Air Cooled Chiller Maintenance

400 kw white chillers with panels open during air cooled chiller maintenance

Air Cooled Chiller Maintenance

A nice day to carry out air cooled chiller maintenance at a new site we have taken over in the South East.

News Article No.6

Our engineer attended site at around 9am with the risk assessment method statement having been sent in advance. A site survey was carried out to see if there were any additional risks. Should there have been any changes- the RAMS have a section for the additional risks and control measures. After gaining a permit to work, our engineer was issued with a security pass to access the chiller compound. Three chillers are located in the compound which feed air handlers for a critical application. Two of the chillers are multiple system, scroll compressor, air cooled chillers. The other is a single system screw chiller.

Program Settings During Air Cooled Chiller Maintenance

A complete download of the program settings is available in our engineer’s phone. This is to cross reference the settings, should one of them be accidentally changed by the maintenance engineers. Onsite engineers are the first port of call for chiller trip outs, with the responsibility to get the plant up and running. We offer real time assistance, over the phone from our Technical Support Desk and can send user manuals in PDF form, direct to their computer. The settings were found to be nominal, so a detailed analysis of the alarm history was carried out:

Alarm History During Air Cooled Chiller Maintenance

In reverse date order, the alarm history of all the systems was interrogated. There had been several system shut downs to carry out the periodic maintenance by the onsite personnel. The electricity having been shut down, there was a subsequent oil pre heating timer in the history too. On Chiller 2, System 1 however, there had been several low pressure trip outs. Our engineer decided to start the maintenance with this system by carrying out a full diagnosis of the low side of the refrigerant system:

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Superheat During Air Cooled Chiller Maintenance

The system runs on R410a refrigerant. This refrigerant has higher operating pressures in comparison with other HFC refrigerants. It has an efficient temperature range which can be seen on a pressure enthalpy chart. Below or above this range- the refrigerant loses efficiency and so has a lower coefficient of performance. The most common saturation point for this refrigerant is 0° which corresponds to a 7 bar suction pressure in the evaporator. Above this is the superheat of the refrigerant returning to the compressor. On this occasion there was found to be 26° of superheat and a suction pressure of 4 bar- close to the low pressure trip out. After careful diagnosis, our engineer decided to focus his attention on the expansion valve:

Thermostatic Expansion Valve

There are 4 forces acting on a TEV:

Liquid line pressure coming from the condenser.
Versus
Suction pressure down the equalising line from the far side of the evaporator. This compensates for the pressure drop across the evaporator and shows the true compressor side pressure.

Spring pressure acting upwards and closing the valve.
Versus
Bulb pressure forcing the valve open.

To reduce the superheat, the bulb should have forced the valve open. The refrigerant charge in the bulb acts upon the bellows to achieve this. The reason for the malfunction, on this occasion, was found to be the failure of the expansion valve orifice. It had become jammed- causing a shortage of refrigerant in the evaporator/ high superheat.

Latent Heat

Our engineer was carrying out the above fault finding with one compressor running and the other two being held off. This was to prevent a low pressure trip. Where chillers are left running with a high superheat condition, the reduced amount of latent heat causes a higher cost in electricity relative to refrigeration effect (COP) The refrigerant carries on superheating without absorbing latent heat- pointless and inefficient for a chiller.

Chiller Pump Down

For convenience, this chiller can be pumped down and valved off using the service valves. The evaporator can be worked on after breaking in procedures are carried out. Therefore, we have arranged for this to be carried out before fitting the new expansion valve parts. These chillers also have the ability to pump down the refrigerant on receiving a fault feedback from the electronic leak detector. This is an added measure to lower the environmental impact of refrigerant leaks.

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Subcooling During Air Cooled Chiller Maintenance

Cooling the refrigerant vapour down, through the latent heat phase and then subcooling the liquid down further. On System 2 of the same chiller, a subcooling issue was identified. 21 bar/ 36° saturation was normal for that system as defined by the fan speed controller. Now, the system pressure was higher at 28 bar/ 47° saturation, so our engineer decided to work out the subcooling. A very high reading of subcooling was recorded at 28° this was diagnosed to be due to non condensables in the refrigerant:

System Non Condensables

Non condensables are gases that will not condense, such as, air and nitrogen. If nitrogen is not vented properly and a deep vacuum then achieved, the gasses will remain in the refrigerant system. When calculating the subcooling, the readings work out incorrectly due the presence of the gasses. This can lead to false diagnosis. The remedy for the issue was to arrange a full refrigerant decant, pressure testing and dehydration, before charging with new refrigerant.

