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 http://www.osha.gov.

April 28, 1994

Mr. Grahame Barker
Baker Performance Chemicals Incorporated
3920 Essex Lane
Houston, Texas 77027

Dear Mr. Barker:

This is in response to your March 23 letter, requesting interpretation of the Process Safety Management (PSM) of Highly Hazardous Chemicals standard, 29 CFR 1910.119. Specifically, you requested clarification on what constitutes the boundaries of a process. Your question and our replies follow.

Question 1:

Concerning the physical limits of our covered process, would a storage tank which is hard-pipe connected to the process be considered part of the process?

Reply:

Yes. By the definition of "process" defined at 1910.119(b), a storage tank interconnected to a process would be considered part of that process.

Question 2:

If the storage tank is considered part of the covered process, would the storage tank be considered part of the process if it could be isolated from the process by a valve?

Reply:

Yes. The storage tank would be considered part of the process whether or not the tank could be isolated by valve closure.

Question 3:

If the storage tank is isolated by disconnection or only occasionally connected by hoses to the covered process, would it be considered part of the process?

Reply:

Yes. The storage tank would be considered part of the process specifically because it is occasionally connected to the covered process. Also, a permanently disconnected or independent storage tank nearby would be considered part of the covered process when it could be affected by an incident in the covered process. Refer to the second half of the "process" definition cited in the reply to question 1.

Question 4:

If a storage tank that is not related to the covered process but is downwind from the process and could be affected by a failure in the process, would it be considered part of the covered process?

Reply:

Yes. The second part of the reply to question 3 applies.

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

Sincerely,



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