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Old 03-28-2008, 03:54 PM
Alan Bates Alan Bates is offline
Join Date: Apr 2006
Posts: 841

Bob, I do not know when hydrostatic tests were first required by law, but it was well before 1900, not only for steamboats but for practically ALL boilers On the Belle of Louisville we called it "squeezing." The technique was to run the pressure up to 1.5 times the allowed pressure, close the valve at the pump and wait a required time watching a pressure gauge. If the pressure dropped a search was made for the leak(s) throughout the steam system and repairs made. Safety valves had to be gagged to prevent their opening at the allowed pressure. I do not recall how long the test pressure had to be sustained. The reason for testing with water is that water under pressure will not explode - at least not like steam. In addition a water leak can be seen. Steam is invisible. The tests had to be observed by a Steamboat Inspection Service inspector.

There are a lot of reasons for boiler explosions other than tampered-with safety valves. Dirt, excessive foaming, tubes or flues not covered by the water in the boiler, dirt, scale formation, tools carelessly left inside, the list is endless.

Chet Foster, engineer on the Belle of Louisville served on a couple of boats with the old-time lever safety valves. He said they did not hang extra weight on the lever because it could still open and they would "lose their water," so they jammed a post between the lever and the deck overhead! That way the valve absolutely could not open. They were careful to let the pressure drop before removing the post.

Those lever safety valves were "grandfathered" into the 1930's.
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