As already described in previous posts (such as here and here), I was involved in EPC project. Creating piping and instrumentation diagram (P&ID) is one of my responsibility. I think P&ID is a collection of information and collaboration of every discipline, such as process, mechanical, electrical, and instrumentation. Once I think creating P&ID is easy enough, but I change my mind then. It is not.
I revised my P&ID (water treatment plant, fuel supply system, and wastewater treatment plant) several times. I am not quite sure if I am a kind of diligent person, but I am sure creating “perfect P&ID” requires a lot of works and patience. I sometimes think there’s nothing wrong with my P&ID. However, if you let someone, for example your colleagues, your boss, or someone with more experiences than you to check your P&ID, you will laugh at yourself. It happened to me. My P&ID was far from perfect. I understand now. Perfect P&ID requires continuous improvement.
Today I tried to revise my P&ID and I found there are so many things to consider, a big one and a small one.
Piping and Instrumentation Diagram is a diagram in the process industry which shows the piping of the process flow together with installed equipments and instrumentation (source). It used to operate the process system.
While creating P&ID, I tried to make sure the list below are presented in my P&ID.
- Instrumentation and designation, such as pressure gauge, level switch, temperature control, and so on, and how they work in controlling the system
- Mechanical equipment. Don’t forget to mention tag number, name of equipment, quantity, capacity, dimension, operating and design pressure, operating and design temperature, material, dimension, and other necessary parameters
- All valves. You have to make sure all valves in your P&ID are in correct type and correct size.
- Line identification. Make sure you write the identification of pipe, such as size, material, service, pressure rating
- Flow direction. Don’t make your readers confuse because you don’t write flow direction in your P&ID
- Control inputs and outputs
- Identification of equipment supplied by other. You have to remark which component supplied by vendor which component supplied by yours
- Interconnection references. Don’t forget to write correct references, for example if your water will be supplied to boiler system, then you have to write P&ID document number of boiler system in your water treatment plant P&ID