9/26/2017 7:02 AM | |
Joined: 3/14/2008 Last visit: 10/14/2024 Posts: 2110 Rating: (942)
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Hi, No, block contacts cannot be used by two SFC types. There are two options I can think of... Does it have to be two SFC types? Or could it be SFC charts? In case of two SFC charts, you can use the ShrdResL block. This is a block between your SFC's and Control Module and will determine which SFC can control the valve. You don't want to have one SFC in abort (where it must set the CM to rest position) and the other SFC wants to control the CM because somebody activated the verification run... So what the block does, is prioritizing which SFC can control the CM. Reset, Automode/Handmode all exist on the shared resource block (see attachment). But looking at ISA88, where a Equipment Module controls a Control Module, only one SFC is responsible for controlling the CM, not several, you may want to look at using a Control Strategy which I think is the better choice. You can name the CS: Verification, and you create this for each SFC which has valves you need to use for the verification process. In that CS, you will open and close the valves. When done, the SFC is set to STOP or ABORT, bringing the SFC back to IDLE. Then when the process starts, another Control Strategy (Production) is started and it will start up the process. In that way, the CM is controlled by only one SFC, you can use a general SFC which will start all SFC types (EMOD) to CS: Verification. In the general SFC, check if all SFC went to STOP or ABORT(which means closing all valves) and then ready. |
If I could help you, you can use the RATE button. Thank you. |
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