Link to an amendment published at 91 FR 49357, Aug. 4, 2026.
(a) Periodic qualification of cylinders. (1) Each specification cylinder that becomes due for periodic requalification, as specified in the following table, must be requalified and marked in conformance with the requirements of this subpart. Requalification records must be maintained in accordance with § 180.215. Table 1 follows:
Table 1. to Paragraph (a)—Requalification of Cylinders 1 Specification under which cylinder was made Minimum test pressure (psig) 2 TestRequalification period (years) DOT 3 3000 psig 5. DOT 3A, 3AA 5/3 times service pressure, except noncorrosivenon-corrosive service (see § 180.209(g)) 5, 10, or 12 (see § 180.209(b), (f), (h), and (j)). DOT 3AL 5/3 times service pressure 5 or 12 (see § 180.209(j) and (m) DOT4). 3AX, 3AAX 5/3 times service pressure 5. 3B, 3BN 2 times service pressure (see § 180.209(g)) 5 or 10 (see § 180.209(f)). 3E Test not required 3HT 5/3 times service pressure 3 (see §§ 180.209(ik) and 180.213(c)). 3T 5/3 times service pressure or UE3 5. 4AA480 2 times service pressure (see § 180.209(g)) 5 or 10 (see § 180.209(eh)(14). 4B, 4BA, 4BW, 4B-240ET 2 times service pressure, except non-corrosive service (see § 180.209(g)) 5, 7, 10, or 12 (see § 180.209(e), (f), and (j)). 4D, 4DA, 4DS 2 times service pressure 5. DOT 4E 2 times service pressure, except non-corrosive service (see § 180.209(g)) 5, 10, or 12 (see § 180.209(e)). 4L Test not required 8, 8AL 10 or 20 (see § 180.209(i)). Exemption or special permit cylinder See current exemption or special permit, or UE3 as allowed by CGA C-20 (2014) See current exemption or special permit. Foreign cylinder (see § 173.301(j) of this subchapter for restrictions on use) As marked on cylinder, but not less than 5/3 of any service or working pressure marking 5 (see §§ 180.209( k
l
) and 180.213(d)(
iii
2
))
.
1 Any cylinder not exceeding
2
two
inches outside diameter and less than
2
two
feet in length is excepted from volumetric expansion test. 2 For cylinders not marked with a service pressure, see § 173.
301
301a
(
e
b
)
(1)
of this subchapter.
3 Minimum test pressure is not applicable to those cylinders and tubes requalified using ultrasonic examination. 4 This provision does not apply to cylinders used for carbon dioxide, fire extinguisher, or other industrial gas service.
(b) DOT 3A or 3AA cylinders. (1) A cylinder conforming to specification DOT 3A or 3AA with a water capacity of 56.7 kg (125 lb) or less that is removed from any cluster, bank, group, rack, or vehicle each time it is filled, may be requalified every ten years instead of every five years, provided the cylinder conforms to all of the following conditions:
(i) The cylinder was manufactured after December 31, 1945.
(ii) The cylinder is used exclusively for air; argon; cyclopropane; ethylene; helium; hydrogen; krypton; neon; nitrogen; nitrous oxide; oxygen; sulfur hexafluoride; xenon;
chlorinated hydrocarbons,
fluorinated hydrocarbons, liquefied hydrocarbons, and mixtures thereof that are commercially free from corroding components; permitted mixtures of these gases (see § 173.301(d) of this subchapter); and permitted mixtures of these gases with up to 30 percent by volume of carbon dioxide, provided the gas has a dew point at or below minus (52 °F) at 1 atmosphere.
(iii)
Before each refill, the cylinder is removed from any cluster, bank, group, rack or vehicle and passes the hammer test specified in CGA Pamphlet C-6 (incorporated by reference; see § 171.7 of this subchapter).
[Reserved]
(iv) The cylinder is dried immediately after hydrostatic testing to remove all traces of water.
(v) The cylinder is not used for underwater breathing.
(vi) Each cylinder is stamped with a five-pointed star at least one-fourth of an inch high immediately following the test date.
