires a manual reset which permits
relatching only after all safety interlock parameters have been
satisÞed. Refer to API RP 556, Manual on Installation of
Instruments and Control Systems for Fired Heaters and
Steam Generators.
7.4.4.2 An EBV is required for each feed line to a Þred
heater that contains ßammable ßuid. The EBV should be
located outside the Þrewall or Þrezone, which contains the
heater.
Copyright American Petroleum Institute
Provided by IHS under license with API
No reproduction or networking permitted without license from IHS
7.5.1.1 This is the Þrst choice for a gate valve. Because the
electric motor will fail stationary upon power loss, any valve of
this type which is in the Þre zone must have its actuator Þreproofed. Also, that portion of the control cable which is in the
Þre zone should be Þreproofed. Fire/rated cable is an option.
7.5.1.2 For EBV service, it is more important to close the
valve than to protect the actuator motor. Therefore, the following wiring precautions should be observed:
7.5.1.3 For motor actuated valves, the actuator-to-valve
adapter should be able to withstand the stall torque of the
motor operator.
7.5.2 Pneumatic Actuator
7.5.2.1 This is the Þrst choice for quarter-turn valves.
Fail-safe here refers to fail closed in the event of instrument air failure.
7.5.2.2 Fail-to-Safety in a Fire
This valve is remotely operable under normal circumstances, but the actuator is sacriÞced in the event of a Þre. A
spring-return piston actuator on top of a metal-seated ball
valve is recommended. The pneumatic tubing connected to
the open port of the actuator should be sunlight-resistant
polyethylene tubing and be wrapped around the actuator.
Alternately, a fusable plug can be used. When the valve is
involved in a Þre, the tubing will melt and the valve will
close. The valve will remain closed despite involvment in the
Þre. No ÞreprooÞng is necessary.
7.5.2.3 Operable During a Fire
This actuator should be hard-piped (no soft tubing) and
should be Þreproofed. A spring-closed actuator or a doubleacting piston actuator with a fail-safe trip valve with two
check valves in series and air bottle may be used.
7.5.2.4 Actuator to Valve Adaptation
For pneumatic actuated valves, the adapter should be able
to withstand the maximum torque generated by the actuator
with the maximum design air pressure applied to the piston.
The adapter must also be made of materials that will withstand a Þre until the valve can be closed.
Not for Resale
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API RECOMMENDED PRACTICE 553
7.6 FIREPROOFING
7.6.1 FireprooÞng must withstand a 2000¼F petroleum Þre
while keeping all internal electrical controls and wiring below
2000¼F for a period of at least twenty minutes. The Þreproofing should be able to withstand a sustained water stream from
a Þre hose. The ÞreprooÞng should be weatherproof and sunlight resistant. Refer to API Publication 2218, FireprooÞng
Practices in Petroleum and Petrochemical Processing Plants.
8 Vapor Depressuring Valves
8.1 GENERAL
8.1.1 Vapor depressuring systems are often installed on
large volume hydrocarbon systems, especially those operating at higher pressures. They are used to prevent upset conditions from actuating safety relief valves or to automatically
depressure the equipment in emergency conditions, especially in case of Þre. If there is a Þre around a vessel containing both liquid and vapor, the unwetted portion of the vessel
will probably reach a temperature at which the strength of the
material will be reduced. In this case, the relief valve would
not protect against vessel rupture, whereas a vapor depressuring system could reduce the pressure to a safe level. A vapor
depressuring system should be provided for process equipment within a designated Þre area where, as a result of Þre
exposure, the internal pressure would exceed 100 psig or 50%
of design pressure, whichever is lower.
8.1.2 Emergency vapor depressuring facilities should consist of locally and remotely operated, manually and/or automatically controlled depressuring valves discharging into a
closed system.
8.1.3 Depressuring valves should be sized in accordance
with API RP 521 for conditions of Þre exposure, density
change, and liquid ßash, assuming that depressuring starts at
the normal operating pressure or at the set point of the automatic pressure controller. The valves should be sized to
depressure the system within 15 minutes to 100 psig or 50%
of design pressure, whichever is lower, unless this depressuring rate would subject equipment to unacceptably low temperatures. Low temperature materials may be required for the
depressuring valve and its outlet piping.
