Issues regarding the interlock bypass for the tank farm
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In standard interlock circuits, a bypass for the interlock signal source is usually provided within the PLC. However, in the high liquid level interlock bypass, the high liquid level switch may interlock several inlet valves; bypassing this liquid level switch would result in all valves being unable to operate. In such a case, is it reasonable to provide a separate bypass for each valve?
We all bypass the input, but not the output.
This post was last edited by liuyuqian on 2016-9-12 at 16:48 to bypass the input signal. Signal shielding is implemented to indicate that there is a problem with this interlock signal or that maintenance is underway, and the system is not to be stopped. A valve’s interlock sometimes involves more than one interlock condition; if the final actuation signal is bypassed directly, doesn’t that increase the risk?:)