They are installed to relieve pressure before a valve is opened.
They are connected to all piping and hose connections to prevent a massive release in the event of a catastrophic line break; NH3 only.
They measure the pressure inside a tank, usually a range of 0 - 400 psi.
They indicate when a tank reaches the 85% liquid level. Trace vapors are released when liquid level is below 85%; A puff of white smoke is released when liquid level is at or above 85%.
Liquid level gauge reads the percent (%) of total tank capacity. Capacity of tank (gallons) times the percent reading equals gallons.
It transmits the pressure readings to the PLC to display on the screen for operators.
It transmits the level readings to the PLC to display on screen for operators.
It transmits the temperature readings to the PLC to display on screen for operators.