Posted by Cliff Weir on November 13, 2001 at 20:33:26:
In Reply to: Re: PITTING ON TUBES posted by Allan Greene on November 13, 2001 at 15:49:22:
: : : : JUST OPENED A BOILER THAT WAS FULL OF WATER ,IT HAD BEEN IDLE FOR 1 1/2YEARS HAD BEEN TOLD IT HAD BEEN RETUBED 1YEAR EARLIER ,NOW IT HAS PITTING ON THE TUBES ,RESULTING IN TUBE LEAKS ,POOR LAYUP TO BE THE BLAME ? NEED SOME CURES TO THIS SITUATION AS IT IS GOING TO BE DIFFICULT TO DEAL WITH THANKS
: : When we lay up our boilers, we keep them pressurized with 175# steam, with the condensate removed through steam traps on the open blow down lines. We can recover the condensate that way. When laying up the boilers, we open the drum vent until we get about 50# pressure to remove the air, since oxygen causes the pitting.
: :There are two options, wet layup or dry layup, when you wet lay up you should fire your boiler (dry out) then chemical treat your feedwater in the boiler with a recommended dosage from a chemical company (depending on water volume) then apply a nitrogen cap to the boiler (ensures all oxygen is removed), The dry lay up basically consists of a dry out fire, draining the entire boiler then inserting a dessicant in the drum or water space of the HRT boiler. Hope this helps
The purpose of laying up any boiler for any length of time is to prevent internal damage to the boiler proper. The methods of lay-up are many and vary in outcome. Most books that can be consulted on this issue illustrate that any thing greater than one month should be a dry layup using lime or a desecant as a moisture obsorber. This is of course after the boiler has been completely drained of all its water and the low spots sponged of the moisture remaining. The moisture absorbet placed in and all doors closed.
The doors should not be opened until the moisture absorber needs to be checked (usually once a month) and replaced.
Hopefully this helps, and take care of your boilers