Document 5DErjwR6JKBYgpjq8dq3xw7pz

CHEMICALS INTEROFFICE / LAKE CHARLES TO Wilton Wallace FROM Jon Manns DATE January 27, 1984 SUBJfpt liquid Cl- User Upsets During December ^Hard Freeze During the hard freeze the last week of December, 1983, three liquid Cl- users, TE-II, Tetra and VCM-II, suffered upsets that resulted in a signficant increase in the Cl2 flow to their vaporizers subsequently shutting them down. There was a concern in Plant A of a potential hazard of filling up a Cl- surge drum and getting liquid Cl_ into the reactor. Supervisors from the involved units were interviewed about the sequence of events during the upsets. The following is a result of these discussions. On December 24 at 6:10 p.m., the TE-II operator observed that the Cl2 line ! pressure from Liquefaction had dropped =60 psi and notified Liquefaction. The initial thought in both control rooms was that the excess flow check valve had seated. The Liquefaction "B" operator responded by putting the backup TE-II liquid feed tank in operation and lined it up to them. When he went to take th original feed tank out of service he noticed that it had not seated the check and ^reported this to the lead operator. Liquefaction personnel called back TE-II and 'informed them that they had apparently never stopped receiving Cl2 feed. The TE-II operator then investigated his unit and found that the steam chest pressure impulse line was not giving a correct indication and shut the unit down. It is felt that the impulse line had frozen up. co co UD o o CO At 8:30 p.m. that same night, the Tetra operator responded to a low steam chest pressure alarm on the Tetra Cl_ vaporizer by raising the set point on the steam pressure control valve. Shortly afterwards, the SRV on the steam chest blew, indicating too much steam pressure. The operator lowered the set point on the steam pressure controller until the SRV seated. At approximately the same time th Tetra liquid Cl- feed pressure dropped significantly. The Liquefaction Lead Operator sent the HB" operator up to check the Tetra pump and called the Tetra control room, suspicious they might be having problems similar to TE-II. The Tetra operator knew that the Cl2 line pressure fluctuations were caused by his steam pressure control problems but apparently felt it would line out. u When the Liquefaction "B" operator verified that the Tetra pump was still feeding ^ g Tetra and the line pressure continued to drop, the Liquefaction Lead Operator T3 U again called Tetra to express concern. During the phone conversation Tetra O 4J tripped on low temperature in the Cl2 surge tank. It was determined that the vaporizer steam chest pressure impulse line had frozen. ** ><L) -LHV. -3 -u in < -U Id ijf M U -H i~| On December 26, at 7:45 p.m, the VCM-II unit got an alarm on low liquid Cl2 H Dh feed .pressure. A supervisor,- tpresent at t-h-e-- time, observe^ d- t-h-e- va--porizer ME O i H f--i Ipstteeaam chest pressure Iindication had pegged out due to a frozen impulse line ^anndd ddiirreecctteedd tthhee ooppeerraattoorr ttoo ttrriipp tthhee uunniitt.. S m ^ o. o +Q> -'Or-f Ho In recounting each of their these events with the Plant "B" units have two shutdown devices stoupperrovtiesoctrst,hethefaycipliotyintfrodmouotvethrW tV^O> I'D filling a Cl2 surge drum with liquid Cl2. The Cl. surqe drum inlet line from theo5 Z3 *--f *W Liquid Cl2 Us r Upsets During Decemb r Hard Freeze - c ntinu d > Pap 2 J. P. Manns vaporizer and the bottom of the surge drum have temperature indication that shuts down the unit and closes the Cl., pressure controt valve in the event of low t mperature (EDC #1. plant only has 1 low temperature trip on each of Its surge drums). In the Tetra incident it was one of these shutdown devices that tripped the unit. All the supervisors felt confident that these shutdown devices adequately protected their facility from a disaster similar to the 1971 Tetra explosion, (The Tetra facility at that time did not have these protective devices.) it waj-recommended;to each sup^<fspr^ha^E^q^i^<^i^ the operating Ji^iild .Cl,'users sufferda the exact sameqproi^^ hard freeze that sqiQfte .method of forewarning the operators of .the prob^fyltityof this occurrence.and what the symptoms are should be part of theIr.freeze precautions. /da cc: J. M. Porter I CONFIDENT I Order Subject to ^^pistrict Court Qt 14th 3oaxc _ SL 006331