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Valve Inspection and Testing
API STANDARD 598
EIGHTH EDITION, MAY 2004


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Valve Inspection and Testing
Downstream Segment
API STANDARD 598
EIGHTH EDITION, MAY 2004

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SPECIAL NOTES
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
warn and properly train and equip their employees, and others exposed, concerning health
and safety risks and precautions, nor undertaking their obligations under local, state, or
federal laws.
Information concerning safety and health risks and proper precautions with respect to
particular materials and conditions should be obtained from the employer, the manufacturer
or supplier of that material, or the material safety data sheet.
Nothing contained in any API publication is to be construed as granting any right, by
implication or otherwise, for the manufacture, sale, or use of any method, apparatus, or
product covered by letters patent. Neither should anything contained in the publication be
construed as insuring anyone against liability for infringement of letters patent.
Generally, API standards are reviewed and revised, reaffirmed, or withdrawn at least
every five years. Sometimes a one-time extension of up to two years will be added to this
review cycle. This publication will no longer be in effect five years after its publication
date as an operative API standard or, where an extension has been granted, upon
republication. Status of the publication can be ascertained from the API Standards
department telephone (202) 682-8000. A catalog of API publications, programs and
services is published annually and updated biannually by API, and available through
Global Engineering Documents, 15 Inverness Way East, M/S C303B, Englewood, CO
80112-5776.
This document was produced under API standardization procedures that ensure appropriate
notification and participation in the developmental process and is designated as an API standard.
Questions concerning the interpretation of the content of this standard or comments and questions
concerning the procedures under which this standard was developed should be directed in writing to
the Director of the Standards department, American Petroleum Institute, 1220 L Street, N.W.,
Washington, D.C. 20005. Requests for permission to reproduce or translate all or any part of the
material published herein should be addressed to the Director, Business Services.
API standards are published to facilitate the broad availability of proven, sound engineering and
operating practices. These standards are not intended to obviate the need for applying sound engineering
judgment regarding when and where these standards should be utilized. The formulation and publication
of API standards is not intended in any way to inhibit anyone from using any other practices.
Any manufacturer marking equipment or materials in conformance with the marking
requirements of an API standard is solely responsible for complying with all the applicable
requirements of that standard. API does not represent, warrant, or guarantee that such
products do in fact conform to the applicable API standard.

All rights reserved. No part of this work may be reproduced, stored in a retrieval
system, or transmitted by any means, electronic, mechanical, photocopying, recording,
or otherwise, without prior written permission from the publisher. Contact the
Publisher, API Publishing Services, 1220 L Street, N.W., Washington, D.C. 20005.
Copyright © 2004 American Petroleum Institute


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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 from its use or for the violation of any federal, state, or municipal
regulation with which this publication may conflict.
Suggested revisions are invited and should be submitted to API, Standards department,
1220 L Street, NW, Washington, DC 20005.

iii

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CONTENTS
Page

1 GENERAL. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2 Referenced Publications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2
INSPECTION, EXAMINATION, AND SUPPLEMENTARY EXAMINATION . . . 1

2.1 Inspection at the Valve Manufacturer’s Plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2.2 Inspection Outside the Valve Manufacturer’s Plant . . . . . . . . . . . . . . . . . . . . . . . 1
2.3 Inspection Notice .................................................................................................... 8
2.4 Extent of Inspection ................................................................................................ 2
2.5 Examination ............................................................................................................ 2
2.6 Supplementary Examination ................................................................................... 2
3 PRESSURE TESTS .......................................................................................................... 2
3.1 Test Location .......................................................................................................... 2
3.2 Test Equipment ....................................................................................................... 2
3.3 Tests Required ........................................................................................................ 2
3.4 High-pressure Closure Test .................................................................................... 3
3.5 High-pressure Pneumatic Shell Test ....................................................................... 3
3.6 Test Fluid ................................................................................................................ 3
3.7 Test Pressures ......................................................................................................... 3
3.8 Test Duration .......................................................................................................... 3
3.9 Test Leakage ........................................................................................................... 3
4 PRESSURE TEST PROCEDURES ................................................................................. 6
4.1 General ................................................................................................................... 6
4.2 Backseat Test .......................................................................................................... 6
4.3 Shell Test ................................................................................................................ 6
4.4 Low-pressure Closure Test ..................................................................................... 6
4.5 High-pressure Closure Test .................................................................................... 7
5 VALVE CERTIFICATION AND RETESTING ............................................................. 7
5.1 Certificate of Compliance ....................................................................................... 7
5.2 Re-testing ................................................................................................................ 7

Tables
1-A Pressure Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1-B Pressure Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2
Shell Test
Pressure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 Other Test Pressures . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4
Duration of Required Test Pressure . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . 5

5 Maximum Allowable Leakage Rates for Closure Tests. . . . . . . . . . . . . . . . . . . . . . 5

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v

NOTES TO PURCHASER
1. If required, the following will be specified in the purchase order:
a. Inspections by the purchaser at the valve manufacturer’s plant (see 2.1).
b. Inspections by the purchaser outside the valve manufacturer’s plant (see 2.2).
c. Address for inspection notices (see 2.3).
d. Any supplementary examination required (see 2.6).
e. Type of backseat test (see 3.2.2).
f. Low-pressure closure test (see 3.3.3, 3.3.4 and 4.4.2).
g. High-pressure closure test (see 3.4 and 4.5).
h. High-pressure pneumatic shell test (see 3.5).
i. Test fluid temperature for low temperature valves (see 3.6.1).
j. Use of a wetting agent in the test water (see 3.6.4).
k. Certificate of compliance (see 5.1).
2. If this standard is used for valves not covered by this standard, the purchaser will specifythe extent to which the
standard is to be applied.





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Valve Inspection and Testing
1 General
1.1 SCOPE
1.1.1 This
standard
covers
inspection,
examination,
supplementary examinations, and pressure test requirements for
resilient-seated, nonmetallic-seated (e.g., ceramic), and metalto-
metal-seated valves of the gate, globe, plug, ball, check, and
butterfly types. Resilient seats are considered to be:
a. Soft seats, both solid and semi-solid grease type (e.g.,lubricated
plug).
b. Combination soft and metal seats.
c. Any other type valve designed to meet resilient seat leak-age rates
as specified in Table 5.
API Std 598 supplements the API standards that reference it, but
it may also be applied to other types of valves by agreement
between the purchaser and the valve manufacturer.
1.1.2 The inspection requirements pertain to examinations and
testing by the manufacturer and any supplementary examinations
that the purchaser may require at the valve manufacturer’s plant.
The test requirements cover both required and optional pressure
tests at the valve manufacturer’s plant.
1.1.3 The following tests and examinations are specified in this
standard:
a. Shell test.
b. Backseat test.
c. Low-pressure closure test.
d. High-pressure closure test.
e. Visual examination of castings.
f. High-pressure pneumatic shell test.
1.2 REFERENCED PUBLICATIONS
1.2.1 The most recent editions of the following standards, codes, and
specifications are cited in this standard:
ASME
1


B16.11
Forged Steel Fittings, Socket-Welding and
Threaded
B16.34
MSS
2

Valves—Flanged, Threaded, and Welding
End
SP-45
Bypass and Drain Connections

SP-55
Quality Standard for Steel Castings for
Valves, Flanges and Fittings and Other
Piping Components—Visual Method

1 ASME International, 3 Park Avenue, New York, New York 10016.
www.asme.org
SP-91
Guidelines for Manual Operation of
Valves
1.2.2 This standard supplements the following API valve
standards:
API

