Document qkVxBMxzk12J3Q1mv7JgOQ3Nk

Conoco Chemicals Company Division of Conoco Inc. P 0. Box 91. Now Highway 25 Abordton. MS 39730 F-2 A October 26, 1981 Mr. Charles R. Jeter Regional Administrator Region IV United States Environmental Protection Agency 345 Courtland Street, N.E. Atlanta, GA 30308 Dear Mr. Jeter: At approximately 11:05 p.m. on October 16, 1981, our plant experienced a relief valve discharge. Pursuant to the National Emission Standard for vinyl chloride (40 CFR, Part 61, Subpart F, paragraph 61.65 a) we are reporting this Incident to your office. This discharge was reported to the National Response Center under the Comprehensive Environmental Response Com- _ pensatlon and Liability Act of 1980. The vessel involved was a surge tank, T-201, in the VCM railcar unloading area of the plant. The vessel relieved through a 24" X 34" relief valve which had a 2" rupture disk between it and the surge tank. The rupture disk was rated at 150 psig at 72F. The relief valve setting was 150 psig. The pressure rating of the surge tank is 150 psig at 366F. The stack from the relief valve is sixteen feet above grade. The release occurred during the unloading of VCM from railroad cars into the VCM storage sphere. The operator inadvertently did not open a valve on the discharge of one of the VCM unloading compressors. As a result of operation of the compressor in a blocked in condition the pressure at the compressor discharge increased and relieved through the relief valve on the compressor into the surge tank. This resulted in overpressuring the surge tank causing the relief valve on the surge tank to discharge. The operator then shut the compressor off and the relief valve reseated. The operator estimates the relief valve discharged for approximately two and one-half minutes. The weather conditions from the plant weather station at the time of the release were as follows: Barometric Pressure 29.96 in. mercury Temperature - 64F Wind Direction - From Northeast Wind Speed - Trace Sky - Cloudy 4 VAB.0001132409 Mr. Charles R. Jeter United States Environmental Prctectlon Agency October 26, 1981 Page 2 F-2 The amount of vinyl chloride released is estimated to be 357 pounds. This is based on a two and one-half minute release and on a relief valve capacity calculational procedure provided by Consolidated, the relief valve manufacturer. Relieving conditions of 150 psig and 158F are used in the calculation. A copy of the calculation is attached. To minimize the possibility of future discharges of this type, the operators at the VCM unloading area will be reinstructed in the proper unloading pro cedures with special emphasis placed on not operating a compressor blocked in. Also high temperature switches will be installed on the compressors to shut them down if they are started up in a blocked in condition. A high pressure switch* will be installed on the surge tank to trip an alarm and shut down all of the unloading compressors in case of high pressure in the surge tank. The reporting requirements of the Standard pertaining to relief valve discharges are summarized below: Source: Surge Tank, T-201 Nature: Cause: Date: Time: Discharge through relief syste on surge tank. T-201 Overpressure of surge tank, T-201, due to operation of a VCM unloading compressor in a blocked in condition. October 16, 1981 11:05 p.m. Approximate Discharge: Method of Determining Discharge: 357 pounds of vinyl chloride Relief valve calculation Action Taken Co Prevent lischarge: Compressor shutdown leasure s Taken 'o Prevent uture Discharge: 1. Operators reinstructed in proper VCM unloading procedures. 2. A high temperature shutdown will be installed on each unloading compressor. A high pressure switch which will shutdown all VCM unloading compressors will be installed in surge tank. T-201. 4 * A VAB.0001132410 Mr. Charles R. Jeter United States Environmental October 26, 1981 Protection Agency Page 3 * l *t 1;I i * <601 voui; fny q"eStJi0t13 eoncernin8 Jo9-8111, extension 2239. this report, please contact me at Sincerely, A. Frohreich tap V . J\JZy ofbe: Jp, CRBMa, nPksE'M,BuSrJeVa,u DLM,PJoJlHlution Control / AI I f VAB.0001132411 Relief Valve Discharge Calculation Surge Tank, T-201 11:05 P.M. - October 16, 1981 From: Consolidated Safety Relief Valves Catalog No. 1900 B, page 46 a - w vr \ir wc P Where: A - Orifice area, in , G orifice 0.503 in^ W * Relieving Rate, lb./hr. T * Inlet Relieving Temperature, R * 618R Z * Compressibility Factor, 0.82 C Nozzle Gas Constant, page 48, * 295 P Relieving Pressure, psia 164.7 psia M * Molecular Weight of Vapor * 62.5 Then: (0.503 > (295) (164.7) V618 X V 0.82 8580 lb./hr. Vinyl chloride discharged in 2.5 minutes * 8580 lb. X 1 hr. X 2.5 min. * 357 lb. hr. 60 min. F-2 i A -, j iidn 4 VAB.0001132412 *.