Developing the Piping and instrumentation diagram (P&ID)
- Know the symbols for all kinds of valves
- Know how to represent various instruments on P&IDs using ISA 5.1 standard
- Know how to construct the various abbreviations for instruments on P&ID
- Know the common signals and their representation on P&IDs
On the developed P&ID, please note that:
(a) we were told the gas vessel instrumentation should have an inlet valve. On the P&ID, inlet valve HV 107 is provided to manually regulate gas flow into the vessel.
(b) A pressure transmitter and a pressure indicator is to be provided to indicate inlet pressure. On the developed piping and instrumentation diagram, PT 101 and PI 101 are provided for this purpose. PT 101 measures the inlet pressure and sends the measured value via electrical signals to the pressure indicator, PI 101
(c) A flow transmitter and a flow indicator are to be provided to measure and indicate flow. Also, instrument for alarming high and low flow rates are to be included. On the developed P&ID, FT 102 measures the flow and FI 102 indicates the flow. Also FAH 102 is a flow alarm switch for indicating high flow rates while FAL 102 is for indicating low flow rates
(d) A pressure safety valve is to be provided in the instrumentation to relieve and vent excess pressure to a flare system. On the developed P&ID, PSV 104 is provided to relieve excess pressure and protect the gas vessel.
(e) A manually controlled hand valve is to be provided on the gas vessel outlet header. On the developed P&ID, hand valve, HV 105 is provided.
(f) A pressure transmitter, a pressure indicator and controller and a control valve are to be provided. On the developed P&ID, PT 103 is the pressure transmitter that measures the gas vessel pressure and sends the signal (electrical) to PIC 103, a pressure indicator and controller to indicate the measured pressure and at the same time send a command pneumatic signal depending on its setpoint to actuate the pressure control valve, PCV 103
(g) Instrumentation for alarm to indicate high vessel pressure is to be provided. On the developed P&ID, pressure alarm switch PAH 103 is used to signal an alarm for high vessel pressure
(h) A check valve on the outlet header is to be provided in the vessel instrumentation. On the developed P&ID, CV 106 is the check valve provided to prevent back flow into the gas vessel
(i) Lastly, a pressure transmitter and pressure indicator is to be provided to measure and indicate gas outlet pressure. On the developed P&ID, PT 108 and PI 108 are performing this function.
If after going through this piece you still have some difficulty, I will advise you go through all the introductory posts on piping and instrumentation diagrams before coming back to study Tutorials II