Is there any specific basis for the hold position of the FC/FO/FL accident switch? Are there any standards that specify this?
Thread Content
Is there any specific basis for the hold position of the FC/FO/FL accident switch? Are there any standards that specify this? For example, in the case of normal discharge, the original design called for a shut-off mechanism in emergency situations, so as to ensure that the liquid level in the reactor and the pressure do not become too high under such conditions. However, third parties believe that the inlets and outlets of all equipment equipped with safety valves should be designed to shut off in emergencies, preventing flow toward downstream processes, and that release should occur through the safety valves in such situations. Is this logical?
What standards are there for this? It depends on the manufacturing process; third parties aren’t professional enough.
In the past, we handled the abnormal situations of our control valves in accordance with the process flow: the feed valve was closed while the discharge valve remained open. Now, it is proposed to carry out control within the equipment itself; in case of any problems, safety valves are used to handle them. This isn’t necessarily wrong, but I’m not sure how to convince others of this approach
The FO/FC settings for control valves are determined with regard to the \"safety\" of operations. In your example, the outlet valve of the reactor needs to be set to an open position; it is also logical that for equipment equipped with safety valves, the inlet and outlet control valves should be set to FC. It’s like when a fire breaks out near the pump; the system stops operating, and the shut-off valves between the discharge tank and the pump, as well as those between the pump and the equipment downstream, are closed to contain the incident to a specific area. Of course, some safety devices may be activated, such as nitrogen purging (to reduce the concentration or temperature in the system)
If we follow the principle of \"closing the feed inlet and opening the discharge outlet,\" then the discharge from the upstream side will become the feed for the downstream side. How should this be configured? The general settings are determined after analysis based on the principle that \"actions should keep the system safe.\"