Screw Chiller Compressor Maintenance

Green Bitzer screw chiller compressor with oil separator removed on bench in our workshop

Screw Chiller Compressor Maintenance

Open Drive Screw Chiller Compressor Maintenance

Open drive screw chiller compressor maintenance involves changing the shaft seal at intervals, or if it leaks. This kind of compressor is used with ammonia as this refrigerant corrodes the copper windings and the insulation. It is also used with most large HFC (hydrofluorocarbon) and HFO (hydrofluoroolefin) chillers.

Semi Hermetic Screw Chiller Compressor Maintenance

Because all of the components are internal, this kind of compressor needs less maintenance. It is most often used with smaller chillers running on HFC and HFO refrigerants. This is the compressor type featured in the photo.

Matched Helical Rotors

This kind of compressor design uses a matched pair of helical rotors. These are accurately machined so as to trap, then compress the refrigerant as it travels along the screw. Oil injection is used to create a seal between the rotors. The two rotors are different in shape: the male rotor is driven by the motor and usually has 4 lobes. The female rotor meshes with male and usually has 6 interlobe spaces. The cylinder casting around the rotors is equally important as it seals in the vapour along the screw. Both rotors are helixes with the male rotor moving more rapidly. This compressor design provides a continuous pumping action, rather than pulsating as with a reciprocating compressor. Another advantage of this kind of compression is that there is very little vibration. Indeed, you can place a coin, on its side, on top of the compressors we look after and it does not fall over. This lack of vibration helps to prevent refrigerant leaks around the compressor.

Single Screw with Gate Rotors

This kind of compressor design uses one main rotor, meshing with 2 star gate rotors. These are at right angles with the main rotor. The main rotor usually has 6 grooves.

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Screw Chiller Compressor Maintenance and Reliability

Both of these compressor designs are very reliable with a long bearing life. A maintenance free lifespan of 30 years for the bearings is not uncommon. It is quite common that the compressor will outlive the chiller. In the unlikely event of bearing wear, a characteristic is for there to be undue noise from the compressor at part load which goes away at full load. Higher oil temperature and an unsatisfactory oil analysis are also indicators.

Slide Valve

The capacity is seamless as it is regulated with a slide valve. A spring returns the valve to the unloaded position and a gear type oil pump gives above discharge pressure to load it. The oil pump is not for lubrication, it is just to give the valve enough force to slide with the discharge pressure acting against it. A slide valve potentiometer is fitted to a sliding rod on the end of the valve. It translates the movement along this rod into usually 4-20mA. This signal feeds back to the controller which converts it into a percentage loading reading.

Lubrication during Screw Chiller Compressor Maintenance

Pressures and temperatures are taken during the maintenance to ensure seamless operation. The oil sump is usually inside the base of the oil separator which is at discharge pressure. An oil return pipe is available from the oil sump to the suction side of the screw. Because of the pressure difference from discharge to suction, the oil naturally lubricates the compressor without any need of an oil pump. The oil lubricates the bearings and is injected with the refrigerant along the screw. This provides a seal between the rotors or gate rotors, it also lubricates the rotors to prevent excessive wear.

Oil Separator

The oil enters the oil separator after being discharged with the refrigerant from the compressor. This vessel is insulated so as to stop refrigerant condensing inside as it would in the condenser. An oil heater keeps the oil at the optimum temperature for the compressor. This heater also prevents liquid from forming in the oil separator during off cycles. A check valve on the outlet also prevents this from happening by stopping the migration of refrigerant from the condenser. As the oil sump is the oil supply to the compressor, a temperature sensor will make the program lock the compressor out, should the oil be too cold. This is usually because the main power supply to the chiller has been off during maintenance. The larger volume inside the oil separator slows the speed of the refrigerant so as to allow the oil to drop out. A common design is for the discharge to be directed to the top of the vessel, with a spiral going down to the sump. The oil falls out of the refrigerant vapour during this process. For additional oil recovery, the oil goes up through finer and finer layers of mesh. The oil sticks to this mesh and runs down into the sump.

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Oil Return

Small amounts of oil that have escaped the oil separator will end up in various vessels around the system. On smaller HFC systems there is less of a problem as the oil is entrained by the refrigerant, round the system and back to the compressor. In larger, flooded HFC systems, the oil mainly ends up in the bottom of the evaporator. For ammonia systems, the oil does not entrain with the refrigerant, so oil return devices must be used.

