PT Loop Diagram Faults

Determine whether or not the following pressure transmitter (PT) loop faults (considered individually) could account for this air pressure regulating system failing with zero pressure in the receiver vessel.

PT Loop Diagram

Answer either “yes” or “no” for each fault mentioned below:

• Receiver vessel drain valve left open
• Transmitter block valve shut and bleed valve open
• Transmitter block valve open and bleed valve shut
• PIC left in manual mode, 100% output (20 mA to I/P)
• Cable PV-6 severed (failed open) •
• I/P air supply shut off
• Short between TB-52, terminals 1 and 2
• Short between TB-52, terminals 15 and 16
• PT-6 miscalibrated, registering 5 PSI too high
• PY-6 output failed high (15 PSI)

Answer:

Receiver vessel drain valve left open – No

Transmitter block valve shut and bleed valve open – No

Transmitter block valve open and bleed valve shut – No

PIC left in manual mode, 100% output (20 mA to I/P) – Yes

Cable PV-6 severed (failed open) – No

I/P air supply shut off – No

Short between TB-52, terminals 1 and 2 – Yes

Short between TB-52, terminals 15 and 16 – No

PT-6 miscalibrated, registering 5 PSI too high – No

PY-6 output failed high (15 PSI) – Yes

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Credits: Tony R. Kuphaldt