TSH and TSHH

[Dale Hayes]

What is the difference between a TSH (Temperature Switch High) and a TSHH (Temperature Switch High High). What characteristics determines how a temperature switch is labeled on a P&ID. The TSH can also designate (Temperature Shutdown High)

 

[weressl]

What is the difference between a TSH (Temperature Switch High) and a TSHH (Temperature Switch High High). What characteristics determines how a temperature switch is labeled on a P&ID. The TSH can also designate (Temperature Shutdown High)

S as the Second letter is reserved for Switch according toth e ISA S5.1.

The H indicates a value above normal range, the HH indicates a value above H.

Most frequently H is used for alarm and HH is for shutdown, but that is not functionally determined, they can do many other things.