A manual ¼ turn ball valve (#1) was the lead isolation valve in a Double Block and Bleed arrangement. The valve handle was incorrectly secured using a run of pipe BELOW the valve. As shown, the valve handle would swing down in order to OPEN the valve. With the chain securing the valve on the piping below it, it was not secured in its SAFE/CLOSED position. The bleed valve (#3), at ground level, was LOCKED OPEN as required. A worker on a scaffolding overhead of valve #1 drops a large pipe wrench which made contact with the handle of valve #1 and cracked opened the valve, causing a reportable release of chlorine and trapping dozens of workers on the scaffolding – unable to evacuate the unit.
CLICK HERE to download the .pptx