Document p2gQovZYDan63y2QzvgjyEaDa

- CHLOR - ALKALI 2 1994 REACTIVE CHEMICALS REVIEW CELL AREA \ CELL AREA Chlorine Cells Potential Problem: Loss of Anolyte Level Result: Hydrogen in Chlorine Explosion; Arcing within cell Preventative Measures: - 2 level transmitters and 1 low level carbon probe - 4" rectifier shutdown (2/3,2/2,1/1) - backup side feed level controller - low level alarms ---------- low low-low 55" 5.0" - 6" minimum operating head - VRD conforming to CATC guidelines - Level selection - high reading at >16* low reading at < 16" - visual rounds Potential Problem: High Series Hydrogen Pressure Result: Hydrogen in Chlorine Explosion Preventative Measures: - 2 series relief on hydrogen stack at 45 - 6.0 " - high H2 pressure alarm at 4" - foam drains October 6,1994 Dow Confidential Information efp 00 A 037] p'p CONF T DENT IA( Potential Problem: High Hydrogen During Operation Result: Hydrogen in Chlorine Explosion Preventative Measures: - 2" air dilution valves - open air dilution valves between 0.5 and 1.0% - "quickie H2" and "total gas H2" analyzers - Troubleshooting plugged radial feeders take salt off (300 gpl max salt) look for restricted H2 outlets bad cells - Follow CATC guideline concerning air dilution and shutdown - series voltage alarm to detect possible dip drop voltage prob. - dip drop profiles quarterly by cell crew - anolyte and catholyte temperature alarms > 80 C October 6,1994 Dow Confidential Information efp DO A 037133 OONFrOFNTTAl' Potential Problems Oxygen in hydrogen Result: Explosion in hydrogen header ("pop" if minor in nature) Incidents: - 1993 Mod5 code problem resulted in no N2 purge on shutdown which lead to an explosion S-5/S-8 @ CA-2 - 1993 CA-2 Hydrogen log fire due to arcing at boot connection on S-8 hydrogen log caused by ground on series - 1994 S-4 at Cl-1 plant; failure to bottle series before lowering head to stop under-cell leak. - 1994 S-5 at CI-1 between cell leak caused loss of catholyte level; H2 ignited above caustic trap. Preventative Meaures: - Nitrogen purge activated in startup/shutdown steps for the hydrogen stacks - Low nitrogen flow alarm at 200 lb/hr; normal rate 500 lb/hr - Nitrogen valve position alarms - hydrogen compressor shutdown -1.5 INWA instantaneous or 1/8 INWA for 2 seconds - standard operating procedure to "bottle" series on all shutdowns (purges the cell with brine) - off-line procedures for cell maintenance - cell sprayers and housekeeping October 6,1994 Dow Confidential Information efp DO a coMr rf