After a long time of usage, even the best-designed heat exchangers can be susceptible to scaling. Scaling, otherwise referred to as fouling, is the accumulation and deposition of unwanted materials such as suspended solids, scale, algae, and insoluble salts on the internal surfaces of a heat exchanger. If left untreated, accumulated deposits will calcify and prevent the heat exchanger system from working efficiently and at an optimum rate.
Scale formation can increase heat transfer resistance and create effective insulation, which is undesirable for water cooling and heating equipment. In this article, you will learn about scaling in heat exchangers-how to remove and prevent them.
Where Does Scale Come From?
Typical scale components may include minerals like magnesium, silica, and calcium present in hard water supplies. Hard water has a higher quantity of dissolved materials that can accumulate and calcify in the heat exchanger causing scales. There are various scale compositions; however, the CaCO3 or calcium carbonate is the most common. When CACO3 falls out of suspension, it forms a continuous deposit layer on the internal surface of the heat exchanger, which leads to the formation of a calcium carbonate scale.
The build-up of scale on tubes, walls, and other cooling and heating equipment surfaces is typically due to the continuous flow of hard water. Thus, scaling accumulates faster when the flowing water in the system has high mineral content. Although magnesium and calcium are the most prevalent minerals, other particles, including rust and lime deposits, could cause scale deposition.
How to Prevent Scaling
The most efficient way to prevent the build-up of scale in your system is to avoid its initial formation. There are effective measures to control water mineral content or prevent scale formation in a heat exchanger. Below are some of them:
- Pretreating water in the system: As established, hard water is a major cause of scale formation. You can target and extract minerals in hard waters likely to lead to scale formation by using reverse osmosis, water softeners, or demineralizes to treat the water.
- Conduct Regularly Water Treatment Program: Establishing a regular maintenance program with periodic mechanical and chemical cleaning will prevent scale formation in your water heating or cooling equipment.
- Monitoring the Mineral Content in Water Sources; Calcium, magnesium, and other minerals can cause scale formation. To prevent this, users can employ various solutions, including cation exchange softening, membrane separation softening, and chemical softening.
How to Remove Scaling
If there is already a build-up of scale in a heat exchanger, you can restore the system to a productive and efficient state by thorough cleaning and taking preventive measures to prevent reoccurrence. Read on to learn step-by-step cleaning guidelines to follow.
- The first step is isolating the heat exchanger by closing the supply water valves.
- To create an entry point for descaling solutions, place a ball valve on the bottom of the heat exchanger. You can close the valve to prevent backflow.
- Carefully connect your circulation hoses to pump your descaling solution directly into the bottom of the heat exchanger, so the fluid returns out the top.
- Then, estimate your cleaning solution quantity. You want to ensure your cleaning solution equals double the volume of the heat exchanger. The total estimate for shell and tube heat exchanger is about 30% tower water, while plate-frame is about 40% tower water.
- The heat exchanger’s highest points should be used as the exit point. Ensure your hoses are positioned at the top above your tubes. This action ensures the liquid volume is increased, so the higher tub is flooded and doesn’t become obstructed with CO2 or foaming during cleaning.
- For the cleaning solution to work effectively, it must be circulated through the system. Gradually fill the exchanger with water and power on the circulation pump. While the pump is powered, continue adding water until it pours out of the return line and enters the solution tank.
- While the circulation pump is on, add an anti-foam agent or 8 ounces of CTA-800 into the cleaning solution tank.
- Then, add a gallon of CA-100, Scalzo, Ox-Sol, or any cleaning product of your choice into the cleaning solution tank.
- The pH of the solution needs to be between 2 to 3. Use pH paper to measure the pH concentration accurately, and add more acid to the solution if necessary.
- Repeat the process every 5 minutes to ensure the pH doesn’t increase above 3. If the pH remains between 2 and 3 for over 30 minutes, you can stop checking as the heat exchanger is now clean.
- You can then begin the flushing process of your heat exchanger. Turn off the circulation pump, detach the return hose from the system, and drain the tank to a sanitary sewer.
- Turn the circulatory pump back on and circulate fresh water through the heat exchanger for about fifteen minutes or until clear water with a maintained pH of 6-7.
- For final rinsing, add half a gallon of Tube Bright to passivate surfaces with raw metal. You can then circulate for another 15 minutes before draining.
- Detach the return hose, close open valves through which water circulation occurred, and re-open the supply water valve in the heat exchanger.
- Your Heat exchanger is now thoroughly descaled and ready to use.
Prevent Scaling in Heat Exchangers with our Maintenance Products
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