Cooling Tower Layup Procedure

Purpose

Cooling tower systems are susceptible to microbiological growth and corrosion when they have stagnant water left in them during the off season. By following a few proactive steps during shutdown, these issues can be minimized and potentially eliminated. The steps below will help you properly layup your cooling system over the winter months.

Process

1. Pull corrosion coupons, if implemented as part of your validation program.
2. Reduce the conductivity setpoint on the towers by 50% 2 to 3 days prior to the shutdown or cleaning to reduce the solids in the system.
3. Prior to shutdown, add 2 to 3 timesthe normal non-oxidizing biocide to the system and allow to circulate for 4-6 hours to ensure proper disinfection of all water contact areas.
4. Brush and/or pressure wash the distribution deck during operation to allow for movement of solids to more accessible areas.
5. Drain down the tower and wash out the tower fill and sump.
6. Remove and clean all strainers. Reinstall the strainers.
7. Isolate the cooling tower control system by shutting off water supply.
8. Ensure the tower chemical controllers are turned off from the system so chemical cannot be fed during down time.
9. Remove tower probes, clean and place in air (conductivity sensor) or solution (ORP, PH) to help preserve.
10. Clean and flush the chemical feed pumps. Place the suction line (foot valve) of each pump in a bucket of warm water and operate the pump to completely flush it of treatment products. Leave the foot valve out of the chemical tank for the off-season.
11. If adding a lay-up chemical for corrosion passivation go to step 12, if not, skip to step 15.
12. Refill the tower system (It does not need to be refilled to the normal operating level and this will help reduce the system volume).
13. Vent all chillers to ensure that they are filled with water and then close the vents.
14. Add the appropriate amount of tower layup chemical suggested by AWS Representative and circulate per instructions to ensure proper protection of all wetted surfaces.
15. Completely drain the system from the lowest point.
16. See AWS’s VAC-1001 Chiller Shutdown and Layup bulletin for more information on chiller handling.

Payoff

Properly laying up the system will help ensure a sterile system, so if there is a little water remaining it won’t allow bacteria populations to flourish the next cooling season. In addition, the critical monitoring, control and feed systems will be properly preserved so that when the warmer weather comes again next cooling season the equipment is ready to be put into service and the system isn’t compromised due to improper monitoring, control and chemical protection.