Overturned tank cars pose special problems. When impact or loss of balance rotates the tank past 45^o, relief valves automatically seal to prevent environmentally hazardous spillage. This seal must be released under controlled circumstances to allow drainage without leaks. When the specialized Perry Valve Tool (shown right) is attached to the tank car's valve stem, it uses distinctive packing glands and pressure containment housing to mechanically overcome spring tension, allowing the valve to be opened. At that point, the tank car's contents can be safety pumped through a hose or pipe connection into alternate storage or transport facilities.

For more information see: Ethylene oxide successfully removed from overturned tank car