(2) If, since the last required requalification, a cylinder has not been used exclusively for the gases specifically identified in paragraph (b)(1)(ii) of this section, but currently conforms with all other provisions of paragraph (b)(1) of this section, it may be requalified every 10 years instead of every five years, provided it is first requalified and examined as prescribed by § 173.302a(b) (2), (3) and (4) of this subchapter.
(3) Except as specified in paragraph (b)(2) of this section, if a cylinder, marked with a star, is filled with a compressed gas other than as specified in paragraph (b)(1)(ii) of this section, the star following the most recent test date must be obliterated. The cylinder must be requalified five years from the marked test date, or prior to the first filling with a compressed gas, if the required five-year requalification period has passed.
(c) DOT 4-series cylinders. A DOT 4-series cylinder, except a 4L cylinder, that at any time shows evidence of a leak
,
or of
internal or external corrosion, denting, bulging or rough usage to the extent that it is likely to be weakened appreciably, or that has lost
five
5
percent or more of its official tare weight must be requalified before being refilled and offered for transportation. (Refer to CGA
Pamphlet
C-6 or C-6.3
(IBR
,
see § 171.7 of this subchapter),
as applicable, regarding cylinder weakening.) After testing, the actual tare weight must be recorded as the new tare weight
on the test report and marked on the cylinder
.
The previous tare weight must be strike-lined through, but not obliterated.
(d) Cylinders 5.44 kg (12 lb) or less with service pressures of 300 psig or less. A cylinder of 5.44
kg
(12 lb) or less water capacity authorized for service pressure of 300 psig or less must be given a complete external visual inspection at the time periodic requalification becomes due. External visual inspection must be in accordance with CGA
Pamphlet
C-6 or
CGA
C-6.1 (
incorporated
IBR,
by reference;
see § 171.7 of this subchapter). The cylinder may be proof pressure tested. The test is successful if the cylinder, when examined under test pressure, does not display a defect described in § 180.205(
i
j
)(1)
(ii) or (iii). Upon successful completion of the test and inspection, the cylinder must be marked in accordance with § 180.213.
(e)
Proof
Cylinders
pressure
in
test
non-corrosive gas service
. A cylinder made in conformance with
specifications
DOT
Specifications
4B, 4BA, 4BW, or 4E
used
protected
exclusively
externally
for:
by
liquefied
a
petroleum
suitable
gas
corrosion-resistant
that
coating
meets
and
the
used
requirements
exclusively
in Table I of ASTM D 1835, Standard Specification
for
Liquefied Petroleum (LP) Gases (incorporated by reference; see § 171.7 of this subchapter); anhydrous dimethylamine; anhydrous methylamine; anhydrous trimethylamine; methyl chloride; methylacetylene
non
-
propadiene
corrosive
stabilized;
gas
or
that
dichlorodifluoromethane,
is
difluoroethane, difluorochloroethane, chlorodifluoromethane, chlorotetrafluoroethane, trifluorochloroethylene, or mixture thereof, or mixtures of one or more with trichlorofluoromethane; and
commercially free from corroding components
and protected externally by a suitable corrosion-resistant coating (such as galvanizing or painting)
may be requalified by volumetric expansion testing every 12 years instead of every
five
5
years. As an alternative, the cylinder may be subjected to a proof pressure test at least two times the marked service pressure, but this latter type of test must be repeated every
seven
10
years after expiration of the
first
initial
12-year period. When subjected to a proof pressure test,
as prescribed in CGA C-1 (IBR, see § 171.7 of this subchapter),
the cylinder must be carefully examined under test pressure and removed from service if a leak or defect is found.
(f) Poisonous materials. A cylinder conforming to specification DOT 3A, 3AA, 3B, 4BA, or 4BW having a service pressure of 300 psig or less and used exclusively for methyl bromide, liquid; mixtures of methyl bromide and ethylene dibromide, liquid; mixtures of methyl bromide and chlorpicrin, liquid; mixtures of methyl bromide and petroleum solvents, liquid; or methyl bromide and nonflammable, nonliquefied compressed gas mixtures, liquid; commercially free of corroding components, and protected externally by a suitable corrosion resistant coating (such as galvanizing or painting) and internally by a suitable corrosion resistant lining (such as galvanizing) may be tested every 10 years instead of every five years, provided a visual internal and external examination of the cylinder is conducted every five years in accordance with CGA Pamphlet C-6
(incorporated by reference; see § 171
.