Std 594
Check Valves: Wafer, Wafer Lug and
Double Flanged Type
Std 599
Metal Plug Valves—Flanged, Threaded
and Welding End
Std 602
Compact Steel Gate Valves—Flanged,
Threaded, Welding and Extended Body
Ends
Std 603
Corrosion-Resistant, Bolted Bonnet Gate
Valves—Flanged and Butt-Welding Ends
Std 608
Metal Ball Valves—Flanged, Threaded,
and Butt-Welding Ends
Std 609
Butterfly Valves: Double Flanged,
Lugand Wafer-Type
2 Inspection, Examination, and
Supplementary Examination
2.1 INSPECTION AT THE VALVE
MANUFACTURER’S PLANT
The purchaser will specify in the purchase order his intention
to inspect valves and witness tests and examinations at the valve
manufacturer’s plant. The purchaser’s inspector shall have free
access to any part of the plant concerned with manufacture of
the valves whenever work on the order is under way.
2.2 INSPECTION OUTSIDE THE VALVE
MANUFACTURER’S PLANT
When the purchaser specifies that the inspection will include
shell components manufactured at locations other than the valve
manufacturer’s plant, these components shall be subject to the
purchaser’s inspection at the location where they are
manufactured.
2.3 INSPECTION NOTICE
When inspection by the purchaser is specified, the valve
manufacturer shall notify the purchaser 5 working days prior to
the required valve testing and any specified supplementary
inspections or examinations, addressing the notice as stated in
the purchase order. The valve manufacturer shall also give the
purchaser 5 working days’ notice of where and when shell
components manufactured outside the valve manufacturer’s
plant may be inspected, if such inspection is required.

2 Manufacturers Standardization Society of the Valve and Fittings
Industry, Inc., 127 Park Street, N.E., Vienna, Virginia 22180.
www.mss-hq.com
2
API STANDARD 598
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Table 1-A—Pressure Tests
Valves: NPS ≤ 4 & ASME Class ≤ 1500 NPS > 4 & ASME Class ≤ 600
Test Description


Valve Type


Gate
Globe
Plug
Check
Floating Ball
Butterfly and
Trunnion
Mounted
Ball
Shell
Required
Required
Required
Required
Required
Required
Backseata
Required
Required
NA
NA
NA
NA
Low-pressure Closure
Required
Optionalc
Requiredb
Optionalc
Required
Required
High-pressure Closured
Optionalc, f
Requirede
Optionalb, c, f
Required
Optionalc, f
Optionalc, f
Notes: NA = Not applicable.
aThe backseat test is required for all valves, except for bellows seal valves, that have the backseat feature.
bFor lubricated plug valves, the high-pressure closure test is mandatory and the low-pressure closure test is optional. cWhen the purchaser
specifies an “optional” test, the test shall be performed in addition to the required tests.
dThe high-pressure closure test of resilient-seated valves may degrade subsequent sealing performance in low-pressure service. eFor power-operated
and manually operated gear actuated globe valves, including non-return type globe valves, the high-pressure closure test shall be performed at 110%
of the design differential pressure used for sizing of the operator. fA high-pressure closure test is required for all valves specified to be double block
and bleed valves.
2.4 EXTENT OF INSPECTION
The extent of inspection may be specified in the purchase
order and, unless otherwise indicated, will be limited to the
following:
a. Inspection of the valve during assembly to ensure compli-
ance with the specifications of the purchase order.
Inspection may
include
the use of
specified
nondestructive methods.
b. Witnessing of the required and specified optional
pressure tests and examinations.
c. Witnessing of any supplementary examinations (see 2.6).
d. Review
of mill
records
and
nondestructive
examinationrecords (including specified radiographs).
2.5 EXAMINATION
2.5.1 A visual examination shall be performed by the valve
manufacturer of all castings of bodies, bonnets, covers, and
closure elements to assure conformance with MSS SP-55.
2.5.2 The valve manufacturer shall examine each valve to
assure compliance with this standard and the referenced
purchase specification (e.g., API Std 599).
2.5.3 All examinations shall be performed in accordance
with written procedures that comply with the applicable
standards.
2.6 SUPPLEMENTARY EXAMINATION
Supplementary types of examination are required only if
specified in the purchase order and only to the extent
specified. Magnetic particle, radiographic, liquid penetrant,
and ultrasonic examination of steel castings or forgings shall
be in accordance with Part 8 of ASME B16.34 or with the
purchaser’s own procedures and acceptance criteria, if so
specified. These examinations shall be made by the valve
manufacturer subject to witnessing by the purchaser’s
inspector.
3 Pressure Tests
3.1 TEST LOCATION
Pressure tests shall be performed by the valve
manufacturer at the valve manufacturer’s plant.
3.2 TEST EQUIPMENT
The equipment used by the valve manufacturer to perform
the required pressure tests shall not apply external forces that
affect seat leakage. If an end-clamping fixture is used, the
valve manufacturer shall be able to demonstrate that the test
fixture does not affect the seat sealing capability of the valve
being tested. End clamping is allowed for valves designed to
function between mating flanges, such as wafer check and
wafer butterfly valves.
3.3 TESTS REQUIRED
3.3.1 The pressure tests listed in Table 1-A or 1-B shall be
performed on each valve in accordance with written
procedures that comply with this standard.
3.3.2 At the manufacturer’s option, the backseat test for
valves that have the backseat feature may be either a
highpressure or a low-pressure test unless stated otherwise
in the purchase order.
3.3.3 Valves NPS 4 and smaller having pressure ratings up
to and including ASME Class 1500 and valves larger than
NPS 4 having pressure ratings up to and including ASME
Class 600 shall be tested in accordance with Table 1-A.
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VALVE INSPECTION AND TESTING
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Table 1-B—Pressure Tests
Valves: NPS ≤ 4 & ASME Class > 1500
NPS > 4 & ASME Class > 600
Notes: NA = Not applicable.
aThe backseat test is required for all valves, except for bellows seal valves, that have the backseat feature. bWhen an
“optional” test is specified by the purchaser, the test shall be performed in addition to the required tests. cThe high-pressure
closure test of resilient-seated valves may degrade subsequent sealing performance in low-pressure service. dFor power-
operated and manually operated gear actuated globe valves, including non-return type globe valves, the high-pressure closure
test shall be performed at 110% of the design differential pressure used for sizing of the operator. eA high-pressure closure
test is required for all valves specified to be double block and bleed valves.
The purchaser may elect to require an “optional” pressure
test in Table 1-A.
3.3.4 Valves NPS 4 and smaller having pressure ratings
greater than ASME Class 1500 and valves larger than NPS
4 having pressure ratings greater than ASME Class 600 shall
be tested in accordance with Table 1-B.
The purchaser may elect to require an “optional” pressure
test in Table 1-B.
3.4 HIGH-PRESSURE CLOSURE TEST
The high-pressure closure test is required for several valve
types, as shown in Table 1-A and 1-B. For the valve types
for which, according to Table 1-A and 1-B, the high-pressure
closure test is optional, the valves are still required to be able
to pass the test (as a test of the design of the valve closure
structure). Results of tests confirming the capacity of the
valve design to pass the high-pressure closure test shall be
supplied when requested in the inquiry purchase requisition,
or by the purchaser.
3.5 HIGH-PRESSURE PNEUMATIC SHELL TEST
When specified by the purchase order, a high-pressure
pneumatic shell test shall be performed. This test shall be
performed after the hydrostatic shell test, using appropriate
safety precautions. The pneumatic shell test pressure shall be
110% of the maximum allowable pressure at 100°F (38°C)
or as specified in the purchase order. Visible leakage is not
allowed.
3.6 TEST FLUID
3.6.1 For shell, high-pressure backseat, and high-pressure
closure tests, the test fluid shall be air, inert gas, kerosene,
water, or a non-corrosive liquid with a viscosity not higher
than that of water. Unless otherwise specified in the purchase
requisition, the test fluid temperature shall be within the
range 41°F (5°C) to 122°F (50°C).
3.6.2 For the low-pressure closure and low-pressure
backseat tests, the test fluid shall be air or inert gas.
3.6.3 When air or gas is used for closure, shell, or backseat
tests,
the valve manufacturer shall be capable of
demonstrating the adequacy of the method of leakage
detection.
3.6.4 Water used for any test may contain water-soluble oil
or rust inhibitor. When specified by the purchaser, a wetting
agent shall be included in the water. For testing of austenitic
stainless steel valves, water with chloride content not
exceeding 100 parts per million shall be used. The valve
manufacturer shall be able to document the chloride content.
3.7 TEST PRESSURES
3.7.1 The shell test pressure shall be as listed in Table 2.
3.7.2 Other test pressures shall be as listed in Table 3.
3.8 TEST DURATION
For each type of test, the required test pressure shall be
maintained for at least the minimum time specified in Table
4.
3.9 TEST LEAKAGE
3.9.1 Shell, Stem Seals, and Backseat
3.9.1.1 For shell tests, visually detectable leakage through
the pressure boundary walls and any fixed body joint is not
permitted.
3.9.1.2 For backseat tests, visually detectable leakage is not
permitted.
Test Description


