Chiller Repair Service

New fan decks being lifted onto ammonia chiller during chiller repair service

Chiller Repair Service

An effective chiller repair service is what you need to get you up and running- fast! Here at Maximus Chillers, no job is too small, or too big. We have the capability to do anything from replacing contactors to centrifugal compressor remanufacturing- we are a one stop shop for all of your needs.

News Article No.26

Customer Orientated Chiller Repair Service

We also know the reason why we are an expanding company: you- the customer! Listening to your requirements goes a long way to help us achieve your objectives. We assign the same engineer to each site, so that you have the chance to build up a relationship and he gets to know your plant. Read on for an insight into some of the repairs that we carry out…

All new fan decks in place on large air cooled chiller during chiller repair service
Fast supply chain for retrofitting fans

Fan Deck Retrofitting Chiller Repair Service

The photos show the fans being lifted up, then when they are in position on a 200kw ammonia chiller. The fans had been failing one at a time until the chiller started experiencing high pressure trip outs. Action was not immediately taken because there were insufficient funds in the customer’s budget. When the customer was allocated a new budget, they gave us the Order to carry out the work. We decided to change all 8 fans.

Odd Size

The old fans were 790mm blade diameter instead of the standard 800mm. Manufacturers ask suppliers for odd sizes and specifications along with an OEM data plate in an attempt to monopolise the customer. A bonafide chiller company, however, is adept at making square pegs fit round holes. Not really a round hole though with this one- we just plonked our fan decks on top where the old ones had been fitted.

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Refrigerant Leak Chiller Repair Service

HFC refrigerants are becoming more expensive due to the HFC phase down. Therefore, as well as the environmental cost of a leaking chiller, there is the cost on your pocket too. At Maximus Chillers we find the root cause of the leak instead of just brazing it up. Some of these causes are:

Condenser Vibration

Some head pressure control systems bring the fans on, forwards and backwards in different stages. This causes the chiller frame to judder and vibration related leaks to occur on the condenser. The solution is easy- fit stand alone fan speed controllers.

Compressor Vibration

Some chillers are designed to fit into a small footprint of space. A good example of this is a particular model of laser chiller that had been designed to fit down the side of a laser cutter. That’s alright until, years after production, reoccurring leaks start happening around the compressor. There is no room to fit vibration eliminators, besides, they only work if they are fitted horizontally and vertically with the far end being clamped. Brazing the leak up just causes the already work hardened copper pipe to further anneal and become even more brittle- another leak will happen shortly there after. The solution is to remove the whole piece of pipework, go up a pipe size and replace it with new.

Component Failure

We find some components are flawed and are prone to leaking. An example of this are refrigerant hoses which are prone to rubbing through against the chiller. The solution is to fit anacondas or static copper pipework.

Reduced Service Costs

All of these measures and more are how we reduce the frequency of refrigerant leaks on your plant.

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Compressor Remanufacturing Chiller Repair Service

Weather you have scroll, reciprocating, screw or centrifugal compressors, we have the capability to get it out, rebuild it and get it back in again. With same day delivery of internal compressor components- we won’t keep you waiting around. Our expert team are adept at ensuring that your compressors are rebuilt with minimal run out and have clearances that are within tolerance. All bolts are touqued up to the correct setting too. The last part of the job is the compressor paint re spray to the same colour as before, or to our standard battleship grey.

Controls Retrofitting Chiller Repair Service

When a controller fails it is often found to be obsolete. Don’t worry because we can fit a new controller to any machine. For HFC chillers we fit Carel controllers, we fit Beijer Electronics to ammonia chillers and MCS controllers to centrifugal chillers.

Strip Out

The easiest way to do a controls retrofit is to start all over again from scratch. We remove the defunct controls from the panel and pull all the control wiring out too. We leave the three phase wiring in place, the contactors and the common neutral.

Rewire

One wire at a time, we rewire the chiller. All of the analogue inputs are wired in along with the digital inputs. Then, the outputs are wired to the contactors and relays. The transformers in the panel are often reused to get the various voltages that are required for the new controller, contactor coils and relay coils.

Commissioning

The new controllers come pre set with default parameters so only minor adjustments are needed to get the chiller to settle down. We then spend the rest of the day monitoring the chiller so as to watch it running in the various stages of loading and under different running conditions.