Eductor

This is a pot at the bottom of the vessel where the oil collects. At periodic intervals, discharge gas is blown across the top of the oil which has collected. This has the effect of picking it up and carrying it into the suction of the compressor.

Periodic Oil Changes

We at Maximus Chillers have the full range of refrigerant grade oil for all refrigerant types. It is part of what we call the MAXIMUS ADVANTAGE™ Any Chiller- Any Problem- Any Part- Any Refrigerant- Anywhere. It is critical that the correct oil is selected otherwise compressor failure will result. During each maintenance visit, we make a note of the compressor run hours and carry out oil changes at the correct intervals.

Oil Analysis

We take oil samples which we analyse in our laboratory for signs of compressor wear, oil quality and contaminants. This way, we can prevent untimely compressor failure. If one of your compressors were to fail, however, we have a remanufacturing facility and a lift and shift team to get the job done fast! 

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Oil return solenoid removed during industrial chiller service

Industrial Chiller Service

On an industrial chiller service visit, the ammonia alarm was found to have been triggered.

News Article No.10

Industrial Chiller Service Faults

The onsite engineer had fault found the chiller and silenced the alarm, the yellow light was still flashing. The red light was lit on the panel and the red LED was illuminated on the ammonia alarm console. He had reported a smell of ammonia to us over the phone. This gave us a priority of getting to site, as many other alarms of this nature are often spurious. Our engineer attended site within an hour and confirmed that the fault finding was correct as described by the onsite engineer. The chiller is containerized in design as it is situated outside. All around the chiller are door panels for access to the various system components.

Breathing Apparatus and PPE

He donned his mask and full length ammonia resistant PPE before opening one of the panel doors. This was to ensure that he did not get overwhelmed by the refrigerant when he opened the door. He started with the door into the storage area of the containerized chiller. A strong blast of ammonia came out in his face- lucky for the PPE!

Localising the Fault

Working his way around the chiller, our engineer found more and more hazardous door openings! Eventually he found the culprit: one of the two flanges were leaking on the oil return solenoid. The refrigerant vapour was coming out in its usual white form. The oil return pipe feeds off the oil pot which is a chamber that the oil sinks into from the refrigerant economizer. This vessel was valved off and the other end of the pipe valved off too.

Pinpointing the Fault

Now that the ammonia refrigerant leak had started to calm down- it was possible to see through the white vapour to exactly which of the flanges was leaking. It was the right one as seen in the picture. It consists of an ‘o’ ring made of ammonia resistant rubber material.

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Industrial Chiller Service in Local

The above mentioned chiller runs in local in a lead/ lag configuration with the adjacent chiller. That is to say- there is no wire or modem to a remote location. A panel is available in between the two chillers to sequence the switch over between the two. When the chiller tripped out due to the fault, the other chiller was supposed to have been enabled. This did not happen, so our engineer investigated the situation. The sequencer panel sends out a 24v fault feedback signal to each chiller. This, in turn, goes through a relay and back to the sequencer panel if all is good. When a fault occurs, the volts drop out to the relay in the chiller and a relay drops out in the sequencer. When the relay drops out in the sequencer, a normally closed contact makes and brings a red light on. This was not happening, so our engineer followed it through with his multimeter. He found a blown 1 Amp control fuse in the chiller, he replaced it and it blew again. After some careful research he found that there was an earth leakage due to the ingress of water into a safety switch. This switch was nothing to do with the above, but it blew the whole control circuit. Having reinstated the fuse, he found that the panel switched over satisfactorily in local.

Advantages

This kind of operation method has an advantage in its simplicity. There are no complicated BMS systems for the chiller to be integrated into. A sequencer panel is easy to construct and maintain- keeping the costs down to the end user.

Disadvantages

The disadvantage of this kind of system is that the first thing the factory usually notices is that they are loosing the process. The water temperature getting too high is the first alarm signal. With this site, however, there is a permanent onsite engineer on hand. He is experienced with the first checks to carry out and can often get the plant running with no problem.

