Loopchecking procedure is just a simple thing. You have TDC3000 DCS. And you have Rosemount smart transmitters. It should be Hart compitable. Firstly connect your hart communicator to the feild device or anywhere in the loop with a 250 ohm load resistor. Go to loop check menu and simulate 4,12,20 mA. Cross check on the system to get the exact values in % on the system.Apply this to all analog inputs and for digital inputs changeover the contacts and check on the system. For control valves open in percent from the system and check in the feild.
We have a TDC3000 utilizing Honeywell transmitters (instead of the before mentioned Rosemount). Loop check is a means to shorten the time for "cutover" (or actually commissioning the new instrument). During the loop check, the entire loop is connected from transmitter to DCS Gus. The instrument is not connected to the process at this time. Communication from DCS to instrument is verified. In some cases air pressure is applied to the instrument (for a PT, I/P, etc.) and a movement on the indication (or pressure) is verified. These steps are done prior to the cutover so that during the cutover phase, work can proceed in an accelerated manner (otherwise you would have to check all this each time for each loop). Many times wiring is not terminated right, etc. These problems are caught early and fixed. Our cutover was done with the unit running, so commissioning the loops in a accelerated fashion was very valuable to us. All we had to worry about were the process connections (not the electrical connections).
A DCS GUS is what Honeywell calls a "Global User Station". It is the acutal computer that interfaces between the IOP cards (Input Output Processors) and the Operator. The monitors that operators use to veiw and control the unit processes are connected to these GUS computers. The field inputs and outputs are connected to the IOP cards.
