How to create an instrumentation loop drawing, say for instrument air vessel?
Piping and Instrumentation (P&ID) diagram shows the several instrumentation loops connected with particular equipment.
P&ID shows the signal path of instruments and gives an overall picture of the connected loops in the system, whereas Instrument loop diagram gives a clear idea of the instrument connected with the system.
How-to Create Instrument Loop Diagram
- Instrument loop diagram (ILD) represents a connection from the field instrument to Control Room. (vice versa)
- Instrument loop diagram is divided into two basic sections. One is the field side and other is Control Room side. (vice versa)
- Fieldside is again divided into field area and Junction box.
- Control Room side is divided into marshalling cabinet rear, Marshalling Cabinet Front.
The following data is required before starting drawing on paper for a loop diagram
- Tag No of the instrument, JB Number, Terminal block and its termination number, Marshalling cabinet and Termination details. System card and I/O details.
Sample Instrumentation Loop Drawing (ILD)
- Pressure transmitter PIT-01 mounted field-side it is connected by a single pair cable with red and black cable with red as (+) as 1 black (-) as 2.
- The cable connecting to junction box Tagged (JBA-01) is a single pair. Terminating in JB terminal block (at TB15, TB-16). The termination is square-shaped cable connects at IN and OUT.
- Cable from JB is terminating in Marshalling cabinet (MXA-01) number and Terminal Block number (terminal number TB15, TB16).
- Instrument sleeve is grounded at marshalling cabinet only, need not at an instrument or at junction box.
- Cable from Marshalling cabinet is connected to System I/O card.
- On the bottom right below, the details of the organization name, drawn by, verified by, approved by can be seen.
Example Loop Diagram
Author: R. Jagan Mohan Rao
- Instrumentation Functional diagram
- Transmitter Calibration Procedure
- Process Flow Diagram (PFD)
- Single Line Diagram (SLD)
- Setpoints and Alarms in Control System