Chiller Repair Service that is Second to None

The above examples are just an insight into our extensive range of capabilities in the repairs of your plant. Basically- if you have a problem- then we have a solution. This is just part of what we call the MAXIMUS ADVANTAGE™ Any Chiller- Any Problem- Any Part- Any Refrigerant- Anywhere. With customers around the world in places like Saudi Arabia, Spain and the United States of Amarica we continue to exceed the expectations of our customers. We have a network of engineers around the UK too, so we are never farer than a couple of hours away. For the best service, the choice is clear- Maximus Chillers!

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Dirty tubes on the left and clean tubes on the right after chiller condenser tube cleaning

Chiller Condenser Tube Cleaning

A nice job for our overseas engineer: to carry out chiller condenser tube cleaning in Cadiz, Spain. We have The Spanish Office near Malaga with a manager and an engineer out in the field- so our Spanish engineer assisted our overseas engineer.

Centrifugal Chiller Condenser Tube Cleaning

The factory has 4x water cooled centrifugal chillers with a combined cooling capacity of 8 MW. The chillers cool down a process involved with the production of an industrial chemical.

High Condenser Pressure

When we looked through our Tick Sheets we could see a gradual deterioration of the high side readings over a period of time. This showed us that an overhaul needed to be carried out on the condensers.

Water Tower Contaminants

We think that the fouling was due to contaminants that were carried in the air from around the factory. Each condenser has a water tower which is open to atmosphere. The condenser cooling water enters the cooling tower at the top. It runs down along plastic slats which are stacked on top of each other. In the opposite direction, air is blown up using large blowers. The air flow cools down the water, which then returns to the condenser. This process is how the contaminants from the air end up in the water.

N+1 Redundancy

This is an algebraic way of saying that there is twice as much cooling as is needed. Where N is an amount of something and +1 means another one. Redundancy is needed when a process is critical. In this instance, the factory would grind to a halt if the chillers went down. Therefore, only two of the 4 chillers run at any one time.

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Sequencer

A sequencer is available to switch between the chillers when they go into fault and to balance the compressor run hours. We decided to start work on Chiller 1 as this was a system in standby. The next chiller in standby was Chiller 2. After this chiller had been overhauled, we switched Chiller 3 off which brought Chiller 1 on. Then, when we isolated Chiller 4, the sequencer brought Chiller 3 on. Before leaving site, we temporarily lowered the setpoint for all 4 chillers to watch the sequencer bring all of the chillers on together. We then put the set point back to its usual setting, whereby Chillers 1 and 2 remained running.

Shipping for Chiller Condenser Tube Cleaning

We keep tube cleaning equipment in our stores in Jeddah, Saudi Arabia which we ship to our Middle East customers. We also have tube cleaning equipment in our stores at Head Office in Manchester, UK. We use a pallet shipping company based in Rochdale to ship parts, materials and equipment overseas. Therefore, we packed all of the necessary equipment on to a pallet, then shipped it to Cadiz. For the consumables used on the job, we have suppliers in Spain, but we usually prefer to ship these smaller things from the UK along with the equipment. This is because our engineers are more used to the brands and types of consumables that we get from our UK suppliers.

RAMS for Chiller Condenser Tube Cleaning

All of our paperwork, Tick Sheets and Risk Assessment Method Statements have been professionally translated into Spanish. Therefore, our Spanish engineer carried out a site survey to assess the risks, he then sent a report to Head Office. We decided upon the appropriate measures to control the risks, then sent the RAMS to site prior to the visit.

Permit to Work for Chiller Condenser Tube Cleaning

The onsite health and safety officer looked at our RAMS and decided how to compose his Permit to Work. Then, both of our engineers signed it at the start and at completion of the job.

Walk Round before Chiller Condenser Tube Cleaning

On completion of the paperwork, our engineers, the onsite health and safety officer and an onsite engineer had a walk round to assess the job. This was to make sure that all was okay to carry out the tube cleaning.

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Chiller Condenser Tube Cleaning Operation

Each of the 4 chillers was worked on in turn in the order as described above.

