Category Archives: Chillers

 

Taking things for granted is part of human nature. We rarely consider the way everything works and stays working each day when we go about our routines. The ignition fires up our cars, the coffee pot brews up some motivation every morning and we rarely give the things that make our lives comfortable much thought until they aren’t working. This is no different than HVAC systems. A big part of the HVAC system is the chiller, and the tubes that make it work. Understanding chiller tube cleaning helps us keep our chillers working and our buildings cool during the warmer weather in Arizona.

To keep chillers and HVAC systems efficient they need to have regular maintenance and coatings. It is no small task to care for these critical components of the cooling system for large commercial spaces. Coatings help prevent buildup and cleanings kick out deposits that reduce thermal transfer.

Large commercial spaces use a lot of energy and the chiller can be one of the largest consumer of energy. As the price of energy increases, the savings of regular cleaning and chiller coatings increases. Keeping daily logs, making preventative maintenance a priority, and scheduling regular chiller maintenance will keep your overhead costs down.

Key Chiller Tube Cleaning Considerations

Tube Cleaning

The efficiency of the chiller tubes is completely dependent upon heat transfer. Thermal efficiency is limited by buildup on the inside of the chiller tubes. Most large chillers are comprised of literally miles of tubing which helps achieve the heat transfer in the evaporator and condenser. Keeping the tubing clean therefore is the way these critical HVAC components do their job and use less energy. The best way to keep tubes clean is to have planned outages for cleaning, keeping up with water treatment, and having chiller tube coatings which help control buildup.

The efficiency of chillers drop steeply as buildup develops inside the chiller. It is deposited by contaminants in your water that is recycling through your system and by contaminants being brought in from the air cycling through your cooling tower. The contaminants found in your chiller can range from algae, mud, sand and even minerals that develop into scales that all sap the heat transfer.

The percentages of decreased thermal transfer drop quickly even with what seems like thin layers of contaminants. Even a coating as thin as .0045 can drop chiller tube efficiency by as much as 44%.

Water Treatments

Water used in cooling towers and chillers usually comes from local water supplies. This means there can be additives, sand, minerals, and other elements that cause fouling and deposits in chiller tubes. Even the atmospheric conditions around the cooling tower have a significant effect on the quality and contents of the water used in HVAC systems.

This means that there needs to be water treatment in the system to help fight biological growth, scaling, and other deposits. The most contaminated the water the greater need for water treatment and a more frequent and robust water treatment plan.

Chiller Motors & Electrical Components

The chiller motor in your HVAC system is potentially the greatest user of electricity in your entire building. We might obsess about shutting off lights in our homes and offices, but the chiller is responsible for using an enormous amount of electricity to keep our commercial properties cool and comfortable.

Chiller motor maintenance is a critical part of keeping your system efficient and your energy bills as low as possible. The shaft seals, and air vents should be checked and kept clean.  All of the insulation, wiring, and connections should be maintained to keep the system running properly and avoid unscheduled downtime.

Methods Of Tube Cleaning

For the best thermal performance it is clear that regular cleaning and maintenance of the chiller tubes is not optional. It is mission critical and should be carried out on a regular schedule by properly trained and equipped chiller maintenance technicians. There are different methods that these technicians use to get your tubes clean and maintain the thermal efficiency of your chillers.

Chemical Cleaning

One of the older methods of tube cleaning, is has seen a decrease in use in the last decade. Acid solutions are used in chemical cleaning that soften and break down the scale and deposits in the tubes. The acidic solutions are circulated through the tube bundles and help remove the layers of energy robbing debris.

Chemical cleaning does have the advantages of breaking down mineral scale so brushes can effectively remove them, and it can take tubes back to bare metal. It has lost some of its former popularity because it is time consuming, the chemicals are costly, requires increased training, and the chemicals are dangerous and difficult to dispose of.