Efficiency

Having good subcooling values on a refrigerant system is critical to efficiency. Where there is no subcooling- the refrigerant has not fully rejected all the latent heat from the condenser. This can be seen when looking at a PH chart and plotting the pressures and temperatures. This heat remains in the refrigerant and adds to the system along with heat added from the compressor and heat from the process. This is another reason the coefficient of performance is reduced and so incurring increasing electricity costs for the plant.

Economizer

These chillers are also fitted with refrigerant economizers- one for each system. They work by diverting some of the refrigerant from the condenser, through a small expansion valve, then through a plate heat exchanger. The rest of the liquid refrigerant passes on the other side of the plate heat exchanger and so is further subcooled.

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To read more about air cooled chiller maintenance hit the Tag at the top of the page.

For further reading on chilled water visit Wikipedia | Click Here


Large white chiller being inspected to compose a chiller maintenance schedule

Chiller Maintenance Schedule

The chiller maintenance schedule in essence is as follows:

  • What is the plant? According to the asset list for that particular contract.
  • What are we going to do with it? The checks, procedures and diagnosis in the pursuit of the maintenance of the chillers.
  • How Often? The periodic maintenance schedule defining the required interval between visits to ensure seamless operation of the plant.

News Article No.5

Chiller N+1

N+1 is intrinsic in the development of a chiller maintenance schedule. N+1 means the amount of cooling required + the same amount again in parallel. It can also be represented as 2N. Two water system pumps are a good example: where the pipework splits in two- one pipe for each pump. When a pump fails, the redundant pump comes online. Chillers are arranged in parallel, in this way, on the water system. This redundancy allows for a stress free maintenance of the plant. The failed system can be rectified and brought back online while the redundant system takes the load.

Intervals of Chiller Maintenance Schedule

The intervals in the contract are influenced by the redundancy of the chillers on site. The less run hours the compressor does, the less maintenance is required. We at Maximus Chillers can tailor make a maintenance schedule exactly to your needs by looking at how much the chillers are used and how hard they work.

Load affecting Chiller Maintenance Schedule

For some applications, the chiller operates under a high load condition all the time, with a redundant system in standby. On other applications, the chiller works in minimal load conditions. Regardless of the load conditions, the chiller is critical to the cooling of buildings or for an industrial process.

Lead/ Lag of Chiller Maintenance Schedule 

An important thing to remember is to balance compressor run hours and bearing wear by rotating the lead/ lag duty of the chillers. This can usually be done in the in the sequencer (if fitted) by changing a program setting. Otherwise, the switchover controls can be changed on the off/hand/run toggle switches. Where manual changeover is required, the onsite engineers are usually conversant with the procedure concerning the water system pumps, valves and controls. During the maintenance, the stop checks can be carried out on the redundant system, while the run checks are carried out on the system which is online.

Chiller Maintenance Schedule for Reciprocating Compressors

Reciprocating compressors require a log of the compressor run hours. This is because the valves and bearings should be changed at pre prescribed intervals as laid down by the maintenance schedule. Particularly important to reciprocating compressors are regular oil changes and oil sampling- a small change in the result of an oil sample can prevent a serious compressor smash up. A check list including the model number and serial number is completed on each visit and kept in a file on site. This file can be consulted during diagnosis and maintenance to decide on the beast way forward with an on going issue.

Chiller Maintenance Schedule for Air Cooled Chiller Condensers

Air cooled chiller condensers can often be looked after by the onsite engineers in between maintenance visits. Just a quick brush down every few months is usually all it takes. Where the environment lends to a type of contaminant being collected on the condenser coils, an effective chemical is selected from our stores and used on the coil. Where there is an issue with the serviceability of the condenser, we can put together a plan to keep on top of it. We can even retrofit a new condenser- it’s what we at Maximus Chillers call the MAXIMUS ADVANTAGE™

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Shell and Tube Evaporators

The shell is made from a heavy steel sheet rolled into a circle. The seam is welded together to form a cylinder. The tubes are pushed though the tube holders which are made from steel and are welded into the shell of the evaporator. The tubes are copper because of its good thermodynamic properties.

