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Gauges, Indicating Pressure,
for Compressed Gas Service
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UL Standard for Safety for Gauges, Indicating Pressure, for Compressed Gas Service, UL 404
Seventh Edition, Dated January 31, 2005
Revisions: This Standard contains revisions through and including May 8, 2006.
SUMMARY OF TOPICS
These revisions to ANSI/UL 404 provide clarification and additional detail regarding testing
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MAY 8, 2006 − UL 404
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JANUARY 31, 2005
(Title Page Reprinted: May 8, 2006)
ANSI/UL 404-2006
1
UL 404
Standard for Gauges, Indicating Pressure, for Compressed Gas Service
The first and second editions were titled High-Pressure Gas Gauges and the first
edition was numbered UL 252(b).
First Edition – March, 1948
Second Edition – June, 1953
Third Edition – May, 1973
Fourth Edition – July, 1979
Fifth Edition – June, 1993
Sixth Edition – September, 1997
Seventh Edition
January 31, 2005
The most recent designation of ANSI/UL 404 as an American National Standard
(ANSI) occurred on May 8, 2006.
This ANSI/UL Standard for Safety, which consists of the Seventh Edition, with
revisions through May 8, 2006 is under continuous maintenance, whereby each
revision is ANSI approved upon publication. Comments or proposals for revisions
on any part of the Standard may be submitted to UL at any time. Proposals
should be submitted via a Proposal Request in UL’s On-Line Collaborative
Standards Development System (CSDS) at http://csds.ul.com.
An effective date included as a note immediately following certain requirements
is one established by Underwriters Laboratories Inc.
The Department of Defense (DoD) has adopted UL 404 on October 3, 1994. The
publication of revised pages or a new edition of this Standard will not invalidate
the DoD adoption.
Revisions of this Standard will be made by issuing revised or additional pages
bearing their date of issue. A UL Standard is current only if it incorporates the
most recently adopted revisions, all of which are itemized on the transmittal notice
that accompanies the latest set of revised requirements.
ISBN 0-7629-1023-2
COPYRIGHT © 1979, 2006 UNDERWRITERS LABORATORIES INC.
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GAUGES, INDICATING PRESSURE, FOR COMPRESSED GAS SERVICE - UL 404
JANUARY 31, 2005
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3
CONTENTS
INTRODUCTION
1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
2 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
2.1 Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
2.2 Units of measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
2.3 Undated references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
CONSTRUCTION
3
4
5
6
7
8
9
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Sizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Dials and Pointers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Elastic Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Graduations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
PERFORMANCE
10
11
12
13
14
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Accuracy Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Over-Pressure Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Impulse Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Internal Explosion Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
MARKING
15 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
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GAUGES, INDICATING PRESSURE, FOR COMPRESSED GAS SERVICE - UL 404
JANUARY 31, 2005
INTRODUCTION
1 Scope
1.1 These requirements cover indicating pressure gauges of the elastic element type usually employed in
the high-pressure side of regulators or reducing valves used on compressed gas containers or cylinders
of oxygen, hydrogen, nitrogen, and other gases. Such gauges usually have pressure ranges of 0 – 1500,
0 – 2000, 0 – 3000, or 0 – 4000 pounds per square inch (psi) (0 – 10.34, 0 – 13.78, 0 – 20.68, or 0 –
27.56 MPa).
2 General
2.1 Components
2.1.1 Except as indicated in 2.1.2, a component of a product covered by this standard shall comply with
the requirements for that component.
2.1.2 A component is not required to comply with a specific requirement that:
a) Involves a feature or characteristic not required in the application of the component in the
product covered by this standard, or
b) Is superseded by a requirement in this standard.
2.1.3 A component shall be used in accordance with its rating established for the intended conditions of
use.
2.1.4 Specific components are incomplete in construction features or restricted in performance
capabilities. Such components are intended for use only under limited conditions, such as certain
temperatures not exceeding specified limits, and shall be used only under those specific conditions.
2.2 Units of measurement
2.2.1 If a value for measurement is followed by a value in other units in parentheses, the first stated value
is the requirement.
2.2.2 Unless otherwise indicated, all voltage and current values mentioned in this standard are
root-mean-square (rms).
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5
2.3 Undated references
2.3.1 Any undated reference to a code or standard appearing in the requirements of this standard shall
be interpreted as referring to the latest edition of that code or standard.
CONSTRUCTION
3 General
3.1 The assembly and design of pressure gauges with regard to location of pressure connections, type of
pressure connections, size of pressure connections, stop pins, outside diameters of shells and rings,
outside diameters of cases, dial figures, graduations, and indicating pointers shall conform to the
requirements for gauges in the Standard for Gauges – Pressure Indicating Dial Type – Elastic Element,
ANSI/ASME B40.1-91.
3.2 In addition to the foregoing, the following requirements for original calibration and accuracy, and
calibration and accuracy following subjection to over-pressures and extended operation, as well as
hazards attendant to bursting tests, shall apply.
4 Sizes
4.1 The nominal size of a gauge shall be the inside diameter of the case in inches measured at the face
of the dial.
4.2 The size of a gauge shall be not less than 1-1/4 inches (31.75 mm).
4.2 revised May 8, 2006
5 Dials and Pointers
5.1 A dial shall be produced in a manner which will result in the dial having sharp lines for graduations
and numerals. Methods found suitable include silvering and lacquering, etching and filling, photographic,
and lithographic processes.
