ASHRAE Project Number 1361-RP

The topic of Non Chemical Device (NCD) water treatment seems to always be popular. ASHRAE Project Number 1361-RP focused on Biological Control in Cooling Water Systems using Non-Chemical Treatment Devices. Five different NCD devices were analyzed in the study from the following categories: Magnetic, Pulsed Electric Field, Electrostatic, Ultrasonic, and Hydrodynamic Cavitation.

The experiment concluded, "...no statistically significant difference...in planktonic or sessile microbial concentrations (HPC) was observed between the control tower and a tower treated by any of the five NCDs evaluated in this study...", (i-ii).

You can download the entire report here: http://rp.ashrae.biz/page/ASHRAE-D-1361-RP-20101005.pdf

Water Treatment Case Study: Low Cycles of Concentration (CoC)

Size: 800 Ton Tower
Load: 90% Summer; 30% Winter
Location: Tokyo, Japan
Problem Description: The tower achieved target operating cycles of concentration (CoC) of 7.0 during the summer months. During the winter it was hard to achieve a CoC of >5.0.
Assumption: Cooler temperatures did not enable enough evaporation for tower to “Cycle Up”.
Finding: The calculated summer blowdown rate is 3.6 gallons per minute (GPM) @ 90% load. The calculated winter blowdown rate is 1.2 GPM @ 30% load. Upon inspection a condenser water pump was found with a badly leaking seal (see photo). An impromptu field test was conducted to measure the amount of water being lost through the seal leak. Using a sample bottle to capture the water loss from the pump and a watch to calculate the time it took to fill the bottle it was estimated that just under 2.0 GPM were being lost at the seal.
Conclusion: Water loss through a seal leak has the same effect on a tower that excessive blowdown does. Since the leak rate of 2.0 GPM exceeds the winter blowdown rate of 1.2 GPM it is not possible to achieve the results desired. This problem was not noticed in the summer because the summer blowdown rate of 3.6 GPM exceeds the leak rate of 2.0 GPM.

Recommendation: Repair seal

Chiller Inspection

When is the best time of year for selling cooling tower water treatment? It is during the winter months. During the cooler season many clients will begin to do their preventative maintenance on Chillers, Cooling Towers, and Heat Exchangers. It is during this maintenance period that the effects of water treatment will become apparent. When a chiller is opened up for an inspection you want to be there to give your professional opinion. Having a boroscope, digital camera, and a flashlight will assit you in making a quality inspection.

Dirty Tower Sump

This 1,000 ton tower was drained at the end of the cooling season. There was a considerable amount of mud and debris left behind. While in operation this mud/debris created an environment favorable for microbiological growth and accelerated under deposit corrosion. Biocide feed rates had to be increased (raising treatment cost) to keep micro biological dip slide counts at an acceptable number.

Cooling towers need to be cleaned regularly to achieve lower operating costs, maintain efficiency, and to lengthen equipment life.

Broken Cooling Tower Fan Blades

When a cooling tower fan blade breaks it can create significant damage and/or injury. When one blade breaks it puts the fan out of balance. The combination of high speed and lack of balance can cause other blades to break, the shaft to bend, and/or gear box damage. The broken blades in the picture came out of a 500 ton tower installed at grade level. Both blades broke and shot out through the side of the fan shroud. Fortunately, there were no personnel in the area at the time of the failure.

Griswold SBC Non Chemical Water Treatment Device

Here is a picture of an installed Griswold SBC Non Chemical Device (NCD) for water treatment. It is claimed to prevent scale and eliminate biofilm in cooling towers and closed loops. Traditional water treatment chemistry is still being utilized to treat the system. The system volume is 65,000 gallons with a constant 42 gpm make up rate.

The unit claims to treat the water through "electronic resonance". The advertising brochure claims that the treatment chamber "uses less energy that a standard 100 W light bulb". Who in the scientific community can explain how there is enough energy to perform the tasks this unit claims it can do? If you choose to defend the unit please list your credentials.

Wasted Resources

During a recent central plant survey I came across these boiler blowdown controllers. Both were controlling on line boilers with similar run time, load, and make up water characteristics. The controller on the right is in alarm due to low conductivity. Unfortunately, the plant operator hadn't noticed the alarm. No corrective action was taken. Running the boiler in this condition is costly. It wastes water, chemical, and electricity. The water treatment cost associated with running a poorly controlled boiler can easily be double the cost of running a similar program with good controls. If you find that your water, chemical, and electrical costs have suddenly increased it may be time to revisit the control parameters of your water treatment program.