How to Read a P&ID - Pressure Control

This diagram displays a pressure control scheme for a Hot Water Storage vessel (V-100). The pressure inside the vessel is regulated by a pressure indicator controller (PIC 101) which controls a nitrogen supply valve (PY 101A) and a vent valve (PY 101B). The system also features a temperature control loop using a heat pad and a level monitoring system.

Source: images.png · Components: 15 (1 equipment, 9 instrument, 5 valve)

Equipment (1)

Tag Description Details Connects to
V-100 Hot Water Storage Tank Service: HOT WATER STORAGE, includes HEAT PAD V-1, V-2, TT-102, PCV-101A, PCV-101B, PY-101B-mid, relief-valve-1, LG-2, LT-100, TIC-102

Instruments (9)

Tag Function (ISA 5.1) Description Details Connects to
TT-102 TT = Temperature Transmitter, loop 102 Temperature Transmitter — V-100, TIC-102
TIC-102 TIC = Temperature Indicating Controller, loop 102 Temperature Indicating Controller — TT-102, V-100
PY-101A PY = Pressure Relay / Solenoid / Convertor, loop 101A Pressure Transducer / Relay — PIC-101, PCV-101A
PIC-101 PIC = Pressure Indicating Controller, loop 101 Pressure Indicating Controller — PY-101A, PY-101B-top, PY-101B-mid
PY-101B-mid PY = Pressure Relay / Solenoid / Convertor, loop 101B Pressure Transducer / Relay — PIC-101, V-100
PY-101B-top PY = Pressure Relay / Solenoid / Convertor, loop 101B Pressure Transducer / Relay — PIC-101, PCV-101B
LG-2 LG = Level Gauge, loop 2 Level Gauge — V-100
LT-100 LT = Level Transmitter, loop 100 Level Transmitter — V-100, LI-100
LI-100 LI = Level Indicator, loop 100 Level Indicator — LT-100

Valves (5)

Tag Description Details Connects to
V-1 Normally Closed Valve N.C. (Normally Closed), Hot Water Line V-100
V-2 Normally Closed Valve N.C. (Normally Closed), Outlet to Users Line V-100
PCV-101A Nitrogen Pressure Control Valve — PY-101A, V-100
PCV-101B Vent Pressure Control Valve — PY-101B-top, V-100
relief-valve-1 Pressure Relief Valve Vents directly to atmosphere V-100

Notes on drawing