Valve Configuration

Each condenser was valved off with the configuration of the pipework changed. This was to ensure that the flow rates were correct for all 4 of the chillers. Otherwise, a catastrophic failure of the chillers could occur.

Drain Down

The condensers were then drained down and vented using a selection of fittings that were shipped out with our equipment.

End Plates

Our engineers unbolted the end plates and lifted them to the side using specialist lifting equipment.

Tube Cleaning

In Spain they just use a 220v supply for electrical equipment instead of the 110v equipment that we commonly use in the UK. As our equipment is 110v, we shipped our transformer on the pallet. Once the equipment was set up- we carried out the cleaning of each condenser tube according to standard industry guidelines.

Rebuild

The seal on the end plates is prone to leak after breaking into the system so we shipped replacements from Head Office. Our engineers found it a fiddly job as the new seals had been folded up in a different position in the packet. This meant that they kept jumping out of the grooves. When the seals eventually remained in the grooves, the end plates were bolted into position according to the correct torque setting.

Air Purge and Valve Configuration

The air was purged from the shell of the condensers and the valve configuration was returned to the original position.

Test Operation

Each of the 4 chillers was run tested in turn and the system readings were recorded on our paperwork. A dramatic increase in performance was recorded on each system. The refrigerant pressures and temperatures were a lot better and the coefficient of performance was markedly higher. This means a lower carbon footprint and lower electricity costs.

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Chiller maintenance service Tick Sheets showing readings

Chiller Maintenance Service

Maximus Chillers have just carried out our quarterly chiller maintenance service at a factory in the North West. We look after 6MW of cooling across 12 industrial process chillers. This was a minor visit, so no need for oil changes and checking the head gear on the reciprocating compressors. Instead, we took oil samples which we analysed in our laboratory. Read on for an insight into our engineer’s findings on each of the chillers…

News Article No.25

Chiller 1 Maintenance Service

System 1 has a compressor that had blown all three of the 200 amp centred tag fuses. On inspection with a multimeter, our engineer found a dead short to earth on the internal electric motor. We have submitted a Quote for the lift and shift, remanufacturing at our facility, then the lift back in. Several oil changes will then be carried out at planned intervals.

Chiller 2

More or less textbook readings were taken and no problems to report.

Chiller 3 Maintenance Service

Slightly poor readings were taken on the low side of all 4 of the systems. This issue has now been flagged in our system for monitoring. If it deteriorates, we will submit a Quote to take the evaporator end plates off and carry out a chiller tube cleaning operation.

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Chiller 4 Maintenance Service

Compressor 3 has had an issue that has been developing over a period of time. Occasionally, it throws the breaker, then when the electrical readings are taken- they all check out okay. The contactor condition had been inspected, the wiring and motor connectors had all been tightened up too. Shortly before the visit, our customer rang to say “Chiller 4 has gone for a Burton!” When we attended the call out, we found the contactor had blown against the inside of the panel. We have submitted a Quotation for the replacement.

Chiller 5

System 2 had a flashing sight glass in some conditions, but the other fridge readings were okay.

Chiller 6

This system had low side readings similar to Chiller 3. Again, they were not deemed to be an issue yet, but if we decide to do a chiller tube cleaning operation, we will prepare one Quote for both chillers.

Chiller 7

No problems to report.

Chiller 8

Only a short run was available due to the process load conditions, but no problems were found by our engineer.

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Chiller 9 Maintenance Service

All the way through to chiller 9 and the fault finding was easy, now this: external interlock alarm. When our engineer logged the issue with our Technical Support Desk using our real time app on his phone, he stated that to his knowledge, there were no external interlocks.

Fan Motors

Therefore, he decided to check the fan motor overload switches. All 5 fans on each system are linked together in series, so he looked for the volt feedback in the panel for System 1 and System 2- this checked out okay.

External Switch

Therefore, he decided to look for an external switch as the fault suggests. He walked along the gantry and down into the plant room below the chillers...

Pump Set Panel

There is a panel that controls the chilled water pump sets. No wire from the chiller was found to go into this panel.

Remote Monitoring Panel

This is a display that conveys the running condition of the chiller down to the plant room below. It saves a process engineer from having to go up the stairs and onto the chiller gantry. This panel is indeed connected to the chiller with electrical wiring. However, no switch was found that could have caused this fault.