Direct Expansion Evaporators

Direct expansion is achieved in an evaporator with a thermostatic, or electronic expansion valve. The refrigerant enters the valve from the condenser as a high pressure, hot liquid. The pressure drop on the evaporator side of the valve makes the refrigerant flash off into a cold, saturation point liquid and vapour mix. The liquid boils off, absorbing latent heat through the inside of the copper tubes. On the outside of the copper tubes is the return water from the process, or the cooling of buildings.

The parts of the maintenance schedule that relate to DX evaporators are:

Oil Pooling

The inside of the tubes are in the clean environment of the fridge system. This means they do not become fouled. A tube insulating issue can be caused on the inside by oil. If there are issues with the oil return system, the oil can pool in the evaporator. A low refrigerant charge can have the same effect. Written into the maintenance schedule are manual oil return and oil draining visits. During these visits, the monitoring of the refrigerant charge is also carried out.

Sensor Location

If a sensor is not located in its pocket correctly, or without sufficient heat transfer paste- it will read incorrectly back to the electronic expansion valve driver. This will cause the expansion valve to malfunction.

Pressurisation Units

A full maintenance of the pressurisation unit is carried out. This includes the pumps, controls and program adjustments as required. Incorrect pressure in the water system will cause a knock on effect of faults on the chillers.

Pump Sets

As above with chiller lead/ lag change over, water system pumps are manually changed over from lead to lag in the building controls. Carrying out this procedure reduces the chance of pump failure between visits. This is because it balances the pump run hours and so prevents bearing seizure after a long period not running.

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Flooded Evaporators

Flooded evaporators are the reverse of the above DX evaporators. The refrigerant is on the outside of the tubes, with water on the inside of the tubes. Gravity and refrigerant charge determine the refrigerant level in the condenser and evaporator. In between the two is located the liquid pipe with the orifice located in the pipe for the expansion of the refrigerant. The cooling water flows through the condenser tubes and off to the cooling towers. On the low side, the chilled water flows through the evaporator tubes and off to the process, or the cooling of facilities.

The parts of the maintenance schedule that relate to flooded evaporators are:

Tube Fouling

Because the condenser cooling water and chilled water systems are pumped through the pipes, the tubes become dirty over time. This occurs more often on the condenser as the water towers are open to atmosphere. Contaminants from surrounding buildings and factories gets into the water system and thermally insulates the tubes. This thermal insulation reduces the heat exchange through the copper tubes. The knock on effect is higher head pressures and eventually high pressure trip outs.

Specialist Cleaning Equipment

We at Maximus Chillers have in our stores the required equipment to carry out the cleaning of the tubes. Our engineers can attend site and liaise with the onsite engineers as regards the draining, strip down and lift out of the heat exchanger end plates.

Flushing Agents

A water sample is taken from the cooling and chilled water systems. These samples are sent off to our laboratory for analysis. Bacteria can build up in the water system causing slime- this can be rectified with a careful selection of chemical agents. Also, silt can build up- various chemicals are added to positively charge the silt and so carry it around the system to the strainer. Where the issue is caused by rust- an inhibitor can be added to prevent, or slow the oxidization of the steel.

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F-gas Chiller Leak Testing

The frequency of F-gas leak testing is determined by the size of the plant. This will be detailed in your F-gas file which is kept on site. Another record of this is kept by the chiller company at their registered office. The copies of the periodic leak testing sheets are kept by both parties. These detail the result of the test, refrigerant added to the system, refrigerant removed from the system and the required follow up actions. Some methods of leak detection are:

Visual Inspection

On each visit our engineers remove the coverings of the ends of the condensers and panels. This is to inspect the whole machine for a sign of a leak. Any potential leak is marked for future identification of the location. A visual inspection will always be backed up with a further diagnosis such as:

Superheat and Subcooling

These readings are taken during a maintenance visit to determine the refrigerant charge of the chillers. The engineer, however, has to bear in mind that the subcooling and superheat readings can read abnormally due other reasons.

Bubble up Leak Spray

Various makes are available from the suppliers. Each engineer having his own preference. We at Maximus Chillers stock leak sprays and a wide selection of other materials.

