The request
“Create an interlocked valve ladder with open and close pushbuttons, seal-in contacts, a normally closed emergency stop, a valve B closed permissive, and separate open and close outputs for valve A.”
Then tryAdd open and closed limit switches for valve A.Add an alarm output for emergency stop.
What is in this drawing
Read the decisions behind it.
01
Seal-in logic for maintained command using parallel branched contacts
02Cross-cancellation
open pushbutton drops close command and vice-versa
03
Series XIO contacts for emergency stop and permissive interlock (valve B closed limit)
Any process automation where safe valve sequencing is critical, e.g., chemical dosing, water treatment, pharmaceutical batch control.
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