Re: Sumpter Valley Boiler Work - WH Eccles #3

I had a lesson on lapping this throttle years back by CMO Scott Hutton. The trick to getting it or perhaps any double seated throttle tight is to lap one seat more than the the other so it is not quite tight when cold. When hot and the throttle body expands perhaps a bit more than the spool, it will be steam tight. One does this by lapping both seats, then cleaning the abrasive off of one and simply oiling it, and lapping the other just a magic bit more. At that time he lapped it with an electric drill, rather than the usual back and forth motion. I have no idea the pros and cons, but I thought the concept of allowing for unequal expansion of the body with respect to the spool was interesting. As an after thought I will add the circumstances whence I got this lesson. We were expecting the FRA the following morning to witness the hydrotest as part of the annual inspection. We decided the evening before to give it a pre-hydro test just to make sure everything would go right the next morning. We were still using the old manual pump for the hydrotest that would use up the arms of several volunteers before it was over. I for one pumped and pumped and pumped and never could get it up to pressure as we had such a leaky throttle. I was delegated to call Scott our volunteer CMO at home and ask him to come out that evening so we could be sure all would be well in the morning. He was not entirely pleased with being called to the late evening mech. session, so I shadowed him to give him every help I could. Being the good natured guy that he is, was pretty jovial and good about sharing how the process should work.



Edited 2 time(s). Last edit at 05/20/2015 10:10PM by J.B.Bane.