OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at https://www.osha.gov.

January 31, 1991

Mr. Robert Brenton Director,
Tech Services Distribution Facilities
CF Industries, Inc.
Salem Lake Drive
Long Grove, Illinois 60047

Dear Mr. Brenton:

This is in response to your letter of December 7, 1990, which pertained to back-welding of threaded connections in anhydrous ammonia service in compliance with the latest American National Standards Institute (ANSI) standard, published in 1989. We apologize for the delay in our response.

In your letter, your question reads: "If we have seal welded threaded connections in compliance with the ANSI K61.1-1989 (and referenced ASME codes), are we in compliance with 29 CFR 1910.111?"

As indicated in your letter, the applicable Occupational Safety and Health Administration (OSHA) standard for back-welding of non-refrigerated anhydrous ammonia system piping is at 29 CFR 1910.111(b)(7)(iv), which in part states: "Threaded connections shall not be back-welded."

OSHA referenced the ANSI K61.1-1966, Storage and Handling of Anhydrous Ammonia, in the development of the its standards at 1910.111. The referenced ANSI standard (1966 edition) did not allow back-welding on the threaded connections, but the current ANSI standard (1989 edition), section 5.6.3 of ANSI K61.1-1989, allows back-welding on threaded connections.

Under OSHA's de minimis violations policy, copy enclosed, OSHA recognizes an employer to be in compliance with the Occupational Safety and Health Act (OSH Act), if that employer complies with the requirements of the most current applicable industry consensus standards (such as ANSI K61.1-1989), which provide equal or greater protection to employees who may be exposed to hazards. Therefore, under this policy, back-welding of threaded connections in compliance with the ANSI K61.1-1989 for anhydrous ammonia systems is acceptable to OSHA, if all other requirements specified in the ANSI K61.1-1989 are met. OSHA will accept back-welding on the threaded pipes, only if the pipes are of schedule 80, and the fittings on these pipes are not made of cast iron.

If we may be of further assistance, please contact us. Thank you for your interest in safety and health.

Sincerely,



Patricia K. Clark, Director
Directorate of Compliance Programs

Enclosure



December 7, 1990

Occupational Safety & Health Admin.
Directorate of Compliance Programs
200 Constitution Ave., Room N 3469
Washington, DC 20210
Attn: Mr. Sanji Kanth

RE: Back-welding of threaded connections in anhydrous ammonia service

Dear Mr. Kanth:

To recap our phone conversation of November 20, 1990:

* 29 CFR 1910.111(b)(7)(iv), which address non-refrigerated ammonia piping, states in part: "Threaded connections shall not be back-welded."

* ANSI K61.1 - 1989 addresses piping practices in 5.6.3 and specifies conformance to ASME B31.3 for non-refrigerated piping and ASME B31.5 for refrigerated piping. ASME 31.3(328.5.3) and 31.5(537.4.5) specifically permit seal welding of threaded connections.

Question: If we have seal welded threaded connections in compliance with ANSI K61.1 - 1989 (and the referenced ASME codes), are we in compliance with 29 CFR 1910.111?

Sincerely,



M. Robert Brenton Director,
Tech Services Distribution Facilities