U.S. Air Force Senior Airman Jason Holmes, a 316th Civil Engineer Squadron firefighter, connects a gate valve to a fire hydrant during a hazardous materials (HAZMAT) exercise Feb 1, 2010, at Joint Base Andrews, Md. Gate valves help the firefighter slowly release water to the fire engine, to control pressure changes and ensure there is no air in the hose. HAZMAT exercises are conducted to maintain proficiency in response procedures and decontamination techniques. (U.S. Air Force photo by Airman 1st Class Perry Aston/Released)

Boiler pressure relief valve works then. 26041 waits outside Achnasheen with the 0705 Kyle of Lochalsh to Inverness on the 17th march 1984. My annual spring trip to Scotland was not a dissapointment this year however no 40s were had but plenty of McRats and some 37s and a bag full of nice shots.