Valve Type


Gate
Globe
Plug
Check
Floating Ball
Butterfly and
Trunnion
Mounted
Ball
Shell
Required
Required
Required
Required
Required
Required
Backseata
Required
Required
NA
NA
NA
NA
Low-pressure Closure
Optionalb
Optionalb
Optionalb
Optionalb
Required
Optionalb
High-pressure Closurec
Required
Requiredd
Required
Required
Optionalb, e
Required
4
API STANDARD 598
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2—Shell Test Pressure
Valve Type
Class
Shell Test Pressure (Minimum)
Pounds per Square Inch
Gauge
Bar
Ductile Iron
150
400
26
300
975
66
Cast Iron
125


NPS 2-12
350
25
NPS 14-48
265
19
Cast Iron
250


NPS 2-12
875
61
NPS 12-24
525
37
Steel



Flanged
150 – 2500
b

Buttweld
150 – 4500
b

Threadeda and
Socketweld
800
c

150 – 4500
b

Notes:
a ASME B16.34 limits threaded-end valves to Class 2500 and lower. b Per ASME B16.34.
c For Class 800 valves, the shell test pressure shall be 11/2 times the pressure rating at 100°F (38°C), rounded
off to the next higher increment of 25 pounds per square in. gauge (or 1 bar) (see Table 2 of API Std 602).

Table 3—Other Test Pressures
Test
Test Pressured
Pounds per
Square Inch Gauge
Bar
Valves Except Butterfly and Check
High-pressure closure and backseat a
b

Low-pressure closure and backseata
60 – 100
4 – 7
Butterfly Valve
High-pressure closure
c

Low-pressure closure
60 – 100
4 – 7
Check Valve
High-pressure closure


Class 125 (cast iron)


NPS 2-12
200
14
NPS 14-48
150
11
Class 250 (cast iron)


NPS 2-12
500
35
NPS 14-24
300
21
Class 150 (ductile iron)
250
17
Class 300 (ductile iron)
640
44
Carbon, alloy, stainless steel, and special alloys
b

Low-pressure closure (See Tables 1-A and 1-B)
60 – 100
4 – 7
Notes:
aThe backseat test is required for all valves that have this feature.
b110% of maximum allowable pressure at 100°F (38°C) in accordance with the applicable
purchase specification.
c110% of design differential pressure at 100°F (38°C) in accordance with the
applicable purchase specification.
dSingle values shown are minimum test pressures. A range of values indicates both
minimum and maximum test pressures.
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Table 4—Duration of Required Test Pressure
Valve Size
(NPS)
Minimum Test Duration (Seconds)a
Shell
Backseat
Closure
Check Valves
(API Std 594) Other Valves
All Valves
with Backseat
Feature
Check Valves
(API Std 594) Other Valves
≤ 2
60
15
15
60
15
21/2 – 6
60
60
60
60
60
8 – 12
60
120
60
60
120
≥ 14
120
300
60
120
120
Note: aThe test duration is the period of inspection after the valve is fully prepared and is under full
pressure.

Table 5—Maximum Allowable Leakage Rates for Closure Tests













Notes:
aFor the liquid test, 1 milliliter is considered equivalent to 16 drops.
bThere shall be no leakage for the minimum specified test duration (see Table 4). For liquid test, 0 drops means no visible
leakage per minimum specified test duration. For gas test, 0 bubbles means less than 1 bubble per minimum specified test
duration.
cThe maximum permissible leakage rate shall be 0.18 cubic in. (3 cubic centimeters) per minute per in. of nominal pipe size.
dThe maximum permissible leakage rate shall be 1.5 standard cubic ft (0.042 cubic meter) of gas per hour per in. of nominal
pipe size.
eFor valves greater than or equal to NPS 14, the maximum permissible leakage rate shall be 2 drops per minute per in. NPS.
fFor valves greater than or equal to NPS 14, the maximum permissible leakage rate shall be 4 bubbles per minute per in. NPS.
3.9.1.3 For valves with adjustable stem seals, leakage
through the stem seals during the shell test shall not be
cause for rejection. However, the manufacturer shall
demonstrate that the stem seals are capable of retaining
pressure at least equal to the 100°F (38°C) valve rating
without visible leakage.
3.9.1.4 For valves with non-adjustable stem seals (o-rings,
fixed single rings, and the like), visually detectable leakage
during the shell test is not permitted.
3.9.1.5 Where no visual detectable leakage is permitted,
the following definitions apply:
a.
If the test fluid is a liquid, there shall be no visible
evidenceof drops or wetting of the external surfaces of the
test valve.
b.
If the test fluid is air or inert gas, no leakage will be
revealed by the established detection method.
3.9.2 For both the low-pressure closure test and the
highpressure closure test, visual evidence of leakage through
the disk, behind the seat rings, or past the shaft seals (of valves
that have this feature) is not permitted and structural damage
is not permitted. (Plastic [permanent] deformation of resilient
seats and seals is not considered structural damage.) The
allowable rate for leakage of test fluid at the seatsealing
surface interface, for the duration of the tests, is listed in Table
5.
3.9.3 The allowable leakage rate for closure tests of valves
with nonmetallic (e.g., ceramic) seat materials shall be equal
to that specified in Table 5 for a metal-seated valve of
equivalent size and type.
Valve Size
(NPS)
All Resilient
Seated Valvesb
All Metal-seated Valves Except Check Metal-seated Check Valves
Liquid Testa
(Drops Per Minute)
Gas Test (Bubbles
Per Minute)
Liquid Test
Gas Test
≤ 2
0
0b
0b
c
d
21/2 – 6
0
12
24
c
d
8 – 12
0
20
40
c
d
≥ 14
0
e
f
c
d
6
API STANDARD 598
ight American Petroleum Institute
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4 Pressure Test Procedures
4.1 GENERAL
4.1.1 Valves designed to permit emergency or supplemental
introduction of an injectable sealant to the seat area shall be
tested with the injection system empty and not in use, except
for lubricated plug valves.
4.1.2 When a liquid is used as the test fluid, the valve shall be
essentially free from trapped air during the test.
4.1.3 Required protective coatings, such as paint, which may
mask surface defects, shall not be applied to any surface
before inspection or pressure testing. (Phosphatizing and
similar chemical conversion processes used to protect valve
surfaces are acceptable even if applied before the tests,
provided that they will not seal off porosity.)
4.1.4 When closure testing valves, the valve manufacturer’s
test procedure shall ensure that excessive force is not used to
close the valve. The applied force may be determined from the
appropriate figures in MSS SP-91, but in any case shall not
exceed the values published by the valve manufacturer.
4.1.5 The valve shall be visually examined for leakage after
it has been fully prepared and is under full test pressure.
4.2 BACKSEAT TEST
4.2.1 The backseat test is required for all valves, except for
bellows seal valves, that have the backseat feature and shall
be performed by applying pressure inside the assembled valve
with the valve ends closed, the valve fully open, and the
packing gland loose or packing not installed. If the backseat
test is performed after the shell test, the packing shall be
installed and/or packing glands re-tightened after the backseat
test. The successful completion of the backseat test shall not
be construed as a recommendation by the valve manufacturer
that, while the valve is pressurized, the valve stuffing box may
be repacked or the packing may be replaced.
4.2.2 For valves 4 in. NPS and smaller, the backseat test may
be combined with the shell test when volumetric devices are
used to monitor leakage from the shell and backseat. When
tested by this method, the packing shall be loose. The
manufacturer shall be responsible for demonstrating that the
packing will not leak at the valve’s rated pressure at 100°F
(38°C).
4.3 SHELL TEST
Except as provided in 4.2.2, the shell test shall be made by
applying the pressure inside the assembled valve with the
valve ends closed, the valve partially open, and any packing
gland tight enough to maintain the test pressure, thereby,
except for bellows seal valves, testing the stuffing box.




