The facility uses xylene as a cleaning agent to clean the reactors. Xylene is an extremely hazardous flammable substance, and is stored at the facility. On August 14, 2017, at 11:24am, an operator was cleaning the RX-2 reactor with xylene between tolling processes. The operator overfilled the reactor with xylene, leaving the reactor without a vapor space. The pressure increased causing the mpture disk to fail and release 4500 pounds of xylene into the atmosphere.
The primary root cause for the reactor upset was that the reactor was charged with an excess of xylene, leaving insufficient vapor space in the reactor. In addition, the reactor pressure transmitter for the reactor was set at an insufficient scan rate. As a result, the process control computer did not read any increase in pressure, failed to control the nitrogen pad pressure, and did not alarm the control room operator that an increase pressure was occurring.