Rod & Brush Cleaning

The rod & brush method is very similar to the cleaning of a gun barrel. It is probably the oldest type of chiller cleaning. A rod of metal is tipped with a wire or nylon brush that is larger than the tube. The process generally involves flushing the tubes with water, and then forcing the rod and brush through the tubes. After the rod has been pushed through water is sprayed again to remove any debris.

This is a popular method because it is inexpensive, but it does have some disadvantages. It is labor and time intensive. The chiller might be in an area that prevents the longer rods being used. Smaller sections might have to be assembled as the brush is inserted into the tube, adding to the time of the job. Also the bristles on the brush tend to fold down and end up swabbing instead of brushing. Another limitation of this process can be if the tubes brushed first dry and the debris reattaches before the final rinse is completed.

Rotary Tube Cleaners

Using either an air or electric motor these chiller tube cleaning machines include a cleaning tool that uses water and circular motion to help remove debris. A flexible shaft is set inside a plastic casing which directs water directly to the cleaning head. The tools used with these machines include scrapers, hones, brushes, and buffing tools. This combination of tools is what makes the rotary tube cleaners some of the best at removing deposits, including hard scale. The job is done by one operator feeding the shaft through each of the tubes. Best of all it only takes one pass for each tube.

This is one of the most used, and popular chiller tube cleaning types. It is due to the fact that is it one of the most effective cleaning methods paired with the low cost. The process takes little time and uses less consumables that other cleaning methods. It also only requires one technician, only opening one side of the chiller, and is the best type of cleaning for internally enhanced chiller tubes.

Tube Cleaning Guns

As the name suggests this method of tube cleaning features a gun that uses air or water to shoot a projectile through the tubes. These projectiles vary from metal or plastic scrapes to brushes and even rubber bullets.

This is a popular type of cleaning for light deposits and is very fast. With the right conditions tubes can be cleaned quickly, even in a matter of seconds per tube. It does have the limitation when it comes to the type of deposits it can remove. Harder scaling or stubborn deposits are more difficult or impossible to remove with this method. It also requires the opening of the chiller on both ends to allow the transfer of air as the projectile goes through the tube.

The equipment can be costly to buy and maintain along with some units being somewhat dangerous to operate. The pressure released into the tube might not make it through and be rejected at the operator when the gun is removed. Some units include pressure relief valves that prevent this danger to operators.

On Line Cleaning Systems

Cleaning systems are available for use while the system is active. This means that they help reduce the frequency of downtime. There are two on line tube cleaning types available today. One uses foam balls that circulate through the tubes in the chiller and the other includes the use of plastic brushes that are installed into each of the tubes. The idea behind the foam balls is that they should work through each and every tube in the bundle often enough that they will clean the tubes from becoming dirty. The plastic brush system features plastic baskets which are permanently attached to both sides of the chiller. Periodically the direction of the flow of water is reversed to cause the baskets and brushes to travel the length of each tube, removing debris.

With proper water treatment these systems can reduce or even eliminate the needs for tube cleaning. However these systems are costly to purchase and install. They also are not suitable for chillers that use hard water that promotes hard scaling.

Internally Enhanced Tubes

The only cleaning method for this type of chiller tube is rotary tube cleaning. These chiller tubes are making advancements with thermal efficiency and are becoming more and more common. Internally enhanced chiller tubes are those that include rifling on the inside. Rifling is when spiral groves run the length of a tube. They cause the water to circulate more evenly and provide increased surface area. Both of these elements increase the chiller’s thermal efficiency.

The rifling does mean there are areas that are below the surface of the metal. This means that many cleaning methods are simply not suited for getting into these crevices that increase efficiency. The best type of rotary tube cleaners to use in these applications are bi-directional units. This means that on the way in, and the way out, the brushes can be moving in the same direction as the spiral inside the tube. Specialized heads have also been developed to get into these grooves.

Chiller Maintenance in Arizona

If you have a chiller in or near the Phoenix valley All Kote Inc. can help you extend the life of your chiller and your cooling towers. Regular maintenance and repair keeps the system energy efficient and can save users huge amounts of energy and that means real savings on electricity bills. If you have a commercial space that uses and chiller or cooling tower make sure that you have a plan for maintenance and have All Kote help you with your chiller and cooling tower needs.

