Document bBK28XE91Qa6XrBonVOKYvdY3

Lake Charles VCM Plant CERTIFIED MAIL # 8090858 RETURN RECEIPT REQUESTED conocoi Conoco Chemicals Company A Division of Conoco Inc. P. O. Box 605 Westlake, Louisiana 70669 (318) 491-5211 SU)$r June 24, 1982 Ms. Adlene Harrison, Regional Administrator U.S. Environmental Protection Agency Region VI 1201 Elm Street Dallas, TX 75270 Dear Ms. Harrison: The following is a report of a relief valve discharge to the atmosphere at the Conoco VCM Plant in Westlake, Louisiana which occurred on June 20, 1982. Reporting of the relief valve discharge is required under Section 61.65(a) of the National Emission Standard for Hazardous Air Pollutants for vinyl chloride. At 2:45 am on June 20, the relief valve on top of the Caustic Decanter and the relief valve on top of the Caustic Dryer relieved due to an over pressure situation in the system. The release allowed 94.2 Lbs. of VCM to be discharged to the atmosphere through the Vent Scrubber vent stack. The amount of VCM released was based on: 1) A release duration of 10 seconds. This was the time interval between the start of the release and the time when the Caustic Decanter high pressure alarm shut off. 2) The relief valves being wide open at the start of the release. The valves then were assumed to return to their fully-closed position as a linear function of time over the 10 second release period. This is a very conservative estimate, because it is most likely that the valves never fully opened. 3) Flashing of VCM across the relief valve. The VCM released would be a vapor at the temperature and pressure just downstream of the valve (temperature = 100F, pressure = 5 psig max.). The Caustic Decanter relief valve is a 3"x4" Consolidated Type 1905-30LC relief valve with a set pressure of 115 psig, and the Caustic Dryer relief valve is a 3"x4" Consolidated Type 1905-30KC relief valve with a set pressure of 120 psig. Both relief valves are balanced bellows valves. CCR 000023591 Adlene Harrison Page 2 The overpressure condition was caused by operator error. A valve upstream of a Vinyl Check Tank was closed by mistake, and the pressure in the system rose quickly. The error was noted immediately and the valve was re-opened within 10 seconds. Corrective action to prevent recurrence includes counseling of the operator on the correct operating procedures. Also, design changes in the Caustic Decanter's relieving system have been studied and a final design has been issued. Tie-ins for the design changes have been made, and the remainder of the project will be installed by the end of the First Quarter of 1983. Installation of this project will successfully contain releases of this type. Please let me know if you have any questions concerning this report or if you require any additional information. Sincerely, J. A. DeBernardi Plant Manager Conoco VCM Plant br bcc: CRH-MGH-BIR-JWW-RB-PLF-DLD-JCL-SWS OCR 000023592