Isolation verification test
Single valve isolation integrity test
M1- Operational (upstream) monitoring point.
M2- Monitoring point between valve and off position (downstream).
Ensure that the flow rate at M1 and M2 is unimpeded and that the pressure gauges installed there are working properly.
Close the isolation valve and hold it in the closed position.
Record the M1 and M2 pressures.
Vent/purge the downstream section of the pipe to be opened and monitor the M2 pressure reading close to 0.
Close the downstream vent/vent valve and monitor M2 readings for at least 10 minutes. (No pressure increase at M2 indicates single valve integrity)
Open the vent/vent valve on the downstream disconnect section and maintain its open position.
Accident Case 4
Insufficient isolation resulting in death by contact with live cable!
An electrician was checking an existing wire in an office ceiling when he came in contact with a live wire coming from another floor through the ceiling. Building managers have placed the office floor under electrical isolation, but live lines from the other floor have not been isolated. The electrician was later found collapsed on a cable bridge and died after emergency treatment.