What’s the safest way to simply interlock a pig launcher door?

Pigging operations, involving the loading and unloading of cleaning or inspection pigs into the launcher or receiver have the potential cause serious injury, death and damage to equipment if not carried out under the strictest procedural guidelines.

Pig Launcher System

Even the best training or written procedures cannot safeguard against human error. Fundamentally, the potential for incident occurs when opening the pig launcher or receiver door. At this time, the launcher/receiver vessel can be under pressure, charged with hazardous liquids and gases. Opening the vessel without correctly isolating, venting and draining can cause the trap door to fly open with the pig exiting the vessel like a missile.

There are anecdotal accounts of such accidents available on the internet. Two links are provided here.

http://www.ncbi.nlm.nih.gov/pubmed/15553280

http://www.bsee.gov/Inspection-and-Enforcement/Accidents-and-Incidents/incidents/96-0069-pdf