In my time in petro chem I had two releases (Cl2 and Br) that were caused when the handle of a 1/4-turn ball valve (bleed) was accidentally OPENED (one by a utility hose and one by a pant’s leg). Here is another example from The European Process Safety Centre (EPSC)
What Happened:
During scaffolding maintenance work, a valve was inadvertently opened. This valve was in the refill line of a pump seal pot containing a flammable liquid. As the outflow of the seal pot was also inadvertently open, approximately 9 tons of the liquid were released through a header to a sump.
Aspects:
- The red ball-valve handles can be easily opened when touched accidentally. The presence of the scaffolding increased the likelihood, as people walk close by, and scaffold builders carry pipes that can touch the handle.
- The pump isolation plan, should include the closure of seal liquid, both in and out the seal pot. A LOTO system can help to avoid accidental change of the valve position.
- When checking scaffolding and releasing it for use, it is good practice to check for vulnerable hand valves, that can be easily changed in their position, and lock these.
- Some valve handles are less prone to by moved accidentally, as you first need to squeeze or press them.
Source: https://www.epsc.be