PROCEDURE APPROVAL SHEET
CONTRACT No: 9009
CONTRACT DESCRIPTION:
PURCHASER: Vogt Power International
PROCEDURE No: P&S WI-13
PROCEDURE TITLE: Post Weld Heat Treatment Procedure for diverter damper
PROCEDURE REVISION STATUS: 1
PROCEDURE APPROVED
NOT APPROVED
FOR USE ON THIS PROJECT
COMMENTS;
CONTRACTOR
COMPANY (BALTEC)
PURCHASER (VPI)
NAME: Mr. Prasong Singthom
NAME:
NAME:
POSITION: Project Manager
POSITION:
POSITION:
SIGNATURE:
SIGNATURE:
DATE:
DATE:
SIGNATURE:
Prasong
DATE: 28th May, 2018
Post Weld Heat Treatment Procedure
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CLIENT NAME:
BALTECIES
PROJECT NO.: 9009
DOCUMENT NO. :
P&S WI-13
JOB NO.:

Post Weld Heat Treatment
Rev.
Issue Date
Issued for
Prepared by
0
18th April, 2018
Approval
Prasong.S
Reviewed By
Approved by
Post Weld Heat Treatment Procedure
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REV0.
Index
1. Scope
2. Reference
3. Definitions
4. Responsibilities
5. Temperature Constraints
6. Heat Treatment Procedure
7. Temperature Recording, Control and Measuring
8. Heating
9. Heated/Insulated Zones
10.
Thermal Insulation
11.
Operation if Post Weld Heat Treatment
12.
Hardness Testing
13.
Attachment
1.
Post Weld Heat Treatment Procedure
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SCOPE:
REV 0.
1.1
2.
These procedures apply to local Post Weld Heat Treatment (PWHT), of piping
fabrication and mechanical parts assembly.
1.2
Post Weld Heat Treatment (PWHT), shall be performed when required by the
applicable code or specification, depending on the material and shell thickness.
1.3
The Heat Treatment procedures described within this document are based on:
A)
Type of Heat Treatment
B)
Material Composition
C)
Configuration of Work Piece
D)
Code Requirement
REFERENCES:
2.1
3.
DEFINITIONS:
3.1
4.
PWHT (Post Weld Heat Treatment)
RESPONSIBILITIES:
4.1
5.
ASME Section VIII Div.1 (UCS 56)
The Heat Treater shall be responsible for conducting and reporting the results of
PWHT in accordance with related ASME and / or Client’s specifications
whichever is more stringent.
TEMPERATURE CONSTAINTS
P NO.
MATERIAL
WALL THICKNESS
(mm)
TEMPERATURE (°C)
HOLDING TIME
MINUTES/mm
1
Carbon Steel
> 20 mm
600°C - 650°C
2.4/mm Min 1Hrs
4
1.25 Cr-0.5Mo
P11
> 13 mm
700°C - 750°C
2.4/mm Min 2 Hrs.
5A
2.25 Cr-1Mo P22
All
720°C - 760°C
2.4/mm Min 2 Hrs.
5A
5Cr-0.5Mo P5
ALL
720°C - 760°C
2.4/mm Min 2 Hrs.
5B
9Cr-1Mo P91
ALL
720°C - 760°C
2.4/mm Min 2 Hrs.
6.
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HEAT TREATMENT PROCEDURE
HEATING REQUIREMENT
The heating from ambient to 300°C shall be controlled at a moderate rate. During
heating up
and cooling down, no temperature gradient shall exceed 200°C/m in axial
direction or 40°C/m in tangential direction. For shell thickness of pipe or plate up to and
including 25 mm the heating rate shall not exceed 200°C - 250 °C/Hr. for shell thickness
of pipe or plate over 25 mm the heating rate shall not exceed: 5500/t°C/Hrs.
(t=maximum section thickness) or 55°C/Hr. whichever is greater. During cooling the work
piece must remain under insulation until the temperature of all heated parts with shell
thickness over 25 mm has fallen below gradient shall exceed 200°C/m in axial direction, or
40°C/m in tangential direction?
The work piece shall be cooled to 300°C where by the cooling rate is limited as follows:
Shell thickness of pipe or plate ≤ 25 mm: 200°C/Hr.
Shell thickness of pipe or plate > 25 mm: 6875/t°C/Hr.
(T = maximum section thickness) or 55°C/Hr. whichever is greater.
7.
TEMPERATURE RECORDING, CONTROL AND MEASURING
7.1 Thermocouple
7.1.1 Thermocouple shall be Type K B 54937, made of nickel-chromium / nickelaluminum (Ni- Cr/Ni-Al) directly capacitance discharge welded onto the work piece
within 12.7 mm of the weld joint. Certification of conformance is available of each reel of
wire utilized.
7.1.2 Thermocouple attachment: thermocouple wires are to be capacitive discharge
welded directly to the substrate surface.
