Unexpected vacuum ...

[Frank S]

I don't think he saved the PTO either.

Some PTO driven rotary vacuum pumps have ceramic vanes in them others have a fiber vane set what happens is a sudden implosive loss of vacuum will mean the building negative pressure on one side of the vanes instantly becomes neutral or possibly a positive pressure causing the vanes to shatter inside of the groves of the rotor.
Now as to what should have been done to prevent this. First off the operator was not even in his vehicle to monitor any gages if he even had any to monitor.
As to what caused the implosion the suction line became blocked with solids somewhere along the length or most probably at a connection or valve. Quite possibly it may have never been opened in the first place after the operator had pre-charged his tanks with vacuum, in combination to this the relief vent valve would have had to fail. and about the only way those can fail is for the tanks to have been previously over filled or the sloshing of the materials in side the tanks had sloshed in transport and solidified on the vent stem and spring. Every time the tanks are emptied the operator is supposed to physically force the vents open and allow to close several times to insure nothing has built up on them. Since vacuum tanks are also pressure vessels since positive pressure is how they are emptied they would also have pressure relieving valves. the Vacuum pump is normally ran in reverse turning it into a compressor.
Operator training and maintenance are vital to these as well as any other type of machinery.