Oil&Gasfag / Valvefag here.
The Massachussets gas overpressurizations and explosions are exceedingly unlikely / close to impossible to be "accidental". Fuckery afoot here.
My experience with oil & gas and valves is mostly upstream and offshore, but I have some downstream natural gas pipeline experience.
Too improbable to have multiple, simultaneous failures of independendent Safety systems.
● Overpressurization safety system will automatically trip systems to relieve pressure
● Emergency Shutdown systems will automatically trip and shut down compressors
● Blowdown systems will automatically trip and divert excess pressure from the main lines.
"Trip" means to automatically activate, by force. No manual intervention is required. It is difficult but possible to manually override a safety trip.
In this mess of gas explosions in MA is fairly obvious that multiple, independent safety systems failed to operate, at the same time.
Do you have a boiler for a water heater in your house? It has an automatic Blowdown system to release excess pressure so the boiler cannot explode. It is spring operated, and it is automatic. A spring holds a seal in place against a small blowdown opening. If the pressure exceeds the rated capacity of the boiler, it is sufficient pressure to push the spring open and allow pressure to vent out of the boiler, until the pressure drops back to normal, and the pressure is no longer enough to push the spring in an open position. This is a simple physical example of an overpressure Safety system, which is independent of the operating system.
Example of Emergency Shutdown valve system. The Emergency Shutdown (ESD) valve is held open by standard 80 psi instrument air, which is provided by separate 1/4" stainless steel tubing. The instrument air is provided by the compressors which provide 80 psi instrument air throughout the plant. If the instrument air fails (compressor stops due to fire, explosion, electrical failure, etc) then the compressed springs which are held open by the 80 psi instrument air are tripped and the compressed springs force the valve to close, shutting off the flow of oil and gas.
Think of the trigger on a gun. Once the compressed spring is tripped, the trigger moves forward from the open to the closed position, which also strikes the bullet.