Document e7mO4yJenJwgyR7wZmwn4gx2G

(conoco) Interoffice Communication To J. C. Ledvina - Houston From J. A. DeBernardi ate Subject June 25, 1981 Proposed Fugitive Emission Standard Another thought has come to my mind related to your letter of June 5 on the subject and comments on safety of block valves under relief valves. A far greater safety problem than block valves is presented by the fact that rupture disks are installed in the system. A small leak in a rupture disk that equalizes process pressure on both sides of the disk, means that the relief pressure of the disk is increased by the addition of the process pressure. Therefore, the disk will not relief until a much higher pressure than disk design is reached. Tracking this situation with procedures is much harder than tracking whether a block valve is open or not under the relief valve. The basic problem remains that rupture disk installation will increase, not decrease, emissions to atmosphere. J. A. DeBernardi Plant Manager Conoco VCM br CC: RDG CCR 000067108