In late 1992, a salesman called on Duane Pindell, then maintenance supervisor for the Laramie County (Wyo.) School District NO. 1. The rep, Dave Dillion of Electrostatic Technologies, was offering a product Pindell had never heard of: a device that uses electrostatic fields to prevent scale deposits in food service and HVAC equipment.

The device inhibits scale by interfering with the ability of calcium carbonate molecules to bond to each other or to a heat-exchanging surface. Because the molecules cannot bond, they are incapable of forming hard calcite deposits.

The district’s 36 schools are relatively far apart, so each has its own cafeteria, including steam equipment for cooking and serving. The heating elements and oven walls were often plagued with scale development. Scale is an efficient insulator, and a 1/8-in.-thick deposit can cut heat transfer efficiency by up to 25 percent. This made the district’s equipment more expensive to run and reduced the operating life of the heating elements.

Laramie County addressed this problem by routinely removing the heating elements and chipping the scale away. This could only be done when the kitchens were shut down, so maintenance people were usually paid at overtime rates. Pindell liked the idea of being able to eliminate scale without this extra labor expense.

The district initially tested the equipment at a site with only one steam convection oven. Usually, the district’s equipment had to be descaled every three months. But a series of monthly inspections at the test site showed that no new scale was developing, and that the equipment was helping to remove existing deposits.

Pindell conducted a second test in early 1993 with three stream ovens at the junior high. This time, a single system took care of the scale in all three ovens. Pindell calculated a 28-month payback period for the unit, which has since dropped in price from $1,850 to $1,500. Though budget constraints have kept the district from installing the equipment systemwide, seven of its school kitchens are now using the technology.

Boiler Chemicals Eliminated

The district is also testing electrostatic technology in its boilers. One unit was installed in summer 1994 at the junior high, which has a tandem boiler system. A recirculation system pushes water from the boiler make-up tank through an electrostatic treatment chamber, eliminating the need for pretreatment chemicals previously used on the boiler water.

The change did not have any adverse effect on boiler operations, and an inspection a year later showed that the boiler had been flushed clean. About 20 pounds of old scale had actually fallen to the bottom of the boiler.

Three of the district’s schools now have electrostatic-treatment systems for their boilers. Cleaning requires only that the boiler tanks be sprayed down periodically to remove any sludge remaining at the bottom. The state inspector has allowed the schools to discontinue all chemical pretreatment of boiler water. In this case, the equipment not only helped the district cut its maintenance costs but also reduced its dependence on polluting chemicals.

Gene Osborne, Laramie County’s current maintenance supervisor, says additional units will be installed as funds allow until every school in the district acquires scale-protection systems for its kitchen and boiler.

Cooling Tower - Injection Molding

APPLICATION:

For more than eight years Richco Plastics has utilized electrostatic fluid treatment systems (EFTS) to control scale development in their process water system. Richco is an injection molding operation that has a total of 34 machines, ranging in size from 45 tons to 550 tons. Their cooling system consists of four 50 ton cooling towers and four chillers ranging in size from 5 to 20 tons. The system is divided into two loops each carrying half the equipment load.

PERFORMANCE ANALYSIS:

The initial decision to install the EFTS was based on the company’s desire to control scale, without the need to add chemicals to their system. They also felt that the EFTS allowed a passive approach they would eliminate the need to monitor their system constantly to determine if proper chemical quantities were being added to the system to maintain water quality. With the EFTS in place the company’s maintenance personnel are no longer required to handle potentially harmful chemicals, move heavy barrels into place or stock quantities of expensive chemical treatments.

BENEFITS:

Perhaps Richco, should be considered a company willing to look ahead in its planning process. At the time of installation the aspects of environmental impact of discharge water from the cooling tower or the concern over the amounts of chemical carried by wind drift from their plant were not the critical issue they are becoming today. However, they also were driven by the economic factors associated with the use of the passive EFT systems. The installation of our systems have allowed them to operate totally scale free for over eight years. Because of this fact they have realized savings in the following areas: no chemical cost, reduced maintenance requirement and increased productivity, now amount to several thousand dollars.

Richco has been very satisfied with the performance of our equipment to the point that they have recommended its installation to sister companies in the same industry. Perhaps the best from of appreciation by a customer is – Their willingness to recommend the use of this system to aid other companies in controlling the costs associated with scale control and improved productivity. It is the opinion of this company that the installation of these systems has been their best choice to insure water quality. They have emphatically stated they would not return to chemical use.

Frequently Asked Questions (FAQ):

How Does It control Scale Deposits?

The FluidTron system creates a strong electrostatic field within the immediate proximity of the electrode. This field acts to impair the bonding characteristics of calcium carbonate and other scale forming compounds. Calcium carbonate is a strange compound in that it has an inverse solubility ratio. This means that as temperatures rise or pH rises these compounds will attempt to drop out of solution and form deposits. Pressures changes can also create circumstances that are conducive to scale deposits developing more rapidly. In order for scale to form, the particles must mass together to create a particle that is sufficiently large enough and has sufficient surface charge to adhere to a grounded surface. By keeping the particles from forming into these larger masses the tiny particles remain in suspension and will be carried by the fluid through the system.

In addition to the control of new scale deposits, old scale will be gradually removed. The time period in which this will occur varies dependent upon three primary factors: 1) composition of scale deposits, 2) the temperatures under which they are formed and 3) the length of time they have been in existence. Each of these three factors has an impact on the strength of the molecular bonds of the deposits. The tighter the bond the longer it will take to remove existing deposits.

Does The Electrostatic System Kill Bacteria?

The electrostatic system is not biocidal. That is it does not immediately kill bacteria that passes through the treatment chamber or within close proximity to the electrode. However, the system will help control the formation of biofilm and will gradually remove this layer of material that serves as a food source and algae colonies will be controlled. While this may help eliminate the need to for biocides in most applications, we highly recommend that you monitor your system for bacterial development.

Are there any dangers associated with the use of an electrostatic system?

These systems are designed to protect the environment in which it is installed and those who are in close contact with the treated fluid. In the event that a failure should occur, the system is designed with safety features that immediately reduces output voltage well below hazzard range. In fact, the amperage of the output power used to drive the electrode is well below the hazzard level for humans. The possibility of receiving a shock is no greater than would be expected with the use of a standard household appliance or power hand tool.

Will I experience an increase in corrosion rates using an electrostatic treatment system?

No, in actuality, coupon tests have shown that the corrosion rates experienced using electrostatic treatment systems is no greater than that experienced using chemical treatments. Chemical treatments have to use additional chemical additives to prevent corrosion because of the addition of scale control and biocidal treatment additives.

Our system do not does not transfer electrons to the fluid flow that could result in the breakdown of metallic surfaces. Scale formation and biological fouling are two of the primary causes of corrosion in process water systems. Our ability to maintain both in check will allow your system to operate within normally acceptable levels of metallic corrosion.

What are the operating costs associated with an electrostatic treatment system?

The cost to operate the electrostatic treatment system is minimal. In fact, it uses about as much power as a 7 watt night light on a daily basis. This means that the cost of operating your system will be just a few cents per day.