4.4 LOW-PRESSURE CLOSURE TEST
4.4.1 The low-pressure closure test shall be performed with the
seat sealing surface interface clean and free from oil, grease,
and sealant. If necessary to prevent galling, the sealing surfaces
may be coated with a film of oil that is not heavier than
kerosene. This requirement does not apply to a valve that uses
a lubricant as its primary seal (e.g., lubricated plug valves).
4.4.2 Any leakage at the seat sealing surface interface, behind
the seat ring, or through the disk on the open side of the valve
shall be detected when bubbles are observed coming from the
closure (disk, seat, and seat ring), which is either covered with
water or coated with a soap or similar solution.
As an alternative, displacement measuring devices may be
used, provided that the detectable leakage rate is equivalent to
that given in Table 5, the valve manufacturer can demonstrate
and validate that the procedure yields results equivalent to the
requirements of this standard, and the device has been accepted
by agreement between the purchaser and the manufacturer.
Bubbler testing, when used for valves larger than NPS 2, shall
only be acceptable when agreed to by the purchaser.
When volumetric devices (bubblers) are used to measure
leakage, the test duration shall not begin until flow through the
test tubing is established and stabilized. The device shall be
calibrated to yield results equivalent to the units per minute
listed in Table 5. Volumetric devices shall be calibrated with the
same test fluid and at the same temperature as used for the
production tests.
4.4.3 When closure testing gate, plug, and ball valves, the valve
manufacturer shall use a method of testing seat leakage that fills
and fully pressurizes the body cavity to the test pressure
between the seats and the bonnet area, as applicable, with the
test fluid. This will ensure that no seat leakage can escape
detection because of gradual filling of these volumes during the
test period.
For a valve (other than a double block-and-bleed valve or
globe valve) designed to close against pressure from either
direction, the pressure shall be applied successively to each side
of the closed valve with the other side open to the atmosphere
to check for leakage at the atmospheric side of the closure. For
a globe valve, pressure shall be applied in one direction with the
pressure applied under the disk.
For a valve designed to close against pressure from one
direction only and so marked, the pressure shall be applied on
the pressure side of the valve only. For a check valve, the
pressure shall be applied on the downstream side.
For a double block-and-bleed valve, the pressure shall be
applied successively to each side of the closure through the
valve port. Leakage into the body cavity between the seats shall
be checked through observation at a tapped opening between
the seats. Valves shall be tested with the stem in the
--`,``,,,`,``,,````,,,,`````,`-`-`,,`,,`,`,,`---



VALVE INSPECTION AND TESTING
7
ight American Petroleum Institute
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vertical upright position. Leakage from the seats shall not
exceed rates shown in Table 5.
A closure test is required only in one direction for
butterfly valves furnished with encapsulation or resilient
internal liners and designed for use with Class 125 or Class
150 flanges (API Std 609 Category A valves). For other
resilient-seated butterfly valves (API Std 609 Category B
valves), the closure test is required in both directions. For
valves with a preferred flow direction, the closure test in
the non-preferred direction shall be based on the reduced
differential pressure rating in that direction.
4.4.4 Trapping test air or gas in the body cavity between
the seats of a one-piece (solid or flexible) wedge gate valve
and subsequently covering the seats with water or coating
them with soap or a similar solution does not constitute an
acceptable low-pressure closure test.
4.4.5 If a tapped connection in the body cavity is made to
permit
testing procedures described under double
blockand-bleed valve in 4.4.3, the connection shall be in
accordance with MSS SP-45 and shall be fitted before
shipment with a solid pipe plug (in accordance with ANSI
B16.11) whose material composition is equivalent to that
of the valve shell.
--`,``,,,`,``,,````,,,,`````,`-`-`,,`,,`,`,,`---

4.5 HIGH-PRESSURE CLOSURE TEST
5 Valve Certification and Retesting
5.1 CERTIFICATE OF COMPLIANCE
When specified by the purchaser, the valve manufacturer
shall submit to the purchaser a certificate of compliance as
required in the purchase order.
5.2 RE-TESTING
A completed valve does not require re-testing unless
inspection by the purchaser is specified in the purchase order.
This re-testing may be waived by the purchaser’s inspector
upon written certification by the manufacturer that the valve
has been inspected, tested, and examined for conformance
with the requirements of this standard. Painted valves need not
have paint removed for re-testing. Stored valves shall be
commercially cleaned before re-testing and before shipment.
Copyright American Petroleum Institute