Centrifugal chillers of today offer some of the highest efficiencies ever. The technology may be more advanced, and the refrigerants are newer, but some things remain the same: the systems’ need for regular maintenance.

To help today’s high-efficiency chillers maintain those efficiencies in the field, their major components — tubes, oil, compressor, condenser, refrigerant, and starting equipment, to name a few — need to be inspected and maintained regularly.

Jeff Carpenter, marketing manager, Carrier Commercial Service (Syracuse, NY), said that the top areas that affect chiller efficiency are:

• Tubes (“Make sure they are cleaned and maintained”);
• Controls, which need regular inspection and calibration;
• Refrigerant charge optimization; and
• Regular oil changes and yearly oil analysis.

The most overlooked work, he said, is “taking normal, everyday and weekly readings.” If there are no operating problems, staff might ignore this simple task. Taking regular readings, however, allows them to watch for trends, possibly catching problems before they result in equipment damage and unexpected downtime.

This article provides an overview of regular chiller maintenance pointers provided by Carpenter and Carrier technical literature.

TUBE CLEANING, WATER CIRCUITS

The condition of local water will have a lot to do with the frequency required for tube cleaning and inspection, Carpenter said. Know your water quality. The frequency with which tube cleaning winds up being performed is determined mainly due to water conditions; it may also make you decide to upgrade your chiller’s water treatment system.

“Higher-than-normal condenser pressures, together with the inability to reach full refrigeration load, usually indicate dirty tubes or air in the chiller,” states Carrier. This is where taking daily measurements and tracking them over time really pays off. “If the refrigeration log indicates a rise above normal condenser pressures, check the condenser refrigerant temperature against the leaving condenser water temperature.”

If the reading is higher than design, the condenser tubes may be dirty, or water flow rates may be incorrect.

The first step is to inspect the heat exchanger tubes and flow devices. “Inspect and clean the cooler tubes at the end of the first operating season,” the company advises. “Because these tubes have internal ridges, a rotary-type tube-cleaning system is needed to fully clean the tubes.”

An inspection of the tubes’ condition will help you determine how often future cleaning will need to be done, and whether the system needs improved water treatment in the chilled-water/brine circuit. Look for signs of corrosion and scale. The chilled-water cooler tubes are usually part of a closed circuit and less susceptible to “dirty water.” Nevertheless, they should be inspected after the first season of operation.

While you’re there, inspect the entering and leaving chilled-water temperature sensors and flow devices for corrosion or scale. Remove scale if possible, but replace the sensor or Schrader fittings if they’re corroded.

“Keeping the condenser tubes clean is essential in maintaining peak performance,” Carpenter said. “On the condenser side, at a minimum we recommend yearly tube inspections.”

Cleaning can be done as required depending on the results of the inspections. The presence of scale or other corrosion may require chemical treatment or cleaning beyond just brushing the tubes. Inspect the entering and leaving condenser water sensors and flow devices for signs of corrosion or scale. Again, replace the sensor or Schrader fitting if corroded; remove any scale.

REFRIGERANT CHARGE

Proper refrigerant charge in the chiller is essential for optimal performance and energy efficiency, noted Carpenter. Too much refrigerant in the unit can cause refrigerant carryover, a condition where liquid refrigerant enters the compressor and evaporates. This could lead to reduced capacity, an overloaded motor condition, excess power consumption, and possible damage to the compressor impeller.

On the other hand, Carpenter pointed out, insufficient refrigerant charge can result in the top or uppermost layers of the cooler tube bundle not being submerged in liquid refrigerant. In this situation, the “lift” on the compressor increases, resulting in higher-than-normal power consumption. In undercharged units, add refrigerant to minimize power consumption.