23
cess pressure from 0.0 psig to 110 percent of the relief valve
set pressure, and must hold the valve closed at 110 percent of
the relief valve set pressure. Quick exhaust valves for rapid
depressuring of the actuator may be speciÞed for on/off valves.
8.2.3 For mechanical integrity, the minimum body size
and rating should be 2-inch 300# ANSI ßanged, with
reduced trim as required.
8.2.4 Valve plug should be a single seated metal seat with
quick opening or linear trim characteristic, with process pressure tending to open the valve. Top or cage-guiding is acceptable. Soft-seated trim should not be used.
8.2.5 The depressuring valve and actuator combination
should achieve a Class V shutoff.
9 Hydraulic Slide Valve Actuators
9.1 GENERAL
9.1.1 This section details requirements for hydraulic type
slide valve actuators with a dedicated hydraulic unit for each
valve where the hydraulic unit is separate from the valve actuator. Central hydraulic units that are used to power multiple
valves are sometimes used. Some newer designs have an integral hydraulic unit, which is mounted right on each slide
valve actuator. Other large continuous duty valves may use
these actuators.
9.1.2 Each slide valve can have a totally independent
hydraulic and control system. The following minimum components should be included at or near each valve:
a. A slide valve actuator consisting of high pressure hydraulic cylinders, manual operator, adapter plates to mount the
actuator to the valve bonnets, a position feedback sensor, and
any locally required manifolding, tubing, or valving.
b. A hydraulics skid containing all required hydraulic supply
system components and positioning controls. This includes
the hydraulic oil reservoir, hydraulic pumps and drivers, Þlters, manifolding, valving and interconnecting tubing, servo
valves, high pressure accumulators, pump controls, positioner
electronics, pressure gauges and miscellaneous other
instrumentation.
9.2 HYDRAULIC POWER UNIT (HPU)
8.2 DEPRESSURING VALVES AND ACTUATOR
REQUIREMENTS
8.2.1 Control valves may be used for depressuring service.
Some users specify two-position on/off valves only, while
others may use throttling valves with pressure control pilots
and positioners.
8.2.2 Depressuring valves should be equipped with pneumatic actuators with a spring for positive action on air failure.
Actuator should be designed to open the valve with any pro-
Copyright American Petroleum Institute
Provided by IHS under license with API
No reproduction or networking permitted without license from IHS
9.2.1 The hydraulic ßuid should be a nonßammable synthetic or natural type hydraulic oil suitable for use in high
pressure, high performance hydraulic systems and ambient
temperature range.
9.2.2 The entire hydraulic system should be constructed of
300 series stainless steel. The reservoir should be equipped
with vent and vacuum breaker valves set at no more than 2
psig positive and 0.3 psig negative pressure, or as required by
the reservoir design. The reservoir should be provided with
Not for Resale
24
REFINERY CONTROL VALVES
additional inlets and outlets as required for Þlling and venting
operations. Vents should be provided with Þlters to prevent oil
contamination. Some users blanket the reservoir with nitrogen or provide a desiccant type drier on the vent to prevent
moisture and dirt contamination of the hydraulic oil.
--`,,-`-`,,`,,`,`,,`---
9.2.3 Each hydraulic power unit should be equipped with
dual pumps and drivers. Pumps should be variable stroke positive displacement types and be equipped with internal relief
valves. Each pump on each HPU should be of identical construction. One pump should be driven by a constant speed
electric motor. The second pump is usually speciÞed to be
driven by an air motor, or can be powered by an isolated electrical feeder. Drivers should be sized to provide design
hydraulic oil ßow at the hydraulic oil relief pressure. The
motor starter for the electric motor driven pump is usually
supplied as part of the hydraulic unit.
9.2.4 The hydraulic power unit must include a pump control system which will automatically start the spare pump,
designated by a switch on the HPU front panel, if the hydraulic supply pressure drops below a pre-set pressure. Alarm
contacts indicating that the spare pump is running are
required.
9.2.5 If coolers are required, dual coolers with a dual 3way switching valve should be provided. Coolers should be
installed on the hydraulic oil return stream. If air coolers are
used, they should not require any type of forced air cooling.
9.2.6 The HPU should include high pressure oil accumulators with sufÞcient capacity to provide for two complete valve
strokes (full open to full closed, or vice versa, is one stroke).
