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Posted by tmiller on February 15, 2007 at 21:16:00:
In Reply to: Saftey valve question posted by Bill on February 14, 2007 at 20:24:00:
Bill,
The ASME Code for Power Boilers Section 1 should be your reference for safety valve application, and you should contact your insurance company as well as the Boiler inspector for your juristiction. One of the safety valves is allowed to be set at 3% above MAWP for your boiler. The others have to be within 10% of that setting. The combined capacity should be able to prevent your boiler pressure going over 106% of MAWP.
They should each lift at different pressures so as not to upset your drum water level, in other words if they were to all lift at the same time you will have a very false indication of high water level and soon be in a whole world of operating trouble. The safety valves are each of a different steam PPH capacity so that you can relieve excess drum pressure with the least disruption to the boiler. If you are steaming at anything less than 24,000 PPH with your boiler you obviously will not need all three safety valves to open to prevent your boiler from going 6% over MAWP.
Perhaps others actually involved in design will offer you some feedback. Tom
I have a CB 600 hp fire tube boiler. It has 3 saftey valves on top all are set to pop at 150#. Why is each one a different size? One is 6000# per hr, one is 8000# per hr , and one is 10000# per hr. The total is 24000# why not have 3 8000# valves? Is there some reason for this? Thanks Bill