Re: Thermal Shock

Subject:

Comments:
: Question one: No. What you are talking about is a rather typical : situation. Not enough temperature differential is involved to worry about. : Question two: If an actual thermal shock did take place, I would suspect : possible tube end leakage, in extreme cases possible tube sheet damage. : Question three: Don't worry about it. Firetube boilers like yours are operated : on a daily basis with ambient degree water being fed to them with no damage. : : : Regarding the qeustion of thermal shock and it's : : effects: We have (3) 400 hp firetube boilers, one : : of which we suspect has experienced a rather severe : : thermal shock for the following reasons. Upon opening : : the firsides for yearly cleaning and inspection (both : : firesides and watersides inspection) we discovered : : between 15 and 20 lbs of what appears to be scale and : : rust that obvioulsly came from the tubes (curved : : shaped debris). This boiler was operated for a number : : of days without the Deaerater Tank. The boiler water : : temperature is close to 345 deg. F, and normally with : : the DA tank the inlet water to the boiler (boiler : : feedwater) runs around 220 deg. F, however, without : : the DA tank during these few days the inlet temp. : : never rose above 150 deg. F, compound this with the : : fact that the early morning load increases usually : : result in a boiler load increase of anywhere from : : 30 to 60 percent resulting in the boiler taking a : : 'big drink' of relatively cold water. : : Question one: Is it safe to assume, given the above : : information (on a very carefully maintained boiler : : that has yet to be inspected by a certified : : inspector) that a thermal shock may have occured? : : Question two: If a thermal shock did indeed occur, : : what are the likely damages? : : Question three: How seriously should the possibility : : that a thermal shock did occur be taken? : : The possibility of a thermal shock is presently being : : brushed off as nothing to be concerned about. : : Does anyone know of any web resources that deal with : : this issue? : : If you could reply to akp@ideasign.com it would be : : much appreciated. : : Thanks in advance. : : Tony