Document Ev29b0Jm8xmkE2DOokkznzL7N

CHEMICALS 1 TO FROM INDUSTRIES VDCM Personnel J. P. Shamburger /\ INTEROFFICE LAKE CHARLES DATE SUBJECT June 25, 1985 VDCM Dh Still Vent System Controls The VDCM vents can be tripped by three different switches: 1. VDCM Trip Switch - If the vents are tripped at VDCM, the methane valve will close, 159 will close, 160 will open, 161 will remain closed, the Incinerator valve will remain open (allowing the nitrogen purge to go to the Incinerator). 2. WTU Control Room Trip Switch - If the vents are tripped at WTU in the control room, 159 closes, 160 opens, and 161 remains closed, the WTU Incinerator valve will close (the nitrogen is regulated with a rotometer, so the line will pressurize unless WTU cuts the purge off, or trip the Incinerator switch, see 3). 3. WTU Incinerator Trip Switch - Located at the Incinerator(s). If this switch is tripped, 159 will close, 160 will open, and 161 will open, the Incinerator valve will close (but the header will be purging back to the VDCM scrubber through 161). Vent trips of long periods of time, greater than 10 minutes, should be handled this way allowing the line to backpurge to prevent condensation of VDCM in the line and to prevent blowing the rupture disk. NOTE: The vent header rupture disk (50#) can be blown if WTU trips the Dh vents at their control room and themman^ally blocks the valves at the flame arrestor :vithut stripping -.the-, w switch at the Incinerator. . . . , - r.. *" <; . - - CONCLUSION Valve 161 can only be opened with the switch(es) at the Incinerator(s). /bjm