Digestion Pressure Vessels
The design criteria for the pressure vessels were obtained from original drawings prepared in 1958 by Chicago Bridge and Iron Company. The design criteria were based on 1956 Codes of the American Society of Mechanical Engineers. Design pressures are the maximum pressures allowed at the top of the vessel.

Plate samples from each of the failed vessels were collected for metallurgical testing. The results indicated no defects. Test results are included as Appendix J.

Thickness measurements were taken of the failed flash tanks and blow-off tank shell fragments. These measurements are contained in Appendix R.

Desilicator
The desilicator had a diameter of 11.5 feet, a height of 88 feet and a volume of 9,140 cubic feet. The design temperature was 650ºF, and the maximum allowable working pressure (MAWP) was 600 PSIG. The pressure sensors on the desilicator had an upper limit of 700 PSIG. The desilicator was equipped with temperature transmitters with an upper limit of 550ºF.

Digesters
The four digesters were identified as V-1, V-2, V-3 and V-4. Digesters V-1, V-3 and V-4 had a diameter of 11.5 feet, a height of 88 feet and a volume of 9,140 cubic feet. Their design temperature was 650ºF, and their MAWP was 600 PSIG.

Digester V-2 had a diameter of 15.6 feet, a height of 127.6 feet and a volume of 24,388 cubic feet. The design temperature was 600ºF, and the MAWP was 600 PSIG.

The pressure sensors on all four digesters had an upper limit of 700 PSIG. Each digester was equipped with temperature transmitters with an upper limit of 500ºF.

Flash Tanks
Temperature sensors were not provided for the flash tanks. Each flash tank was equipped with pressure sensors.

Kaiser documents indicate the following relief valve settings for the flash tanks: Flash Tank Nos. 1 through 3, 457 PSIG; Flash Tank No. 4, 220 PSIG; Flash Tank Nos. 5 and 6, 136 PSIG; Flash Tank Nos. 7 through 9, 47 PSIG.

Flash Tank Nos. 1, 2 and 3 each had a diameter of 10 feet, a height of 42.1 feet, and a total volume of 2,880 cubic feet. Each of the three tanks was equipped with pressure sensors with an upper limit of 500 PSIG. The MAWP was 457 PSIG.

Flash Tank No. 4 had a diameter of 15 feet and a height of 42.4 feet, with a total volume of 6,185 cubic feet. Tank No. 4 was equipped with pressure sensors with an upper limit of 300 PSIG. Tank No. 4's MAWP was 220 PSIG. Flash Tank Nos. 5 and 6 each had a diameter of 15 feet, a height of 42.4 feet, and a volume of 6,185 cubic feet. Flash Tank No. 5 was equipped with pressure sensors with an upper limit of 200 PSIG. Flash Tank No. 6 was equipped with pressure sensors with an upper limit of 150 PSIG. Flash Tank Nos. 5 and 6 were rerated in 1990 to allow Kaiser to raise their MAWP to 156 PSIG.

Flash Tank No. 7 had a diameter of 15 feet, a height of 38.8 feet, and a volume of 5,183 cubic feet. It was equipped with pressure sensors with an upper limit of 120 PSIG. The MAWP of Tank No. 7 was 47 PSIG.

Flash Tank Nos. 8 and 9 each had a diameter of 18 feet, a height of 42 feet, and a volume of 6,922 cubic feet. Flash Tank No. 8 was equipped with pressure sensors with an upper limit of 60 PSIG. Flash Tank No. 9 was equipped with pressure sensors with an upper limit of 30 PSIG. The MAWP of each tank was 47 PSIG.

Blow-Off Tank
The blow-off tank was designed according to the American Petroleum Institute Code for Large Low Pressure Storage Tanks. The blow-off tank had a diameter of 18 feet, a height of 40 feet, and a volume of 6,922 cubic feet. The blow-off tank's design pressure was 5 PSIG with a design temperature of 237ºF. The tank was equipped with a temperature transmitter with an upper limit of 300ºF.

Relief Tank
The relief tank was a non-pressurized vessel with a louvered top, and had a volume of 18,320 cubic feet. The tank was not provided with pressure or temperature sensors.