1/2 inches or less in outside diameter.
(i) A pressure relief device is required on a specification 9, 39 (§ 178.65 of this subchapter), 40, or 41 cylinder. A metal pressure relief valve is required on a specification 39 cylinder used for a liquefied flammable gas. A fusible pressure relief device is not authorized on a specification 39 cylinder containing a liquefied compressed gas.
(ii) A pressure relief device is required on a cylinder charged with a liquefied gas for which this part requires a service pressure of 1800 psig or higher.
(iii) A pressure relief device is required on a cylinder charged with a
nonliquefied gas to a pressure of 1,800 psig or higher at 70 °F.
(2) Except for a specification 39 cylinder and a cylinder used for acetylene in solution, a pressure relief device is not required on a cylinder charged with a nonliquefied gas under pressure of 300 psig or less at 70 °F.
(3) A pressure relief device is prohibited on a cylinder charged with a Division 2.3 or Division 6.1 material in Hazard Zone A.
(4) A pressure relief device is prohibited on a cylinder charged with fluorine.
(5) A pressure relief device is not required on a cylinder charged with methyl mercaptan; with mono-, di-, or trimethylamine, anhydrous; with not over 10 pounds of nitrosyl chloride; or with less than 165 pounds of anhydrous ammonia.
(6) Pressure relief devices, if used, must be in the vapor space of cylinders containing pyrophoric liquids, inorganic or organic, n.o.s., covered by § 173.124.
(e) Periodic qualification and marking of cylinders. Each cylinder that becomes due for periodic retest as specified in the following table must be retested and marked in conformance with the requirements of this paragraph (e):
Retest and Inspection of Cylinders\1\
------------------------------------------------------------------------
Minimum retest
Specification under which pressure Retest period
cylinder was made\2\ (p.s.i.)\3\ (years)
------------------------------------------------------------------------
DOT-3.......................... 3,000 psig....... 5
DOT-3A, 3AA.................... 5/3 times service 5, 10, or 12 (see
pressure, except Sec. 173.34
non-corrosive (e)(14), (e)(12),
service (see (e)(16), and
Sec. 173.34(e)(1 (e)(19))
3)).
DOT-3AL........................ 5/3 times service 5 or 12 (see
pressure. (e)(19))
DOT-3AX, 3AAX.................. 5/3 times service 5
pressure.
3B, 3BN........................ 2 times service 5 or 10 (see Sec.
pressure (see 173.34(e)(12))
Sec. 173.34(e)(1
3)).
3C............................. Retest not ....................
required.
3D............................. 5/3 times service 5
pressure.
3E............................. Retest not ....................
required.
3HT............................ 5/3 times service 3 (see Sec.
pressure. 173.34(e)(15))
3T............................. 5/3 times service 5
pressure.
4.............................. 700 psig......... 10
4A............................. 5/3 times service 5 or 10 (see Sec.
pressure (see 173.34(e)(12))
Sec. 173.34(e)(1
3)).
4AA480......................... 2 times service 5 or 10 (see Sec.
pressure (see 173.34(e)(14))
Sec. 173.34(e)(1
3)).
4B, 4BA, 4BW, 4B-240ET......... 2 times service 5, 10 or 12 (see
pressure, except Sec. 173.34
non-corrosive (e)(11), (e)(12)
service (see and (e)(19))
Sec. 173.34(e)(1
3)).
4C............................. Retest not ....................
required.
4D, 4DA, 4DS................... 2 times service 5
pressure.
DOT-4E......................... 2 times service 5
pressure, except
non-corrosive
service (see
Sec. 173.34(e)(1
3)).
4L............................. Retest not ....................
required.
8, 8AL......................... ................. 10 or 20 (see Sec.
173.34(e)(18))
DOT-9.......................... 400 psig (maximum 5
600 psig).
25............................. 500 p.s.i........ 5
26 for filling at over 450 5/3 times service 5
p.s.i. pressure.
