Posted by jmihalov on November 16, 2001 at 12:33:17:
In Reply to: Re: CBLE 800hp Tube End Splitting posted by tom stanton on November 16, 2001 at 07:39:24:
: I am assuming this is a high pressure steam boiler and you are talking aabout the inlet to the 2nd gas pass. The cracking is sometimes due to overfiring(going into high fire too quickly). There is a lot of heat entering the second gas pass. When the seal weld cracks, it will usually propagate into the tube wall, eventually causing the tube to leak. You also might want to check the ligaments (area of the tube sheet between any two tube centers). Oftentimes these ligament cracks will appear, but are not easily seen unless you use some form of NDE, like dye penetrant. I do not see the door as the problem because as the combustion gas exits the furnace tube it immediately enters the 2nd gas pass.
Thanks Tom, That's what we're thinking. I'm mechanically limiting the firing range to avoid the overheating issue. Looks like the 800hp is a trumped up 700hp!