(g) Pressure test.
All components of
the cargo tank wall, as defined in
§178.320(a) of this subchapter, must
be pressure tested as prescribed by
this paragraph.
(1) Test
Procedure —(i) As part of the
pressure test, the inspector must
perform an external and internal
visual inspection, except that on an
MC 338 cargo tank, or a cargo tank
not equipped with a manhole or
inspection opening, an internal
inspection is not required.
(ii) All
self-closing pressure relief valves,
including emergency relief vents and
normal vents, must be removed from
the cargo tank for inspection and
testing.
(A) Each
self-closing pressure relief valve
that is an emergency relief vent
must open at the required set
pressure and seat to a leak-tight
condition at 90 percent of the
set-to-discharge pressure or the
pressure prescribed for the
applicable cargo tank specification.
(B) Normal
vents (1 psig vents) must be tested
according to the testing criteria
established by the valve
manufacturer.
(C)
Self-closing pressure relief devices
not tested or failing the tests in
this paragraph (g)(1)(ii) must be
repaired or replaced.
(iii)
Except for cargo tanks carrying
lading corrosive to the tank, areas
covered by the upper coupler (fifth
wheel) assembly must be inspected
for corroded and abraded areas,
dents, distortions, defects in
welds, and any other condition that
might render the tank unsafe for
transportation service. The upper
coupler (fifth wheel) assembly must
be removed from the cargo tank for
this inspection.
(iv) Each
cargo tank must be tested
hydrostatically or pneumatically to
the internal pressure specified in
the following table. At no time
during the pressure test may a cargo
tank be subject to pressures that
exceed those identified in the
following table:
|
Specification |
Test pressure |
|
MC 300, 301, 302,
303, 305, 306 |
20.7 kPa (3 psig) or
design pressure,
whichever is
greater. |
|
MC 304, 307 |
275.8 kPa (40 psig)
or 1.5 times the
design pressure,
whichever is
greater. |
|
MC 310, 311, 312 |
20.7 kPa (3 psig) or
1.5 times the design
pressure, whichever
is greater. |
|
MC 330, 331 |
1.5 times either the
MAWP or the re-rated
pressure, whichever
is applicable. |
|
MC 338 |
1.25 times either
the MAWP or the
re-rated pressure,
whichever is
applicable. |
|
DOT 406 |
34.5 kPa (5 psig) or
1.5 times the MAWP,
whichever is
greater. |
|
DOT 407 |
275.8 kPa (40 psig)
or 1.5 times the
MAWP, whichever is
greater. |
|
DOT 412 |
1.5 times the MAWP. |
(v)
[Reserved]
(vi) Each
cargo tank of a multi-tank cargo
tank motor vehicle must be tested
with the adjacent cargo tanks empty
and at atmospheric pressure.
(vii) All
closures except pressure relief
devices must be in place during the
test. All prescribed loading and
unloading venting devices rated at
less than test pressure may be
removed during the test. If
retained, the devices must be
rendered inoperative by clamps,
plugs, or other equally effective
restraining devices. Restraining
devices may not prevent detection of
leaks or damage the venting devices
and must be removed immediately
after the test is completed.
(viii) Hydrostatic test method.
Each
cargo tank, including its domes,
must be filled with water or other
liquid having similar viscosity, at
a temperature not exceeding 100 °F.
The cargo tank must then be
pressurized to not less than the
pressure specified in paragraph
(g)(1)(iv) of this section. The
cargo tank, including its closures,
must hold the prescribed test
pressure for at least 10 minutes
during which time it shall be
inspected for leakage, bulging or
any other defect.
(ix) Pneumatic test method.
Pneumatic
testing may involve higher risk than
hydrostatic testing. Therefore,
suitable safeguards must be provided
to protect personnel and facilities
should failure occur during the
test. The cargo tank must be
pressurized with air or an inert
gas. The pneumatic test pressure in
the cargo tank must be reached by
gradually increasing the pressure to
one-half of the test pressure.
Thereafter, the pressure must be
increased in steps of approximately
one-tenth of the test pressure until
the required test pressure has been
reached. The test pressure must be
held for at least 5 minutes. The
pressure must then be reduced to the
MAWP, which must be maintained
during the time the entire cargo
tank surface is inspected. During
the inspection, a suitable method
must be used for detecting the
existence of leaks. This method must
consist either of coating the entire
surface of all joints under pressure
with a solution of soap and water,
or using other equally sensitive
methods.
(2) When
testing an insulated cargo tank, the
insulation and jacketing need not be
removed unless it is otherwise
impossible to reach test pressure
and maintain a condition of pressure
equilibrium after test pressure is
reached, or the vacuum integrity
cannot be maintained in the
insulation space. If an MC 338 cargo
tank used for the transportation of
a flammable gas or oxygen,
refrigerated liquid is opened for
any reason, the cleanliness must be
verified prior to closure using the
procedures contained in §178.338–15
of this subchapter.
(3) Each MC
330 and MC 331 cargo tank
constructed of quenched and tempered
steel in accordance with Part UHT in
Section VIII of the ASME Code (IBR,
see §171.7 of this subchapter), or
constructed of other than quenched
and tempered steel but without
postweld heat treatment, used for
the transportation of anhydrous
ammonia or any other hazardous
materials that may cause corrosion
stress cracking, must be internally
inspected by the wet fluorescent
magnetic particle method immediately
prior to and in conjunction with the
performance of the pressure test
prescribed in this section. Each MC
330 and MC 331 cargo tank
constructed of quenched and tempered
steel in accordance with Part UHT in
Section VIII of the ASME Code and
used for the transportation of
liquefied petroleum gas must be
internally inspected by the wet
fluorescent magnetic particle method
immediately prior to and in
conjunction with the performance of
the pressure test prescribed in this
section. The wet fluorescent
magnetic particle inspection must be
in accordance with Section V of the
ASME Code and CGA Technical Bulletin
TB–2 (IBR, see §171.7 of this
subchapter). This paragraph does not
apply to cargo tanks that do not
have manholes. (See §180.417(c) for
reporting requirements.)
(4) All
pressure bearing portions of a cargo
tank heating system employing a
medium such as, but not limited to,
steam or hot water for heating the
lading must be hydrostatically
pressure tested at least once every
5 years. The test pressure must be
at least the maximum system design
operating pressure and must be
maintained for five minutes. A
heating system employing flues for
heating the lading must be tested to
ensure against lading leakage into
the flues or into the atmosphere.
(5) Exceptions.
(i) Pressure testing
is not required for MC 330 and MC
331 cargo tanks in dedicated sodium
metal service.
(ii)
Pressure testing is not required for
uninsulated lined cargo tanks, with
a design pressure or MAWP of 15 psig
or less, which receive an external
visual inspection and a lining
inspection at least once each year.
(6) Acceptance criteria.
A cargo
tank that leaks, fails to retain
test pressure or pneumatic
inspection pressure, shows
distortion, excessive permanent
expansion, or other evidence of
weakness that might render the cargo
tank unsafe for transportation
service, may not be returned to
service, except as follows: A cargo
tank with a heating system which
does not hold pressure may remain in
service as an unheated cargo tank
if:
(i) The
heating system remains in place and
is structurally sound and no lading
may leak into the heating system,
and
(ii) The
specification plate heating system
information is changed to indicate
that the cargo tank has no working
heating system.
(7) The
inspector must record the results of
the pressure test as specified in
§180.417(b).