26 for filling at 450 psig and 2 times service 5 or 10 (see Sec.
below. pressure, except 173.34(e)(11))
non-corrosive
service (see
Sec. 173.34(e)(1
3)).
33............................. 800 psig......... 5
38............................. 500 psig......... 5
Exemption cylinder............. See current See current
exemption. exemption
Foreign cylinder (see Sec. As marked on the 5
173.301(j) for restrictions on cylinder, but
use)\4\. not less than 5/
3 of any service
or working
pressure marking.
------------------------------------------------------------------------
\1\Any cylinder not exceeding two inches outside diameter and less than
two feet in length is excepted from hydrostatic retest.
\2\A cylinder in chlorine or sulfur dioxide service made before April
20, 1915, must be retested at 500 psig.
\3\For cylinders not marked with a service pressure, see Sec.
173.301(e)(1).
\4\ For CTC cylinders, see Sec. 173.301(i). The retest period for CTC
cylinders authorized under Sec. 173.301(i) is the period specified in
the table for the corresponding DOT specification cylinder.
(1) General requirements. (i) Each cylinder bearing a DOT specification marking (including a cylinder remarked in conformance with § 173.23) must be inspected, retested and marked in conformance with this section, at the frequency specified in the Retest and Inspection of Cylinders Table in this paragraph (e). Each cylinder bearing a DOT exemption number must be inspected, retested and marked in conformance with this section and the terms of the applicable exemption, at the frequency specified in the exemption.
(ii) No cylinder required to be retested by paragraph (e)(1)(i) of this section may be charged or filled with a hazardous material and transported in commerce unless that cylinder has been inspected and retested in accordance with this section and the retester has marked the cylinder by stamping the date of retest, the cylinder retester identification number unless excepted under this section, and any other marking required by this section. No person may mark a test date or a retester identification number on a DOT specification or exemption cylinder unless all applicable requirements of this section have been met.
(2) Retester authorization. (i) No person may mark a cylinder with a test date or retester identification number, or otherwise represent that a DOT specification or exemption cylinder has been retested under this section, unless that person holds a current retester identification number issued by the Associate Administrator and operates in compliance with the terms of the retester identification number issuance letter. With the exception of visual inspections, all functions under this section must be performed or supervised by an individual named as qualified in the retester identification number application or a notification pursuant to paragraph (e)(2)(iv) of this section. A person is not required to obtain a retester identification number, if the person only performs visual inspections on DOT specification or exemption cylinders.
(ii) Any person seeking approval as a cylinder retester shall arrange for an independent inspection agency, approved by the Associate Administrator pursuant to § 173.300a, to inspect its retest facility. The person seeking approval shall bear the cost of the inspection. Independent inspection agencies are not RSPA agents or representatives. A list of approved independent inspection agencies is available from the Associate Administrator, Office of Hazardous Materials Exemptions and Approvals (DHM-32), Research and Special Programs Administration, U.S. Department of Transportation, Washington, DC 20590-0001. Assistance in obtaining an approval may be requested from the same address.
(A) After the inspection, the person seeking approval must submit a letter of recommendation and inspection report from the independent inspection agency and a completed request for approval to the Associate Administrator at the address listed in this paragraph (e)(2)(ii). An applicant must include the following information: company name; facility location; mailing address (if different from location of facility); business telephone number; name of facility manager; the DOT specification/exemption cylinders that will be tested at the facility; a certification that the facility will operate in compliance with the applicable requirements of this subchapter, the date and an authorized signature.
(B) The Associate Administrator reviews the application, the inspection report and recommendation submitted by the independent inspection agency, and other available information. The Associate Administrator for Hazardous Materials Safety issues a retester identification number upon a finding that the applicant's facility and qualifications are adequate to properly inspect, test and mark cylinders under this section. Unless otherwise provided in the retester identification number issuance letter, a retester identification number expires five years from the date of issuance.
