Document G6neyrbLrx2kYxaNv10Z4qgM4

Dccemloer 15, 107 S c i ft ^ O (L* Conoco Chemicals Continental Oil Company P.O. Box 9 1. New Highway 25 Aberdeen, Mississippi 39730 United States Environmental Protection Agency 34 5 Courtla.nd Street Atlanta, Georgia 30303 Attention: Sr. Thomnie A. Gibbs, Chief Air EngineeringBranch Dear Sir: On December 9, 1978, at approximately 4:00 a.m., our plant experienced a minor relief valve discharge. Pursuant to the national Emission Standard for Vinyl C'r.loride (40 CFR, Part 61, Subpart F, d. 61.05 a) we are reporting this discharge to your office. The vessel involved was a fresh \/CM receiver, FA 701. This vessel is equipped with a rupture disc rated at 150 PSIG and a relief valve rated at 150 FSIC. The vessel design pressure is 150 PSIG at 150F. The vessel is used as intermediate vinyl chloride storage between the sphere :-and the reactors. Receiver FA 701 is refilled after each reactor is charged :`.from it. The release occurred as FA ,701 was being refilled. The emission, from g-the relief valve was observed by a plant "A" operator. Upon notin 17 the lifting of the relief valve, the "A" operator noli fled t':.- panel operator by radio. The panel operator immediately shut down the transfer system that was refilling the receiver. The "A" operator estimated the dura a ion of the relief to be approximately ten seconds. The relief valve reseated and did not lift, again. The amount of the release was estimated from the design of the relief valve and t;ie do.sign capacity of the transfer system. Our estimate is that the total emission during the period was 522 pounds of vinyl chloride. 7::e apparent cause of the discharge was due to the failure of a level sen e:: ; device or. the receiver. This device was designed to shut down the transf r system upon a specific liquid level in the receiver and turn on a high level alarm in `\\n control room if the level in the receiver exceeded tide nr-:-~e 1 i cvol. The sensing device failed due to entrained water freezing in zh- t::vice ar..i civir.e low level false readings. SAL 000090628 Mr. Thommie A. Gibbs, Chief Air engineer in i Branch December If, 1 >7S Caere 2 As a result of the low false readings the level sensing device did not shut down the transfer system. The receiver was overfilled with liquid vinyl chloride causing the vessel to overpressure and rupture the rupture disc ard lift the relief valve. To prevent a reoccurance of this problem and future discharges^ the plant will purciiase and install an additional sensing device on thecjBBceivcr which will be tied into the high level alarm. To prevent the exisftifijjfy level device from failing due to cold weather, the plant will purchase and install heat tracing and insulation on the sensing device. If there are any questions on this matter or if further information is desired, please contact Dick Frohreich at AC 601-369-8111, extension 239. j`J, C. Jernigan Senior Process Engineer ta o 0000906 g&\~