Buffer Vessel

A 10,000 ltr buffer vessel is also located in the plant room. As it is open to atmosphere, our engineer looked for a low level switch which may have tripped- no switch was found.

Program Settings

Now that anything external to the chiller had been eliminated, our engineer decided that the fault must indeed be coming from inside the machine. Because the fan overloads had checked out okay, he decided to have a look at the program settings...

Extensive Library

We have an extensive library of manuals and passwords for all chillers. We also have a network of engineers around the country- one of them will know someone who will has a manual or password. When our engineer contacted our Technical Support Desk real time through his app- the manual and passwords were sent to his phone. He found the menu level and parameter for external interlocks which was found to be wrong. To our knowledge, our customer does not have the password for this chiller. The process had been off for some time due to system upgrades with contractors on site doing other work. They could have changed the setting for some reason. We don’t know- but at least the setting was corrected and the chiller came out of fault.

Chiller 10

This chiller uses belts to drive the fans. On inspection, several of them were found to be in poor condition or broken off. We have just replenished the stock of spare fan belts on site, so our engineer replaced them, then tested each fan motor in turn.

Chiller 11

This is the same make and model as Chiller 10. The same issue was found and then rectified.

Chiller 12 Maintenance Service

This chiller is in a part of the factory where the environment is very dusty. Therefore, a blocked condenser and high pressure cut outs are common place. The process engineers are aware of this issue, so they keep on top of the maintenance of the condenser. If the condenser does deteriorate- they know how to reset the fault. No problems were found with this machine.

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Far end plate removed to show the tubes in the shell of a condenser

Chiller Tube Cleaning Service

Our chiller tube cleaning service will improve the efficiency of your plant by up to 30% This is because the dirt on your copper tubes causes thermal insulation which prevents heat transfer. The chiller will therefore load up and stay on longer to achieve the same amount of cooling. Eventually, you will start seeing error messages such as discharge limiting and then a high pressure cut out. Loss of production, or staff walking out of a hot building can easily be prevented through our services…

News Article No.24

Chiller Condenser Tube Cleaning Service

We attended site to carry out the full overhaul of 4 chiller condensers for a customer of ours in Manchester. Our engineer signed in and completed the Permit to Work which was issued by the onsite maintenance engineer.

Risk Assessment Method Statement

The necessary Risk Assessment Method Statement was emailed in PDF format in advance. Our engineer carried out a short site survey of the work location to check if there were any additional risks that were not included in the RAMS. All was okay, but we have an amendments section if there were any additional risks.

Chiller Isolation

Chiller 2 was found to be in standby, so our engineer decided to start with that chiller. The grey toggle switch was turned from the 1 position to the 0 position. He then down powered the control panel. Having done this, he reconfigured the water system butterfly valves to prevent potential failure of the other condensers. Then, he valved off the Water In and Water Out butterfly valves and drained down the condenser.

Unbolt the End Plate

The bolts were removed and the end plate was moved to the side.

Inspection

The photo shows the condenser tubes being inspected. The bottom half of the tubes flow into the end plate and the top half of the tubes return to the other end. You can see red foreign objects blocking the tubes and lowering efficiency.

Equipment for Chiller Tube Cleaning Service

The loose objects were easily removed, but the real difficulty was removing the dirt from the inside of the tubes. We have state of the art tube cleaning equipment which is suitable for normal and internally enhanced tubes. We worked on each tube in turn until the dirt was removed, then we rinsed them all out.

Reassembly

The end plate seal was replaced with our specialist seal kit which we keep on the shelf in our stores. This replacement was required to ensure there would be no leaks when full system pressure was reintroduced into the condenser. Then, the end plate bolts were tightened up to the correct torque setting.

Testing

The final step was to reconfigure the water system butterfly valves ready for the next system. This done, the Water In and Water Out valves were opened and the condenser was purged of air. The chiller was started up and dramatically improved system readings were recorded. It was calculated that this chiller alone was now consuming 23% less electricity than before the job.

