Boiler StorageHow to a lay up a boiler?
Boiler Storage is done dry or wet. The dry method of storage is recommended for periods of one month or longer. When the lay-up will be for shorter periods or where rapid return to service may be necessary, the conventional wet method of storage is preferable. Proper Boiler Storage is important to prolong your boiler life.
How do I dry layup a boiler?
Boiler Storage done dry should begin after the boiler has been drained and flushed, it should be thoroughly dried. This can be done by air circulation or by a very light fire in the furnace. Dessicants traditionally used in this application are quick lime or commercial silica gel. When the boiler is completely dry, place the quick lime or commercial silica gel in suitable trays along the length of the steam and mud drums. These trays should be supported by blocks of wood in such a manner as to permit free circulation of air underneath. Seal all openings completely.The amounts of hydrate required for effective moisture control are 8 lbs. of lime or 4 lbs. of silica gel per 1,000 lbs. per hour of boiler steam capacity. The boiler should be inspected at two to three month intervals and if the hydrating material is found to be damp, it should be replaced. After each inspection the boiler should immediately be re-sealed. Recently, new, easier to use technology has become available for this application. Boiler Lizards, containing a vapor phase corrosion inhibitor, are placed inside a dried boiler, opened, and then the boiler is sealed. Each Boiler Lizard will protect up to 1,000 gallons system capacity per bag (roughly one boiler lizard for each 100 HP of a firetube boiler).
How do I wet lay up the boiler?
Boiler Storage the wet method is done after the boiler has been removed from service, according to the procedure described in the Technical Data Sheet, "Removing Boilers from Service", it should be refilled with water. The water temperature should be raised to approximately 200oF, leaving the top drum vents open so any air present will be driven off. With sufficient firing to keep the water circulating, add a sufficient amount of a sodium sulfite containing product to develop a residual sulfite of 200 ppm. In addition, add sufficient caustic soda or alkalinity builder to increase the 'P' alkalinity to 1000 ppm.As the water cools, an air space will develop at the top of the boiler. The water level must be checked daily and the boiler kept completely full. A sample should be taken once a week and tested for proper chemical content. Make sure the top tubes in a firetube always remain submerged.
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How do I use Nitrogen to layup a boiler?
Boiler Storage with Nitrogen is common for boilers where immediate return to service may be required. This method is a modification of the wet storage method in that the water in the boiler is maintained at the normal operating level and this water is treated as recommended under the wet method. In addition, nitrogen is pressurized into the unit when it is sealed to prevent oxygen intrusion.
How do I start up the boiler after downtime?
Obviously, starting up a boiler after dry storage requires basically the same procedures as when starting up a new boiler or one that has just been cleaned and/or inspected and is being returned to service.For a boiler stored under the conventional wet storage method, it will be necessary to drain it to the normal operating level prior to firing. The water level controls should be checked to assure they are still functioning. Then, the boiler can be fired in the usual manner. During the first day or so, it should be blown down heavily until chemical balances in the boiler water are brought into normal control ranges.For a nitrogen blanketed unit, it is only necessary to turn off the nitrogen and close the valve through which the nitrogen has been added, open the valve to the steam header and fire the boiler. Again, blowdown should be heavy for the first day or so of operation until normal boiler water treatment control levels are re-established.
How do I shut down the boiler?
The purpose of planning the removal of a boiler from service is to minimize the amount of cleaning once the unit is shut down. The proper procedure also aids in keeping soft sludge from being baked on tubes which makes cleaning much more difficult. Proper Boiler Shutdown procedures should be followed.
How to prepare for a boiler shut down?
About a week prior to the Boiler Shutdown, there are two steps to follow in preparation for shutdown. The first of these is to increase the amount of blowdown to get the suspended solids level down as low as possible. This increase in blowdown can be monitored in the same way normal blowdown control is monitored by either conductivity or chlorides. Typically, conductivity or chloride levels are lowered by 25% (i.e. if normal control is say 2000 umhos, the target prior to shutdown would be 1500 umhos). However, this is not an absolute amount and can be varied depending upon the actual blowdown rate, type of boiler, treatment program and feedwater quality. The second important step is to maximize the treatment concentrations. Where the polymer dispersant is being fed separately, the feedrate should be doubled. Where it is being fed as part of a complete formulation, the required control tests should be kept near the top of the required range. This will maintain maximum fluidity of suspended solids for optimum removal by blowdown. Proper Boiler Shutdown is important.
How to cool down the boiler?
Once the Boiler Shutdown is complete, it is important that it be cooled down prior to draining. Too rapid a cool down can cause problems of stress on the boiler metals and refractories. If the boiler is drained when too hot, any remaining sludge can be baked on tubes making removal more difficult. Cool down procedure varies depending on the type of boiler and auxiliary equipment and is normally covered in the boiler operation manual provided with the unit. Once cooled, the boiler should be drained and opened as quickly as possible. It should then be flushed out with a high-pressure hose. The waterside surfaces should then be ready for complete inspection.
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