Procedures designed to safeguard workers from exposure to electrical hazards, the unexpected startup of machinery, or the release of fuel while equipment is being serviced.   This requires, in part, that a designated individual turns off and isolates the equipment from its energy source(s) before performing service or maintenance.   The designated individual either locks or tags the breaker(s) or valve(s) and takes steps to verify that the equipment has been isolated effectively.  


(see PEI RP900 - Recommended Practice for the Inspection and Maintenance of UST Systems)