Lapsed time

Phenomenon and action taken

Deficiency, problem

0 (base)

After 36 h of this batch reaction, which needs 40 h, operation of the steam-using plant was stopped because of problems with the steam.

12 min

after

The Emergency Stop lever was operated; interlock change was effective, and the plant was shut down. The air supply to the oxidation reactor was stopped by the interlock operation, and nitrogen supply began. Cooling water changed from circulating water to emergency-cooling water. Nitrogen supply to the oxidation reactor continued and the temperature fell slowly.

1 h

20 min

after

Interlock was canceled to change cooling water from emergency-cooling water to circulating water, because it was judged that the temperature of the oxidation reactor was not falling. By canceling the interlock, the nitrogen supply was also suspended and churning of the oxidation reactor also stopped.

The emergency shutdown manual was inadequate. Lack of understanding of the purpose of the interlock and of the theory of cooling and agitation. Lack of understanding of the importance of interlock. The interlock release system was inadequate. Training material was inadequate.

1 h

24 min

after

The temperature of the lower part of the liquid phase decreased, but at the upper part, the temperature began to increase gradually because the heat of decomposition of the organic peroxide could not be removed, because of lack of a cooling coil and agitation, as a result of stopping the nitrogen flow.

Monitoring of the upper part of the liquid phase was inadequate. The design of the cooling capacity and churning capability in the event of abnormalities was deficient.

2 h

13 min

after

Although the HI alarm in the upper part of the liquid phase sounded. Operators were convinced that the problem was the temperature of the gaseous part. The decomposition reaction proceeded and the temperature of the upper part of the liquid phase increased.

The operator was unaware that the liquid level was higher than its design base. The change control system was inadequate.

2 h

51 min

after

The decomposition reaction accelerated and the temperature and pressure increased abruptly. Although the pressure-regulating valve was fully opened manually, the pressure relief speed was insufficient. So, the pressure further increased abruptly.

2 h

55 min

after

The oxidation reactor ruptured, exploded and caught fire.