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Valve Inspection and Testing
API STANDARD 598
TENTH EDITION, OCTOBER 2016
Special Notes
API publications necessarily address problems of a general nature. With respect to particular
circumstances, local, state, and federal laws and regulations should be reviewed.
Neither API nor any of API’s employees, subcontractors, consultants, committees, or other assignees
make any warranty or representation, either express or implied, with respect to the accuracy,
completeness, or usefulness of the information contained herein, or assume any liability or responsibility
for any use, or the results of such use, of any information or process disclosed in this publication. Neither
API nor any of API’s employees, subcontractors, consultants, or other assignees represent that use of
this publication would not infringe upon privately owned rights.
API publications may be used by anyone desiring to do so. Every effort has been made by the Institute to
ensure 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 from its use or for the violation of any authorities
having jurisdiction with which this publication may conflict.
API publications are published to facilitate the broad availability of proven, sound engineering and
operating practices. These publications are not intended to obviate the need for applying sound
engineering judgment regarding when and where these publications should be utilized. The formulation
and publication of API publications is not intended in any way to inhibit anyone from using any other
practices.
Any manufacturer marking equipment or materials in conformance with the marking requirements of an
API standard is solely responsible for complying with all the applicable requirements of that standard. API
does not represent, warrant, or guarantee that such products do in fact conform to the applicable API
standard.
Users of this standard should not rely exclusively on the information contained in this document. Sound
business, scientific, engineering, and safety judgment should be used in employing the information
contained herein.
API is not undertaking to meet the duties of employers, manufacturers, or suppliers to warn and properly
train and equip their employees, and others exposed, concerning health and safety risks and precautions,
nor undertaking their obligations to comply with authorities having jurisdiction.
All rights reserved. No part of this work may be reproduced, translated, stored in a retrieval system, or transmitted by
any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission from the
publisher. Contact the publisher, API Publishing Services, 1220 L Street, NW, Washington, DC 20005.
Copyright © 2016 American Petroleum Institute
Foreword
Nothing contained in any API publication is to be construed as granting any right, by implication or
otherwise, for the manufacture, sale, or use of any method, apparatus, or product covered by letters
patent. Neither should anything contained in the publication be construed as insuring anyone against
liability for infringement of letters patent.
Shall: As used in a standard, “shall” denotes a minimum requirement in order to conform to the
standard.
Should: As used in a standard, “should” denotes a recommendation or that which is advised but not
required in order to conform to the standard.
May: As used in a standard, “may” denotes a course of action permissible within the limits of a standard.
Can: As used in a standard, “can” denotes a statement of possibility or capability.
This document was produced under API standardization procedures that ensure appropriate notification
and participation in the developmental process and is designated as an API standard. Questions
concerning the interpretation of the content of this publication or comments and questions concerning the
procedures under which this publication was developed should be directed in writing to the Director of
Standards, American Petroleum Institute, 1220 L Street, NW, Washington, DC 20005. Requests for
permission to reproduce or translate all or any part of the material published herein should also be
addressed to the director.
Generally, API standards are reviewed and revised, reaffirmed, or withdrawn at least every five years. A
one-time extension of up to two years may be added to this review cycle. Status of the publication can be
ascertained from the API Standards Department, telephone (202) 682-8000. A catalog of API publications
and materials is published annually by API, 1220 L Street, NW, Washington, DC 20005.
Suggested revisions are invited and should be submitted to the Standards Department, API, 1220 L
Street, NW, Washington, DC 20005, standards@api.org.
iii
Contents
1
Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2
Normative References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
3
Terms and Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
4
Inspection, Examination, and Supplementary Examination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4.1
Inspection at the Valve Manufacturer’s Plant. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4.2
Inspection Outside the Valve Manufacturer’s Plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4.3
Inspection Notice. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4.4 Extent of Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4.5 Examination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4.6 Supplementary Examination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
5
Pressure Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
5.1 Test Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
5.2 Test Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5.3 Tests Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5.4 High-pressure Closure Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.5 High-pressure Pneumatic Shell Test. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.6 Test Fluid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.7 Test Pressures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.8 Test Duration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.9 Test Leakage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
6
Pressure Test Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.2 Backseat Test. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.3 Shell Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.4 Low-pressure Closure Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.5 High-pressure Closure Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6.6 Double Block and Bleed High-pressure Closure Test. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
7
Valve Certification and Retesting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
7.1 Certificate of Compliance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
7.2 Retesting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
7.3 Material Test Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Annex A (informative) Information to Be Specified by the Purchaser . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Figure
1
Volumetric Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Tables
1
Pressure Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2
Shell Test Pressures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3
Backseat and Closure Test Pressures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4
Duration of Required Test Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5
Maximum Allowable Leakage Rates for Closure Tests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
v
Valve Inspection and Testing
1 Scope
1.1 This standard covers inspection, examination, supplementary examinations, and pressure test requirements
for resilient-seated, nonmetallic-seated (e.g. ceramic), and metal-to-metal-seated valves of the gate, globe, plug,
ball, check, and butterfly types. Resilient seats are considered to be:
a) soft seats, both solid and semisolid grease type (e.g. lubricated plug);
b) combination soft and metal seats (e.g. laminated seat rings);
c) any other type of seat material designed to meet resilient seat leakage rates as specified in Table 5.
API Standard 598 supplements the API standards that reference it, but it may also be applied to other types of
valves by agreement between the purchaser and the valve manufacturer. Reference Annex A for information to
be specified by the purchaser.
1.2 The inspection requirements pertain to examinations and testing by the valve manufacturer and any
supplementary examinations that the purchaser may require at the valve manufacturer’s plant. The test
requirements cover both required and optional pressure tests at the valve manufacturer’s plant or at a facility
mutually agreeable to both the manufacturer and the purchaser.
1.3 The following tests and examinations are specified in this standard:
a) shell test,
b) backseat test,
c) low-pressure closure test,
d) high-pressure closure test,
e) double block and bleed high-pressure closure test,
f) visual examination of castings,
g) high-pressure pneumatic shell test.
2 Normative References
The following referenced documents are indispensable for the application of this document. For dated references,
only the edition cited applies. For undated references, the latest edition of the referenced document (including any
amendments) applies.
ASME B16.11,
1
Forged Fittings, Socket-Welding and Threaded