5.2 A pointer shall be so mounted on its staff as to provide for subsequent resetting without damage to
the staff or pointer.
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GAUGES, INDICATING PRESSURE, FOR COMPRESSED GAS SERVICE - UL 404
JANUARY 31, 2005
6 Windows
6.1 A window shall be a transparent component that closes the front of the case. It shall be heat-treated
glass, laminated glass, plain glass (commercial, single, or double strength plate or sheet), or plastic.
7 Elastic Elements
7.1 An elastic element shall be processed or seasoned to reduce or eliminate internal stresses resulting
from the process of manufacture.
8 Materials
8.1 Metallic materials employed throughout the assembly shall be made of material having strength,
rigidity, and resistance to corrosion equivalent to painted or plated steel or aluminum, yellow brass, or
bronze.
9 Graduations
9.1 The values of the minor, or smallest, graduations on the dial shall conform to those designated in
Table 9.1.
Table 9.1
Value of graduations
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Range,
pounds per square inch
0
0
0
0
–
–
–
–
1500
2000
3000
4000
(kPa)
0
0
0
0
–
–
–
–
Graduations,
pounds per square inch
10345
13793
20690
27586
25 or 50
50 or 100
100
100
(kPa)
172 or 345
345 or 690
690
690
PERFORMANCE
10 General
10.1 Representative samples of each size and pressure range of pressure gauges are to be subjected to
the following tests.
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GAUGES, INDICATING PRESSURE, FOR COMPRESSED GAS SERVICE - UL 404
7
11 Accuracy Test
11.1 A pressure gauge in the ″as received″ condition, tested over the middle three-fifths of its full scale
range, with readings taken going both up and down, shall be accurate to within ±3-1/2 percent of the
maximum pressure shown on the dial.
11.2 The above tests are to be conducted using a properly calibrated dead-weight tester, test gauge, or
the equivalent. During a test using a dead weight tester, the table with the superimposed weight is to be
rotated by hand at approximately 100 revolutions per minute.
11.3 A test gauge shall be three times as accurate as the limits specified in 11.1 and shall otherwise
comply with the requirements for test gauges detailed in the Standard for Gauges – Pressure Indicating
Dial Type – Elastic Element, ANSI/ASME B40.1-91.
11.4 During each test, readings are to be taken at not less than three points spaced at approximately
equal intervals over the middle three-fifths of the scale range and at the maximum point on the scale.
11.5 Six samples are to be tested for accuracy. After this test three samples are to be used for the
Over-Pressure Test, Section 12 and three samples are to used for the Impulse Test, Section 13.
11.5 added May 8, 2006
12 Over-Pressure Test
12.1 Three samples from the accuracy test are to be subjected for a period of 3 hours to a pressure equal
to 125 percent of the maximum scale value for a gauge having a range of 3000 psi (20.68 MPa) or less
and 112 percent for a gauge having a range exceeding 3000 psi.
12.1 revised May 8, 2006
12.2 One hour following the termination of the Over-Pressure Test the gauges are to be tested over the
middle three-fifths of its full scale range, with readings taken going both up and down. They shall be
accurate to within ±3-1/2 percent of the maximum pressure shown on the dial.
12.2 revised May 8, 2006
13 Impulse Test
13.1 Three samples from the accuracy test are to be subjected to 25,000 pulses of hydrostatic pressure
between the limits of 200 psi (1.38 MPa) and 65 percent of the maximum scale value of the gauge.
13.1 revised May 8, 2006
13.2 The test apparatus is to provide for mounting the gauge on a system of piping containing a water
seal between the gauge and a system of air under pressure. The water pressure at the gauge is to be
varied by automatically imposing and releasing air under pressure in the closed system at the rate of 25
to 30 complete cycles per minute.
13.3 One hour following the termination of the Impulse Test the gauges are to be tested over the middle
three-fifths of its full scale range, with readings taken going both up and down. They shall be accurate to
within ±3-1/2 percent of the maximum pressure shown on the dial.
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13.3 added May 8, 2006
8
GAUGES, INDICATING PRESSURE, FOR COMPRESSED GAS SERVICE - UL 404
MAY 8, 2006
14 Internal Explosion Test
14.1 A gauge shall be so constructed that if bursts of the elastic element, or its means for joining occur,
due to an internal explosion or other application of excessive pressure, no part of the gauge is propelled
or thrown from the assembly.
14.2 The explosion test apparatus is to consist of a closed chamber having a tapped opening for the
gauge connector, and a breeching, firing, and safety mechanism to accommodate the firing and resultant
pressure of an explosive charge. The charge is to consist of a smokeless gun powder in sufficient quantity
to produce a pressure of 25,000 psi (172.3 MPa) in the free space provided by the chamber and the
internal sections of the gauge under test.
14.3 Two samples are to be subjected to the test in 14.2.
14.3 added May 8, 2006
MARKING
15 General
15.1 A pressure gauge shall be marked with the following:
a) The manufacturer’s or private labeler’s name or identifying symbol.
b) A distinctive catalog number or equivalent identification to specifically identify the product.
c) The units in which the scale is marked on the gauge face.
d) The words USE NO OIL in prominent red letters on the face of a gauge for oxygen service.
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15.2 If a manufacturer produces gauges at more than one factory, each gauge shall have a distinctive
marking to identify it as the product of a particular factory.
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