How can I read a control loop ??

[zadi]

Hi,
I need a scource of how to read a control loop from a drawing plz
can you help me plz?
Thanks

 

[EmmanuelTop]

How to read P&IDs:

http://www.controleng.com/article/CA152141.html

Going through control narratives, control & safeguarding philosophy etc. will also give you clear understanding of control loops.

 

[JLSeagull]

Things change. The original P&ID symbols were developed with "single loop" controllers in mind whether pneumatic or electronic. The line in the circle indicates a control room panel compared to a local controller with no line. These single loop controllers required two panel instruments to implement the cascade controller shown with a temperature controller providing the setpoint to the flow controller in the Control Engineering example. Microprocessor based controllers were made that could handle both loops within one box. The DCS initially handled several loops and a shared visual display such as a CRT operator console. The control was done in a "blind" rack mounted controller. Many companies are implementing control using Foundation Fieldbus or other communications besides 4-20 mA signals. The PID (proportional, integral, derivative) control can be done in the transmitter, a DCS controller or the valve transducer. Some symbols or notes may be implemented to indicate control if done in the field components. Things change.

 

[zadi]

Thanks EmmanuelTop for providing the link
and thanks JLSeagull for the update