(iii) An approved retester shall apply for retester identification number renewal in a timely manner. A new inspection report and recommendation of an independent inspection agency are required for each renewal. If the Associate Administrator receives a renewal application with the accompanying inspection report and recommendation at
least 50 days before expiration of the retester identification number, the retester identification number remains in effect until the Associate Administrator issues a renewal or notifies the retester that its request for renewal of the retester identification number is denied. The Associate Administrator considers renewal of a retester identification number in accordance with the standard in paragraph (e)(2)(ii)(B) of this section.
(iv) The retester identification number holder shall report in writing any change in its name, address, ownership, testing equipment, or management or personnel performing any function under this section, to the Associate Administrator for Hazardous Materials Safety (DHM-32) within 20 days of the change. A retester identification number remains valid only if the retester's facility and qualifications are maintained at or above the level observed at the time of inspection by the independent inspection agency.
(v) A retester shall maintain, at each location at which it inspects, retests or marks cylinders under this section:
(A) Current copies of those portions of this subchapter that apply to its cylinder inspection, retesting and marking activities at that location.
(B) Current copies of all exemptions governing exemption cylinders inspected, retested or marked by the retester at that location.
(C) Copies of each CGA pamphlet incorporated by reference in § 171.7 of this subchapter that applies to the retester's cylinder inspection, retesting and marking activities at that location. The publication maintained must be the edition incorporated by reference in § 171.7 of this subchapter.
(3) Visual inspection. Except as otherwise provided in this section, each time a cylinder is retested, it must be visually inspected, internally and externally, in accordance with CGA Pamphlets C-6, C-6.1, C-6.2, or C-6.3, as applicable. The cylinder must be approved, rejected or condemned according to the criteria in the applicable CGA pamphlet. Internal inspection may be omitted for cylinders of the type and in the service described under paragraph (e)(13) of this section. DOT 3BN cylinders must be inspected in accordance with CGA Pamphlet C-6.
(4) Pressure retest. (i) Unless otherwise provided, each cylinder required to be retested under this section must be retested by means suitable for measuring the expansion of the cylinder under pressure. Bands and other removable attachments must be loosened or removed before testing so that the cylinder is free to expand in all directions.
(ii) The pressure-indicating device of the testing apparatus must permit reading of pressures to within 1% of the minimum prescribed test pressure of each cylinder tested, except that for an analog device, interpolation to
1/2 of the marked gauge divisions is acceptable. The expansion-indicating device of the testing apparatus must also permit incremental reading of the cylinder expansion to 1% of the total expansion of each cylinder tested or 0.1 cubic centimeter, whichever is larger. Midpoint visual interpolation is permitted.
(iii) Each day before retesting, the retester shall confirm, by using a calibrated cylinder or other method authorized in writing by the Associate Administrator that:
(A) The pressure-indicating device, as part of the retest apparatus, is accurate within ±1.0% of the prescribed test pressure of any cylinder tested that day. The pressure indicating device, itself, must be certified as having an accuracy of ±0.5%, or better, of its full range, and must permit readings of pressure from 90%-110% of the minimum prescribed test pressure of the cylinder to be tested. The accuracy of the pressure indicating device within the test system can be demonstrated at any point within 500 psig of the actual test pressure for test pressures at or above 3000 psig, or 10% of the actual test pressure for test pressures below 3000 psig; and
(B) The expansion-indicating device, as part of the retest apparatus, gives a stable reading of expansion and is accurate to ±1.0% of the total expansion of any cylinder tested or 0.1 cubic centimeter, whichever is larger. The expansion-indicating device itself must have an accuracy of ±0.5%, or better, of its full scale.
(iv) The test equipment must be verified to be accurate within ±1.0% of the calibrated cylinder's pressure and corresponding expansion values. This may be accomplished by bringing the pressure to a value shown on the calibration certificate for the calibrated cylinder used and verifying that the resulting total expansion is within ±1.0% of the total expansion shown on the calibration certificate. Alternatively, calibration may be demonstrated by bringing the total expansion to a known value on the calibration certificate for the calibrated cylinder used and verifying that the resulting pressure is within ±1.0% of the pressure shown on the calibration certificate. The calibrated cylinder must show no permanent expansion. The retester shall demonstrate calibration in conformance with this paragraph (e)(4) to an authorized inspector on any day that it retests cylinders. A retester shall maintain calibrated cylinder certificates in conformance with paragraph (e)(8)(iii) of this section.
