Abstract: A rupture disk assembly comprising two rupture disks which form a chamber. The chamber is connected by a first line to the interior of a vessel on which said rupture disk assembly is mounted and a valve in the line reduces the pressure in the chamber to less than 90% of the pressure of said vessel. A second line connects the vessel and a pilot valve, and a third line connects the chamber to the pilot valve and has a pressure reduction valve in the line to prevent flow from the pilot valve to the chamber. The pressure in the chamber is static and said pilot valve is closed while the pressure in the vessel is at or below the set pressure of the pilot valve and a flow is established through said chamber when the pressure in the vessel exceeds the set pressure of the pilot valve.

Abstract: A device for providing visual indication and record of the actuation of a tank vent opening the comprising a rod contacting a tank vent pallet at one end and a magnet affixed to another end of said rod, which moves in a chamber adjacent to a set of vertically positioned rotationally mounted magnetic wafers with visually distinguishable sides. The magnets all have the same polarity then the rising magnet occasioned by the opening tank vent will flip the wafers as far as the magnet travels, but will not affect the wafers when it goes down after the vent closes.