CHAPTER 13 | Cooling Tower Testing

The purchase of a pound of meat or gallon of gasoline are easy to verify. Cooling tower capacity, on the other hand, is considerably harder to quantify as it requires the accurate, simultaneous measurement of water flow, inlet and outlet water temperatures, wet bulb temperature and power consumption. Water and wet bulb temperatures do not remain constant and it is necessary to average readings- typically over one hour. The average readings are then compared against manufacturer supplied capacity data to verify thermal compliance.

The complexity of such testing is reflected in the cost- perhaps $5-6,000 for the test technician plus the necessary participation of the contractor and owner personnel, modifications to the piping to accommodate test measurements and the production of sufficient thermal load for testing. Through preparation by all parties is required in order to reduce the chance of an invalid test result for lack of sufficient and sustained heat load or water flow. Mother nature must also cooperate with wet bulb temperatures, wind velocities, etc. within the allowable parameters of the test being performed. The importance of thermal performance is critical, however, regardless of project size for while the system may �work� with an undersize cooling tower, cooling water temperatures will be higher than design compromising system efficiency.

Poor efficiencies have increased economic impact on large projects making testing for such towers critical. Large projects also tend to employ field erected cooling towers where unique designs and field assembly practices become more important. Here, the expenditure of perhaps $10,000 becomes well worth the assurance of full thermal performance.

Factory assembled designs often carry certification of compliance to CTI Standard STD-201. This is a program offered by CTI-Cooling Technology Institute- where it reviews a manufacturer�s submitted product offering and capacity ratings. CTI then lists those product lines that meet published ratings. In my opinion, the need to comply with CTI STD-201 should be part of every factory manufactured cooling tower specification and that field testing of towers that are listed under STD-201 is a waste of money.

The cooling tower industry has largely embraced STD-201 because it helps prevent unqualified manufacturers from enjoying undeserved sales. System designers and owners also benefit with predictable performance. All field erected cooling towers should be specified with a specific test and penalties for failure clearly laid out in advance. Field tests procedures are CTI Standard ACT-105 (Available from CTI at www.cti.org/) and ASME PCT-23 (www.asme.org/cns/). Each costs about $50. If a test is anticipated, the piping design should include the necessary flow and temperature measurement ports as it can be quite expensive to add them later.

Someone desiring a ligitimate CTI test must contract with CTI which will supply a list of preapproved test companies. The selected test company will provide test instruments for temperature, flow and power measurement. Test results are submitted to CTI for review and verification and an official test result provided by CTI.