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Old 10-21-2008, 02:31 PM
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platypus20 platypus20 is offline
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Default Rotary Damper Bushing Replacement

I've shown this before, but this time I had more time to take more and better pictures, so please bear with me.

In boilers, the fuel and air flows are carefully controlled, by means of dampers, control valves and the linkages that tie it all together. On this 800 hp boiler (34,000,000 btu input), the rotary damper that controls the air flow seized, shutting the boiler down on a safety interlock. Sometimes the burner can be disassembled, clean and reassembled and will function properly, in this case the damper bushing was so badly galled, it couldn't be depended on to continue working properly until the next annual inspection in June 09. I'll give a basic play by play of each posted picture.

Jack

1. the burner assembly as removed from the boiler
2. the proper low fire position
3. the proper high fire position
4. on disassembly, the diffuser and air straightener
5. the gall bearing surface on the cast aluminum rotary damper blade
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Last edited by platypus20; 10-21-2008 at 02:49 PM.
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Old 10-21-2008, 02:35 PM
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6. rotary damper back plate
7. the galled bushing
8. the old bushing after removal
9. homemade bushing press
10. bushing going in, using press
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Old 10-21-2008, 02:40 PM
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11. installed bushing
12. bushing surface
13. rotary damper blade, after bearing surface clean up
14. gas spuds, after burner is installed, natural gas is injected into air through these
15. linkage system, drive motor is silver box in lower left of picture
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Old 10-21-2008, 02:48 PM
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From start to finish, the bushing replacement took about 4 hours, while I was at it I change all of the heim ends on the linkage rods. Making sure all of the linkage was free of stiction points and that the drag on the drive motor was minimal. After this work was all done, a combustion flue gas analyzer, was used to check for lowest emissions and best efficency possible, through the complete firing range. This is not a real common repair, of the hundreds of boilers I see a year, I do only 3-4 bushing replacements a year. With all of the work done, including drive time, this was a 10 hour billable job.

Jack
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Old 10-21-2008, 02:53 PM
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Nice job Jack. is that a Cleaver Brooks?
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Old 10-21-2008, 02:55 PM
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Quote:
Originally Posted by rmack898 View Post
Nice job Jack. is that a Cleaver Brooks?
Yes, in a cottage cheese plant in central New York.

Jack
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Old 10-21-2008, 03:06 PM
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I like your bushing press ... lots of guys would simply grab the BFH & have to do it all over again
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Old 10-21-2008, 05:48 PM
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Thanks for the tutorial. Its been a while since I have worked on a boiler.
I witnessed the aftermath of a Cleaver Brooks start-up, where the Technician forgot to loosen the roller shipping bolts on a 150 HP steam boiler. Wasn't too pretty after the boiler buckled at about 150 psi
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