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Shell & Tube Chiller Condenser Cleaning Service

Midde East

We have a store in Jeddah, Saudi Arabia for our shell and tube chiller condenser cleaning equipment which we use for our customers in the Middle East. We arrange the shipping from Jeddah to our customers who are mainly in Riyadh, The United Arab Emirates and Oman. We also have some customers in Bahrain and Qatar.

Saudi Arabia

The visit to Saudi requires our overseas engineer to have had 3 Covid jabs which are recorded on his NHS Pass. The QR code expires, so it needs to be updated shortly before the trip. Then, the NHS pass has to be uploaded onto the Muqeem Portal. This is a Saudi verification portal to check if an engineer is vaccinated. Having done this, the Tawakkalna app is enabled in his phone which allows entry to public buildings and the factory he will be attending. To obtain the VISA, our site contact has to invite our engineer to the Kingdom as a guest. The VISA process is quite complicated, so we use a company in London to guide us through the process from start to finish.

Site Assistance

This kind of work is a lot easier with a second man to assist. When working in the Middle East, the factory or facility provides us with one of their onsite engineers to help with the manual handling. It is a lot quicker with another engineer to help set up and then stow away the equipment.

United Kingdom

In the UK, we keep our tube cleaning equipment at Head Office. Prior to a site visit, we palletise, then ship the equipment to the customer’s location. We charge the same price to all of our customers anywhere in the UK. This is because we have a network of engineers around the country who are no more than 2 hours travel time to your location. We have a lot of customers in the North West of England, the West Midlands and London. We also have customers in out of the way places, such as, Aberystwyth.

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Chiller Evaporator Tube Cleaning Service

The evaporator of a chiller is less often fouled as the chilled water system is not exposed to a water tower. Therefore, we carry out evaporator cleaning less frequently. We carry out an extensive set of tests during the maintenance to assess the efficiency of chiller evaporators. When the readings are poor, we recommend our tube cleaning service. The process is exactly the same as described above. Often, our customers ask us to clean both heat exchangers on a chiller as this reduces the cost of cleaning them separately at different times.

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Showing how do chillers work with pipework of black centrifugal compressor

How do Chillers Work? Compressors

How do chillers work, this time focusing on compressors. Read below and we will explore the subject in detail…

The compressor can be seen as the heart of a chiller system. As explained in the last article in our Chiller Basics series: it enables the principle of the pressure temperature relationship to take place and circulates the refrigerant.

Evaporator

The sucking action of the compressor drops the pressure in the evaporator. This lower pressure, corresponding to a lower temperature, enables the refrigerant to boil off, absorbing latent heat from the process. The refrigerant, laden with heat energy, is then sucked into the compressor.

Condenser

The refrigerant is discharged from the compressor at a high pressure, relative to a high temperature, this is sufficiently above atmospheric temperature to enable the latent heat in the refrigerant to exchange into the surrounding air.

How do Chillers Work - Mass Flow Rate of Compressors

Compressors enable the refrigerant to flow around the system. The higher the pressure of the refrigerant, the higher the mass and so the higher the mass flow rate. In low temperature systems that run on a vacuum, a very large compressor is needed to achieve the required mass flow rate and so to cool the process.

Below are the 4 main types of compressors and how they work…

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How do Chillers Work - Scroll Compressors

This compressor is more often found on smaller chillers. Scroll is another way of describing a spiral. There are two spirals, one inside the other. One of them is fixed and the other one orbits. This creates crescent shaped gaps in between the two spirals. The volume of these crescent shapes gets smaller towards the middle of the spirals and so compresses the refrigerant. The refrigerant is then discharged through a port at the middle of the scrolls.

Maintenance

Scroll compressors are meant to be maintenance free as they are hermetically sealed with no moving parts on the outside. However, the correct amount and sufficient quality of lubricating oil must be maintained to prolong its life. A lack of routine maintenance by a chiller company causes frequent compressor failures and also allows acid to accumulate in the system. This acid causes further compressor failures to occur. Give us a bell and we will put together a tailor made maintenance schedule to prolong the life of your plant.

How do Chillers Work - Reciprocating Compressors

Small

These compressors can be small and used for low capacity applications. The motor is usually inside the compressor with the cylinder heads being removable. This is described as being a semi hermetic compressor.