7
of this subchapter).
The cylinder must be examined at each filling, and rejected if a dent, corroded area, leak or other condition indicates possible weakness.
(g) Visual inspections. A cylinder conforming to a specification listed in the table in this paragraph
(g)
and used exclusively in the service indicated may, instead of a periodic hydrostatic test, be given a complete external visual inspection at the time periodic requalification becomes due. External visual inspection must be in
accordance
conformance
with CGA
Pamphlet
C-6 or C-6.3, as applicable
(incorporated by reference; see § 171
.
7
of this subchapter).
When this inspection is used instead of hydrostatic
pressure
testing, subsequent inspections are required at five-year intervals after the first inspection.
After
Inspections
September 30, 2003, inspections
must be made only by persons holding a current RIN and the results recorded and maintained in
accordance
conformance
with § 180.215. Records must include:
date
Date
of inspection (month and year); DOT
-
specification number; cylinder identification (registered symbol and serial number, date of manufacture, and owner); type of cylinder protective coating (including statement as to need of refinishing or recoating); conditions checked (e.g., leakage, corrosion, gouges, dents or digs in shell or heads, broken or damaged footring or protective ring or fire damage);
and
disposition of cylinder (returned to service, returned to cylinder manufacturer for repairs or condemned). A cylinder passing requalification by the external visual inspection must be marked in
accordance
conformance
with § 180.213. Specification cylinders must be in exclusive service as shown in
the
table
following
2
table
to this paragraph (g)
:
Table 2 to Paragraph (g)
Cylinders conforming to— Used exclusively for— DOT 3A, DOT 3AA, DOT 3A480X, DOT 4AA480 Anhydrous ammonia of at least 99.95% purity. DOT 3A, DOT 3AA, DOT 3A480X, DOT 3B, DOT 4B, DOT 4BA, DOT 4BW Butadiene, inhibited, that is commercially free from corroding components. DOT 3A, DOT
3A480X
3AA
, DOT
3AA
3A480X
, DOT 3B
,
.
DOT 4AA480, DOT 4B, DOT 4BA, DOT 4BW Cyclopropane that is commercially free from corroding components. DOT 3A, DOT 3AA, DOT 3A480X, DOT 4B, DOT 4BA, DOT 4BW, DOT 4E
Chlorinated hydrocarbons and mixtures thereof that are commercially free from corroding components. DOT 3A, DOT 3AA, DOT 3A480X, DOT 4B, DOT 4BA, DOT 4BW, DOT 4E
Fluorinated hydrocarbons and mixtures thereof that are commercially free from corroding components. DOT 3A, DOT 3AA, DOT 3A480X, DOT 3B, DOT 4B, DOT 4BA, DOT 4BW, DOT 4E Liquefied hydrocarbon gas that is commercially free
from
of
corroding components. DOT 3A, DOT 3AA, DOT 3A480X, DOT 3B, DOT 4B, DOT 4BA, DOT 4BW, DOT 4E Liquefied petroleum gas that meets the
detail
requirements
limits
in Table
I
1
of ASTM
D
1835, Standard Specification for Liquefied Petroleum (LP) Gases (incorporated by reference; see § 171.7 of this subchapter)
or an equivalent standard containing the same limits
. DOT 3A, DOT 3AA, DOT 3B, DOT 4B, DOT 4BA, DOT 4BW, DOT 4E Methylacetylene-propadiene, stabilized, that is commercially free from corroding components. DOT 3A, DOT 3AA, DOT 3B, DOT 4B, DOT 4BA, DOT 4BW
,
DOT 4E Propylene that is commercially free from corroding components. DOT 3A, DOT 3AA, DOT 3B, DOT 4B, DOT 4BA, DOT 4BW
Anhydrous mono, di,
trimethylamines that are commercially free from corroding components. DOT 4B240, DOT 4BW240 Ethyleneimine,
inhibited
stabilized
.