Electronic Leak Detectors

Fixed

This type of leak detector is installed in the chiller low down in the panel. This is because HFC refrigerant is heavier than air. The leaking refrigerant will tend to pool in the bottom of the various panels around the chiller.

Portable

Each of our engineers carries a portable sniff tester. It comes with an extended tip to get into the most tight and awkward places. The leak detector has a replaceable element inside the unit. It also comes with replaceable tips which can be swapped out periodically. They come with a portable plug socket and transformer to charge the on board batteries after use in the field.

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For further reading on chillers and the chiller maintenance schedule- visit Better Bricks | Click Here


Chiller service company's PLC and relay board in a panel

Chiller Service Company

Chiller Service Company Diagnosis

System Testing

A chiller service company can carry out diagnosis even when a wiring diagram is not available- our engineers can trace the wiring around the chiller.

News Article No.3

This often aids with diagnosis even when there is a wiring diagram, as to have your eyes on a component often makes more sense than a symbol. In any case, our engineers carry out system testing with Fluke multimetes and ammeters. We carry a range of thermocouples and probes to be used in conjunction with our calibrated digital thermometers. We use these along with comparators to carry out leak testing…

F-gas Leak Testing

According to the frequency dictated by the quantity of refrigerant, we use the above test equipment to carry out F-gas leak testing. First, we have a visual look around the chiller for a sign of a gas leak. All parts of the pipework and system components are inspected. Then, we carry out a full refrigerant diagnosis to determine that the refrigerant system is operating with a full charge of refrigerant. The report for each chiller being completed and filed in the onsite F-gas leak register. A history can be built up to assess the serviceability of the plant and the frequency of leaks.

Chiller Service Company Monitoring

Where intermittent faults are concerned, on going system monitoring is required. If the job is not progressed on each visit, there is little point in a call out. We carry out tests during monitoring and ensure that the wiring is tight. Hopefully, waiting for the fault to occur whilst next to the machine. Alongside this, we rely on a report from the end user, as regards, the symptoms and the circumstances of the chiller when the fault occurred. From this we extrapolate the diagnosis and decide the next step to take. This may be to attempt to move the fault to another machine or, at least eliminate one thing each visit.

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Chiller Service Company Evaporators

Shell and Tube Evaporators

These have a rolled steel shell, welded down the seam with and end plate on either end. The water system pipes can be bolted to the sides or the end. The endplate can be removed for access to the waterside of the tubes. A strainer is fitted to the inlet to catch any foreign objects that may have been carried around the water system. Inlet and outlet gauges are fitted for the monitoring of the water system readings during a service visit. On larger chillers the screw or centrifugal compressor is mounted directly on top of the evaporator- sucking directly off the top of a flooded evaporator…

Flooded Evaporators

This kind of evaporator has the refrigerant in liquid form on the outside of the tubes. These are a rack of copper tubes extending through the length of the shell. The warmer process water running through the tubes causes the refrigerant to boil off. A sight glass is usually available to check the state of the refrigerant evaporating on the copper tubes. The suction from the top of the evaporator goes round a baffle so as to prevent the slug back of liquid refrigerant into the compressor. The refrigerant flow into the evaporator is controlled by the expansion valve…

Expansion Valves

This takes the form of a fixed size orifice on the liquid line in between the shell and tube condenser and the flooded evaporator. The size of the orifice previously being calculated to match the mass flow rate of the refrigerant dictated by the compressor. Some newer systems have a variable orifice for the more efficient running of the plant. This is controlled electronically along with the loading of the compressor, relative to the available load condition.

Multiple System N+1

Smaller DX evaporators are usually multi system. This gives an N+1 redundancy of the plant. Indeed, when one side of a 2 system evaporator is having service work carried out, the other side continues to operate normally. Thinking ahead and allowing for additional capacity is essential when the application is critical, such as, a data centre or a hospital. When a redundant system comes online due to a failure- getting the system back up and running is a matter of urgency. For this we offer same day delivery of parts and a fully stocked mobile workshop.