Large

Reciprocating compressors can also be very large and often arranged in multiple compressor systems for high capacity applications. They are open drive when used with ammonia refrigerant which means that the motor is external from the compressor. This is because ammonia corrodes the copper windings of the motor.

How They Work

The circular motion of the crankshaft is converted into the linear motion of the connecting rods and pistons running up and down inside the cylinders- see a video of how they work. Another way of describing back and forth linear motion is reciprocating. The refrigerant is sucked into the cylinder on the down stroke and then the suction inlet valves are closed. The trapped refrigerant is compressed on the up stroke and then the discharge valves are opened when the piston reaches the top of the cylinder.

Maintenance

Reciprocating compressors need regular maintenance and strip downs at pre prescribed intervals. Failure for this to be carried out results in internal components becoming worn or loose. This imbalance in the compressor causes further wear and damage to take place. Eventually something like a piston comes loose and a compressor smash up occurs. The damage is usually limited due a low oil pressure condition occurring from the location of where the part came loose. Sometimes, however, parts of the connecting rods stay attached to the crankshaft which flail around inside the compressor. An example of this is when a compressor we rebuilt had carried on running on the last one of its 8 cylinders. The rest of the internal compressor components were reduced to small, triangle shaped pieces of metal in the sump. Our maintenance saves money!

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How do Chillers Work - Screw Compressors

A pair of matched helical rotors are machined to a high tolerance. One of them is driven by a motor and the other one interlocks with it. The gap between the rotors gets smaller as the refrigerant continues down the screw and so compression is achieved. Oil is injected into the screw to provide a seal, to lubricate and to cool the rotors.

Maintenance

This type of compressor is very reliable and can quite often out live the chiller. The components around the screw, however, require regular maintenance and replacement to enable the compressor to function effectively. Some of these components include the loading solenoids and coils, also the slide valve and its potentiometer which senses its position. When these components are not working as they should, the compressor cannot match the required load and so excessive electricity consumption occurs. The inspection, adjustment and replacement of these components is another way of how our maintenance saves money.

How do Chillers Work - Centrifugal Compressors

These compressors are mostly found on very high capacity systems used for the cooling of large industrial processes, district cooling and the cooling of large facilities. The compressor in the photo, however, is a small centrifugal compressor used for the cooling of a building.

How They Work

The refrigerant is sucked into the middle of the impellor. Then, centrifugal force pushes it out to the tip of the impellor edge and so providing the compression. Unlike the compressors above, these compressors are not positive displacement and so they have a lower compression ratio. That is to say: a lower difference in pressure between the suction and the discharge.

Maintenance

Regular oil and filter changes are required to prolong the life of the bearings. When this kind of compressor fails due to worn bearings and damaged internal components, the rebuild is extremely expensive. Read more about our centrifugal compressor remanufacturing facility

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Read more about types of compressors on the Carel website


How does a grey centrifugal chiller work showing the main system components

How do Chillers Work?

How do chillers work? This is a question we get asked quite a lot from our subscribers. So, in this article I am going to explain the science and also talk you round the main chiller components…

The Basic Refrigeration Cycle

Weather it is the large centrifugal chiller like the one in the photo, or the refrigerator in your kitchen- most cooling systems work according to the basic refrigeration cycle which involves vapour compression. Two scientific principals are at work: latent heat and the pressure temperature relationship. Four chiller components are needed: evaporator, compressor, condenser and expansion valve.

Sensible heat

Heat energy that can be sensed is called sensible heat. Imagine a pan of water with a flame under it and a thermometer resting in it. You are watching the flame licking up the bottom of the pan and you are also watching the thermometer going up, obvious- right? The heat energy from the flame going into the pan is sensible heat.

Example

Now imagine if we pumped a liquid through a heat exchanger at 0°C with warm water being pumped through the other side of the heat exchanger. Some heat energy would exchange into the cold liquid and warm it up, for example, by 6°C. This is sensible heat.

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Latent Heat

Latent is the Latin word for hidden. Something less obvious happens when a pan of water gets to its boiling point of 100°C. You continue watching the flame licking up the bottom of the pan, but the temperature stops going up, strange- right? You carry on watching for a good while and the thermometer still does not go up? Then, eventually- the water boils into steam and the thermometer starts going up again. All of the heat energy that was going into the pan while the thermometer was not going up was latent heat. Latent heat was being absorbed into the water to cause it to change its state into steam. All of this hidden heat caused the liquid atoms to shake apart and become a gas.