Accumulators shall be designed such that they can be
recharged and maintained/removed online without shutdown.
9.2.7 The HPU should include all required interconnecting
manifolding, tubing, valving, etc. Dual high pressure hydraulic oil Þlters with valving necessary to allow switching of Þlters and change-out of Þlter elements should be provided. All
tubing Þttings should be O-ring seal SAE hydraulic type Þttings. Compression Þttings are not recommended.
required. In addition, a local manual hydraulic hand pump
or standby hydraulic accumulator backup hydraulic system
is required. Any manual operation should actuate dry contacts for remote alarm indication.
9.3.4 All systems should be self-contained. Single block
manifolds with a minimum of interconnecting tubing are preferred. Connections to the valve actuator cylinders should be
ßexible braided hose.
9.3.5 The positioner system must lock the slide valve in
place and activate an alarm contact upon any of the following
conditions:
a.
b.
c.
d.
e.
Loss of feedback.
Loss of control signal.
Loss of power.
Electronics failure.
Excessive servo position deviation error.
9.3.6 The positioner should be electronic type and accept a
4Ð20 ma DC control signal. The slide valve will be closed at 4
ma and open at 20 ma. All wiring should be run with appropriate high temperature wiring, or routed to avoid high temperature areas.
9.3.7 Electronic valve stem position feedback should be
provided to the positioner. Magneto-restrictive or LVDT technology is preferred over slidewire or potentiometer techniques. The positioner system should also transmit a 4Ð20 ma
signal proportional to the valve stem position to the reÞnery
control system.
9.3.8 It is desirable to be able to calibrate the position feedback system without stroking the slide valve.
9.3.9 The hydraulic supply and positioner systems must
include outputs for remote indication of diagnostic alarms
(see 9.4.13 for complete list).
9.4 INSTRUMENTATION REQUIRED
9.4.1 Pump discharge pressure gauge on HPU gauge board.
9.3 SLIDE VALVE POSITIONER SYSTEMS
9.4.2 Pump discharge pressure switch with circuit to automatically start the standby pump.
9.3.1 Each slide valve actuator should be provided with a
positioning system complete with a local Þeld panel.
9.4.3 Pump suction pressure gauge on the HPU gauge
board.
9.3.2 Each system should have dual inlet Þlters for hydraulic ßuid. These Þlters should be switchable so that Þlter elements may be changed while on-stream.
9.4.4 Vacuum breaker on oil reservoir.
9.3.3 For manual operation of the slide valves, each
actuator system should include a mechanical handwheel
and the capability to readily bypass the hydraulic system.
The design must permit removal of the hydraulic cylinder
while the valve remains on handwheel control. A local
hydraulic manual ÒOpen-Stop-CloseÓ control is also
Copyright American Petroleum Institute
Provided by IHS under license with API
No reproduction or networking permitted without license from IHS
9.4.5 Rotameter for nitrogen purge to oil reservoir.
9.4.6 Oil reservoir instruments:
a.
b.
c.
d.
e.
Level sight gauge.
Temperature indicator.
High temperature switch.
Low level switch.
Low-low level switch to stop pumps.
Not for Resale
API RECOMMENDED PRACTICE 553
9.4.7 Pressure gauge on HPU gauge board for Þltered high
pressure hydraulic ßuid for distribution.
9.4.8 Accumulator(s) pressure gauge.
9.4.9 Temperature indicator on cooling water return from
hydraulic ßuid heat exchangers.
9.4.10 Accumulator low pressure switch.
9.4.11 Purge instruments (rotameter and pressure switch)
for electrical boxes as required.
9.4.12 Selector switch for determining primary hydraulic
pump. The no-selected pump automatically becomes the
Òstand-by.Ó
9.4.13 Alarms
9.4.13.1 The package must include all required process
switches and an alarm indication system to advise the operator of abnormal conditions. Alarms may be indicated at the
positioner Þeld panels and hydraulic unit (if these are separated) using LEDs, pilot lights, or alarm annunciators. Alarms
should be included for each slide valve actuator for:
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
k.
l.
Low reservoir level*.
High reservoir temperature*.
Spare pump running*.
Low-low reservoir level*.
Low-low hydraulic pressure*.