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Chiller Service Company Condensers

Various configurations are employed to ensure good air flow through the chiller condenser fins. The most popular being a ‘v’ condenser as the surface area is increased with this design. Powerful fans are used to reject the air and heat upwards and away from the chiller. Where system location causes the recirculation of air, duct work can be fitted to direct the air away from the chiller.

Pressure Transducers

Johnson Controls

A popular kind of pressure transducer used on condensers is Johnson Controls. These can be bolted onto the refrigerant discharge pipe to sense the system pressure. They have a 5vdc input that comes into the transducer on a red wire, a black wire is the ground and a white wire is the signal back to the fan speed controller. The transducer has a minimum to maximum range, so a chart can be used to determine if the signal is reading back correctly. On chillers where the transducer is wired directly in the controller- calibration can be carried out to offset the readings.

Keller

Another kind of pressure transducer is the 4-20mA type. It sends a mA signal back to the controller or the fan speed controller. 4mA is the minimum position, so this relates to the minimum of the transducer pressure range.

R134a Refrigerant

R134a refrigerant operates at a lower pressure in a condenser than the other commonly used HFC refrigerants. If you were looking for a chilled water set point of 6° in the UK ambient for example, the R134a refrigerant saturation on the high side of the system would be around 36° Latent heat from the water system and heat added into the refrigerant from the compressor are rejected from the condenser. As the refrigerant passes down the condenser tubes, cool air blowing across the outside of the tubes, cools the refrigerant vapour down through the latent heat phase and into a subcooled liquid.

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Chiller Service Company Compressors

Centrifugal Compressors

This kind of compressor has a lower volumetric efficiency compared with the positive displacement compressors below. This is because the refrigerant is compressed using centrifugal force off the tip of the impeller, instead of being mechanically compressed. The advantage of this kind of compressor is a high mass flow rate of refrigerant. These compressors are used in factories where a large amount of chilled water is required to cool the process. They are also used in countries where district cooling is used. The chillers are arranged in rows in a chiller hall and are piped into the district cooling loop.

Screw Compressors

Oil used to lubricate the bearings is also used to create a seal between the rotors. Computer aided design (CAD) software and computer numerical control (CNC) grinding machines are used in the construction of screw rotors. The shape of the rotors is designed to compress the refrigerant along the screw. The length of the screw that is available to compress the refrigerant can be adjusted with a slide valve. Any stage of loading between 0- 100% can be achieved. This is regulated with a slide valve potentiometer. Screw compressors are very reliable and have a long service life. They also have a low vibration reading which ensures a lower instance of refrigerant leaks around the compressor.

Scroll Compressors

A service free compressor. Service free assuming that the rest of the system is functioning correctly. This kind of compressor relies on oil migration around the system. The oil is entrained along the inside of the pipework, around the system and back to the compressor. An oil level sight glass is fitted into the body of the compressor at the required level. Refrigerant shortage can cause the oil to stay in the bottom of the evaporator, causing a low oil level condition in the compressor. Chiller service companies can be scheduled to attend site to drain the oil, then pump new oil into the compressor.

Compressor Failure

When any of the above compressors fail, you are in safe hands with Maximus Chillers. We have the capability to lift and shift the compressor to our remanufacturing facility for a full overhaul. The reason for the failure is diagnosed to ensure the new compressor does not fail for the same reason. Improving the reliability of your plant and extending its life is what we are all about- if we can reduce your service costs- that makes us happy! All temperatures and pressures are recorded to ensure the replacement compressor goes into seamless operation.

Any Chiller- Any Problem- Any Part- Any Refrigerant- Anywhere- The MAXIMUS ADVANTAGE™

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Chiller Breakdown

Read more about pressure sensors on Wikipedia | Click Here


A pile of completed chiller maintenance checklists on a table

Chiller Maintenance Checklist

Introducing  a series of in depth news articles, this time featuring the chiller maintenance checklist:

News Article No.1

This article has been written with you- the customer in mind. Read below for practical advice on how to keep your chillers in the best condition.

Each day when you walk round, you can check to see if your plant is starting to malfunction. Become accustomed with the usual readings to help you diagnose the faults.

Here are the things to check for and how to remedy them:

Water System Pressure

Keep an eye on the pressure in the water system.

Small Chiller Maintenance Checklist

On a small chiller, there will be a water outlet pressure gauge. Make a mark on the gauge where the pressure is when the chiller is in good working order. You can use this mark to notice if the pressure is starting to drop off.