Example

Now let’s look at the above example again, but this time including latent heat. At Step 5, a different liquid is pumped through the heat exchanger at 0°C which is also its boiling point. The amount of sensible heat, in our example, is still 6°C. Between the outside of the bubble and Step 1, there is 3°C of sensible superheat above the boiling point. Between Step 4 and Expansion, there is 3°C of sensible subcooling below the boiling point. The latent heat is inside of the bubble which, as you can see, has a considerable size. We measure sensible and latent heat energy using kJ/kg.

How does a chiller work on a PH diagram

The Pressure Temperature Relationship

How we produce the above liquid at 0°C is the second scientific principle...

Higher Pressure

If you increase the pressure of a substance- the atoms are pushed together and so they get hot. The higher the pressure- the higher the temperature.

Lower Pressure

If you decrease the pressure of a substance- the atoms spread apart and so they go cool. The lower the pressure- the lower the temperature.

Refrigerant

R134a is a refrigerant that has a pressure of 1.91 barg, relative to a temperature of 0°C.

Refrigerant Saturation Point

The above temperature of 0°C is also the boiling point of R134a. This boiling point can also be called the saturation point because no more heat can be added to the liquid before it boils. The refrigerant liquid is full of heat- or saturated.

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How do Chillers Work with Evaporators? 

This is a heat exchanger which is in between two other chiller components: the expansion valve and the compressor. The expansion valve is a restriction in the chiller system and so there is a pressure drop into the evaporator. The compressor sucks from the evaporator and so maintains this pressure drop. This is the pressure temperature relationship: the lower the pressure- the lower the temperature. Liquid refrigerant flows through the evaporator at 1.91 barg and 0°C. It boils off absorbing latent heat, then it superheats, in our example, by 3°C above its saturation point. The evaporator has absorbed heat energy from the water on the other side of the heat exchanger.

How do Chillers Work with Compressors?  

A bicycle pump is a compressor- notice how it gets hot when you inflate a tyre. This is the pressure temperature relationship: the higher the pressure- the higher the temperature. Therefore, the compressor also adds heat energy into the system. The refrigerant is sucked into the compressor from the evaporator as a cold, low pressure gas at 1.91 barg. It is then compressed into a hot, high pressure gas which is discharged from the compressor at 8 barg.

How do Chillers Work with Condensers? 

The hot, high pressure gas being discharged from the compressor is cooled down with fans which suck air through the fins of this heat exchanger. The gas goes through its latent heat phase again, but this time condensing from a gas and into a liquid. It is then subcooled, in our example, by 3°C below its saturation point into a hot, high pressure liquid. The heat energy absorbed in the evaporator and the heat energy added to the system by the compressor is rejected into the surrounding air.

How do Chillers Work with Expansion Valves?

The hot, high pressure liquid at 8 barg arrives from the condenser at the inlet of the expansion valve. The expansion valve could be seen as being a tap which is partially closed. This restriction causes the refrigerant to back up behind the expansion valve inlet. The refrigerant that gets through the valve and into the evaporator expands into a cold, low pressure liquid/ vapour mix. The vapour is called ‘flash gas’ and is as a result of the refrigerant expanding. Vapour is another word for a gas.

How do Chillers Work with Set Point?

This basic refrigeration cycle continues until the setpoint is achieved and the controller stops the compressor. After some time, the water warms up by a couple of degrees and the controller starts the compressor back up.