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Standing Pressure during Industrial Chiller Service

The standing pressure was taken into account on the return visit to fit the oil return solenoid valve seal. Because the valve is on the low side of the system, when the chiller is off, the pressure is higher than when it is on. Therefore, so long as the seal pressure tests to this pressure, then all will be good when the system is running. That is assuming that the valve seals work satisfactorily at a lower temperature range. There are issues sometimes when a seal will be okay at ambient temperature but will leak when it becomes brittle at a colder temperature. This happens usually on an old seal and, indeed, this condition can be tested for when run testing the system.

Leak Testing during Industrial Chiller Service

On fitting the seal, our engineer donned full length ammonia resistant PPE and breathing apparatus. A little at a time, he introduced refrigerant into the area of the valve seal. Any residual air being purged through a valve.

Pressure and Temperature

The standing pressure of refrigerant is affected by temperature. That is to say- that the higher the temperature- the higher the pressure. On the day this job was carried out, the ambient temperature was 12°C and using an app on his phone, he calculated that the pressure should be 5.6bar. This is consistent with Charles’ Law of Constant Volume with a coefficient added for this particular refrigerant. If the pressure had been higher than this, it would indicate the presence of air in the system. Daltons’ Law of Partial Pressures states that all gasses in a vessel will act as if they are on their own, therefore, causing a higher pressure.

Run Testing during Industrial Chiller Service

After the pressure was built up to full standing pressure and the seal held satisfactorily, the system was then run tested to ensure, as stated above, that the seal performed well across the full temperature range during the operation of the plant.

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Mass Flow Rate during Industrial Chiller Service

The mass of refrigerant passing, which is measured by the second.

Suction Density

In this case of the oil return valve seal, we are looking at the density of the low side refrigerant as it passes into the suction port of the compressor. This is shown on the LP gauge near to the compressor. The higher the pressure of the refrigerant, the more refrigerant there is- so it has a higher mass flow rate. This system has a refrigerant saturation point of 1°C which corresponds to a pressure 3.4bar. That is a high mass flow rate for this kind of refrigerant. This is because this refrigerant is usually used in low temperature applications where the pressure of the refrigerant is below that of the atmosphere. In that condition, when a leak occurs on the low side of the system- air leaks in. Air bleed valves are available to remove this unwanted air from the system.

Compressor Loading

The bigger the compressor on a chiller- the higher the mass flow rate. Most compressors have loading solenoids, vanes, or a slide valve to regulate this.

Piston Displacement

Reciprocating compressors use loading solenoids to increase piston displacement. Usually, oil from the oil pump holds the piston valves open and so preventing compression on that cylinder. When more flow rate is needed- the loading solenoid de energizes- the piston valves drop and the cylinder comes into action. Therefore, increasing the mass of refrigerant through the compressor.

Vanes

Vanes are used on centrifugal compressors to increase the flow of refrigerant through the compressor. An actuator linked to a chain is used to open the vanes. The controls work out the correct position of the vanes for a given load condition.

Slide Valve

The slide valve offers a seamless amount of loading, anywhere between 0% and 100% A slide valve potentiometer senses the position of the slide so that the controls can regulate the flow through the compressor. The screw compressor in this article uses a slide valve- on full load with the slide at 100% all readings were taken with a good read back. Another job done- another happy customer!

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Chiller compressor failure of blue Grasso in enclosure

Chiller Compressors

System Testing for Chiller Compressors

Chiller compressors fail often as a result of ineffective servicing and system testing. At Maximus Chillers, we carry out extensive tests during our visits to ensure that small problems are resolved before they become big problems. If we notice a reading starting to become abnormal, we can carry out the diagnosis and then remedy the problem. Some of the compressor readings we monitor are:

Temperature of Chiller Compressors

The suction, discharge, motor windings and bearing temperatures are recorded for comparison to previous visits. These are often available in the PLC for the chiller, or our engineer can take the readings with his test equipment. Problems with the oil cooler can be the cause of higher compressor temperatures, the system running outside of its nominal operating conditions is another reason. Magnetic drive systems have an advantage as they do not use oil.

Accelerometer

Portable vibration sensors are carried in of each of our company vehicles. This is an accelerometer to measure vibration. Along with other system readings, we keep an on going record of the vibration levels around the compressor. When internal components are coming out of alignment due to wear, this causes an out of balance condition in the compressor. This, in turn, causes a knock on effect- causing other components to go out of balance. Catching this condition early will prevent a compressor smash up resulting in the replacement of expensive internal components.