Carrier recommends that service contractors trim the refrigerant charge to obtain optimal chiller performance. If it becomes necessary to adjust the refrigerant charge, the company says, “Operate the chiller at design load and then add or remove refrigerant slowly, until the difference between the leaving chilled-water temperature and the cooler refrigerant temperature reaches design conditions or becomes a minimum. Do not overcharge.”

The company says that refrigerant can be added through the storage tank or directly into the chiller, per the manufacturer’s procedures. Excess refrigerant should be removed by following the manufacturer’s recommended procedures.

STARTING EQUIPMENT

Often overlooked, but critical to precise operation, are control devices and the control system.

“While less obvious than the need for mechanical maintenance,” explains Carpenter, “servicing controls is just as important to the overall operation and efficiency of the chiller or chiller plant. And because the mechanical and electrical components were designed to work together, servicing your system in its entirety is the only way to ensure optimal performance and prevent serious problems.”

If the chiller is part of a central plant control or integrated into a building energy management system, Carpenter states, “It is good practice to perform regular system evaluations to ensure that performance is optimized. Trend reports can give you a complete picture of your chiller plant or entire building HVAC system. Armed with reliable information, specialists can suggest and make improvements that will enhance system operation and reduce operating costs.”

A chiller controls test is part of this regular evaluation. It “facilitates the proper operation and test of temperature sensors, pressure transducers, compressor guide vane operation, oil pump, water pumps, cooling tower control, and other on/off outputs,” says Carpenter. “Individual sensors can be calibrated on an as-needed basis or in regular intervals.”

Cleaning and examining the control contacts is another aspect of regular control service. During this part, it is less critical that proper safety procedures be followed. “Before working on any starter, shut off the chiller, open and tag all disconnects supplying power to the starter,” the company warns.

The company also warns that “The disconnect on the starter front panel does not de-energize all internal circuits. Open all internal and remote disconnects before servicing the starter. Never open isolating knife switches while equipment is operating. Electrical arcing can cause serious injury.”

First, inspect starter contact surfaces. Look for wear or pitting on mechanical-type starters. “Do not sandpaper or file silver-plated contacts,” the company states. Follow the starter manufacturer’s instructions.

Vacuum or blow off accumulated debris on the internal parts periodically with a high-velocity, low-pressure blower.

The company also notes, “Power connections on newly installed starters may relax and loosen after a month of operation. Turn the power off and retighten them.” Recheck them once a year; loose power connections can cause voltage spikes, overheating, malfunctioning, or failures, the company warns.

OIL, LUBRICATION SYSTEM

Changing the oil, of course, is critical to operation, perhaps more so than it is to efficiency; analyzing it once a year is equally important, said Carpenter. That determines the frequency of future oil changes, and may alert you to other problems in the system that can be addressed during planned maintenance rather than emergency downtime.

“Do an oil and filter change after the first year of operation,” Carpenter said, “then do a yearly oil analysis. If that’s clear, you can go do an oil change, in some cases, up to every five years.” If the oil is dirty, of course, it needs to be changed more often. Particle size can indicate if it’s from a compressor wear problem or normal wear and tear. Regardless, “Change the oil filter on a yearly basis,” the company states, “or when the chiller is opened for repairs.” The refrigerant filter-drier should be changed “once a year or more often if its condition indicates a need for more frequent replacement,” the company says.

The lubrication system should be checked every week, the company says. “Mark the oil level on the reservoir sight glass; observe the level each week while the chiller is shut down.”

If the level goes below the lower sight glass, make sure the oil reclaim system is operating properly. If more oil is required, add it through the oil drain charging valve. “A pump is required when adding oil against refrigerant pressure.” Note the amount and date that any oil is added.

Note: “Any oil that is added due to oil loss that is not related to service will eventually return to the sump,” the company points out. The oil must be removed from the sump when it reaches a high enough level.

STILL MORE TO IT

Chiller maintenance includes many other areas, such as checking for refrigerant leaks and inspecting power transducers. The point is to be regular, and to check the system’s vital signs (temperatures and pressures) daily.

