Boiler Repair Assistance
Boiler Repair Assistance
(OP)
June 21, 2013
Dear All,
I was called by the owner of a candy factory to repair their 150 Bhp Ray Boiler manufactured in 1999 with a maximum design pressure of 150 psig. Their boiler operates at a maximum of 100 psi and uses bunker fuel. It is a three pass boiler which had some leaking tubes at the rear section of the end of the first pass. The boiler is constructed wherein all its ends are expanded/rolled at the tube sheets with flared ends.
The boiler's appurtenances such as main steam valve was blinded including removal/blinding of main steam valve and isolation of safety controls. After which a hydrostatic test at 225 psig was conducted. i was able to identify certain leaking tubes at the rear section of the end of the 1st pass. I had rolled and expanded the tube ends numbering 27 pcs. and conducted another hydrostatic test at 225 psig with no more leaks. I gave instructions that the boiler could be operated normally.
In less than two days of operation, the boiler leaked. We again subjected same to hydrostatic testing and identified the leaking tubes. Later, we inspected water column and found no water blowing off. We decided to open all manholes/covers and flushed scale/sludge out.
After seeing the water clear, we closed all and subjected the boiler to another hydrotest at 225 psig and rerolled the 27 +2 or a total of 29 tubes. With no more laaks we had boiler operated.
Initially after operation of 4 hours, no leaks but after boiler was stopped it leaked again. I was informed that the same tubes expanded leaked.
Would like to know or get feedback why after a successful hydrotest of 1.5 times the maximum operating pressure, boiler leaked. and what other things should i take into consideration in repairing this boiler.
I was also thinking of descaling the boiler and subject same to hydrotest or replace all leaking tubes? Thank you.
Dear All,
I was called by the owner of a candy factory to repair their 150 Bhp Ray Boiler manufactured in 1999 with a maximum design pressure of 150 psig. Their boiler operates at a maximum of 100 psi and uses bunker fuel. It is a three pass boiler which had some leaking tubes at the rear section of the end of the first pass. The boiler is constructed wherein all its ends are expanded/rolled at the tube sheets with flared ends.
The boiler's appurtenances such as main steam valve was blinded including removal/blinding of main steam valve and isolation of safety controls. After which a hydrostatic test at 225 psig was conducted. i was able to identify certain leaking tubes at the rear section of the end of the 1st pass. I had rolled and expanded the tube ends numbering 27 pcs. and conducted another hydrostatic test at 225 psig with no more leaks. I gave instructions that the boiler could be operated normally.
In less than two days of operation, the boiler leaked. We again subjected same to hydrostatic testing and identified the leaking tubes. Later, we inspected water column and found no water blowing off. We decided to open all manholes/covers and flushed scale/sludge out.
After seeing the water clear, we closed all and subjected the boiler to another hydrotest at 225 psig and rerolled the 27 +2 or a total of 29 tubes. With no more laaks we had boiler operated.
Initially after operation of 4 hours, no leaks but after boiler was stopped it leaked again. I was informed that the same tubes expanded leaked.
Would like to know or get feedback why after a successful hydrotest of 1.5 times the maximum operating pressure, boiler leaked. and what other things should i take into consideration in repairing this boiler.
I was also thinking of descaling the boiler and subject same to hydrotest or replace all leaking tubes? Thank you.





RE: Boiler Repair Assistance
How much did you expand the existing tube? Did you measure the percent wall reduction after rolling? Did you have a tube rolling procedure?
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http://www.oatey.com/doc/boilerliq.pdf
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and I've seen the opposite -- it worked fine -- too. Without a detailed exam, everybody [including me] is guessing.
He needs to hire an EXPERIENCED small-boiler repair company to evaluate his boiler prior to comming up with ANY repair recommendations. The tubes could need to be replaced and seal-welding will only stop the leaks for a month or less. Or the tubes could be OK and the previous roll was shallow, and rerolling is the cure. Or the tubes have been rerolled twice before and there is nothing left to roll and ALL the tubes need replaced. And an experienced boilermaker superintendant experienced in small boilers can diagnose the problem quickly, once he/she looks at the boiler. Hire some experience, it will be cheaper than learning the requisite lessons yourself, using trial & error.
Good judgement comes from Experience. Experience comes from Bad Judgement.
RE: Boiler Repair Assistance