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Superheater Tubes Sagging

Superheater Tubes Sagging

Superheater Tubes Sagging

(OP)
What are some of the factors to consider for water tube boiler superheater tubes sagging? What are the causes for this condition?

RE: Superheater Tubes Sagging

Tube bowing or sagging is normally caused by one of two conditions - inadequate tube supports or broken supports between tube spans or thermal bowing caused by start-up conditions where trapped condensate is causing a thermal mismatch in metal temperature and resulting in a bow in the unsupported tube length.

RE: Superheater Tubes Sagging

(OP)
I have a 9 superheater pipes in the horizontal with 8 bends. The bottom superheater tube has sagged 1.25in. 6 others have sagging of less deflection. Is that excessive sagging?

RE: Superheater Tubes Sagging

Over what pipe distance or length is the sag?

RE: Superheater Tubes Sagging

Yes, I reviewed the picture. The sagging is not an issue currently. I would monitor tube sag it during future inspections and determine if it is getting worse or has stablized. If it is getting worse over time, this could be creep deformation.

RE: Superheater Tubes Sagging

(OP)
Do you think this is typically what you would expect for a boiler that was put in service in late 1987 and has an expectancy to last 30 years before it has to be recommissioned? Would this be a normal sag you would expect to see?

RE: Superheater Tubes Sagging

Yes.

RE: Superheater Tubes Sagging

Looks pretty good for a 25 yr. old boiler.

rmw

RE: Superheater Tubes Sagging

It could also be due to overheating from a number of reasons. Sagging could also trap liquid which could be a problem upon restarting the boiler. There should not be any sag even after 25 years of service unless some past event caused this condition. Talk to your boiler inspector for an opinion. What type of a boiler is this?

RE: Superheater Tubes Sagging

(OP)
It is an O type water tube boiler. 1 steam/mud drum. produces superheated 650 deg f steam at 400#

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