Mechanical damage

Mechanical damage
I. The course of the accident

On May 5, 2017, a hydrocracking unit normally started p-1106 /B pump, intermittent external transportation of LIQUEFIED petroleum gas. During the start process, it was found that the pump seal leakage (inlet pressure 0.8mpa, outlet pressure 1.6mpa, medium temperature 40℃). The shift monitor Guan immediately organized personnel to stop the pump, close the inlet and outlet valves, and relieve pressure to the torch line. Nitrogen replacement was carried out. Since gaskets did not arrive, the workshop planned to carry out maintenance on May 6th. At 8:00 on May 6, hydrogenation Workshop 1 notified the refinery maintenance workshop of the construction and repair Company to replace the P-1106 /B seal, and the refinery maintenance workshop arranged six people including squad leader for maintenance and replacement. 9:10, hydrogenation issued a workshop before a job safety analysis, pipeline and equipment after open, work permit, a workshop hydrogenation shift supervisor to close an on-site inspection, open the pump inlet guide deluge valve, and the discharge valve and pressure gauge with the homework personnel for confirmation, guide on the deluge valve without material discharge, pump outlet pressure gauge pressure is shown as “0″, The operation will be started after on-site confirmation by both parties. At 9:40, when the maintenance personnel removed all the pump cover bolts, the pump body suddenly rushed out from the volute, and the operator who was holding the pump body coupling by hand hit the motor semi-coupling with his left arm, causing injury to his left forearm.

2.Cause analysis

(1) Direct cause: In the process of removing the pump, there is nitrogen residual pressure in the pump shell, which causes the pump body to be pushed out from the pump shell, causing injuries.

(2) Indirect cause: On May 5, the shift leader organized personnel to process the P1106/B pump, closed the pump inlet and outlet valves, relieved the pressure to the torch, and carried out nitrogen replacement. On May 6th, the pump inlet shower valve was opened for pressure relief before operation. After confirming that no gas was discharged, the gauge pressure was zero, which mistakenly thought that there was no medium in the pump. In fact, the pump memory had residual pressure due to the insufficient opening position of the shower valve. Pressure gauge range is 4.0mpa, although meet the requirements, but when the pump pressure is low, the residual pressure due to the impact of pressure gauge accuracy can not be displayed.

3. Experience and lessons

(1) Any operation must be properly done process disposal, energy isolation, Lockout tagout work, at the same time do a good job of implementation and confirmation of measures, to ensure the safety and control of the whole process of operation.

(2) Strengthen the safety management of inspection and maintenance operations, improve risk identification ability, and do a good job of prevention. Pre-work safety analysis must be carried out before operation. Equipment inspection and maintenance, especially pipeline and equipment opening operations, must be thoroughly done with purge, displacement, pressure relief and emptying to ensure effective isolation, emptying and emptying.