Control loop P&ID

I am trying to add the control loops to a p&id diagram however I am not sure how to put them in to the system. One example that I have is an orifice plate for flow. Could you guys show me where each component goes in the loop and whether this is the same order for other parameters too?

thanks in advance

Can you give a bit more info/upload the original question?

its not an exact question but the problem is to incorporate a control loop into a p&id to measure flow, where the sensor is an orifice plate and the control action is reverse.