Strainer

The most common cause for low water system pressure is a blocked strainer. It is usually a ‘Y’ type with a bolted fitting. With the chiller off and the water system valves closed, unscrew it and check for debris. If it is blocked, make a note of how long it took to block, then add the cleaning of the strainer into the periodic maintenance schedule.

Pump

Ensure the pump rotation is correct by checking that the cooling fan is sucking into the pump. If it is going backwards: isolate electrically, then swap any 2 of the 3 phase wires. Brush down the inlet to the cooling fan to ensure good air flow and a cool pump motor.

Large Chiller Maintenance Checklist

On a large chiller, the water system pressures may be available in the controller- have a look through the menus. The pressure will be measured in bar. Another popular method on a large chiller is a flow meter. This may be a stand alone device on the chiller panel, or on a control panel nearby. It will read in m3/hr. Check to see if the pressure or flow is lower than usual. If so, ring one of our trained professionals.

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Water System Temperature

The chiller should be:

  • Matching the load and running continuously.
  • Loading and unloading in sequence with other chillers.
  • Going through a cycle and achieving set point.

In any case, you will become accustomed with the usual chilled water temperature according to varying load conditions. If the plant is struggling to achieve set point, or is running higher than usual- this is a sign of system faults.

Walk along the chillers that feed the same water system and make a log of the faults showing on the controllers.

Here are the things to check for high water system temperature:

Small Chiller Maintenance Checklist

Low Refrigerant Pressure

If it has a low pressure gauge, look to see if the pressure is lower than usual. If so, this is a sign of refrigerant shortage in the plate evaporator. A scheduled visit from one of our trained engineers to carry out a pressure test can be arranged.

Breakers

Look for any breakers that have tripped in the panel. One reset can be carried out by a qualified onsite electrician. If the fault reoccurs- ring our support team. If the scroll compressor has tripped, check to see if the compressor is hot. If so, isolate and do not attempt a restart.

Condenser

A blocked condenser will inhibit the rejection of heat. Brush it down and give it a rinse with water. A common occurrence onsite with some condenser designs is a panel being left off with the chiller running! This happens when the onsite engineers are fault finding another issue with the chiller. The fans will suck through the opening as this is the easiest path. The gauge will be higher than usual as the condenser builds in pressure. A high pressure switch trip out will occur.

High Pressure Switch

To locate the switch- first identify the discharge pipe. It is the smaller of the 2 pipes on the compressor. The high pressure switch will either be bolted onto the pipe, or a thin pipe will lead from the discharge to the frame of the chiller. In any case, you are looking for a small box with a button and a wire leading to the panel. Press the button and you should hear it click. If this fault reoccurs- ring our technical support desk.

Large Chiller Maintenance Checklist

Suction

Should there be a refrigerant shortage, the controller will display a pre alarm: suction limiting. This is the controller preventing the compressor from loading up to prevent a low pressure trip out in the shell and tube evaporator. As above, one of our team of engineers can be sent to site to resolve the issue.

Discharge

If the controller is showing: discharge limiting- this is a sign of a condenser issue. A full strip down and cleaning of the tubes may be required. Ring our technical support desk for further advice.

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Chiller Remote Monitoring

We at maximus chiller can install remote monitoring systems to your chillers so we can fault find and diagnose from a laptop. This means we can give you real time advice over the phone. Now you are accustomed with our chiller maintenance checklist- you can give feedback regarding the plant to assist our engineer.

Parts

For our contract maintenance customers: a range of commonly used parts are kept onsite to reduce downtime. We can give practical, step by step advice on the fitting of parts. We often carry out video calls with our customers, as chiller data plates, parts and components can be easier to show than describe.

Any Chiller- Any Problem- Any Part- Any Refrigerant- Anywhere- The MAXIMUS ADVANTAGE™

To read more about air cooled chiller maintenance click the Tag at the top of the page.

