Re: stays ?
Posted by: Jeff Theobald
Date: April 9, 2006 06:39PM
To my knowledge the original Brooks boilers were fitted with steel tubes that were welded at the fireplate end and swaged in the smokebox end, Stanley’s were fitted with copper tubes swaged at both ends, each tube acting as a stay in a minor way, but with so many, so closely grouped the overall effect was the same as stays.
It only seems to be the modern way to fit welded stays, when we had the boiler built for the Brooks, six welded stays were specified, this gave all sorts of problems when the boiler was put in service, it would leak very badly whenever it felt like it, we thought this was being caused by uneven expansion between the welded stays and the swaged tubes, so we had the stays removed and very thick walled 1” dia copper tubes fitted with restrictors to the diameter of the normal tubes, (these are the tubes you can see). This cured the problem and I have had 20 years service from it, although it still does odd things occasionally, when it comes to testing the boiler looks much the same as it did when first fitted, all ultrasonic test have shown little or no deteriation.
We have an endoscope which we use to look inside the boiler wherever a fitting hole has been made. In the areas it is possible to look, it looks clean, with no scaling on the boiler wall, the tubes that can be seen are clean, we have found a very fine coating on the bottom of the boiler, inside on the fireplate, it has the consistency of tooth paste and can be washed out to a degree, I have tried various chemicals to shift it, without much luck, these days I check it each time we inspect the boiler, and during each year of use blowdown after each steaming.
To answer your original question, boilers can run at 500 to 600psi with expanded or welded tubes, we test to 1.5 times working pressure plus 10% for the very first test (1000psi) but never more than 1.5. after that, we feel it is possible to damage your boiler if taken higher.
I hope this helps, Jeff.