Interpretation Response #14-0124 ([HSB Global Standards, Inc.] [Mr. Oberst Mulet])

Below is the interpretation response detail and a list of regulations sections applicable to this response.

Interpretation Response Details

Response Publish Date: 10/22/2014

Company Name: HSB Global Standards, Inc.

Individual Name: Mr. Oberst Mulet

Location State: CT Country: US

View the Interpretation Document

Response text:

October 22, 2014

Mr. Oberst Mulet
Engineer II
HSB Global Standards, Inc.
One State Street
P.O. Box 299
Hartford, CT  06416-0299

Ref. No.: 14-0124

Dear Mr. Mulet:

This responds to your June 23, 2014 letter requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to specification 4L welded insulated cylinders.  Specifically, in your letter you cite § 178.57(h), which states that:

(h) Openings in cylinder.  Openings in cylinders must conform to the following:

(1) Openings are permitted in heads only.  They must be circular and may not exceed 3 inches in diameter or one third of the cylinder diameter, whichever is less.  Each opening in the cylinder must be provided with a fitting, boss or pad, either integral with, or securely attached to, the cylinder body by fusion welding.  Attachments to a fitting, boss or pad may be made by welding, brazing, mechanical attachment, or threading.

(2) Threads must comply with the following:

(i) Threads must be clean-cut, even, without checks and cut to gauge.
(ii) Taper threads to be of a length not less than that specified for NPT.
(iii) Straight threads must have at least 4 engaged threads, tight fit and calculated shear strength at least 10 times the test pressure of the cylinder.  Gaskets, which prevent leakage and are inert to the hazardous material, are required.

In your letter, you ask whether the opening diameter is defined as the opening diameter made to the cylinder body before being provided with a fitting or boss?  Or, is the opening defined as the inside diameter of the fitting or boss after attached to the cylinder body by fusion welding?

As provided in § 178.57(h) of the HMR, the limit on the opening size described in paragraph (h) is the opening on the cylinder head, before a fitting, boss, or pad is applied.  Furthermore, an opening that is not a proper size could affect the stresses in the cylinder head.

I trust this satisfies your inquiry.  Please contact us if we can be of further assistance.

Sincerely,

T. Glenn Foster
Chief, Regulatory Review and Reinvention Branch
Standards and Rulemaking Division

178.57(h)

Regulation Sections