Instrument Loop Diagram- Numbering Philsophy

Are you the end customer, or are you designing a facility for the end customer? Depending on your answer, I would consider asking the customer what they do in other parts of their plant (assuming there is an existing plant).

I guess what I'm saying is that there is no fixed absolute answer, although I would tend to prefer your 2nd approach. The common 182 part of the number indicating all the devices are related to the same piece of equipment, the M, T, and V suffixes indicating different devices on that piece of equipment.

I tend to prefer that to three completely different numbers, like 182 blah blah, 183 blah blah, and 184 blah blah.

What happens when, either during design or during later maintenance of the facility, another device is added to the motor (for the sake of an example, a vibration detector)?

I tend to agree with RH. I often try to follow the ISA convention -

RTDs might be TE-182MA, TE-182MB, etc.

Start/stop (hand switch) - HS-182M (with a SS subscript outside of the bubble).

Vibration sensor could be a ZE-182M

We use the same philosophy with a control loop (for instance a temperature control loop with a valve) would be -

TW-XXX, TE-XXX, TT-XXX, TIC-XXX, TCV-XXX

That would be ThermoWell, Temperature Element, Temperature Transmitter, Temperature Indicating Controller, Temperature Control Valve - all with the same loop number.

Hi Josej

I have been working as an instrument engineer for 35 years. I can tell you that there are no hard and fast rules on this matter. It is preferable to have all the information on one loop assuming there is enough space on the piece of paper.

If there is not enough space on your piece of paper then it is no big deal, simply make 3 separate loop diagrams 1) Motor Winding 2) Vibration 3) Start/stop, local/remote & running indication.

I would suggest 3 separate loops (to much info to put on one drawing) and cross reference the loop drawings against each other in a note on each loop drawing related to that motor.