(v) Minimum test pressure must be maintained for at least 30 seconds, and as long as necessary for complete expansion of the cylinder. A system check may be performed at or below 90% of test pressure prior to the retest. In the case of a malfunction of the test equipment, the test may be repeated at a pressure increased by 10 percent or 100 psig, whichever is less. This paragraph (e)(4) does not authorize retest of a cylinder otherwise required to be condemned under paragraph (e)(6) of this section.
(5) Cylinder rejection. (i) A retester shall reject a cylinder when on visual inspection, it meets a rejection standard in CGA Pamphlets C-6, C-6.1, C-6.2, or C-6.3, as applicable.
(ii) Except as provided in paragraph (e)(5)(iv) of this section, a cylinder that is rejected may not be marked as meeting the requirements of this section.
(iii) When a cylinder is rejected, the retester shall notify the cylinder owner, in writing, that the cylinder has been rejected and, unless requalified as provided in paragraph (e)(5)(iv) of this section, may not be filled with a hazardous material for transportation in commerce where use of a specification packaging is required.
(iv) A rejected cylinder with a service pressure of less than 900 psig may be requalified and marked if the cylinder is repaired or rebuilt and subsequently reinspected and retested in conformance with --
(A) CGA Pamphlets C-6, C-6.1, C-6.2, or C-6.3, as applicable;
(B) Parts 173 and 178 of this subchapter;
(C) Any exemption specific to that cylinder; and
(D) Any approval required under paragraphs (i) and (l) of this section.
(6) Cylinder condemnation. (i) A cylinder must be condemned when --
(A) On inspection, it meets a condition for condemnation in CGA Pamphlets C-6, C-6.1, C-6.2, or C-6.3, as applicable;
(B) The cylinder leaks through its wall;
(C) Evidence of cracking exists to the extent that the cylinder is likely to be weakened appreciably;
(D) For a DOT specification cylinder other than a DOT 4E aluminum cylinder, permanent expansion exceeds 10 percent of total expansion;
(E) For a DOT 4E aluminum cylinder, permanent expansion exceeds 12 percent of total expansion;
(F) For a DOT exemption cylinder, permanent expansion exceeds the limit in the applicable exemption, or the cylinder meets another criterion for condemnation in the applicable exemption; or
(G) For a DOT specification 3HT cylinder, elastic expansion exceeds the marked rejection elastic expansion.
(ii) When a cylinder is required to be condemned, the retester shall stamp a series of X's over the DOT specification number and the marked service pressure or stamp "CONDEMNED" on the shoulder, top head, or neck using a steel stamp. Alternatively, at the direction of the owner, the retester may render the cylinder incapable of holding pressure.
(iii) When a cylinder is required to be condemned, the retester shall notify the cylinder owner, in writing, that the cylinder is condemned and may not be filled with hazardous material for transportation in commerce where use of a specification packaging is required.
(iv) A cylinder that is condemned may not be filled with hazardous material for transportation in commerce where use of a specification packaging is required and may not be marked as meeting the requirements of this section or any DOT exemption. No person may remove or obliterate the "CONDEMNED" marking.
(7) Retester markings. (i) Each cylinder passing retest must be marked with the retester's identification number set in a square pattern, between the month and year of the retest date, in characters not less than
1/8-inch high. The first character of the retester identification number must appear in the upper left corner of the square pattern; the second in the upper right; the third in the lower right, and the fourth in the lower left. Example: A cylinder retested in May 1994, and approved by a person who has been issued retester identification number "A123", would be marked plainly and permanently into the metal of the cylinder in accordance with location requirements of the cylinder specification or on a metal plate permanently secured to the cylinder in accordance with paragraph (c) of this section:
