Why Does My Boiler Need Lay-up Treatment?
During the normal operating cycle of your steam boiler, treatment levels are maintained within specific operating ranges to inhibit corrosion and prevent scale. Even the best boiler chemical treatment program must be supplemented during the non-operating, or lay-up cycle to prevent corrosion.
When your boiler is taken off-line and allowed to cool down, special chemicals must be added at much higher levels to offset the increased level of available oxygen. Oxygen can quickly produce pits in both boiler tubes and tube sheets. Once a pit develops it can corrode completely through the tube in a matter of days.
When should I Lay-up My Boiler?
Steam boilers should treated for lay-up conditions any time the boiler will be off-line for more than two weeks. Consistent treatment levels throughout the operating cycle can add many years to the life of your boiler.
How Should I Use Boiler Lay-up Treatments?
With the guidance of your Chardon Service Technician, drain, thoroughly clean and refill the boiler to operating level. We add a Chardon formula until the pH of the boiler water is 11.0. Then we add additional sulfite chemical treatment until the concentration of sulfite is 200 ppm. Firing the boiler during the addition of these products will aid in mixing the chemicals and help drive off oxygen dissolved in the water.
Once the pH and sulfite levels are within their appropriate ranges, button up all inspection ports, fill the boiler to the top of the steam header and seal the header. The boiler is now properly laid up and will be protected from corrosion during the off-season.
Your Chardon Service Technician will test the boiler water periodically to insure that the treatment levels remain within proper ranges. For a more complete description of the lay-up procedure, request a copy of Chardon’s Boiler Lay-up Procedure.
What About Dry Lay-up For My Boiler?
An alternative to the method described above is the dry lay-up. This method involves completely draining the boiler and allowing it to dry thoroughly. Containers of desiccant are then sealed in the boiler it to prevent moisture from building up.
This method is best used in long-term lay-up situations. Done properly, boilers can remain in dry lay-up for many years with no significant corrosion to the interior.
The wet lay-up method should be followed for boilers that are out of commission for less than one year.
How Should I Restart A Boiler In Lay-Up?
In many cases, you can simply start up the boiler as is and add the required amount of chemical treatment scale inhibitor and return line treatment, although it may be necessary to replace a portion of the boiler water to reduce the alkalinity and conductivity to proper operating parameters.
Steam Boiler Passivation
Clean & Passivate Steam Boilers:
When it is time to clean and passivate, the boiler is filled with water and an appropriate amount of chemicals and biocide to the header valve.
The boiler is then lit off on low fire and warmed up to 120-130 degrees.
The boiler is then shut off and allowed to stand for at least 24 hours.
Natural circulation in the boiler will generate circulation currents and move the cleaner around. At the end of that time, the boiler should be drained completely, opened and rinsed thoroughly, then refilled with treated feedwater.
If the boiler is not going to go on line at that time, it should be properly laid up, your Chardon Representative will advise you on the best method of lay-up and chemical treatment for your installation.