Maintaining the compressor, Carpenter says, is critical to proper operation and overall equipment reliability, minimizing downtime and maximizing uptime; however, it may not be directly related to the big efficiency picture.

To inspect the bearings, the company says, a complete compressor teardown is required. Only a trained service tech should remove and examine the bearings.

Bearings and gears should be examined on a regular, scheduled basis for signs of wear. Gear inspections require a complete compressor teardown. They, too, should only be done by trained technicians. How often? That is determined by the hours of chiller operation, load conditions during operation, and the condition of the oil and lubrication system.

Excessive bearing wear can sometimes be detected through increased vibration or increased bearing temperature.

One problem is, many companies don’t have enough staff available to take daily readings. Carpenter says that’s where a service like Carrier’s National Monitoring Center can help, by monitoring remotely and alerting onsite staff to potential problems. “It speeds up the whole service process,” he says.

Companies that invest in a new, high-efficiency chiller deserve to get their money’s worth. By performing regular maintenance and taking daily readings, you can help ensure that the chiller fulfills its promise.

Phoenix Chiller Maintenance

There is a lot of work that goes into maintaining chillers and it takes training, the right tools and time to get it done right. All Kote Lining, Inc. specializes in chiller maintenance, cooling tower maintenance, and epoxy coatings that preserve metal, fiberglass, concrete, and more.  Chillers need regular maintenance to get the most cooling with the least electricity.  Let us help you keep your chillers running efficiently and make them last longer. Call All Kote at 480-966-4446.

Related Chiller Articles

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Chillers are usually the largest energy consuming element in most office building and industrial facilities. In fact in a lot of situations the chiller is responsible for over 50% of the electricity consumption. Being the largest energy user in your operation addressing and repairing common problems can mean big savings in utility costs.

In our homes we rarely look at our heating or air conditioning units until the simply are not working, and it seems a lot of commercial and industrial properties wait for something to fail as well. Chillers that are either maintained inefficiently or not correctly mean higher energy use, higher bills, and reduced equipment life.

5 Common Chiller Efficiency Killers

While there are more than just 5 reasons chillers could be having efficiency issues there are 5 that come up more often than others. These efficiency killers are: deficient operating practices, deferred or ignored maintenance, oversizing, ignoring cooling tower maintenance, and ignoring alternative-fuel chillers. Each of these different issues can mean very real and significant diminished chiller performance yet can be prevented and corrected with proper maintenance and repairs.

Deficient Operating Practices

When chillers operating practices are not up to par it means reduced efficiency, greater energy use, and ultimately reduced chiller life. This occurs in two basic scenarios, when a chiller is forced to go beyond its design specifications, or through the actions of untrained operators.

A very common situation in chillers is when more coolant is needed and the flow rate is simply increased past the manufacturers specifications.  While the belief is that if more water is going through the chiller more cold water will come out. This is actually the opposite of how chillers function and will limit the efficiency of the chiller. In fact running a higher flow rate than designed causes erosion in tubes and leads to them failing earlier.

Deferred or Ignored Maintenance

Everything in your building needs to be maintained properly to keep your business running properly and keep operating costs down, yet there are few systems that need more attention than your chillers.

When maintenance is deferred to avoid regular system shutdowns or isn’t even thought of chillers require more and more energy to do their jobs, costing operators more and more on utility bills. Poorly maintained chillers use as much as 20-25% more energy to do the same job. This means literally thousands of dollars difference which is much higher cost than simply maintaining your equipment.

Chiller Corrosion & Solutions

The majority of chiller tubes are made from copper and are prone to galvanic corrosion. The loss of carbon steel and corrosion can significantly affect the performance of you chiller caused by poor water flow problems and sediment buildup. Left to fester these issues means coolant loss from tube perforation. To resolve and prevent corrosion in chiller tubes chiller maintenance companies remove debris, sediment, and corrosion. Then the tubes are coated with high quality chemically resistant epoxy coatings. These coatings help prevent sediment from sticking and cover the copper and steel to keep corrosion from forming. Regular coating is critical over the course of your chiller’s lifespan and will not only extend the life of your unit, but it will run more efficiently and save a tremendous amount of energy.