Oil Analysis for Chiller Compressors

Another way of preventing big problems from occurring is periodic compressor oil testing. Samples are taken, usually on alternate visits, which are sent off to a laboratory for analysis. The acid level is tested to provide pre warning of a potential compressor motor windings burn out. This is because acid in the compressor oil rots through the electrical insulation on the motor windings. The presence and quantity of white metal and yellow metal is analysed too. This is a window through to a component starting to wear inside the compressor.

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Screw

The compressor in the photo is a screw compressor. It operates with ammonia refrigerant. This refrigerant is usually used for low temperature applications, mainly associated with food production. This compressor, however, has a 1°C refrigerant saturation and is used to cool computer rooms. Common causes of compressor failure on this kind of compressor are:

Leaking Castings on Chiller Compressors

The various compressor components are sealed together using ‘o’ rings or paper gaskets. ‘O’ rings are especially prone to leaks due to work hardening and flattening of the sealing face. The system can be pumped down and the compressor valved off. Then, our lift and shift team can remove the compressor to our remanufacturing facility for strip down.

Leaking Shaft Seal

The mating surface of a shaft seal has a mirror smooth finish. This is to reduce friction and aid with a better seal. Over time, this starts to wear, causing an ineffective seal with a leak of refrigerant and oil. A service visit can be arranged to change the shaft seal on site. The shaft couplings can be split, the shaft seal can then be removed and replaced. A quick job, then the machine is up and running again.

Slide Valve Potentiometer

This is an electronic device with a slide attached to the moving compressor slide valve. The device has a start and an end position programmed into it during commissioning. The potentiometer converts the slide valve position, usually into a 4-20mA signal which is fed back to the chiller PLC. They are prone to reading out, or the reading being jammed in one position. This results in a trip out from the controls, as the controller is not able to determine the true position of the compressor slide valve. We have an off the shelf stock of slide valve potentiometers for the various compressor range. A service visit can be arranged to replace the part after diagnosis has been carried out. The controls operate the loading and unloading solenoid valves to change the position of the slide valve.

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Centrifugal

Centrifugal compressors are a very reliable kind of compressor but when they go wrong, they can go wrong in a big way. Compressor overhaul is expensive, this can be carried out onsite, or a better option is a lift and shift to our remanufacturing facility. Proximity sensors are usually fitted to monitor the distance between the impeller and the casting. This is an added protection along with the other sensors and transducers around the compressor.

MCS

We are on account with Micro Control Systems- an American company who specialise in building panels to order for specific chiller compressors. We easily fit this control system to any compressor to control the loading of the vanes in accordance to the available load from the process. The control panel has previously been fitted to other machines of the same model number, so any teething issues have already been ironed out. Maximus Chillers can achieve seamless operation of your plant.

Oil System for Chiller Compressors 

Newer centrifugal compressors are oil free so as to eliminate any of the service issues relating to oil. There are a substantial amount of compressors, however, that use oil to lubricate the bearings. This kind of compressor, if properly serviced, can last for 50 years. The oil system picks up impurities which are caught by various filters. These filters can be changed or cleaned according to the prescribed service schedule. Our engineers make sure that spares are ordered and kept onsite prior to a visit.

Cost Effective

Our visits and ongoing upkeep of your plant saves money. Money spent as a preventative measure saves so much more money in the long run. With competitive prices on specialist internal centrifugal compressor parts- Maximus Chillers completes the picture. When compressor failure occurs, you are in safe hands with years of industry experience invested in each of our engineers.

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Scroll

These are some issues affecting a scroll compressor:

High Discharge Pressure

With high discharge pressure, there is a corresponding increase in discharge temperature. This means that the compressor is operating beyond its recommended values. The cause of this is often a poorly maintained condenser. Especially on industrial chillers, there can have been gaps in the schedule where the condenser was not correctly serviced. This condition is often rectified easily by an onsite engineer by giving it a brush down. Where the fins are bent over- we carry a specialist tool to straighten them back out- how they came out of the factory. We also use different formulas of chemicals to rinse the various kinds of dirt from deep within the fins.

High Suction Pressure on Chiller Compressors 

Some chillers are used where very high water temperature can come back from the process if the chiller were to be off line for a short period. Usually, this happens in factories where certain industrial processes are being carried out. When the onsite engineers start the plant back up, the chiller experiences a high heat load to deal with.

