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Layup Procedures

How should I decide which boiler layup method to use?

Waterside surfaces of that are out of service are particularly susceptible to . The length of time the boiler will be out of service and how quickly the Laying up a boiler not only boiler may need to be ready for service will determine the layup method. extends the overall life of DRY STORAGE The dry storage method is recommended whenever a boiler will be out of service your equipment, but also for an extended period of time, but must also be available for unit operation in a reduce downtime and moderately short period of time. maintenace costs. The following steps must be taken to ensure proper storage using this dry storage method: When a boiler is taken 1. Bottom blow the boiler at least twice daily for a few days before the boiler is to be shut down. Once the boiler is turned off, bottom blow the boiler every 10-20 offline and cools down, psi drop in pressure. 2. Begin to drain the boiler once the pressure is at zero and the proper layup is necessary is under 140ºF. Opening the boiler when it is at this temperature helps dry to handle increased internal surfaces. 3. The boiler should be thoroughly cleaned and inspected. If possible, all horizontal in the system and avoid and non-drainable boiler tubes should be blown with compressed air to remove pitting and corrosion. all and moisture. 4. Heat should be applied using an external heat source to dry the boiler walls, insulation, tube internals and refractory. Fuel fired heaters should not be used inside the boiler because of the moisture that is generated during the heating process. Please note, a boiler should never be dry fired to remove moisture. 5. Immediately after the surfaces are dried, one of the recommended drying agents should be spread on water-tight and corrosion-resistant trays: a. Quick Lime: 6-8 lbs per 100 cu. ft. b. Silica Gel: 8-16 lbs per 100 cu. ft. c. Activated Alumina: 8-16 lbs per 100 cu. ft. d. These trays should go into each drum of the boiler or on the top tubes of a fire tube boiler. e. NOTE: Specialty drying agents made specifically for dry layup of a boiler can be very effective and convenient and can in many instances remain in 414.425.3339 the boiler for startup because they volatilize upon heating. Contact your Watertech representative for information on these specialty boiler layup products. [email protected] 6. Manholes, vents and connections should be tightly blanked and closed. The drain between the non-return and main steam stop valves should be left open. The waterside of the boiler should be as air tight as possible. WATERTECHusa.com 7. The boiler should be opened every 3-4 months for inspection of the drying agent. It should be replaced as needed. Watertech of America Although dry storage methods are most recommended, wet storage is an acceptable option in the event of a more temporary standby. The back side of this sheet outlines 5000 S. 110th Street steps for wet storage. Greenfield, WI 53228 WET STORAGE ALTERNATIVE WET STORAGE When using the wet storage method, take at least one of the following precautions to (Continuous Blowdown Method) avoid freezing: This method consists of piping surface • Auxiliary heat blowdown from an operating boiler • Cascade lay up boiler with hot boiler water from an operating boiler to the bottom of the stand-by boiler • Light firing of the boiler to keep the idle boiler filled with hot, • Use of a 50/50 water/ethylene-glycol mixture (this however, requires that treated water. The overflow from the the boiler be drained, flushed, and filled with fresh feedwater, and a boil out vent goes to heat recovery or to the performed prior to start up) drain. This method is typically not used Even though dry storage methods are preferred, wet methods are acceptable on boilers with . whenever a boiler is on emergency standby. • If the unit to be laid-up has not been 1. The boiler should be filled to the normal water level with deaerated feedwater. cooled and drained, connect the Then add 3-4 pounds caustic soda and 1.5-3.0 pounds sulfite per 1000 continuous blowdown line from an gallons of water contained in the boiler. A minimum 200ppm of operating unit to a convenient bottom as CaCO3, and 200 ppm (mg/L) sulfite as SO3 should be maintained at drain line or blowdown line of the all times laid-up boiler. • It is highly recommended that a method of boiler water movement be • If refilling an idle boiler, first open installed such as a circulating pump running water from bottom to top of the a vent line and close it only after boiler to keep chemical mixed. Sulfite will settle to the bottom of the boiler. completely filling the unit with surface 2. Add 4-5 gallons of diethyhydroxylamine (DEHA) per 1,000 gallons for oxygen blowdown water from the operating control and 1 gallon morpholine per 1,000 gallons to raise the pH to 10.0-11.0. boiler. Then open the continuous (NOT FOR FOOD GRADE BOILERS) blowdown line of the stored boiler • With vents open, heat should be applied to boil the water for 1 hour. This will to allow a flow of water from the idle allow for complete mixing of the water and chemical. boiler. The standby boiler must have no • If the boiler is equipped with a non-drainable , fill the superheater air pockets in the upper portion of the with condensate or demineralized water treated with 4-5 gallons of DEHA boiler. per 1000 gallons and 1 gallon morpholine per 1000 gallons. Then fill the boiler • Enough hot surface blowdown from with deaerated feedwater. the operating boiler must be available • If the superheater is drainable or the boiler does not have a superheater, on a continuous basis to keep the the boiler should be allowed to cool slightly after firing. Before a vacuum is standby boiler warm and exterior created, completely fill the unit with deaerated feedwater. surfaces of boiler tubes and other • After filling the boiler, connect a surge tank, such as a 55 gallon drum, components warm enough to prevent containing a solution of treatment chemicals or nitrogen tank at 5 psig (0.35 condensation from forming on those km/cm2) pressure to the vent. This supply will compensate for surfaces. Proper care should be taken volumetric changes as a result of temperature variations. to ensure chemical levels are properly • The drain between the non-return and the main steam stop valve should be maintained in the operating boiler. left wide open. All other drains and vents are to be left closed tight. • The boiler water should be tested on a regular basis, with additional Advantages of this method: treatment being added whenever necessary to maintain the minimum • Good corrosion control due to proper treatment levels. sulfite and alkalinity readings • Boiler contains proper chemical residuals • When chemicals are added, the boiler water is to be circulated by means of when you return it to service an external pump or by reducing the water level to the normal operating level • Boiler remains hot, so less time and thermal and fire the boiler for the short time. You do not want to build pressure, but if energy is needed to get the unit up to steaming is necessary, the boiler should be filled completely in keeping within pressure the above recommendations. • Refractory stays hot and fireside corrosion is eliminated • No need to maintain high chemical residuals. No need to fire the boiler to QUESTIONS? 414.425.3339 CALL YOUR WATERTECH promote circulation SERVICE REPRESENTATIVE Disadvantages of this method: It is not always easy to decide [email protected] • Possible suspended solids deposition if you which layup method is best for your have poor feedwater quality on operating boiler. If you have any questions, or boiler (1 ppm = 1# sludge/100,000 gallons WATERTECHusa.com concerns regarding your facility’s feedwater) program, or which • Installation cost Watertech of America layup method may be best for • Possible short circuiting 5000 S. 110th Street • May not work on multiple boiler operations your operation, reach out to your Greenfield, WI 53228 • May negate blowdown heat recovery Watertech service representative. We are always happy to help!