Isolation Measures 1

Isolation Measures 1

Apr 27, 2020

Isolation measures; Lockout tagout; Equipment failure; handover

In the process of petrochemical equipment maintenance, due to the failure to carry out the maintenance preparation work such as handover safety confirmation, risk identification of dangerous operation, Lockout tagout of equipment maintenance and unclear equipment fault handover before equipment maintenance in accordance with the requirements of "equipment safety maintenance management regulations", a variety of safety accidents are often caused in the maintenance process.

The accident case

In a petrochemical enterprise, the maintenance personnel were overhauling the p-1007a hot oil pump at the bottom of a hydrogenation unit. When the pump cover was removed, the hot oil that exceeded the spontaneous combustion point flowed out and caught fire.

The accident after

At 19:30 the day before yesterday, the external operation personnel found that the pump vibration and abnormal sound, immediately report to the shift monitor and the machine repair monitor, the shift monitor and the machine repair monitor to check, the preliminary confirmation of bearing box bearing abnormal sound, the command to stop pump maintenance, switch standby pump. The shift leader arranges external operators to conduct cooling, isolation and oil discharge of the pump before maintenance. 22:20 external operation personnel inform the squad leader that the bottom pump of the tower to be repaired has been isolated and oil discharge has been completed. At 7:50 in the morning of the next day, before the shift shift, when the shift leader met the shift leader in the central control room, he simply informed the maintenance of p-1004a malfunction of the tower bottom pump and informed the oil discharge of the tower bottom pump last night. 8:00 shift shift, in the handover, when the shift leader did not hand over the bottom of the tower pump troubleshooting problems, on the handover. After the completion of the shift, 8:15, the operator li to the device for inspection, found that the p-1004a blowdown vent valve outlet pipe root oil, inspection found that the vent valve is not closed, close the vent valve. During the inspection, the operator also found that the inlet valve of the pump p-1004a was closed. Therefore, he thought that this spare pump should be in a normal standby state and be put into use as soon as possible when using it. By the way, he also opened the inlet valve of the pump. At 8:30 am, the shift monitor issued the permit maintenance work notice, the machine maintenance monitor received the maintenance work notice, arrange maintenance personnel for maintenance. At 9:00, the maintenance personnel went to the installation site for maintenance. Without further checking the isolation of the pump before maintenance, they opened the pump cover and the hot oil flowed out and caught fire.

Accident cause analysis

Their department, after the accident, the company set up the accident investigation team, accident investigation, and in the survey, according to the physical evidence and the scene of the situation, and ask about the operation and delivery of the entire maintenance process analysis, led up to the bottom of hot oil pump was triggered the root cause of the fire accident basically has the following several aspects:

(1) the accident investigation showed that the inlet valve of the pump was open, while the vent valve was closed. The pump shell was full of medium. When the pump cover was opened, the hot oil beyond the spontaneous combustion point flowed out and caught fire, which was the direct cause of the fire accident.

(2) when the machine pump was reported to repair and to be repaired, it failed to warn the Lockout tagout in strict accordance with the "Lockout tagout management regulations for equipment maintenance", which resulted in the operator mistakenly operating and opening the inlet valve without knowing that the equipment was under repair, which was also one of the indirect causes of the accident.

(3) equipment troubleshooting handover is not standard, not clear, when to handover equipment failure, not carried out in accordance with the company "team succession management system", shift supervisor not in transition team meeting and handover bottom hot oil pump failure, but privately and succession team, after completion of succession, succession monitor without and transition of operating personnel on duty, lead to the operator is also one of the indirect cause of the accident.  

(4) according to the previous operation experience, the operator illegally opened the inlet valve of the standby pump in order to facilitate the operation, which also led to the operator being one of the indirect causes of the accident.  

(5) in the maintenance process, the import and export of the pump "isolation" measures are inappropriate, the choice of the valve for isolation, cut off the pump and pipeline process media, is a non-standard "isolation" measures. If a leak occurs in the valve, it causes the pipeline medium to leak into the pump.

(6) the maintenance safety management system and process are not perfect, and the safety awareness of operators is not strong. In the handover link, the shift leader did not carry out the site safety check again to confirm the situation, issued the permit maintenance work notice; In the maintenance operation, the maintenance personnel did not carry out the risk identification before the operation and the maintenance operation license.