Weekly question: Regarding the process of activating the ESD accident suppression system for Reactor No. 2, provide evaluations or suggestions; a reward of 5 to 15 wealth points will be given
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This post was last edited by Luo Xiaoyang on 2015-7-31 at 11:51. Regarding the process of activating the ESD accident termination system in Reactor #2: At 23:39, when the temperature of Reactor #2 reached 70°C and the pressure inside the reactor reached 1.4 MPa, the ESD system met the conditions for activation, generating an alarm message requesting confirmation of injection. XXX, the workshop supervisor, ordered the activation of the emergency accident termination system. After the DCS operator XXX clicked the “Confirm Injection” button, an alarm message stating “Injection failed” appeared on the ESD control screen ； The ESD screen displayed \"Confirm Injection\" once again, and the DCS operator XXX pressed the \"Confirm Injection\" button once more. At this point, the ESD also showed a message stating \"Injection failed\" (due to the urgency of the situation, the operator did not try to determine the cause of the alarm and pressed the \"Confirm Injection\" button twice in a row). At this time, XXX noticed that the pressure switch PS-V201B-71/74 for the nitrogen cylinder outlet pressure was indicating a low-pressure condition, which caused the injection to fail. Each polymerization reactor is equipped with two nitrogen cylinders in its emergency quenching system; one of them is in use while the other serves as a backup ； Immediately inform the on-site inspector XXX and team leader XX to switch the accident termination agent system to another nitrogen cylinder, whose outlet pressure is 10 MPa; the pressure after the pressure regulator should be set to 5 MPa ； Notify xxx that the site meets the conditions for ESD activation, and then xxx manually presses the emergency shutdown button PB/R201B-84. At 23:42, the ESD display indicated that the accident quenching agent system had completed injection, while the DCS showed an overreading for PS-V201B-87. The level switch LS-V201B-88 for the accident quenching agent tank indicated an underreading (indicating that injection was successful), yet the ESD screen still displayed the message “Injection confirmed” (it should have shown “Injection successful”). At that time, the temperature of the reactor was 80°C and the pressure was 1.6 MPa. After the emergency quenching liquid is injected into the reactor, it needs to be stirred in order to rapidly bring the reaction to an end; therefore, the temperature and pressure in the polymerization reactor continue to rise at this time ； At 23:43, the DCS system showed that the temperature and pressure in Reactor No. 2 had risen to 86°C and 1.68 MPa respectively; the explosion-proof valve at the top of the polymerization reactor burst open, and after the safety valve activated it immediately returned to its original position. At this point, the temperature and pressure in the polymerization reactor began to drop ； By 00:07 the next day, the pressure in the reactor dropped to 0.78 MPa and the temperature was 56.9°C; at that point, the main control system began to recover the monomer from within the reactor.
Workshop cases are worth learning from* There are too many chemical hazards
1. Were emergency measures taken before the pot temperature rose to 70°C, and were there any relevant training and assessments?； 1. Is there any sleeping on duty during the night shift at the DCS? 2. When the ESD system displays a \"Injection failed\" message, is the reason indicated? 3. The outlet pressure of the nitrogen cylinders is low – how long has this been going on, and has any inspection been carried out? ； If it occurs before the batch starts, can the process not begin? 4. Should an emergency terminator be injected, and should one go to the site to verify the actual injection situation? 5. Are relevant emergency drills conducted on a regular basis? 6. Has the simulated addition of an emergency terminator been tried during scheduled maintenance? 7. The ESD system program needs to be modified
This post was last edited by An Ran on 2015-7-30 at 14:45. The analysis on the fourth floor is quite comprehensive; one additional point is that, in the event of an accident, it is necessary to make the operators aware, at a conceptual level, of the serious consequences of improper operations. The principle of \"not letting anything go unaddressed\" should be adhered to – once an accident occurs, the responsibility must be traced to individual persons. Only by making operators fully aware of the seriousness of this issue can improper operations be prevented.
Before making a decision, I’d like to know where the emergency termination agent is injected Bottom? Top?
At the bottom, there are dedicated pipes for emergency shutdown agents, which are pressurized with nitrogen at a pressure of over 4.5 MPA
Chain connections should be increased; when there is a low-level or low-pressure alarm for the emergency shutdown agent, the polymer feeding initialization procedure is paused
The ESD accident panel is used for interlock alarms; it includes alarm points for the liquid level in the emergency shutdown agent tanks and the pressure of nitrogen cylinders. The polymerization reactors are inspected every 40 batches, and feeding is not allowed if the inspection fails.
Firstly, the temperature monitoring of the degree of polymerization needs to be improved; it has already reached 70°C. The temperature alarm can be improved; it will give clear indications when the temperature exceeds a certain threshold, thereby assisting the operators. Secondly, strengthen the daily management of the emergency termination agent system. First, pay attention to the maintenance of this system (nitrogen, terminators, hardware), and also conduct emergency drills for employees. Third, management of abnormal emissions to prevent major safety accidents during pressure release.
Inadequate inspection of the nitrogen pressure for the accident termination system warrants evaluation.
Why wasn’t a regular terminator added before?