ASME B31.

3-2012

345 TESTING 345.2.2 Other Test Requirements

(12) 345.1 Required Leak Test (a) Examination for Leaks. A leak test shall be main-
tained for at least 10 min, and all joints and connections
Prior to initial operation, and after completion of the shall be examined for leaks.
applicable examinations required by para. 341, each pip- (b) Heat Treatment. Leak tests shall be conducted after
ing system shall be tested to ensure tightness. The test any heat treatment has been completed.
shall be a hydrostatic leak test in accordance with (c) Low Test Temperature. The possibility of brittle frac-
para. 345.4 except as provided herein. ture shall be considered when conducting leak tests at
(a) At the owner ’s option, a piping system in metal temperatures near the ductile-brittle transition
Category D fluid service may be subjected to an initial temperature.
service leak test in accordance with para. 345.7, in lieu
of the hydrostatic leak test. 345.2.3 Special Provisions for Testing
(b) Where the owner considers a hydrostatic leak test (a) Piping Components and Subassemblies. Piping com-
impracticable, either a pneumatic test in accordance with ponents and subassemblies may be tested either sepa-
para. 345.5 or a combined hydrostatic-pneumatic test in rately or as assembled piping.
accordance with para. 345.6 may be substituted, recog- (b) Flanged Joints. Flanged joints used to connect pip-
nizing the hazard of energy stored in compressed gas. ing components and subassemblies that have previously
(c) Where the owner considers both hydrostatic and been tested, and flanged joints at which a blank or blind
pneumatic leak testing impracticable, the alternative is used to isolate equipment or other piping during a test,
specified in para. 345.9 may be used if both of the follow- need not be leak tested in accordance with para. 345.1.
ing conditions apply: (c) Closure Welds. The final weld connecting piping
(1) a hydrostatic test would systems or components which have been successfully
(a) damage linings or internal insulation tested in accordance with para. 345 need not be leak
(b) contaminate a process that would be hazard- tested provided the weld is examined in-process in
ous, corrosive, or inoperative in the presence of moisture accordance with para. 344.7 and passes with 100% radio-
(c) require significant support modifications for graphic examination in accordance with para. 344.5 or
the hydrostatic test load or 100% ultrasonic examination in accordance with
(d) present the danger of brittle fracture due to para. 344.6.
low metal temperature during the test 345.2.4 Externally Pressured Piping. Piping subject
(2) a pneumatic test would to external pressure shall be tested at an internal gage
(a) present an undue hazard of possible release pressure 1.5 times the external differential pressure, but
of energy stored in the system or not less than 105 kPa (15 psi).
(b) present the danger of brittle fracture due to
low metal temperature during the test 345.2.5 Jacketed Piping
(d) Unless specified in the engineering design, lines (a) The internal line shall be leak tested on the basis
open to the atmosphere, such as vents or drains down- of the internal or external design pressure, whichever
stream of the last shutoff valve, need not be leak tested. is critical. This test must be performed before the jacket
is completed if it is necessary to provide visual access
345.2 General Requirements for Leak Tests to joints of the internal line as required by para. 345.3.1.
Requirements in para. 345.2 apply to more than one (b) The jacket shall be leak tested in accordance with
type of leak test. para. 345.1 on the basis of the jacket design pressure
unless otherwise specified in the engineering design.
345.2.1 Limitations on Pressure
(a) Stress Exceeding Yield Strength. If the test pressure 345.2.6 Repairs or Additions After Leak Testing. If
would produce a nominal pressure stress or longitudinal repairs or additions are made following the leak test, the
stress in excess of yield strength at test temperature, the affected piping shall be retested, except that for minor
test pressure may be reduced to the maximum pressure repairs or additions the owner may waive retest require-
that will not exceed the yield strength at test tempera- ments when precautionary measures are taken to assure
ture. [See paras. 302.3.2(e) and (f).] sound construction.
(b) Test Fluid Expansion. If a pressure test is to be
maintained for a period of time and the test fluid in the 345.2.7 Test Records. Records shall be made of each
system is subject to thermal expansion, precautions shall piping system during the testing, including
be taken to avoid excessive pressure. (a) date of test
(c) Preliminary Pneumatic Test. A preliminary test (b) identification of piping system tested
using air at no more than 170 kPa (25 psi) gage pressure (c) test fluid
may be made prior to hydrostatic testing to locate (d) test pressure
major leaks. (e) certification of results by examiner

