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.

February 7, 1995

MEMORANDUM FOR: CHARLES E. ADKINS, DIRECTOR
               DIRECTORATE OF TECHNICAL SUPPORT

THROUGH:        JOHN B. MILES, DIRECTOR DIRECTORATE OF COMPLIANCE PROGRAMS

THROUGH:        RAYMOND E. DONNELLY, DIRECTOR OFFICE OF GENERAL INDUSTRY
               COMPLIANCE ASSISTANCE

FROM:           ALCMENE HALOFTIS, CHEMICAL ENGINEER OFFICE OF GENERAL
               INDUSTRY COMPLIANCE ASSISTANCE

Subject:        Evaluation of Variance #2272, Re:  Rayonier Inc.

The application of Rayonier Incorporated for permanent variance and interim order from the requirements of 29 CFR 1910.261(g)(17)(i) has been evaluated. It is recommended that the application be denied for the following reasons.

OSHA Standard, 29 CFR 1910.261(g)(17)(i) states, "A safety valve shall be installed in a separate line from each pressure vessel; no hand valve shall be installed between this safety valve and the pressure vessel. Safety valves shall be checked between each cook to be sure they have not become plugged or corroded to the point of being inoperative. (See the ASME Boiler and Pressure Vessel Code, Section VIII, Unfired Pressure Vessels-1968, with Adenda)."

The digesters are pressure vessels. The standard requires a safety relief valve on each vessel. Reliance on one safety relief valve from the main source of steam does not comply with the requirements of 1910.261(g)(17)(i).

The purpose of the standard is to provide independent protection for each pressure vessel. The following scenario may shed light on the importance of providing a separate relief valve for each digester. Reliance on the main relief valve at the source of the steam would definitely result in a disaster, in case of its failure. However, if each of the vessels is provided with an independent relief valve, this relief valve would be functioning as a stand-by safety device, hence preventing potential disaster in case of the failure of the main valve.

According to the documentation provided by Rayonier, the digesters are supplied steam from a "single dedicated source," however, each digester is not provided with a separate relief valve. Therefore, each digester must be provided with a safety relief valve at the digester, or at the connecting piping, according to the Standard.