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U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

Interpretation Response #PI-76-048 ([Louisiana Gas Service Company] [D. L. Meriwether])

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

Interpretation Response Details

Response Publish Date:

Company Name: Louisiana Gas Service Company

Individual Name: D. L. Meriwether

Location State: LA Country: US

View the Interpretation Document

Response text:

Aug 12, 1976

Mr. D. L. Meriwether
Director of Technical Standards
Louisiana Gas Service Company
P.O. Box 433
Harvey, Louisiana 70058

Dear Mr. Meriwether:

This responds to your letter dated May 10, 1976, requesting an interpretation of Title 49 CFR Part 192.179(c).

Question: Where valves are installed at a closer interval than those as specified in 192.179(a), must a blowdown be installed between each set of valves?

Answer: Yes, Section 192.179(c) states: "Each section of a transmission line, other than offshore segments, between main line valves must have a blowdown valve with enough capacity to allow the transmission line to be blown down as rapidly as practicable. Each blowdown discharge must be located so the gas can be blown to the atmosphere without hazard and, if the transmission line is adjacent to an overhead electric line, so that the gas is directed away from the electrical conductors."

The purpose of the pipeline blowdown valves are for exhausting gas from the line when required by repairs, emergencies, or other conditions.

Question: Is there a guideline that determines the blowdown capacity for a certain size and length of pipeline?

Answer: Guidelines to determine blowdown capacity are not a function of this Office. Because the issuing gas jet from a blowdown valve produces a violent reaction thrust, proper blowdown design is of major importance and is the responsibility of the operator. Blowdown valve sizes may be selected by using various applicable formula and/or charts that are provided in handbooks such as the Gas Engineer's Handbook, or from valve manufacturers' literature.

We trust that this adequately responds to your inquiry.


Cesar DeLeon
Acting Director

Regulation Sections

Section Subject
192.179 Transmission line valves