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 ASME B31.3-2012

These records need not be retained after completion piping or isolated by blinds or other means during the
of the test if a certification by the Inspector that the test. A valve may be used provided the valve (including
piping has satisfactorily passed pressure testing as its closure mechanism) is suitable for the test pressure.
required by this Code is retained.
345.4 Hydrostatic Leak Test
345.3 Preparation for Leak Test 345.4.1 Test Fluid. The fluid shall be water unless
345.3.1 Joints Exposed. All joints, welds (including there is the possibility of damage due to freezing or to
structural attachment welds to pressure-containing com- adverse effects of water on the piping or the process
ponents), and bonds shall be left uninsulated and (see para. F345.4.1). In that case another suitable non-
exposed for examination during leak testing, except that toxic liquid may be used. If the liquid is flammable, its
joints previously tested in accordance with this Code flash point shall be at least 49°C (120°F), and consider-
may be insulated or covered. All joints may be primed ation shall be given to the test environment.
and painted prior to leak testing unless a sensitive leak 345.4.2 Test Pressure. Except as provided in para.
test (para. 345.8) is required. 345.4.3, the hydrostatic test pressure at every point in a
345.3.2 Temporary Supports. Piping designed for metallic piping system shall be as follows:
vapor or gas shall be provided with additional tempo- (a) not less than 1.5 times the design pressure.
rary supports, if necessary, to support the weight of test (b) when the design temperature is greater than the
liquid. test temperature, the minimum test pressure, at the point
under consideration, shall be calculated by eq. (24).
345.3.3 Piping With Expansion Joints When the piping system contains more than one mate-
(a) Unrestrained expansion joints depend on external rial or more than one design temperature, eq. (24) shall
main anchors to resist pressure thrust forces. Except as be used for every combination, excluding pipe support-
limited in para. 345.3.3(c), a piping system containing ing elements and bolting, and the maximum calculated
unrestrained expansion joints shall be leak tested with- value of PT is the minimum test gage pressure.
out any temporary restraints in accordance with
para. 345 up to 150% of the expansion joint design pres- PT p 1.5 PRr (24)
sure. If the required test pressure exceeds 150% of the
expansion joint design pressure and the main anchors where
are not designed to resist the pressure thrust forces at P p internal design gage pressure
the required test pressure, for that portion of the test PT p minimum test gage pressure
when the pressure exceeds 150% of the expansion joint Rr p ratio of ST/S for pipe or components without
design pressure, the expansion joint shall either be tem- established ratings, but shall not exceed 6.5
porarily removed or temporary restraints shall be added p ratio of the component pressure rating at the
to resist the pressure thrust forces. test temperature to the component pressure
(b) Self-restrained metallic bellows expansion joints rating at the component design temperature
(i.e., tied, hinged, pressure balanced, etc.) have restraint for components with established ratings, but
hardware designed to resist the pressure thrust forces. shall not exceed 6.5
Except as limited in para. 345.3.3(c), a piping system S p allowable stress value at component design
containing self-restrained expansion joints shall be leak temperature (see Table A-1)
tested in accordance with para. 345. A self-restrained ST p allowable stress value at test temperature
expansion joint previously shop tested by the manufac-
Alternatively, for carbon steel piping with a minimum
turer in accordance with Appendix X may be excluded
specified yield strength not greater than 290 MPa
from the system to be leak tested, except when a sensi-
(42 ksi), the test pressure for the assembly of compo-
tive leak test in accordance with para. 345.8 is required.
nents, excluding pipe supporting elements and bolting
Restraint hardware for all types of expansion joints shall
(e.g., pipe, fittings, valves, flanges), may be based on Rr
be designed for the pressure thrust forces at the test
for any of the components in the assembly.
pressure.
(c) if the test pressure as defined above would pro-
(c) When a metallic bellows expansion joint is
duce a nominal pressure stress or longitudinal stress in
installed in the piping system subject to a leak test and
excess of the yield strength at test temperature or a
the leak test pressure determined in accordance with
pressure more than 1.5 times the component rating at
para. 345 exceeds the pressure of the test performed by
test temperature, the test pressure may be reduced to
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the manufacturer in accordance with Appendix X, the

the maximum pressure that will not exceed the lesser
required leak test pressure shall be reduced to the manu-
of the yield strength or 1.5 times the component ratings
facturer’s test pressure.
at test temperature. [See paras. 302.3.2(e) and (f).] For
345.3.4 Limits of Tested Piping. Equipment which metallic bellows expansion joints, see Appendix X,
is not to be tested shall be either disconnected from the para. X302.2.3(a).