MOP Expansion Valves

Maximum operating pressure expansion valves limit the pressure in the evaporator to a given level, regardless of the available heat load from the process. They do this by having a limited amount of liquid refrigerant in the bulb. When this runs out, the power element cannot push the orifice open any further- thus limiting the suction pressure. This is important to prevent scroll compressor failure as it prevents putting added strain on the compressor motor windings due to high suction pressure.

Oil and Refrigerant Shortage

Where there is a shortage in refrigerant, there follows a low oil level condition. The refrigerant mass flow rate carries the oil around the system and back to the compressor. This is greatly impaired when the chiller is short of gas. The oil cools the compressor and lubricates the shaft bearings. These bearings and other internal components wear down and seize causing failure. Maximus Chillers can put together a package to minimise chiller compressor failure.

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PLC and relay board in a panel during chiller service company visit

Chiller Service Company

Electrical Testing

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

News Article No.3

Doing this often aids with the diagnosis even when there is a wiring diagram, as having 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.

F-gas Leak Testing by Chiller Service Company

We also 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. After fitting the probes, we first have a visual look around 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. Reports for each chiller are 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 any leaks.

Chiller Service Company Monitoring

Where intermittent faults are concerned, on site 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 feedback 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

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 visit. 

Flooded

On larger chillers, the screw or centrifugal compressor is mounted directly on top of the flooded evaporator. The refrigerant is in its liquid phase on the outside of the tubes. These are arranged in a rack 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.

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 failed 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 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. The pressure is monitored using a HP gauge.

Pressure Transducers

Johnson Controls

A popular kind of pressure transducer that is 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°C in the UK ambient for example, the R134a refrigerant saturation on the high side of the system would be around 36°C 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. We 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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Yellow oil drums, ammonia refrigerant cylinders and flammable flushing agent of chiller supplier

Chiller Parts Supplier

Chiller Parts Supplier of Compressors

Centrifugal

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

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

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

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

This type of condenser is used on water cooled chillers. It is protected from contaminants by a strainer on the water system.

Chiller Parts Supplier of Evaporators

Shell and Tube

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™

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Chiller Condensers

Reciprocating Chiller Compressor Maintenance

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


Carel controller and tick sheet during chilling plant maintenance visit

Chilling Plant Maintenance Visit

On this chilling plant maintenance visit, particular attention was made to compressor loading. This was to ensure that the compressors are capable of operating at 100%. With summer now here- we want the plant capable of running at full capacity.

Controller Loading Timer

On start up, the controller goes through a timer, this is to prevent the compressor from loading up too quickly, achieving set point and going off. With available load, the compressor would start back up and go into a short cycling condition. With 5 minute intervals, the controller brings System 1 screw compressor on at 25%. Then System 2 screw compressor on at 25%. In stages, the controller loads up the compressors until it matches the load.

Compressor Loading Solenoid Coils

These are 24vac. The controller sends out a run signal through the solenoid coil which magnetises the lift valve inside.

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Compressor Loading Solenoid Valves

As the valve lifts, discharge pressure oil passes through a channel and pushes the slide valve open a 25% stage. There are 4 valves for the 4 stages.

Chilling Plant Maintenance Visit at 100%

The chilling plant being maintained on this visit was now running at 100% on both systems. The system readings can easily be read by following the menu in the Carrel controller. Superheat and subcooling readings were found to be within normal operating limits. Also, a good read back was recorded on the water system.

Compressor Unloading

At the end of the day, the three way valves on the air handlers closed down according to the BMS schedule. This meant that the water was diverted away from the heat exchangers in the air handlers. This return water had not picked up any heat, so the controller started unloading the compressors. It did this through 75% to 50% then 25% until the water system was down to setpoint.

Off Cycle at Chilling Plant Maintenance Visit

The BMS stops the chiller with the remote start/ stop signal. Should the BMS malfunction, the chiller would stay off most of the night anyway. The water system pump adds heat into the water system. Therefore, every so often enough load would be available to bring one system on at 25% for a short while.

To read more about chiller compressor systems click the Tag at the top of the page.