 

When you are searching “How Do Chillers Work?“you are likely learning how vapor-compression chiller’s work. How cooling towers work, or what a refrigerant cycle is? Keep reading to find out how these systems work.

Chillers use one of two methods, an absorption refrigerant cycle or a vapor-compression for cooling fluids for the heat transfer. Each type depends on three basic principles to work.

1. Liquid gets heated and vaporized, creating a gas. As gas is cooled, it is condensed to a liquid.
2. By decreasing pressure of a liquid lowers the boiling point, while increasing the pressure raises the boiling point.
3. Heat will flow hot to cold, always.

Basic Cooling Cycle

Both absorption chillers and vapor-compression have the same basic cooling cycle’s. They use liquid refrigerant which changes stages to gas inside an evaporator that absorbs the heat from water, which then gets cooled.

Refrigerant gas gets compressed with higher amounts of pressure by a generator or compressor, then converts back to its liquid state as heat is rejected through the condenser, expanding a lower pressure combination of liquid and vapors which then ends up back in an evaporator section. This starts the cycles over.

Vapor Compressor Chiller

Consisting of four main components, a vapor compression chiller uses a vapor compression refrigeration cycle. These components include the evaporator, compressor, metering device, and condenser.

Usually, vapor compression chillers will use either CFC or HCFC refrigerants to get the refrigeration effect. The force that drives a vapor compression chiller is the compressors, which acts like a refrigerant pump.

The compressor sends compressed refrigerant gases to the condenser which then rejects any heat energy to the air outside or cooling water of the system.

The heat transfer provides the needed refrigerant gas for condensing a liquid that gets sent to the metering device.

The liquid refrigerant flow is restricted by the metering device, which results in a pressure drop. This drop causes a change in warm refrigerant liquid so that it creates a gas which absorbs heat out of the water that is then cooled because of adiabatic flash evaporation.

Metering devices are placed so expanding refrigerant gases are contained inside the evaporator, which transfers heat energy between the water that needs to be cooled and into a refrigerant gas. The warmed refrigerant gas then goes back into the compressor to begin the whole cycle over, with the recently chilled water being in a separate loop and used for the cooling process.

Absorption Chiller

A heat source is used by an absorption chiller to drive refrigeration cycles in the place of mechanical compressors. Two fluids are used for the absorption chillers, including a refrigerant that is often water, and an absorbent which is often ammonia or a lithium bromide mixture.

The absorption cycle separates and recombines these liquids, where the lower pressures allow the water to change phases easier than usual, with a high affinity of the liquids promoting easier absorption.

This cycle starts with a combination of liquid absorbent and refrigerant water which gets heated at higher pressures, boiling water from the solution. Then, the vapor from the refrigerant water gets sent to the condenser coil, heat is rejected and condensed to a high pressure liquid. This liquid then gets put through the lower pressure evaporator using the method of adiabatic flash evaporation to convert it back into a gas, which absorbs heat from the water which is to be cooled. The liquid absorbent is now concentrated in the generator, and gets recombined with a lower pressure refrigerant vapor that is returned by the evaporator, and the cycle starts over.

Cooling Towers

Heat energy which was absorbed by the chiller process then needs to be rejected from the system, back into the atmosphere. Usually, cooling towers are used for lowering water temperatures within a larger chiller system, also known as evaporative heat rejection devices.

Phoenix Valley Chiller Maintenance

Chiller Maintenance keeps equipment in good condition, operating more efficiently, and saves money by using less energy. All Kote Lining, Inc. offers chiller maintenance and repair to the Phoenix Valley. We keep chillers and cooling towers operating at their highest possible performance. Refurbishment is one of our services which saves companies and municipalities significant operating costs in comparison to needing cooling tower or chiller replacement. Get in touch with All Kote Lining, Inc. to learn more about what we can do for your chillers and cooling towers.

Call 480-966-4446 Today!