DOT 4BW Alkali metal alloys, liquid, n.o.s., Alkali metal dispersions or Alkaline earth metal dispersions, Potassium, Potassium Sodium alloys and Sodium that are commercially free of corroding components.
(h) Cylinders containing anhydrous ammonia. A cylinder conforming to specification DOT 3A, 3A480X, or 4AA480 used exclusively for anhydrous ammonia, commercially free from corroding components, and protected externally by a suitable corrosion-resistant coating (such as paint) may be requalified every 10 years instead of every five years.
(i) Requalification of DOT-8 series cylinders. (1) Each owner of a DOT-8 series cylinder used to transport acetylene must have the cylinder shell and the porous filler requalified in accordance with CGA Pamphlet C-13 (
incorporated
IBR,
by reference;
see § 171.7 of this subchapter). Requalification must be performed in accordance with the following schedule:
Date of cylinder manufacture Shell (visual inspection) requalification
Initial Subsequent
Porous filler requalification Initial Subsequent
Intial Subsequent
Before January 1, 1991 Before January 1, 2001 10 years Before January 1, 2011 Not required. On or after January 1, 1991 10 years 1 10 years
3
5
to 20 years 2 Not required. 1 Years from
the
date of cylinder manufacture. 2
For
No
a cylinder manufactured on or after January 1, 1991, requalification of the porous filler must be performed no
sooner than
3
5
years, and no later than 20 years
,
from the date of manufacture.
(2) Unless requalified and marked in accordance with CGA Pamphlet C-13
(incorporated by reference; see § 171.7 of this subchapter)
before October 1, 1994, an acetylene cylinder must be requalified by a person who holds a current RIN.
(3) If a cylinder valve is replaced, a cylinder valve of the same weight must be used or the tare weight of the cylinder must be adjusted to compensate for valve weight differential.
(4) The person performing a visual inspection or requalification must record the results as specified in § 180.215.
(5) The person performing a visual inspection or requalification must mark the cylinder as specified in § 180.213.
(j) Cylinder used as a fire extinguisher. Only a DOT
-
specification cylinder used as a fire extinguisher
and
in
meeting
conformance
Special
with
Provision 18 in
§
172
173
.
102
309
(
c
a
)
(1)
of this subchapter may be requalified in
accordance
conformance
with this paragraph (j).
The testing procedures, calibration of the testing equipment, accuracy of the pressure indicating device, accuracy of the testing equipment must be as prescribed in CGA C-1.
(1) A DOT 4B, 4BA, 4B240ET or 4BW cylinder
used as a fire extinguisher
may be tested as follows:
(i) For a cylinder with a water capacity of 5.44 kg (12
lb
pounds
) or less, by
volumetric expansion test using
the water
-
jacket
,
method
direct
expansion
or
by
proof pressure test
methods as prescribed in CGA C-1
. A requalification must be performed by the end of 12 years after the original test date and at 12-year intervals thereafter.
(
A) Each cylinder must be tested to a minimum of two (2) times service pressure.
(B) When testing using the water-jacket or direct expansion test method, the permanent volumetric expansion may not exceed 10 percent of total volumetric expansion at test pressure.
(C) When testing using the proof pressure test method, the cylinder must be carefully examined under test pressure and removed from service if a leak or defect is found.
(
ii) For a cylinder having a water capacity over 5.44 kg (12
lb
pounds
)
—
(A)
,
By
by
the water-jacket, direct expansion or
proof pressure test
methods as prescribed in CGA C-1
.
A
For
the water-jacket or direct expansion test, the
requalification must be performed by the end of 12 years after the original test date and at
7
12
-year intervals
;
or
theafter. For the proof-pressure test, a requalification must be performed by the end of 12 years after the original test date and at seven (7) year intervals.
(
A) Each cylinder must be tested to a minimum of two (2) times service pressure.
(
B)
By
When
testing using the water-jacket or direct expansion test method, the permanent
volumetric expansion
may not exceed 10 percent of total volumetric expansion at
test
pressure.
(C) When testing
using the
water
proof
jacket
pressure
test
method
.
