CHAPTER 17 | Cooling Tower Checklist

This chapter is designed as a checklist for the system designer. Experience has shown that most installation short comings fit under one or more of the following headings. It is therefore recommended that the following be considered before finalizing the design:

-Should the tower be blow thru, draw thru, counterflow, crossflow, centrifugal fan, prop fan,...?
(Ch.2)

-Has the proper type tower- open or closed circuit- been selected? If it is closed circuit (Ch.14), would an open tower in conjunction with a heat exchanger have economic, weight, freeze protection, water treatment or connected horse power advantages?

-Is the base of the tower indoors? Make sure the tower is outlined by a curb that will collect water and direct it to a drain. The added containment must be sealed against leaks so as to prevent water damage to the floors below. During the normal life of a tower, several episodes of substantial leakage can be expected.

-Is it mounted on the roof? If so, it should be mounted on elevated support steel that allows access to the underside of the tower to address leaks that WILL OCCUR during the life of the tower. Do not allow the tower to merely rest on a roof cap that can be compromised over time by minor tower leaks eventually allowing water to enter the space below. Design the roof to be completely replaceable without moving the tower.

-Are there multiple towers? Separate them enough for access all around

-Is the water treatment squared away? Note that individual and multi cell closed circuit coolers need separate systems for the open loop(s).(Ch.12)

-Are the construction materials sufficient for the duty? (High temperatures, corrosive environments, 'dirty' water, etc. need special consideration.) (Ch.3)

-Are the proper accessories specified? "Big" towers may need ladders, stairways, platforms, walkways, handrails, etc. (inside and out). Also items such as vibration cutouts, extented lube lines... even access doors and make-up valves are considered 'accessories' by some manufacturers. (Ch.3, 6 & 8)

-Is the water inlet to the cooling tower the highest point in the system? Is the piping sized properly? Is the piping as symmetrical as possible for optimum water distribution? Are horizontal pipe runs above the operating water level of the cooling tower minimized? Are there flow control valves for multiple hot water basin inlets? (Ch.5)

-Is the support adequate? (Ch.10)

-Is the support steel long enough to hold individual cells (of multicell towers) before they are slid into place?

-Do multiple cells have properly sized flume connectors or equalizer lines? (Ch.5)

-When valving off the inlet to one cell of a multi cell tower, is the corresponding outlet valved off also? (Ch.5)

-Is there sufficient back-up should anything fail?

-Can cooling tower cells be isolated for maintenance?

-Are the make-up water line and valve big enough? Is there sufficient make-up water pressure to keep up with evaporation and bleed? Will the tower fill in a reasonable amount of time after draining? (Ch.5)

-Is the sewer drain sized adequately for: Blow down? Draining the tower for maintenance in a reasonable length of time? Filter backwash?

-Is the pull down volume sufficient? (Ch.5)

-Is the turn down too severe? (Ch.5)

-Does the tower meet the mfgr.'s requirements for maximum airflow restriction at the inlet? Discharge? (Ch.4)

-If indoors, are the fans capable of overcoming the external static pressure? (If the fans are prop fan type and the tower is indoors, STOP!) (Ch.2, 4)

-Is the air discharge higher than surrounding walls? (Ch.4)

-Does the installation require: Inlet louvers? Wind walls? Inlet screens? Bottom screens?

-Could neighbors find objection to: Noise? Vibration? (Ch. 10) Plume? (Ch. 4) Obstruction to view?

-Is the tower capacity CTI certified? (Ch.13)

-Will the cooling tower air discharge be drawn into the building's air inlet? (Think 'sick building', 'legionella')

-Are the combustion air requirements for boilers and furnaces sufficiently distant from the cooling tower's air inlet?

-Are cooling tower air inlets kept from boiler stacks? (Products of combustion can make cooling tower air/water corrosive.)

-Will there be leaves, blossoms, twigs, etc. drawn in by the fans?

-Will the small water particles in the air discharge spot the finish on adjacent windows, walls or automobiles? Corrode switch gear or conduit? (Avoid placement near pedestrian areas or food courts.)

-If applied with a VFD connected to the fan motor, are objectionable critical speeds blocked out? Will there always be sufficient RPM for splash lubrication (gearbox applications)? Is the motor suitable for VFD duty? (Ch. 6)

-Is the pump set to start first followed by the fan motor once full flow has been established? Does the fan shut off first followed by the pump?

-Do the motor specs match the duty? Are the electrical characteristics made clear? Does the starter match the motor? Are the higher amp ratings of 'air over' motors taken into account? (Ch.6)

-Has separate, single phase power been made available for capacity controls, oil pumps, vibration cutout switches, oil level switches, heat tracing, etc.?

-Have local requirements been considered such as freeze-up, fire and building codes, peculiar water quality requirements, seismic, snow and wind loading?

-Are reduced insurance rates available for cooling towers that subscribe to Factory Mutual?

-Is capacity control needed? (Ch.6)

-Has proper internal air baffling been considered before attempting to cycle individual fan motors?
(Ch. 6)

-Is there adequate room for maintenance such as fan shaft removal, wet deck replacement, etc.?

-Is vibration isolation required? Are the isolators grounded out from the lack of flexible piping connections? (Ch.5,10)

-If the project has an absorption chiller, is the heat rejection about 23,000BTU/HR/Ton? (Ch.1, 15)

-Pump selection ok? Take into account added static lift for "remote sump" applications? Adequate NPSH?

-Can the specified tower be transported to the job site? (Ch.2)

-Have provisions been made to keep the system water clean? (Sand bed filter or centrifugal separator. Ch.12)


Special considerations for installers:

-Did you order the equipment with the piping connections, air inlet, motors, etc. optimally located to improve operation and reduce installation costs?

-Did you review the rigging instructions prior to equipment arrival in order to see if any special tools are required? (Several slender drift pins are extremely helpful when attempting to align bolt holes. A full 1/2" drive socket set plus extra 3/8" drive ratchets with 3/8" thru 9/16" sockets, ratchet and speed handle for fasteners, wrecking bar and hammer to open crates, sheet metal cutters for removing banding, a knife for cutting open boxes, a carpenters apron to hold fasteners, a ladder to get to the bolted joints, etc. are all helpful.)

-Do you plan to lift the tower at the factory recommended lift points? (Answer: Yes)

-Do you like to cover items in storage? Don't tarp cooling towers with PVC fill or eliminators. The heat build up can damage these vulnerable components.

-Do you have to remove an old tower? Don't over look that old cooling towers often contain hazardous materials. (ex: Never cut or saw old, dry wet deck containing asbestos if you value your lungs.) Wood can harbor chemicals from water treatment or preservatives. Be sure to include special disposal requirements in you quotation.

-Use only specified lubricants.