Seasonal Lay-up of Cooling Systems

Corrosion often takes place in piping, condenser water boxes and on condenser tube sheets during winter months due to microbiological growth and stagnant or damp conditions. A few precautions undertaken in the fall will eliminate the majority of this type of corrosion. The objectives of the lay-up program are to:

  1. Kill any microorganisms in the system, which might facilitate corrosion during the idle period
  2. Dislodge and flush the system of any microorganisms, sediment or other debris, (which can harbor bacteria which could prevent the formation of a strong lay-up corrosion inhibiting film)
  3. Establish a heavy corrosion inhibition film and maintain it throughout the lay-up period

 

Lay-Up Procedure:

  1. Two weeks prior to shutdown manually remove any accumulations of mud and sludge from the tower basin or sump.
  2. Twenty-four to forty-eight hours prior to final shutdown, add biocide to the system at two or three times the normal maintenance dosage. At the same time, add CE Water BIO-DISPERSANT at the rate of one to two gallons per one thousand gallons of system capacity. Circulate for twelve to twenty-four hours. (Your CE Water representative will recommend the correct dispersant for your needs.)
  3. Put Cooling Tower Seasonal Layupthe system on HEAVY bleed off to de-concentrate the circulating water and insure the removal of as much of the dispersed debris as possible. Special attention should be given to the blow down of the condenser (and absorber) water boxes to insure that they are free of sediment and debris. This is especially important if the condenser (and absorber) is not scheduled to be opened for cleaning and inspection.
  4. Add CE Water TOWER LAY-UP TREATMENT at the rate specified by your CE Water representative. Biocide should also be added at this time at three times the normal maintenance level. Circulate for at least six hours with the bleed off closed, fan off, and no cooling load on the system. While the system is circulating, test the water for the proper level of lay-up treatment for your needs based on the system and local discharge restrictions.
  5. Drain only those portions of the system, which are subject to freezing. The inhibitor film laid down by the CE Water TOWER LAY-UP TREATMENT will help protect this piping from corrosion. The best protection is afforded to those portions of the system, which can be left in a flooded condition.
  6. At start-up in the spring, flush the lay-up treatment from the system and begin the new season with fresh water treated with twice the maintenance level of corrosion inhibitor, or add CE WATER PASSIVATION TREATMENT as specified by your CE Water representative.
  7. If the condenser (and absorber) is scheduled to be opened for cleaning or inspection during the idle period, it is best to open them as soon as possible, as this minimizes the chances for corrosion, especially to the tube sheet, during the idle period. Even if the cleaning and other maintenance cannot be scheduled until later, opening the heat exchangers and allowing them to thoroughly dry out can prevent corrosion. The balance of the system should be isolated and left filled with inhibitor solution if possible.
  8. Be sure the corrosion inhibitor readings in the chilled water system are at or near the top of the recommended limits prior to shutdown. Down period treatment at up to twice-normal levels may be indicated. Follow your CE Water representative’s instructions.

Other Lay-Up Suggestions:

  • Pump clear water through all chemical pumps to insure that the pumps and injection lines are free of chemical treatment during the winter. If maintenance work must be done to a pump or if it should lose its prime over the winter, it will be much safer to work on.
  • Don’t forget to drain the parts of the system that are subject to freezing. If the make-up water meter is subject to freezing, remove it for storage in an area where it won’t freeze.
  • Consult the cooling tower maintenance manual for any special winter precautions such as covering the motor and gearbox, overfilling the gearbox with oil, etc.
  • Drain any chilled water coils, which may be subject to freezing and flush them with a glycol solution. Traces of glycol should be flushed from these coils in spring before refilling with chilled water. The traces of glycol may harbor bacteria, which can cause serious microbiological fouling of the chilled water system. Be sure to follow all discharge regulations for glycol.