ASME B16.34, Valves—Flanged, Threaded, and Welding End
MSS SP-45,
2
Bypass and Drain Connections
MSS SP-55, Quality Standard for Steel Castings for Valves, Flanges and Fittings and Other Piping Components
Visual Method for Evaluation of Surface Irregularities
1
ASME International, 3 Park Avenue, New York, New York 10016-5990, www.asme.org.
2
Manufacturers Standardization Society of the Valve and Fittings Industry, 127 Park Street, NE, Vienna, Virginia 22180-4602,
www.mss-hq.com.
1
2
API STANDARD 598
3 Terms and Definitions
For the purposes of this document, the following terms and definitions apply.
3.1
backseat test
A pressure test used to verify leakage past the stem or shaft to bonnet seal (backseat).
3.2
class
A dimensionless number used to designate the pressure-temperature rating of a valve or piping component.
3.3
closure test
Pressure test used to confirm leakage past or through a valve’s closure mechanism.
3.4
cold working pressure
CWP
Rated pressure at ambient temperature.
3.5
diameter nominal
DN
An alphanumeric designation of size that is common for components used in a piping system, used for reference
purposes, comprising the letters DN followed by a dimensionless number indirectly related to the physical size of
the bore or outside diameter of the end connection as appropriate. The dimensionless number following DN does
not represent a measurable value and is not used for calculation purposes except where specified in ASME B16.34.
3.6
double block and bleed valve
DBB
Single valve with two seating surfaces that, in the closed position, provides a seal against pressure from both
ends of the valve with a means of venting/bleeding the cavity between the seating surfaces.
NOTE This valve does not provide double isolation and bleed where two separate seating surfaces work in series when
one side is under pressure (see API Specification 6D[11] for further information).
3.7
nominal pipe size
NPS
An alphanumeric designation of size that is common for components used in a piping system, used for reference
purposes, comprising the letters NPS followed by a dimensionless number indirectly related to the physical size of
the bore or outside diameter of the end connection as appropriate. The dimensionless size identification number
following NPS does not represent a measurable value and is not used for calculation purposes except where
specified in ASME B16.34. Prefix NPS usage is applicable to valves bearing class designations.
3.8
shell test
A pressure test in excess of the cold working pressure (CWP) rating of the valve for the purpose of validating the
soundness and strength of the valve pressure-containing structures.
3.9
visually detectable leakage
Leakage during a valve pressure test, either through or past a pressure boundary or closure member that is
validated by normal vision.
VALVE INSPECTION AND TESTING
3
4 Inspection, Examination, and Supplementary Examination
4.1
Inspection at the Valve Manufacturer’s Plant
The purchaser shall specify in the purchase order intention to inspect valves and witness tests and examinations
at the valve manufacturer’s plant. With proper notification per paragraph 4.3, the purchaser’s inspector shall have
access to any part of the plant concerned with manufacture of the valves whenever work on the order is under way.
4.2
Inspection Outside the Valve Manufacturer’s Plant
When the purchaser specifies that the inspection will include pressure-containing parts or components
manufactured at locations other than the valve manufacturer’s plant, these parts and components shall be subject
to the valve purchaser’s inspection at the location where they are manufactured.
4.3 Inspection Notice
When inspection by the purchaser is specified, the valve manufacturer shall notify the purchaser prior to the
required valve testing and any specified supplementary inspections or examinations, addressing the notice as
stated in the purchase order or as mutually agreed with the purchaser.
4.4 Extent of Inspection
The extent of inspection may be specified in the purchase order and, unless otherwise indicated, will be limited to
the following:
a)
inspection of the valve during assembly to ensure compliance with the specifications of the purchase order;
b) witnessing of the required and specified optional pressure tests and examinations;
c) witnessing of any supplementary examinations (see 4.6);
d)
review of mill records and nondestructive examination records (including specified radiographs).
4.5 Examination
4.5.1 A visual examination shall be performed by the valve manufacturer on all castings of bodies, bonnets,
covers, and closure elements to ensure conformance with MSS SP-55.
4.5.2
Each valve shall be examined to ensure compliance with this standard, purchase order requirements, and
the referenced product standard (e.g. API Standard 599[2]).
4.5.3 All examinations shall be performed in accordance with written procedures that comply with the applicable
standards.
4.6 Supplementary Examination
Supplementary types of examination are required only if specified in the purchase order and only to the extent
specified. Magnetic particle, radiographic, liquid penetrant, and ultrasonic examination of castings or forgings shall
be in accordance with ASME B16.34 or with the purchaser’s own procedures and acceptance criteria, if so specified.
5 Pressure Tests
5.1 Test Location
Pressure tests shall be performed by the valve manufacturer at the valve manufacturer’s plant or at a facility
mutually agreeable to both the manufacturer and purchaser.
4
API STANDARD 598
5.2 Test Equipment
The equipment used to perform the required pressure tests shall not apply external forces that affect seat or body
seal leakage. If an end-clamping fixture is used, the valve manufacturer shall be able to demonstrate that the test
fixture does not affect the seat or body joint sealing capability of the valve being tested. End clamping is allowed for
valves designed to function between mating flanges, such as wafer check and wafer butterfly valves.
5.3 Tests Required
5.3.1
The pressure tests listed in Table 1 shall be performed on each valve in accordance with written procedures
that comply with this standard.
Table 1—Pressure Tests
Test
Description
Size
ASME Class
Valve Type
Gate
Globe and
Parallel
Slide Gate
Plug
Check
Floating
Ball
Butterfly and
Trunnion
Mounted Ball
Shell
All
All
Required
Required
Required
Required
Required
Required
Backseat
a
All
All
Required
Required
NA
NA
NA
NA
Low-pressure
closure
DN (NPS) ≤ DN
100 (NPS 4)
Class ≤ 1500
Required
Optional
b
Required
f
Optional
b
Required
Required
Class > 1500
Optional
b
Optional
b
Optional
b
DN (NPS) > DN
100 (NPS 4)
Class ≤ 600
Required
Required
f
Required
Class > 600
Optional
b
Optional
b
Optional
b
High-pressure
closure
c
DN (NPS) ≤ DN
100 (NPS 4)
Class ≤ 1500
Optional
b e
Required
d
Optional
b e f
Required
Optional
b e
Optional
b e
Class > 1500
Required
Required
Required
DN (NPS) > DN
100 (NPS 4)
Class ≤ 600
Optional
b e
Optional
b e f
Optional
b e
Class > 600
Required
Required
Required
NA Not applicable
a
The backseat test is required for all valves that have the backseat feature, except for bellows seal valves.
b
When an “optional” test is specified by the purchaser, the test shall be performed in addition to the required tests.
c
The high-pressure closure test of resilient-seated valves may degrade subsequent sealing performance in low-pressure service.
d
For power-operated and manually operated gear actuated globe valves, including nonreturn type globe valves, the high-pressure closure test shall be
performed at 110 % of the design differential pressure used for sizing of the operator.
e
A high-pressure closure test is required for all valves specified to be double block and bleed (DBB) valves, unless specified otherwise by the
purchaser.
f
For lubricated plug valves, the high-pressure closure test is mandatory and the low-pressure closure test is optional.
VALVE INSPECTION AND TESTING
5
5.3.2 At the manufacturer’s option, the backseat test for valves that have the backseat feature may be either a
high-pressure or a low-pressure test unless stated otherwise in the purchase order.
5.3.3
Leakage rates for reduced bore valves shall be based on the DN (NPS) of the valve.
5.4 High-pressure Closure Test
The high-pressure closure test is required for several valve types, as shown in Table 1. For the valve types for
which, according to Table 1, the high-pressure closure test is optional, the valves are still required to be able to
pass the test (as a test of the design of the valve closure structure). Results of tests confirming the capacity of the
valve design to pass the high-pressure closure test shall be supplied when requested in the purchase order. See
Table 3, footnotes
b
and
c
, for calculation of test pressure.
5.5 High-pressure Pneumatic Shell Test
When specified in the purchase order, a high-pressure pneumatic shell test shall be performed. This test shall be
performed after the shell test, using appropriate safety precautions. The pneumatic shell test pressure shall be
110 % of the maximum allowable pressure at 38 C (100 F) or as specified in the purchase order. Visible leakage
is not allowed.
5.6 Test Fluid
5.6.1 For shell, high-pressure backseat, and high-pressure closure tests, the test fluid shall be air, inert gas,
kerosene, water, or a noncorrosive liquid with a viscosity not higher than that of water. Unless otherwise specified
