Gramercy Works Report of Investigation

APPENDIX M

Recorded Pressure Levels for Vessels in the Digestion Area



Kaiser monitored all critical process data in the digestion area using a computerized data collection system. After the time of the explosion, the data collected by the system was invalid.

Although the time settings in each computer were close to one another, the computer clocks were not synchronized to exhibit identical times. For purposes of this report, the time of the power failure and the time of the explosion were determined from documentation provided by Louisiana Power and Light.

Desilicator

Between 4:00 a.m. and 4:47 a.m., the pressure level recorded in the desilicator ranged from 537 pounds per square inch gauge (PSIG) to 540 PSIG. Several subsequent pressure readings are set forth below:

 

Time PSIG Time PSIG
4:48 a.m. 542 4:58 634
4:50 544 4:59 639
4:52 546 5:00 645
4:53 564 5:01 652
4:55 611 5:02 667
4:56 631 5:05 667
4:57 633 5:06 a.m. 675



After 5:06 a.m., the pressure level began to decrease. The pressure level in the desilicator continued to fall, reaching 584 PSIG at the time of the explosion.

Digesters

The recorded pressure level at the top of the V-1 digester ranged from 503 PSIG to 536 PSIG between 4:00 a.m. and 4:52 a.m. At 4:53 a.m., the recorded pressure level was 504 PSIG. Several subsequent pressure readings were as follows:

 

Time PSIG Time PSIG
4:54 a.m. 548 5:02 631
4:55 595 5:06 632
5:00 603 5:07 a.m. 633
5:01 620



The recorded pressure level decreased after 5:07 a.m. The pressure level continued to drop, reaching 567 PSIG at the time of the explosion.

Between 4:00 a.m. and 4:48 a.m., recorded pressure at the top of the V-2 digester ranged from 470 PSIG to 471 PSIG. At 4:49 a.m., the recorded pressure level was 476 PSIG. Several subsequent pressure readings were as follows:

 

Time PSIG Time PSIG
4:54 a.m. 474 5:06 538
4:55 497 5:07 555
4:59 500 5:08 597
5:00 514 5:09 599
5:01 522 5:10 608
5:02 533 5:11 a.m. 617

The pressure level began to fall after 5:11 a.m., reaching 548 PSIG at the time of the explosion.

Recorded pressures at the top of the V-3 digester ranged from 487 PSIG to 493 PSIG between 4:00 a.m. and 4:54 a.m. At 4:54 a.m., the pressure reading was 490 PSIG. Several subsequent pressure readings were as follows:

 

Time PSIG Time PSIG
4:55 a.m. 519 5:11 564
5:07 523 5:12 617
5:08 555 5:14 a.m. 621
5:10 557

After 5:14 a.m., a reduction in the pressure occurred. This continued until the explosion at 5:21 a.m., when the pressure was 558 PSIG.

On the V-4 digester, recorded pressures at the top of the unit ranged from 469 PSIG to 477 PSIG between 4:00 a.m. and 4:54 a.m. At 4:54 a.m., the pressure reading was 471 PSIG. Several subsequent pressure readings at the top of the V-4 digester were as follows:

 

Time PSIG Time PSIG
4:55 a.m. 505 5:11 519
5:08 510 5:12 554
5:09 511 5:16 597
5:10 514 5:17 a.m. 598



After 5:17 a.m., the pressure began to fall, and continued to decrease until the explosion, when the pressure was recorded at 537 PSIG.

Flash Tanks

Recorded pressure at the top of Flash Tank No. 1 ranged from 317 PSIG to 323 PSIG between 4:00 a.m. and 4:52 a.m. At 4:53 a.m., the recorded pressure was 329 PSIG. Between 4:53 and 5:00 a.m., the recorded pressure rose rapidly to 414 PSIG and continued to gradually increase, reaching 510 PSIG, the limit of the instrumentation, at 5:19 a.m.

Recorded pressure at the top of Flash Tank No. 2 ranged from 256 PSIG to 262 PSIG between 4:00 a.m. and 4:52 a.m. At 4:53 a.m., the recorded pressure for that tank was 260 PSIG. Between 4:53 and 5:00 a.m., the pressure rose rapidly to 388 PSIG and continued to increase, reaching 481 PSIG at the time of the explosion.

Recorded pressure at the top of Flash Tank No. 3 ranged from 187 PSIG to 192 PSIG between 4:00 a.m. and 4:52 a.m. At 4:53 a.m., the recorded pressure was 190 PSIG. Between 4:53 and 5:00 a.m., the pressure rose rapidly to 331 PSIG. It continued to rise, reaching 428 PSIG at the time of the explosion.

Recorded pressure at the top of Flash Tank No. 4 ranged from 159 PSIG to 165 PSIG between 4:00 a.m. and 4:52 a.m. The recorded pressure at 4:53 a.m. was 163 PSIG. Between 4:53 and 4:55 a.m., the pressure level quickly rose to 215 PSIG and continued to increase, reaching 251 PSIG at 5:10 a.m. Between 5:10 and 5:14 a.m., there was another rapid increase in pressure to 306 PSIG, the instrumentation limit.

Flash Tank No. 5 was out of service for maintenance and there were no internal pressures at the time of the explosion. The digestion process was reportedly designed to allow for continued operation even with certain combinations of pressure vessels being out of service. The flow of slurry was simply directed from Flash Tank No. 4 to Flash Tank No. 6. Additionally, a system of bypass piping allowed Sweeta slurry to flow directly from the pretreater into Flash Tank No. 6.

The removal of Flash Tank No. 5 from the process did not create any inherent safety hazards. However, the removal of a tank does cause an increase in operating pressures downstream.

Recorded pressure at the top of Flash Tank No. 6 ranged from 93 PSIG to 98 PSIG between 4:00 a.m. and 4:52 a.m. At 4:53 a.m. it was 96 PSIG. Within 12 minutes, at 5:05 a.m., it rose to 153 PSIG, the instrumentation limit.

Recorded pressure at the top of Flash Tank No. 7 ranged from 52 PSIG to 56 PSIG between 4:00 a.m. and 4:53 a.m. Within 10 minutes, at 5:03 a.m., it rose rapidly to 122 PSIG, the instrumentation limit.

Recorded pressure at the top of Flash Tank No. 8 ranged from 20 PSIG to 23 PSIG between 4:00 a.m. and 4:53 a.m. Within 3 minutes, at 4:56 a.m., it rapidly increased to 61 PSIG, the instrumentation limit.

Recorded pressure at the top of Flash Tank No. 9 was 3 PSIG between 4:00 a.m. and 4:53 a.m. Within 2 minutes, at 4:55 a.m., it rose rapidly to 30 PSIG, the instrumentation limit.