7.1.3 Care shall be taken to ensure that the thermocouple conductor wires do not touch
each other. Wherever possible, thermocouple shall not be located under heating pad. They
shall be routed between heating pads or out through the insulation to avoid close contact
with the heating pad.
7.1.4 Thermocouple to compensating lead connections shall be a minimum of 0.5 mm
from the heated zone.
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7.2 Number of Thermocouple
Pipe Size
Up to 10”
12” to 16”
18” to 32”
Thermocouples
Two
Three
Four
Position
180o/ 360o
120o/240o/360o
90o/180o/270o/360o
7.3 Thermocouple Compensating Cable
7.3.1 Copper constantan compensation cable shall be used for the connection of the
thermocouple with the temperature-recording instrument.
7.3.2 The copper (+ve) shall be connected to the nickel-chromium conductor of the
thermocouple (non-magnetic), and the constantan lead (-ve) to the nickel-aluminum
conductors (magnetic).
7.4 Temperature Recording
7.4.1 Temperature recording shall be of the potentiometer, ready to run, a hybrid chart
recorder, with continuous writing or multipoint dotting system, measuring range 01200°C.
7.4.2 All recording equipment shall be accompanied with calibration check certificates,
and shall be recalibrated every six (6) months.
7.4.3 Chart speed shall be set at 25 or 50 mm/hour and be checked during calibration.
7.4.4 Charts usually comprise the following information:
-
System Number
Line Number
-
Weld Number
-
Thermocouple Number (color)
-
Operated Date
-
Sketch of Thermocouple Location
-
Recorder Chart Speed
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8.
HEATING
8.1 The heat treatment operation shall be performed by utilizing flexible ceramic pad
(FCP)
8.2 The heating element shall be attached to the pipe in the manner that equal distribution
of heat will be achieved.
8.3 heating element location.
9.
HEATED / INSULATED ZONES
Width of the zone at soaking temperature (T) will be at least 2.5√RT left and right of weld
to be heat- treated. (R=Radius) of pipe; (T=Wall thickness) of pipe in mm.
Width of the zone insulated will be at least 5√RT and has to cover all area with
temperature (1/2 T) half soaking temperature and higher.
10.
11.
12.
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THERMAL INSULATION
10.1 The area to be heat-treated shall be insulated with ceramic fiber insulation, 25 mm
thick, with minimum density of 128 kg/m3, capable of withstanding the maximum
temperature 1200°C.
10.2 All heat bands shall be insulated, extending on either side to provide gradual thermal
gradients.
10.3 The number of layers of insulation to be applied and their extent is dependent on the
shell thickness, pipe diameter and gradient requirement, and site conditions.
OPERATION OF POST WELD HEAT TREATMENT
Sequence of Operation
The operation of Post Weld Heat Treatment generally shall be performed in sequence
described here with:
11.1 Obtain and review the Heat Treatment work instruction.
11.2 Acquire ISO DWG for work piece identification, joint number, cleaning condition
and mapping the location of the thermocouples.
11.3 Attach thermocouples by Thermocouple Welding Unit (T.W.U.)
11.4 Wrap the required number of flexible ceramic pads as determined by shell thickness
and size of the work piece.
11.5 Apply ceramic fiber material to make thermal insulation.
11.6 Confirm the calibration status of temperature recorder by using the calibration check
instrument, also having a current Calibration certificate.
11.7 Connect thermocouples and power cables to the recording and controller
respectively.
11.8 Seal all open pipe ends.
11.9 Check/or recommend of temporary support to ensure dimensional integrity of the
work pieces.
11.10 Check all heat treatment machines and instrument.
11.11 Prior to switching on for heat treatment operation, have the inspector to recheck
again with respect to Hot-Zone, Thermocouple Location. And the Extent of Insulation.
11.12 Switch on the power.
11.13 Monitor temperature reading during PWHT operation on recorders.
11.14 Rate of temperature rise and fall, and range of holding time shall be as per
heat treatment specification.
11.15 Upon completion of heat treatment, disassemble all connectors and heat elements.
11.16 Check damage by visual.
HARDNESS TESTING
12.1 The hardness of weld and heat affected zone (HAZ) is used as acceptance criteria for
PWHT.
12.2 The hardness tester to be used is number of tests shall be in accordance with pipe
diameter.
12.3 For local heat treatment 100% of base materials weldment and HAZ to be performed
testing. On furnace heat treatment is requires at last 10% of weldment and HAZ.
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12.4 The proper location for hardness testing:
12.5 When dissimilar metals are welded together the hardness limits specified for base and
welding materials as in ASME B31.3, Table 331.3.1 shall be applied of each material
13.
ATTACHMENT
13.1 PWHT report
13.2 Hardness test report
13.1 PWHT report
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13.2 Hardness test report
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