in the purchase order, the test fluid temperature shall be within the range 5 C (41 F) to 38 C (100 F).
5.6.2 For the low-pressure closure and low-pressure backseat tests, the test fluid shall be air or inert gas.
5.6.3 When air or gas is used for closure, shell, or backseat tests, the valve manufacturer shall be capable of
demonstrating the adequacy of the method of leakage detection.
5.6.4
Water used for any test can contain water-soluble oil and/or corrosion inhibitor. When specified by the
purchaser, a wetting agent shall be included in the water. For testing of austenitic stainless steel valves, water
with chloride content not exceeding 50 ppm shall be used. The valve manufacturer shall be able to document the
chloride content.
5.7 Test Pressures
5.7.1 The shell test pressure shall be as listed in Table 2.
5.7.2 Backseat and closure test pressures shall be as listed in Table 3.
5.8 Test Duration
For each type of test, the required test pressure shall be maintained for at least the minimum time specified in
Table 4.
6
API STANDARD 598
Table 2—Shell Test Pressures d
Valve Type
Class
Shell Test Pressure (Minimum)
Bar Gauge
Pounds per
Square Inch
Gauge (psig)
Ductile iron
150
26
400
300
66
975
Gray iron
125
DN 50 to 300 (NPS 2 to 12)
25
350
DN 350 to 1200 (NPS 14 to 48)
19
265
Gray iron
250
DN 50 to 300 (NPS 2 to 12)
61
875
DN 350 to 600 (NPS 14 to 24)
37
525
Steel and nonferrous alloys
Flanged
150 to 2500
b
b
Butt weld
150 to 4500
b
b
Threaded
a
and socket weld
800
c
c
150 to 4500
b
b
a
b
c
d
ASME B16.34 limits threaded-end valves to Class 2500 and lower.
Per ASME B16.34, the shell test pressure shall be 1
1
/2 times the pressure rating at 38 C (100 F),
rounded off to the next higher bar (25 psig). The attachment of hubs, flanges, or other end connections
with ambient working pressures lower than the primary valve assembly will require lower test pressures.
For Class 800 valves, the shell test pressure shall be 1
1
/2 times the pressure rating at 38 C (100 F),
rounded off to the next higher bar (25 psig) (see API Standard 602[4]).
Shell test pressure for API Standard 609 Category A valves shall be 11/2 times the maximum CWP of the valve.
VALVE INSPECTION AND TESTING
7
Table 3—Backseat and Closure Test Pressures
Test
Test Pressure
d
Bar Gauge
Pounds per
Square Inch
Gauge (psig)
Valves Except Butterfly and Check
High-pressure closure and backseat
a
b
b
Low-pressure closure and backseat
a
5.5 ± 1.5
80 ± 20
Butterfly Valve
High-pressure closure
c
c
Low-pressure closure
5.5 ± 1.5
80 ± 20
Check Valve
High-pressure closure
Class 125 (cast iron)
DN 50 to 300 (NPS 2 to 12)
14
200
DN 350 to 1200 (NPS 14 to 48)
11
150
Class 250 (cast iron)
DN 50 to 300 (NPS 2 to 12)
35
500
DN 350 to 600 (NPS 14 to 48)
21
300
Class 150 (ductile iron)
17
250
Class 300 (ductile iron)
44
640
Carbon, alloy, stainless steel, and special alloys
b
b
Low-pressure closure (see Table 1)
5.5 ± 1.5
80 ± 20
a
The backseat test is required for all valves that have the backseat feature, except for bellows seal valves.
b
110 % of maximum allowable pressure at 38 C (100 F) in accordance with the applicable purchase
specification.
c
110 % of design differential pressure at 38 C (100 F) in accordance with the applicable purchase
specification.
d
Single values shown are minimum test pressures. Values with a tolerance indicate both minimum and
maximum test pressures.
8
API STANDARD 598
Table 4—Duration of Required Test Pressure
Valve Size
Minimum Test Duration (Seconds)
a
DN
NPS
Shell
Backseat
(for Valves
with
Backseat
Feature)
Closure
Check
Valves
(API 594
[1]
)
Closure
Other Valves
 50
 2
15
15
60
15
65 to 150
2
1
/2 to 6
60
60
60
60
200 to 300
8 to 12
120
60
120
120
 350
 14
300
60
120
120
a
The test duration is the period of inspection after the valve is fully prepared and is under full
pressure.
5.9 Test Leakage
5.9.1 Shell, Stem Seals, and Backseat
5.9.1.1 For shell tests, visually detectable leakage through the pressure boundary walls and any fixed body joint
is not permitted.
5.9.1.2 For backseat tests, visually detectable leakage is not permitted.
5.9.1.3 For valves with adjustable stem seals, leakage through the stem seals during the shell test shall not be
cause for rejection when tested at prescribed pressure and duration. However, the manufacturer shall
demonstrate that the stem seals are capable of retaining pressure at least equal to the 38 C (100 F) valve rating
without visible leakage.
5.9.1.4 For valves with nonadjustable stem seals (O-rings, fixed single rings, and the like), visually detectable
leakage during the shell test is not permitted.
5.9.1.5 Where no visually detectable leakage is permitted, the following definitions apply:
a) If the test fluid is a liquid, there shall be no visible evidence of drops or wetting of the external surfaces of the
test valve.
b) If the test fluid is air or inert gas, no leakage will be revealed by the established detection method.
5.9.2 Closure
5.9.2.1 For both the low-pressure closure test and the high-pressure closure test, visual evidence of leakage
through the disc, behind the seat rings, or past the shaft seals (of valves that have this feature) is not permitted
and structural damage is not permitted. (Plastic [permanent] deformation of resilient seats and seals is not
considered structural damage.) The allowable rate for leakage of test fluid at the seat-sealing surface interface, for
the duration of the tests, is listed in Table 5.
5.9.2.2 The allowable leakage rate for closure tests of valves with nonmetallic (e.g. ceramic) seat materials shall be
equal to that specified in Table 5 for a metal-seated valve of equivalent size and type.
VALVE INSPECTION AND TESTING
9
Table 5—Maximum Allowable Leakage Rates for Closure Tests c
Valve Size
All
Resilient-
seated
Valves
Metal Seated Valves Except
Check
Metal Seated Check Valves
DN
(mm)
NPS
(in.)
Liquid Test
a
(drops/min)
Gas Test
a
(bubbles/min)
Liquid Test
(cc/min)
Gas Test
(m
3
/h)
Gas Test
(ft
3
/h)
 50
 2
0
0
b
0
b
6
0.08
3
65
2
1
/2
0
5
10
7.5
0.11
3.75
80
3
0
6
12
9
0.13
4.5
100
4
0
8
16
12
0.17
6
125
5
0
10
20
15
0.21
7.5
150
6
0
12
24
18
0.25
9
200
8
0
16
32
24
0.34
12
250
10
0
20
40
30
0.42
15
300
12
0
24
48
36
0.50
18
350
14
0
28
56
42
0.59
21
400
16
0
32
64
48
0.67
24
450
18
0
36
72
54
0.76
27
500
20
0
40
80
60
0.84
30
600
24
0
48
96
72
1.01
36
650
26
0
52
104
78
1.09
39
700
28
0
56
112
84
1.18
42
750
30
0
60
120
90
1.26
45
800
32
0
64
128
96
1.34
48
900
36
0
72
144
108
1.51
54
1000
40
0
80
160
120
1.68
60
1050
42
0
84
168
126
1.76
63
1200
48
0
96
192
144
2.02
72
a
For the liquid test, 1 mL is considered equivalent to 16 drops. For the gas test 1 mL is considered equivalent to 100 bubbles.
b
There shall be no leakage for the minimum specified test duration (see Table 4). For liquid test, 0 drops means no visible leakage
per minimum specified test duration. For standard gas test, 0 bubbles means less than 1 bubble per minimum specified test
duration. For high-pressure pneumatic closure test refer to paragraph 5.4.
c
Leakage rates for sizes above DN 1200 (NPS 48) shall be calculated by the following formulas:
Liquid Test for Metal Seated Valves except Check: 2 x NPS (drops/min)
Gas Test for Metal Seated Valves except Check: 4 x NPS (bubbles/min)
Liquid Test for Metal Seated Check Valves: 3 x NPS (cc/min)
Gas Test for Metal Seated Check Valves: 0.042 x NPS (m
3
/h)
Gas Test for Metal Seated Check Valves: 1.5 x NPS (ft
3
/h)
10
API STANDARD 598
5.9.2.3 As an alternative, displacement measuring devices may be used, provided that the detectable leakage
rate is equivalent to that given in Table 5, the valve manufacturer shall demonstrate and validate that the
procedure yields results equivalent to the requirements of this standard, and the device has been accepted by
agreement between the purchaser and the manufacturer.
5.9.2.4 When volumetric devices (bubblers) are used to measure leakage, the test duration shall not begin until
flow through the test tubing is established and stabilized. The device shall be calibrated to yield results equivalent
to the units per minute listed in Table 5.
5.9.2.5 Bubbles per minute as tabulated are a suggested alternative based on a suitable calibrated measuring
device, in this case, tubing with an ID ranging from 2 to 4 mm (0.100 to 0.150 in.) submerged in water to a depth
of from 3 to 6 mm (0.125 to 0.250 in.). The tube end shall be cut square and smooth with no chamfers or burrs,
and the tube axis shall be perpendicular to the surface of the water (see Figure 1).
Figure 1—Volumetric Device
6 Pressure Test Procedures
6.1 General
6.1.1 Valves designed to permit emergency or supplemental introduction of an injectable sealant to the seat
area shall be tested with the injection system empty and not in use, except for lubricated plug valves.
6.1.2 When a liquid is used as the test fluid, the valve shall be essentially free from trapped air during the test.
6.1.3 Required protective coatings, such as paint, which can mask surface defects, shall not be applied to any
surface before inspection or pressure testing. (Phosphatizing and similar chemical conversion processes used to
protect valve surfaces are acceptable even if applied before the tests, provided that they will not seal off porosity.)
6.1.4 When closure testing valves, the valve manufacturer’s test procedure shall ensure that excessive force is