,
A
the
requalification
cylinder
must be
performed
carefully
12
examined
years
under
after
test
the
pressure
original
and
test
removed
date
from
and
service
at
if
12-year
a
intervals
leak
thereafter
or defect is found
.
(2) A DOT 3A, 3AA, or 3AL cylinder must be requalified by
:
(i)
volumetric
The
expansion
water-jacket
test
or
using
direct
the
expansion
water jacket
method. A requalification must be performed 12 years after the original test date and at 12-year intervals thereafter.
(
ii) Each cylinder must be tested to a minimum of 5/3 times service pressure.
(iii) When testing using the water-jacket or direct expansion test method, the permanent volumetric expansion may not exceed 10 percent of total volumetric expansion at test pressure.
(
k)
3HT cylinders. In addition to the other requirements of this section, a cylinder marked DOT-3HT must be requalified in accordance with CGA C-8 (IBR, see § 171.7 of this subchapter).
(l)
Requalification of foreign cylinders filled for export. A cylinder manufactured outside the United States, other than as provided in §
§
171.
12a
12(a)
and 171.23(a)
of this subchapter, that has not been manufactured, inspected, tested and marked in accordance with part 178 of this subchapter may be filled with compressed gas in the United States, and shipped solely for export if it meets the following requirements, in addition to other requirements of this subchapter:
(1) It has been inspected, tested and marked
(with only the month and year of test)
in conformance with the procedures and requirements of this subpart or the Associate Administrator has authorized the filling company to fill foreign cylinders under an alternative method of qualification; and
(2) It is offered for transportation in conformance with the requirements of §
§
173
171
.
301
12
(
l
a
)
(4)
or 171.23(a)(5)
of this subchapter.
(m) DOT-3AL cylinders manufactured of 6351-T6 aluminum alloy. In addition to the periodic requalification and marking described in § 180.205, each cylinder manufactured of aluminum alloy 6351-T6 used in self-contained underwater breathing apparatus (SCUBA), self-contained breathing apparatus (SCBA), or oxygen service must be requalified and inspected for sustained load cracking in accordance with the non-destructive examination method described in the following table. Each cylinder with sustained load cracking that has expanded into the neck threads must be condemned in accordance with § 180.205(j). This paragraph (m) does not apply to cylinders used for carbon dioxide, fire extinguisher, or other industrial gas service.
Table 4 to Paragraph (m)—Requalification and Inspection of DOT-3AL Cylinders Made of Aluminum Alloy 6351-T6 Requalification requirement Examination procedure 1 Sustained Load Cracking Condemnation Criteria 2 Requalification period (years) Eddy current examination combined with visual inspection Eddy current—In accordance with Appendix C of this partVisual inspection—In accordance with CGA Pamphlet C-6.1 (IBR; see § 171.7 of this subchapter) Any crack in the neck or shoulder of 2 thread lengths or more 5 1 The requalifier performing eddy current must be familiar with the eddy current equipment and must standardize (calibrate) the system in accordance with the requirements provided in Appendix C to this part. 2 The eddy current must be applied from the inside of the cylinder's neck to detect any sustained load cracking that has expanded into the neck threads.
[67 FR 51660, Aug. 8, 2002, as amended at 68 FR 24662, May 8, 2003; 68 FR 55544, Sept. 26, 2003; 68 FR 48572, Aug. 14, 2003; 68 FR 75764, Dec. 31, 2003; 70 FR 73166, Dec. 9, 2005; 71 FR 51128, Aug. 29, 2005; 72 FR 55696, Oct. 1, 2007; 74 FR 53189, Oct. 16, 2009; 81 FR 3685, Jan. 21, 2016; 81 FR 35545, June 2, 2016; 85 FR 68797, Oct. 30, 2020; 85 FR 75716, Nov. 25, 2020; 85 FR 85434, Dec. 28, 2020; 89 FR 15667, Mar. 4, 2024]
Editorial Note:At 71 FR 54397, Sept. 14, 2006, § 180.209 was amended in (a)(1) table 1; however, because of the inaccurate amendatory language, the amendment could not be incorporated.
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