Process Chiller Maintenance Plan Checklist

Process chillers are vital cooling systems for many industrial and commercial applications. They are expensive to install and operate, especially if they are not running efficiently. Therefore, it makes sense to protect your investment, prevent downtime, and keep up with regular maintenance. These maintenance procedures are for a water-cooled process chiller; an air-cooled chiller will have different maintenance requirements.

1- Tube Cleaning Process Chillers

There are two main ways to clean process chiller tubes. Fouling and scale will build up over time on chiller tube surfaces. It is essential to clean your tubes, as it significantly enhances heat transfer. If there is any sort of debris or fouling on the tubes’ service, heat will not transfer efficiently as it would with clean metal surfaces, resulting in more energy wasted to cool the same amount.

Brush cleaning- This is the fastest and most common way to clean process chiller tubes. It can involve a brush and a metal rod or a brush and a hose. The brush and hose combination is much more effective. Friction from the brush and water pressure from the hose work in tandem to effectively remove fouling and other debris stuck in the heat exchanger. Goodway is the most popular brand for chiller tube hose cleaners.  There are several brush manufacturers; the most common brush material is nylon. This effectively removes fouling but may have trouble with hardened scale. Ideally, the scale would be chemically softened to be able to effectively remove it.

Acid Wash- A more time-consuming approach that can yield even cleaner results is acid cleaning. It could cause downtime; therefore, it is best to do it when its downtime would have the least impact (such as starting it before use if it is a seasonal application). To perform an acid wash, you feed a significant amount of acid into your system. This will then dissolve scale and other solids stuck on your chiller tube surfaces. After acid washing, it is important to flush the system to remove suspended solids and acid chemicals. After around 15 minutes of clean water running through the system, it is important to restore the pH in the water by adding alkalinity builder chemicals. This counteracts the corrosive nature of acid.

2- Chemical Water Treatment for Process Chillers

A well-executed chemical water treatment program will result in less effort needing to be spent on other types of maintenance, such as cleaning, repair, and replacement. The makeup water that comes from municipal sources is not ideal to have in your system unless it is chemically treated. The chemical treatments available for your condenser water will reduce scale, corrosion, and bacteria/fouling. In addition to this, chemical treatment will extend the lifetime of your process chiller and improve its efficiency. Automatically fed pumps and remote monitoring can be set up to effectively run a chemical water treatment program. There are 4 main types of chemicals needed for process chiller maintenance:

• Scale Inhibitor- Hard water is the biggest culprit of scale deposits in a process chiller. Scale forms large layers of calcium or other minerals that reduce water flow and insulate heat transfer. The way a scale inhibitor works is by disrupting the formation of scale from the present minerals floating in the water. Another effective way to prevent scale is with a water softener, as it entirely removes the “scale minerals” and replaces them with “soft minerals” like sodium or potassium. Chemical examples: Polymers, phosphates, and phosphonates.
• Corrosion Inhibitor- Corrosion weakens the metal surfaces of a chiller and can lead to significant repair issues. In addition to this, it impedes heat transfer. Open loops are more susceptible to corrosion due to a higher amount of air entering the system; however, both open and closed loops will have corrosion if left untreated. Corrosion inhibitors typically work by either slowing down the “cathodic reaction” that causes most corrosion or by forming a protective film on the system’s surfaces. This protective film is dual-purpose, protecting from both corrosion and scale. Chemical examples: Molybdate, phosphates, phosphonates, nitrites, silicates.
• Biocides- Bacteria present in chillers can cause significant fouling (including biofilm). Biofilm is an especially resistant byproduct of bacteria that protects them and amplifies their growth. Fouling occurs and can clog up your chiller tubes, resulting in inefficiency. Bacteria in process chillers also pose a Legionella risk if they are connected to a cooling tower, as they will aerosolize and possibly infect nearby people. To combat bacteria, biocides are used. They come in two forms, oxidizing and non-oxidizing. These will eliminate both aerobic and anaerobic types of bacteria. They function by either inhibiting the growth of the bacteria or by killing them. Chemical examples: DBNPA, glutaraldehyde, chlorine, and bromine.
• pH Adjusters- Generally, 6.8-8.0 is the ideal range to run a process chiller, depending on other factors and manufacturer guidelines. The pH level is important as low pH (acidity) causes corrosion and high pH (alkalinity) causes scale. There are two types of chemicals that can be fed into your system to achieve an optimal pH range. Alkalinity builders increase the pH in the water, and acids decrease the pH in the water. Chemical examples: Sodium hydroxide, sodium carbonate, potassium hydroxide, sulfuric acid, hydrochloric acid, and nitric acid.

3- Chiller Refrigerant Leaks

Refrigerant leaks can become costly and pose a safety hazard. In addition to monitoring refrigerant levels used, there are two major ways to detect a refrigerant leak:

• Sniffer (Electronic leak detector)- These come with a “heat sensor” that detects airborne refrigerant. They are handheld and rechargeable.
• Water/soap test- spraying a mix of water and soap on various common surfaces for a refrigerant leak on a chiller (such as at valves and other fittings). In areas where it bubbles, there is a possible refrigerant leak.

4- Glycol Measuring

Glycol is an essential antifreeze protection for your chiller process system. If it were to reach freezing temperatures for too long, your chiller would burst, leading to significant repair costs. Measuring the level of glycol present in your system is important; in addition to antifreeze protection, glycol provides some level of corrosion inhibition and bacteria mitigation.

5- Measuring Oil Levels

It is important to check the pressure of your oil, measure the level of oil used and, in your system, and monitor leaks. Additionally, you will need to perform regular compressor oil filter changes, typically on an annual basis.

6- Variable Speed Drive Pump Installation

It manages actuaction states of electric pump motors. It significantly impoves efficiency, electric usage can optimistically go down on the system by 30-50%. An additional benefit of it is that it allows for soft starting the motor and pump.

7- Additional Maintenance Checks

1. Check temperature.
2. Listen for potential odd noises.
3. Regular condenser coil cleaning.
4. Water flow monitoring.
5. Electrical functionality and sensor calibration.
6. Monitor compressor run time.
7. Motor inspection.

Chardon Labs Process Chiller Waterside Maintenance Services

Maintaining the ideal water chemistry for your process chiller can be a challenge. There are tens of water quality indicators that can be optimized with the right chemical treatment and equipment. Water treatment pays for itself, offering significant efficiency savings and preventing costly, large repairs and replacements. To learn more about our water treatment services, reach out here.

Matt Welsh

Matt Welsh is the Vice President and Water Consultant at Chardon Labs. He helps consult a wide range of customers utilizing various methods of water treatment, from chemical to chemical-free approaches, large and small applications, and across a wide range of geographical influences. With 20 years of water treatment experience, including a wide range of troubleshooting and service in potable water and non-potable HVAC and industrial applications, he is an expert in water treatment chemistry for cooling towers, boilers, and closed-loop systems.