The Loop checking is defined as pre-Commissioning activity which is initiated after installation of instruments at x location to y location instruments or systems.
Loop checking is basically done to ensure the instruments installed at x and y location has continuity signal with each other potential’s.
If we want to loop check the continuity from instrument to junction box this is achieved by laying a cable between instrument and junction box.
Normally after installation and cable laying during construction activity is to be ensured that instrument and cable and junction terminals and cable which is layed underground or above ground & is not damaged to confirm this damage it is mandatory to carry out loop checking between instruments-junction box- DCS that is from field to control room.
Simple Process:- is short the two cores of cable at one end and check with digital multi-meter at other end if the circuit resistance is ok then the same cores have the cont unity which means that the cable cores are’nt damaged. above procedure also helps to identify the particular cable cores for specific system function
Above process is called as Cold Loop Checking loop checking without any external source simulation.hence called as cold loop check