Related Articles:
Air Cooled Chiller Planned Maintenance

Water Chiller Maintenance

Process Chiller Maintenance Visit

Chilled Water System Maintenance

Centrifugal Chiller Maintenance

Industrial Chiller Maintenance

Air Cooled Chiller Condenser Maintenance

Glycol Chiller Maintenance

Chiller Maintenance Schedule

Air Cooled Chiller Maintenance

Chiller Maintenance Company

Chilling Plant Maintenance

Read more about chillers on Wikipedia | Click Here


Yellow oil drums, ammonia refrigerant cylinders and flammable flushing agent of chiller parts supplier

Chiller Parts Supplier

Chiller Parts Supplier of Compressors

Centrifugal Compressors

As a chiller parts supplier, all kinds of centrifugal compressors are remanufactured in our workshop. With an over head gantry crane and specialist equipment to hand- Maximus Chillers completes the picture.

Screw Compressors

Screw compressors are remanufactured on the bench. With compressed air and bearing tools- our skilled screw compressor technicians are seasoned in high tolerance measurements.

Scroll Compressors

We have a range of off the shelf Copeland compressors for a fast lead time on process chiller repairs.

Chiller Parts Supplier of Condensers

Air Cooled Condensers

When the condenser on an air cooled chiller is in poor condition- our site survey team will attend to measure up for a new bespoke condenser.

Shell and Tube Condensers

This type of condenser is used on water cooled chillers.

Chiller Parts Supplier of Evaporators

Shell and Tube Evaporators

This is the most popular type of evaporator for large chillers. The low temperature refrigerant is on the outside of the tubes in liquid form. The water is pumped through the tubes, releasing heat from the process into the refrigerant. This is latent heat as the liquid refrigerant boils off into a vapour.

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Chiller Parts Supplier

Vibration Eliminators

We have all the sizes of anacondas on the shelf in our stores. This saves on the delivery time to site when your process if off due to the chiller. Maximus Chillers will get you up and running- fast!

Flushing Agent

For when things go wrong… we stock a solvent based flushing agent which is blown through the system with nitrogen.

Refrigerant Economizers

These are another term for a subcooler. If the refrigerant is further subcooled after the condenser- the system will run more efficiently.

Chiller Parts Supplier of Controls

Pressure Transducers

We can make temporary repairs to faulty pressure transducers using our test equipment. This will keep your plant running while the part arrives onsite.

Chiller Parts Supplier of Ammonia and HFC refrigerant

A full selection of refrigerants are available in our stores including: anhydrous ammonia, R407c, R134a and R410a.

Chiller Parts Supplier of Compressor Oil

Low, medium and high viscosity oils in 5ltr cans and 20ltr drums are ready for shipping from our storage area.

Any Chiller- Any Problem- Any Part- Any Refrigerant- Anywhere- The MAXIMUS ADVANTAGE™

To read more about chiller evaporators- click the Tag at the top of the page.

Related Articles:
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R407c Chiller Condenser Retrofitting

Chilled Water System Condenser Repair

Chiller Compressor Failure

Read more about the centrifugal vapour compressor at the Institute of Refrigeration | Click Here


Two dark green centrifugal chillers undergoing maintenance in plant room

Centrifugal Chiller Maintenance

At the beginning of the year we completed centrifugal chiller maintenance for one of our customers in America. A last overseas trip for the moment given the current world lockdown. The chillers in the photo chill water that is pumped around a university campus.

Centrifugal Chiller Maintenance of Redundant System

The plant has a water cooling shell and tube evaporator and a water cooled shell and tube condenser. It has been designed according to the N+1 principle: N being the amount of cooling required and 1 being that same amount of cooling again. Each chiller has enough capacity to satisfy demand. Given the large size of the campus, this principle was critical to keeping the University functioning should system failure occur. The chiller on the right was the lead chiller on arrival. After taking detailed readings during the maintenance, our engineer switched that chiller over into being the lag chiller and took readings from the chiller on the left. He rotates the lead/ lag of the chillers on each visit to balance the run hours of the compressors.

Volumetric Efficiency

Centrifugal chillers have a lower volumetric efficiency compared with positive displacement compressors such as screws and repips. This is because the impeller does not mechanically compress the refrigerant like a piston in a reciprocating compressor. This kind of compressor relies on centrifugal force to spin the refrigerant off the tip of the impeller and onto the next stage. The refrigerant is then discharged from the compressor.

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Mass Flow Rate

The above is more than compensated for with a high mass flow rate. That is to say: a high volume of refrigerant circulates around the system at its operating density. A large capacity machine is cost effective when considering energy efficiency and centrifugal chiller maintenance costs.