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 ASME B31.3-2012

345.4.3 Hydrostatic Test of Piping With Vessels as a the pressure in the liquid filled part of the piping shall
System 4 not exceed the limits stated in para. 345.4.2.
(a) Where the test pressure of piping attached to a
vessel is the same as or less than the test pressure for 345.7 Initial Service Leak Test
the vessel, the piping may be tested with the vessel at This test is applicable only to piping in Category D
the piping test pressure. Fluid Service, at the owner’s option. See para. 345.1(a).
(b) Where the test pressure of the piping exceeds the
vessel test pressure, and it is not considered practicable 345.7.1 Test Fluid. The test fluid is the service fluid.
to isolate the piping from the vessel, the piping and the
345.7.2 Procedure. During or prior to initial opera-
vessel may be tested together at the vessel test pressure,
tion, the pressure shall be gradually increased in steps
provided the owner approves and the vessel test pres-
until the operating pressure is reached, holding the pres-
sure is not less than 77% of the piping test pressure
sure at each step long enough to equalize piping strains.
calculated in accordance with para. 345.4.2(b).
A preliminary check shall be made as described in
345.5 Pneumatic Leak Test para. 345.5.5 if the service fluid is a gas or vapor.

(12) 345.5.1 Precautions. Pneumatic testing involves 345.7.3 Examination for Leaks. The examination for (12)
the hazard of released energy stored in compressed gas. leaks required by para. 345.2.2(a) shall be conducted
Particular care must therefore be taken to minimize the while the system is at operating pressure. It is permissi-
chance of brittle failure during a pneumatic leak test. ble to omit examination for leaks of joints and connec-
Test temperature is important in this regard and must tions previously tested in accordance with this Code.
be considered when the designer chooses the material
of construction. See para. 345.2.2(c) and Appendix F, 345.8 Sensitive Leak Test (12)
paras. F323.4 and F345.5.1. The test shall be the Bubble Test — Direct Pressure
Technique in accordance with the BPV Code, Section V,
345.5.2 Pressure Relief Device. A pressure relief
Article 10, Appendix I or another leak test method that
device shall be provided, having a set pressure not
has a demonstrated sensitivity not less than 10−3 std
higher than the test pressure plus the lesser of 345 kPa
ml/s under test conditions.
(50 psi) or 10% of the test pressure.
When the Bubble Test — Direct Pressure Technique
345.5.3 Test Fluid. The gas used as test fluid, if not is used
air, shall be nonflammable and nontoxic. (a) the test pressure shall be at least the lesser of
345.5.4 Test Pressure. The test pressure shall be 105 kPa (15 psi) gage or 25% of the design pressure.
not less than 1.1 times the design pressure and shall not (b) the pressure shall be gradually increased until a
exceed the lesser of gage pressure equal to the lesser of one-half the test
(a) 1.33 times the design pressure pressure or 170 kPa (25 psi) is attained, at which time
(b) the pressure that would produce a nominal pres- a preliminary check shall be made. Then the pressure
sure stress or longitudinal stress in excess of 90% of the shall be gradually increased in steps until the test pres-
yield strength of any component at the test temperature sure is reached, the pressure being held long enough at
each step to equalize piping strains.
345.5.5 Procedure. The pressure shall be gradually
increased until a gage pressure which is the lesser of 345.9 Alternative Leak Test
one-half the test pressure or 170 kPa (25 psi) is attained, The following procedures and leak test method may be
at which time a preliminary check shall be made, includ- used only under the conditions stated in para. 345.1(c).
ing examination of joints in accordance with
para. 341.4.1(a). Thereafter, the pressure shall be gradu- 345.9.1 Examination of Welds. Welds, including (12)
ally increased in steps until the test pressure is reached, those used in the manufacture of welded pipe and fit-
holding the pressure at each step long enough to equal- tings, which have not been subjected to hydrostatic or
ize piping strains. The pressure shall then be reduced pneumatic leak tests in accordance with this Code, shall
to the design pressure before examining for leakage in be examined as follows:
accordance with para. 345.2.2(a).
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(a) Circumferential, longitudinal, and spiral (helical

seam) groove welds shall be 100% radiographed in
345.6 Hydrostatic-Pneumatic Leak Test accordance with para. 344.5 or 100% ultrasonically
If a combination hydrostatic-pneumatic leak test is examined in accordance with para. 344.6.
used, the requirements of para. 345.5 shall be met, and (b) All welds, including structural attachment welds,
not covered in (a) above, shall be examined using the
4
The provisions of para. 345.4.3 do not affect the pressure test liquid penetrant method (para. 344.4) or, for magnetic
requirements of any applicable vessel code. materials, the magnetic particle method (para. 344.3).

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 ASME B31.3-2012

345.9.2 Flexibility Analysis. A flexibility analysis prepare the records required by this Code and by the
of the piping system shall have been made in accordance engineering design.
with the requirements of para. 319.4.2 (b), if applicable,
or (c) and (d).
345.9.3 Test Method. The system shall be subjected 346.3 Retention of Records
to a sensitive leak test in accordance with para. 345.8.
Unless otherwise specified by the engineering design,
346 RECORDS the following records shall be retained for at least 5 years
346.2 Responsibility after the record is generated for the project:
It is the responsibility of the piping designer, the manu- (a) examination procedures
facturer, the fabricator, and the erector, as applicable, to (b) examination personnel qualifications

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