not used to close the valve. The applied force may be determined from the appropriate figures in MSS SP-91
[12]
and shall be made available to the purchaser or testing facility upon request. The use of a supplemental
leveraging device to aid in achieving a passing leakage rate is acceptable provided that the applied force does not
exceed the manufacturer’s documented value. Where the manufacturer does not document or otherwise make
available the maximum permissible force for valve closure, the test procedure shall restrict the use of supplemental
leveraging devices.
VALVE INSPECTION AND TESTING
11
6.2 Backseat Test
6.2.1 The backseat test is required for all valves, except for bellows seal valves, that have the backseat feature
and shall be performed by applying pressure inside the assembled valve with the valve ends closed, the valve
fully open, and the packing gland loose or packing not installed. If the backseat test is performed after the shell
test, the packing shall be installed and/or packing glands retightened after the backseat test.
6.2.2 For valves DN 100 (NPS 4) and smaller, the backseat test may be combined with the shell test when
volumetric devices are used to monitor leakage from the shell and backseat. When tested by this method, the
packing shall be loose. The manufacturer shall be responsible for demonstrating that the packing will not leak at
the valve’s rated pressure at 38 C (100 F).
6.2.3 The successful completion of the backseat test shall not be construed as recommendation by the valve
manufacturer that, while the valve is pressurized, the valve may be repacked or packing may be replaced.
6.3 Shell Test
Except as provided in 6.2.2, the shell test shall be made by applying the pressure inside the assembled valve with
the valve ends closed, the valve partially open, and any packing gland tight enough to maintain the test pressure,
thereby, except for bellows seal valves, testing the stuffing box.
6.4 Low-pressure Closure Test
6.4.1 The low-pressure closure test shall be performed with the seat sealing surface interface clean and free
from oil, grease, and sealant. If necessary to prevent galling, the sealing surfaces may be coated with a film of oil
that is not heavier than kerosene. This requirement does not apply to a valve that uses a lubricant as its primary
seal (e.g. lubricated plug valves).
6.4.2 Any leakage at the seat sealing surface interface, behind the seat ring, or through the disc on the open
side of the valve shall be detected when bubbles are observed coming from the closure (disc, seat, and seat ring),
covered with water or leakage that is channeled to a volumetric device for measurement.
6.4.3 When closure testing gate, plug, and downstream seated ball valves such as floating ball valves, a method
of testing seat leakage shall be used that fills and fully pressurizes the body cavity to the test pressure between
the seats and the bonnet area, as applicable, with the test fluid. This will ensure that no seat leakage can escape
detection because of gradual filling of these volumes during the test period.
For a valve (other than a DBB valve or globe valve) designed to close against pressure from either direction, the
pressure shall be applied successively to each side of the closed valve with the other side at atmospheric
pressure to check for leakage at the atmospheric side of the closure. For a globe valve, pressure shall be applied
in one direction with the pressure applied under the disc. DBB valves shall be tested as described in 6.6.
For a valve designed to close against pressure from one direction only and so marked, the pressure shall be
applied on the pressure side of the valve only. For a check valve, the pressure shall be applied on the
downstream side.
A closure test is required only in one direction for butterfly valves furnished with encapsulation or resilient internal
liners and designed for use with Class 125 or Class 150 flanges (API Standard 609
[7]
, Category A valves). For
other resilient-seated butterfly valves (API Standard 609
[7]
, Category B valves), the closure test is required in both
directions. For butterfly valves with a preferred flow direction, the closure test in the nonpreferred direction shall
be based on the reduced differential pressure rating in that direction.
6.4.4 Trapping test air or gas in the body cavity between the seats of a one-piece (solid or flexible) wedge gate
valve and subsequently covering the seats with water or coating them with soap or a similar solution does not
constitute an acceptable low-pressure closure test.
12
API STANDARD 598
6.4.5
If a tapped connection in the body cavity is made to permit testing procedures described under DBB valve
in 6.6, the connection shall be in accordance with MSS SP-45 and shall be fitted before shipment with a solid pipe
plug (in accordance with ASME B16.11) material composition of which is equivalent to that of the valve shell.
6.5 High-pressure Closure Test
The procedure for the high-pressure closure test shall be the same as the procedure for the low-pressure closure
test except that, in the case of a liquid test, leakage shall be detected when drops, not bubbles as described in 6.4
are observed.
6.6 Double Block and Bleed High-pressure Closure Test
For a DBB valve, the pressure shall be applied successively to each side of the closure through the valve bore.
Leakage into the body cavity shall be checked through an opening in the bottom of the valve (Position “G” per
ASME B16.34). Where operational considerations do not allow for an opening in the bottom of the valve, an
alternative opening location may be specified by the purchaser, and the valve shall be DBB tested in a position
that results in the alternative opening location being at the bottom of the valve during test. Testing in all positions
and specifically in alternative positions will require procedures that meet the requirement of 6.1.2. Test duration
shall be no less than twice (2) the values provided in Table 4.
7 Valve Certification and Retesting
7.1 Certificate of Compliance
When specified by the purchaser, the valve manufacturer shall submit to the purchaser a certificate of compliance
as required in the purchase order.
7.2 Retesting
A completed valve does not require retesting unless inspection by the purchaser is specified in the purchase
order. This retesting may be waived by the purchaser’s inspector upon written certification by the manufacturer
that the valve has been inspected, tested, and examined for conformance with the requirements of this standard.
Painted valves need not have paint removed for retesting. Stored valves shall be commercially cleaned before
retesting and before shipment.
7.3 Material Test Report
Where material test reports (MTRs) are requested with the purchase order for specific valve components, the
manufacturer may transcribe data produced by other organizations provided that:
— the manufacturer accepts responsibility for the accuracy and authenticity of the data and maintains a file
containing the test report from the originator of the data;
— the manufacturer shall certify (on the MTR) the source of the data and the location of the file containing the
test report from the originator of the data.
Annex A
(informative)
Information to Be Specified by the Purchaser
Information to be specified by the purchaser:
1) Deviations from this standard should be specifically stated in the purchase order.
2)
If this standard is used for valves not covered by this standard, the purchaser will specify the extent to which
the standard is to be applied.
3)
If required, the following will be specified in the purchase order:
a)
inspections by the purchaser at the valve manufacturer’s plant (see 4.1);
b)
inspections by the purchaser outside the valve manufacturer’s plant (see 4.2);
c) address for inspection notices (see 4.3);
d) any supplementary examination required (see 4.6);
e)
type of backseat test (see 5.3.2);
f)
optional low-pressure closure test (see Table 1 and 6.4);
g) optional high-pressure closure test (see Table 1 and 5.4 and 6.5);
h) optional high-pressure pneumatic shell test (see 5.5);
i)
DBB high-pressure closure test with optional drain location (see 6.6);
j)
test fluid (see 5.6);
k) use of a wetting agent in the test water (see 5.6.4);
l)
certificate of compliance (see 7.1);
m) components for which MTRs are requested (see 7.3).
13
Bibliography
[1] API Standard 594, Check Valves: Flanged, Lug, Wafer and Butt-welding
[2] API Standard 599, Metal Plug Valves—Flanged, Threaded, and Welding Ends
[3] API Standard 600, Steel Gate Valves—Flanged and Butt-welding Ends, Bolted Bonnets
[4] API Standard 602, Gate, Globe, and Check Valves for Sizes DN 100 (NPS 4) and Smaller for the Petroleum and
Natural Gas Industries
[5] API Standard 603, Corrosion-resistant, Bolted Bonnet Gate Valves—Flanged and Butt-welding Ends
[6] API Standard 608, Metal Ball Valves—Flanged, Threaded, and Welding Ends
[7] API Standard 609, Butterfly Valves: Double-flanged, Lug- and Wafer-type
[8] API Standard 623, Steel Globe Valves—Flanged and Butt-welding Ends, Bolted Bonnets
[9] API Recommended Practice 591, Process Valve Qualification Procedure
[10] API Recommended Practice 621, Reconditioning of Metallic Gate, Globe, and Check Valves
[11] API Specification 6D, Specification for Pipeline Valves
[12] MSS SP-91, Guidelines for Manual Operation of Valves
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Product No. C59810