Gantry Crane for Centrifugal Chiller Maintenance

The gantry crane in the picture is available to aid with the lift and shift of the compressor, should compressor failure occur. Maximus Chillers are specialists in the overhaul of centrifugal compressors. We can arrange the lift out, transportation, strip down and reassembly of your compressors. All of our strip downs come with a 12 month warranty to give you peace of mind and confidence in our ability.

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Follow this link to read about centrifugal compressors at The Engineering Mindset | Click Here


Green chiller panel with doors open, showing contactors and PCBs during water chiller maintenance

Water Chiller Maintenance

Maximus chillers provides water chiller maintenance to all kinds of machines. Some of which have kilowatt hour meters fitted. This means we can monitor the reduction in energy consumption, directly as a result of our maintenance being carried out.

Efficient Water Chiller Maintenance

Maintenance is carried out to ensure every aspect of your chiller is running efficiently. We believe our maintenance checklist is the best in the industry. It looks in detail at the running conditions of the plant, component adjustments and the parameters in the controls. The checklist is used to assess if there are problems that are starting to occur before a safety shutdown happens. Below are some of the issues that we keep on top of to increase the efficiency of your plant.

Shell and Tube Insulation

The build up of dirt acts as an insulator in shell and tube heat exchangers. These are used for the evaporation and the condensing of the refrigerant.

The Evaporator

In the evaporator, should the tubes be fouled, there will be a reduction in latent heat absorbed into the system. This will cause the plant to stay on longer and use considerably more energy. Should the tubes become considerably fouled, the chiller will malfunction and eventually system shutdown will occur.

The Condenser

In a shell and tube condenser, the reverse of the above will occur. Tube fouling, acting as an insulator, will prohibit the rejection of heat from the system. The head pressure control will open the condenser controls to try and assist in heat rejection. Heavy fouling will cause an increase in the consumption of energy. Eventually a safety shutdown will occur causing loss of production.

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Compressor Loading

If the loading of the reciprocating compressors is faulty, the plant will not be able to effectively match the load.

Over Loading

Too much loading may occur, causing the water chillers to achieve set point too quickly. The plant will then go through the off cycle. This means that the plant will have to load back up, using more energy than matching the load continuously.

Under Loading

Should the plant be unable to load up to the required level to match the load, this will cause the water temperature to creep up and the lag chillers being called for to match the load. More water chillers running than necessary dramatically increases energy consumption.

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Visit the Refcom site to read about leak checking during water chiller maintenance | Click Here


Water chiller service of evaporator showing lagging removed and blue compressor

Water Chiller Service of Evaporator

Not often does a water chiller service of evaporator fault occur. The evaporator can freeze up and burst the tubes inside the shell. This fault involved the shell itself bursting. On close inspection- the shell was made out of thin steel- not the usual heavy rolled steel. It looked like the near end on the photo had sagged down, causing the evaporator shell to buckle.

Replacement of Evaporator

This option would be expensive due to the cost of the evaporator. It would be a difficult visit because of access issues. The builders decided to site the water chillers round the back of the building, this makes them very difficult to service. Our lift and shift guys would be needed to get the old chiller evaporator out and the new one in. There is a difficult corner to get round where the evaporator would have to be tilted up to get it round. Also, a fence wound have to be taken down around the chillers. Of course security is an issue but so is access to the chillers.

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Water Chiller Service of Evaporator using Silver Solder

Because of the above, it was decided by the customer that we would fix the leak using silver solder. The Risk Assessment Method Statement allowed for the job to be carried out with a half hour fire watch. The oxy-acetylene lines were leak tested prior to the job. Both leaks were soldered up but despite the evaporator being drained down, there was still water and steam trying to get out. Not the best soldering resulted- but it held.

Water Chiller Service of Evaporator Paintwork

Because the chillers are outside, the paintwork is essential- poor paintwork will reduce it's life. After preparing the surface, specialist paint was applied so as to protect the evaporator for the future.

Lagging

The purpose of lagging is to reduce heat gain from the environment and provide protection from the elements. Therefore, the lagging was reinstated after the job.

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See the Institute of Refrigeration Evaporator Efficiency | Click Here

 


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