Unchecked Process/Plant change cause Incident
A decarboxylation reaction was carried out in a 30cu.m GLMS vessel, the charge was 24 tons at 35% concentartion. The original basis of safety relied on a heat-up rate of 20-150°C over 4-5 hours
The reaction strength was increased to 45%, at the same time the vessel was changed to Hastelloy due to corrosion of the GLMS.
The change in heat transfer meant that the heat up period was reduced to 2 hours
The change in strength obviously increased the volume of gas to be discharged
These factors worked together to cause a large proportion of the batch to be ejected via the vent system
Further calculation later showed that the increase in strength would probably have been processed safely, however the critial change was the heat up rate which meant that any batch size over 18 tons would give rise to two-phase flow, and loss of contents.