HM-234 NPRM Clarification Questions

This letter is in response to your September 7, 2016, email and subsequent conversations requestin
g clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to re
qualification requirements in § 180.209(b)(1) for a specification DOT 3AA cylinder. Specifically, you s
tate that your company uses DOT 3AA cylinders filled exclusively with oxygen. Based on your compa
ny practices, the cylinders are routinely refilled before the pressure falls below 50 psi and are requali
fied every 10 years instead of 5 years in accordance with § 180.209(b)(1). You also reference the Ju
ly 26, 2016 Notice of Proposed Rulemaking (NPRM) titled, "Hazardous Materials: Miscellaneous Ame
ndments Pertaining to DOT Specification Cylinders (RRR)" [HM-234; 81 FR 48977], which proposes t
o amend some of the requalification requirements in § 180.209(b).

We have paraphrased and answered your questions as follows:

Q1. You ask if a DOT 3AA cylinder is subject to the hammer test requirement in § 180.209(b)(1)(iii)
at the time of refill. You note that your company interprets the meaning of "refill" as it applies to § 1
80.209(b) as filling an oxygen cylinder when it contains less than 50 psi.

A1. The answer is yes. If your company wishes to requalify a DOT 3AA cylinder every 10 years inste
ad of every 5 years, as outlined in § 180.209(b)(1), the cylinder must meet all applicable requireme
nts, including the hammer test, prior to being refilled. The HMR is silent on the definition of "refill" f
or this exception, but generally "refill" has meant the filling of a cylinder regardless of the pressure a
t the time of refill.

As it is currently written in the HMR and as a condition to allow a 10-year requalification period inste
ad of a 5-year period, the cylinder must pass the hammer test in accordance with CGA C-6 before e
ach refill. The test protocol calls for the cylinder to be empty prior to performing the hammer test. F
or the purposes of the HMR, a cylinder containing a permanent Division 2.2 gas is empty when the
pressure is less than 29.0 psig at 20 ºC.

Q2. You ask if an internal inspection is required each time you refill a DOT 3AA cylinder.

A2. The answer is no. There is no regulatory requirement to conduct an internal inspection each tim
e a cylinder is refilled. However, there is a requirement to internally inspect a DOT 3AA cylinder at t
he time of requalification. Specifically, § 180.205(f)(1) requires that a steel cylinder be visually inspe
cted in accordance with CGA C-6, which requires an internal inspection be conducted each time a cy
linder is requalified or if the cylinder fails the hammer test.

Please note that if the cylinder is subject to the hammer test at the time of refill, such as is required
in § 180.209(b)(1), failure of the hammer test may present conditions rendering the cylinder unsafe
and subject to testing and inspection in accordance with § 180.205(d)(1).

Q3. You ask if it was PHMSA's intention in the HM-234 NPRM [81 FR 48977] to remove the authoriz
ation to requalify a DOT 3AA cylinder every 10 years. Specifically, you reference the table in § 180.2
09(a), which proposes to list a 5- or 12-year requalification period for a DOT 3AA cylinder.

A3. The answer is no. The § 180.209(a) table should specify a 5-, 10-, or 12-year requalification peri
od for a DOT 3AA cylinder. This was an inadvertent error and will be amended in the publication of t
he final rule.

Q4. You ask if it was PHMSA's intention in the HM-234 NPRM to restrict those cylinders removed fro
m aircraft from the 10-year requalification period exception as outlined in § 180.209(b)(1).

A4. The answer is no. It is not PHMSA's intention to restrict cylinders removed from aircraft from the
10-year requalification in § 180.209(b). This will be addressed in the final rule.