Instrument loop checking and calibration are important activities performed at the end of an installation to ensure that all components of a loop function properly and can support successful startup, commissioning, and qualification procedures. Loop check and calibration are performed concurrently to verify that ranges, scale, and graphics are correct from the front end to the field devices.
Preparation for loop checking and calibration should include the development of loop sheets and step-by-step calibration procedures that specify whether single-point or three-point calibration is to be performed. Calibration sheets must identify critical and non-critical instruments and specify at what intervals the devices will need to be calibrated. Calibration should be scheduled as close to validation as possible.
A thorough walk-down of the installation should be always performed prior to loop check to make sure everything is in place and ready. It is advantageous on larger projects to have a second team follow up and correct identified problems and anomalies on larger projects while the first team continues with loop check and calibration. Close communication, organization, and follow-up are key components to a smooth and successful loop checking and calibration process.