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Read all about solenoid valves on Wikipedia | Click Here


R134a chilling plant maintenance showing screw compressor and oil separator with tick sheet and digital thermometer on top

R134a Chilling Plant Maintenance

We recently carried out R134a chilling plant maintenance at our customer’s factory in the North West. The chiller is 600kw with 2 single compressor systems. It has an ‘in house’ controller on it with occasional spurious trip outs. We are working with the problem so far, but an option if the problem persists is to fit a reliable, cheap, off the shelf controller. The factory requires a process water temperature of 6°C. The plant is around the middle of the lifespan and has been properly maintained.

Unlock Controller during R134a Chilling Plant Maintenance

The customer had accidentally locked the controller by pressing the wrong buttons. The machine still functioned as it should, but the customer was unable to modify User settings or look at the readings. Our engineers carry a book with an extensive list of information for any controller which has been built up over time. The procedure was followed to unlock the controller, then the settings were checked.

0161 370 7193

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R134a Chilling Plant Sensor Maintenance

The sensors can be offset to compensate for a sensor reading out slightly. No offsets were saved and the sensors all read to within a degree or two of our digital thermometer. Our engineer then checked the sensor locations to ensure they were fitted correctly and insulation had not deteriorated.

Fan speed Controllers and Subcooling

During the R134a chilling plant maintenance, particular attention was paid to the fan speed controllers and the subcooling of the refrigerant. This is because of occasional spurious high pressure trips. All the wiring was tightened and the plugged connections were checked and tested. The controller sends a variable run signal to the fan speed controllers. This is worked out from the analogue input signal from the high pressure transducer. If the problem persists, we will have to look into fitting more reliable head pressure controls.

Compressor Slide Valve

The oil solenoids which push and pull the compressor slide valve were operating correctly. The controller sends volts to the solenoids to control the position of the valve. A slide valve potentiometer sends feedback so the controller can work out the percentage position of the valve.

To read more about chiller control systems click the Tag at the top of the page.

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Follow this link to read more about pressure sensors on Wikipedia Click Here


Ammonia refrigerant cylinder being winched up a cat ladder using a block and tackle

Industrial Refrigeration Ammonia

The industrial refrigeration ammonia visit was at a site in Aberystwyth. We look after 2 ammonia chillers for a blue chip customer. They are 10 year old chillers that have been designed to need ongoing attention. Quite easy job as the faults they go into are reoccurring round in a circle. They have previously had the same problems.

Ammonia Shaft Seal for Industrial Refrigeration

The shaft seal had started to leak ammonia. It was replaced by removing the shaft seal cover, splitting the coupling and sliding the shaft seal over the shaft. After removing the non condensables, we reintroduced the ammonia back into the compressor- now the 'o' rings leaked.

Leaking Industrial Refrigeration Ammonia 'O' Rings

Leaks on ‘o’ rings occur because they become flattened and plastic like. This is caused by heat around the high side of the screw compressor. When there is pressure in the system- the oil if forced against the gap- making a seal. After the ammonia refrigerant had been handled- the oil ran away- causing a leak when the ammonia was reintroduced.

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Lift and Shift Visit

The pipework and ancillaries had been removed from the compressor prior to the visit. Our lift and shift guys arrived and set up their lifting equipment. They raised the compressor and manoeuvred it on across the roof. They then manoeuvred it up then down some steps. They used lifting equipment to get the compressor, end on- down a cat ladder.

Compressor Strip Down

It is always better to strip down this kind of compressor in a workshop- on a bench with compressed air and all the tools nearby. We unbolted the castings and slid the screw out. The various castings being laid out in a line. We replaced the ‘o’ rings for new the rebuilt the compressor.

Industrial refrigeration ammonia being charged by an engineer wearing breathing apparatus and gloves
Ammonia refrigerant being sucked into the low side of a flooded evaporator

Ammonia Refrigerant Charge

Part of the ammonia refrigerant had been handled during the visit. This left the compressor pipework, compressor and the oil separator open to atmosphere. The non condensables were evacuated. In the photo we are lifting the cylinder up a cat ladder into the plant room. From there it needed to be man handled up some steps, down some steps and out onto the roof. We charged the ammonia plant with liquid ammonia until the superheat and subcooling values were within industry known limits. The sight glass levels and condition were monitored too.

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If you would like to buy an introduction to ammonia refrigeration from the iiar | Click Here


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