Low accumulator pressure.
Positioner in local mode.
Loss of control signal.
Loss of feedback signal.
Excessive servo error.
Loss of power.
Electronics purge failure (if used).
* Only one set of alarms required if a common HPU is
used. Locate at HPU skid.
25
3. Spare hydraulic pump running*.
4. Low accumulator pressure*.
5. Positioner purge failure (if used).
b. Positioner Common Failure Alarm.
1. Positioner in local mode.
2. Loss of control signal.
3. Loss of feedback signal.
4. Loss of power.
5. Excessive servo error.
6. Loss of positioner power.
7. Low-low reservoir level*.
8. Low-low hydraulic supply pressure*.
* Only one set of alarms if a common HPU is used. If dedicated HPUs are used, alarms are required for each HPU.
9.5 PERFORMANCE CHARACTERISTICS
9.5.1 Linearity of stroke and the transmitted position signal
versus the input control signal should be within ± 0.25 percent full stroke.
9.5.2 Tracking error (setpoint deviation) should be ± 2 percent maximum.
9.5.3 Adjustable stroking speeds should be provided.
9.5.4 Stability of movement at constant position control
signal input should not exceed 0.1 percent of full stroke
(cyclical, peak to peak).
9.6 ELECTRICAL REQUIREMENTS
9.6.1 Area ClassiÞcation: Minimum Class 1, Division 2,
Group D. The electrical equipment must be suitable for the
area electrical classiÞcation.
9.7 TESTING AND INSPECTION
9.4.13.2 Provide dry Form C contacts to indicate positioner common trouble and positioner failure alarms to the
reÞnery control system.
9.7.1 A factory functional acceptance test, demonstrating that
the entire system performs properly, is highly recommended.
9.4.13.3 The following alarm groups should be provided
for each slide valve:
9.8 SLIDE VALVE ACTUATOR SERVICE
a. Positioner Common Trouble Alarm.
1. Low reservoir level*.
2. High reservoir temperature*.
9.8.1 Following is an example of a typical slide valve/actuator data sheet:
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Copyright American Petroleum Institute
Provided by IHS under license with API
No reproduction or networking permitted without license from IHS
Not for Resale
26
Location:
Valve Size:
Stroke Including Overlap:
Controlling Stroke:
Welded or Flanged:
Hot or Cold Wall Valve:
Jacking Conn. on Body:
Lip Seals Provided:
Purges:
OriÞce Opening:
OriÞce Shape:
Actuator Type:
Operating Modes:
Input Control Signal:
Local Control:
Cylinder ID:
Stroke Travel Time:
Handwheel:
Air Motor:
Positioner Type:
Position Indicator:
Limit Switches:
Hydraulic System Pressure:
Hydraulic Fluid:
Multiple or Local System:
Filter Location:
Filter Elements:
REFINERY CONTROL VALVES
Regenerator
36"
23"
191/8"
Welded
Hot
Yes
Yes
Bonnet
292 sq inches
Bonnet
Hydraulic
Auto/Manual
4Ð20 ma.
Yes
14"
30 seconds
Yes
No
Electronic
Yes
No
250 psig or 2000 psig in high
pressure service
Hydraulic Synthetics
Multiple
Hydraulic Skid
Supply: 3 micron, high beta
Return: 50 micron
Accumulator Capacity:
Backup # of Strokes:
--`,,-`-`,,`,,`,`,,`---
Copyright American Petroleum Institute
Provided by IHS under license with API
No reproduction or networking permitted without license from IHS
Not for Resale
--`,,-`-`,,`,,`,`,,`---
Copyright American Petroleum Institute
Provided by IHS under license with API
No reproduction or networking permitted without license from IHS
Not for Resale
--`,,-`-`,,`,,`,`,,`---
9/98—5C
Copyright American Petroleum Institute
Provided by IHS under license with API
No reproduction or networking permitted without license from IHS
Not for Resale
Additional copies available from API Publications and Distribution:
(202) 682-8375
Information about API Publications, Programs and Services is
available on the World Wide Web at: http://www.api.org
--`,,-`-`,,`,,`,`,,`---
Copyright American Petroleum Institute
Provided by IHS under license with API
No reproduction or networking permitted without license from IHS
Order No. C55301
Not for Resale