Propane tank pressure relief valve keeps opening?

[Jotel me this]

500 gal residential propane tank. the propane company came last month and zip tied the rubber dust cover closed so that "the wind wont blow it open or someone wont brush against it"... they think im lying.

i come home tonight and low and behold.. the cover is popped off AGAIN. no smell of propane, no hissing.

what is going on? its cold, its winter.. how is pressure building up to 300psi and blowing the cap off??

The real thing im wondering is.. do i LOSE propane every time it blows? the gauge doesnt seem like its gone down any.

They constantly give me a hard time.

 

[peakbagger]

If a propane tank is overfilled and there is a sudden warm up it can vent.

I had a friend that used 5 gallon propane bottles in his ice shack in the winter. He would have the propane dealer fill them as full as possible and I expect over what they should have put in the tanks. It worked as long as the tanks were not put in warm place. He had a heated garage and one time he had brought them in after filling and we could smell propane and hear the reliefs hissing. I wonder if its the same issue? In this situation the relief will pop and vent propane but not very long. I expect your gauge would not see it.