Discussion on the 7.16 accident at Rizhao Shida Technology
Thread Content
Based on the accident reports that have been released so far, one of the reasons is that the safety valve manual valve of the spherical tank was closed, and a blind flange was installed on the vent line. In my opinion, based on the brief description provided by the facility, the unit is currently under maintenance and shut down; there are flammable substances inside the spherical tank, so it should be isolated from any external areas related to the maintenance work. Blind flanges should be installed to isolate the safety valves and vent lines of the spherical tank as well. If it is in operational status, the safety valve manual valve should be open. I’m not sure whether this reason mentioned in the report is based on an analysis of startup conditions or on an analysis of shutdown conditions; it seems a bit contradictory. I’m not certain if my view is correct – what do my colleagues think?
I disagree with the original poster’s view; even if production has stopped, as long as there is material in the tanks, they should still be considered in use, and the safety accessories cannot be isolated. Only when the material is emptied and the pressure drops to zero can the equipment be considered not in use.
How do you handle the spherical tank during maintenance?
If it is only an external inspection, the spherical tank and its accessories, pipelines, and instruments are all in service. If internal or external inspections are to be carried out or the tank is to be repaired, it is necessary to use up or empty the contents, isolate the pipelines and instruments, and then perform nitrogen purging followed by air purging to ensure a safe condition.
What about hot work maintenance on the torch system? What should be done with the spherical tank connected to the torch?
When performing internal inspections of spherical tanks, since it involves working in a confined space, is the tank not isolated from the outside world by using blind plates?
It is necessary to check which part of the flare system is involved to determine whether it affects the operation of the flare system. If the flare system must be shut down, the equipment discharging into the flare system should not be able to emit gases to the flare.
Of course, I said “isolate the pipelines and instrumentation.” Blind plugging must be carried out in full before entry into the tank is permitted.
A maintenance flare should be installed in the pressure tank area; in other words, an additional small flare is provided for use during the maintenance of the main flare
This post was last edited by ylb913 on 2015-7-28 08:39. 1. Someone is transferring liquid gas, with tank number 7 pouring liquid gas into tank number 6; before the transfer, tank number 6 was filled with water (to displace the air inside the tank). Cylinder inversion is carried out through the safety valve bypass: liquid gas is collected from tank No. 6 while water is released from tank No. 7 at its water level. 2. The key issue is that the water cut-off valve at the bottom of tank No. 6 is shutting off the water flow (a hose is connected to the valve, and the water flows directly onto the ground). Once the water runs out, liquefied gas is released, which then causes an explosion when it comes into contact with air. Was there anyone on site during the water cut who wasn’t aware of it? 3. The ruptured tank was blown up during baking; the safety valve was not activated, and there was a blind flange on the low-voltage main pipe.
Isolation blind plates should only be installed when there are conditions for maintenance or access