Process safety coverage of flammable-liquid storage and use

NOTICE: This is an OSHA Archive Document, and may no longer represent OSHA Policy. It is presented here as historical content, for research and review purposes only.

December 12, 1995

Mr. Bry Roberson
EMPE Inc.
[Recipient address omitted]
Dear Mr. Roberson:

This is in response to your November 29 letter requesting an interpretation of the process safety management (PSM) of highly hazardous chemicals standard, 29 CFR 1910.119. Specifically, you requested clarification on whether the exception under paragraph 1910.119(a)(1)(ii)(B) as it applies to flammable liquids stored in atmospheric tanks or transferred which are kept below their normal boiling point without benefit of chilling or refrigeration applies to the process described in the following scenario.

Scenario: There are two non-refrigerated atmospheric tanks, each of which contains flammable liquid in quantities exceeding 10,000 pounds. This flammable liquid is heavier than and immiscible with water. The tanks are located on piers above a water-filled moat which has a capacity greater then the contents of the two storage tanks. As the flammable liquid is pumped from the tanks, it is replaced by water; thus, the tanks are maintained in a full condition (i.e., with minimal headspace) with a water blanket above the flammable liquids at all times.

The flammable liquid is pumped (by means of a pump which is located above the aforementioned water-filled moat) from the tanks to a building which is located approximately 60 feet away and into a 55-gallon "measuring pot." This pump will not run unless the operator is physically actuating the electrical contact. The measuring pot, which is located in an intrinsically safe reactor room, is completely sealed with a standpipe that determines the correct measure. Excess is returned to the storage tank via the standpipe.

The measuring pot is piped to the reactors of a manufacturing activity. The entire contents of the pot flow by gravity to the reactor when the operator opens the manually-actuated valve. The operator observes the liquid flow through a sight glass, and closes the valve when flow ceases.

The flammable liquid storage described in the scenario above would not be excepted under paragraph 1910.119(a)(1)(ii)(B) from coverage by the PSM Standard. The following clarification applies.

The exception under paragraph 1910.119(a)(1)(ii)(B) is applicable to a process that only includes the activities of storage and associated transfer of flammable liquids under the conditions noted above. This exception would not be applicable to a process which includes any one or combination of the following flammable liquid activities: use, storage (other than described previously), manufacturing, handling, or on-site movement and also storage in atmospheric tanks and associated transfer which are kept below their normal boiling point without the benefit of chilling or refrigeration. See the definition of process under paragraph 1910.119(b). For the purposes of this definition, any group of vessels which are interconnected and separate vessels which are located such that a highly hazardous chemical, including a flammable liquid, could be involved in a potential release are considered a single process.

We appreciate your interest in occupational safety and health. If we can be of further assistance, please contact Mr. Ronald J. Davies of my staff at (202) 219-8031, extension 110.

Sincerely,
Raymond E. Donnelly, Director
Office of General Industry Compliance
Assistance

[Requester letter reproduced on OSHA page; omitted here.]