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Read more about vapour compression refrigeration on Wikipedia

 


Two large air cooled chillers during condenser testing

Air Cooled Chiller Condenser Testing

We at Maximus Chillers have recently carried out air cooled chiller condenser testing at a new 3 year maintenance contract in the North West. The last of 4 systems had gone down on the morning that we first attended site. 1.2 MW of cooling had been lost which resulted in the water system temperature rising to 31°C. These chillers are used to cool an office block, so we wanted to get some of the systems up and running as quickly as possible…

News Article No.16

Air Cooled Chiller Condenser 1 Testing

One of the systems was disabled due to a condenser fan failure. 1 of 5 fans was found to be seized and disconnected. Fan speeds have sufficient redundancy built in to allow for a high ambient and a partially blocked condenser. There was a high ambient condition, but the condenser was found to be clean. Therefore, our engineer decided to run test the system and monitor the condenser pressure…

Fan Speed Transformer

3 fan speeds available on this chiller- low, medium and high. The fan speeds are achieved using a transformer which makes a different voltage for each fan speed. This is quite a good way of controlling the condenser pressure, as all of the fans run smoothly together. The program looks at the condenser pressure using a transducer, then selects the required fan speed.

Medium Fan Speed

As expected, the chiller program selected the medium fan speed. This provided the required saturation pressure in the condenser and so adequately subcooling the refrigerant.

Compressor Protection

All of the system pressures and temperatures were nominal, so the compressor was protected. There was a good oil return and sufficient cooling to the suction housing from the refrigerant. This cooling ensured that the internal motor windings did not overheat.

Monitoring

Having got this system away- our engineer monitored the water system temperature which started to come down. More cooling was required, however, to get the water system temperature down to set point…

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Air Cooled Chiller Condenser 2 Testing

Another system had been the only system running for some time.

Blocked Condenser

Grass pollination had caused a covering of organic material to accumulate on the condenser. The increased head pressure had caused the high pressure switch to trip. This type of material was easy for our apprentice to remove, as it clumped together when brushed.

HP Reset

The high pressure switch was reset and the system was run tested. It did not trip again, but a high pressure condition still persisted in the condenser.

Chemical Clean

Therefore, our engineer decided to carry out a chemical clean. After the whole of the ‘v’ type condenser was cleaned- the pressure came down a little.

Non Condensables

This system stayed running, but in the high fan speed. On the upcoming maintenance visit, a refrigerant diagnosis will be carried out to assess whether there are non condensables in the system. If this is the case, a false reading of subcooling will be recorded, as the non condensables throw out the calculation.

Cool Building

With 2 systems now running, the water system got down to set point. Our customer was really happy as the situation had gone from: office workers walking out of the building- to a cool building before 10 o’ clock on the first day of the contract.

Air Cooled Chiller Condenser 3 Testing

The third system had been on pressure test for the past 2 months with the condenser valved off. There was still pressure in the system, but our engineer decided to confirm the pressure test for himself. He did this by leaving it on pressure while having a drive round the suppliers. Several hours later, the pressure had remained constant, so he was able to start the evacuation process. After this was completed, the system was recharged and run tested. Now there were 3 systems up and running.

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Air Cooled Chiller Condenser PRV Testing

The pressure relief valves on the condensers have recently been changed. Industry guidelines state that they should be tested or replaced every 5 years. There is no guarantee that the PRVs will re seal satisfactorily after they have been tested. Therefore, in practice they are usually replaced. We inspected the date of the replacement, the burst pressure, the associated certification and paperwork- all was found to be satisfactory.

Air Cooled Chiller Condenser 4 Testing

The fourth system has a leak on the condenser with some refrigerant remaining in the system. This refrigerant will need to be decanted on a subsequent visit using a pump out unit and a recovery cylinder.

F-gas Leak Testing

The entire system will be pressure leak tested to identify the location of all leaks. Then, the leaks will be repaired using oxy-acetylene. After this, the system will be pressure tested to ensure its integrity.

Dehydration

Then, the dehydration process will be carried out. The achievable pressure of the vacuum pump will be tested and recorded. Evacuation will be carried out until this recorded pressure is achieved. Our engineers are issued with a powerful 10 cfm vacuum pump to speed up this process. This system will then be recharged and its operation tested.

Air Cooled Chiller Condenser Testing and Calibration

One of many tests that we will carry out on the upcoming maintenance visit is condenser transducer calibration. Transducer readings are not linear, so care will be taken to achieve an accurate calibration. A password will be entered into the controller to gain access to the required menu. Then, each of the transducers will be adjusted. The result of this means that accurate diagnosis can be carried out and the correct subcooling readings can be recorded.

The above is just part of the service that we provide to you- the customer! Having the capability to do anything and to extend the life of your chillers is part of what we call the MAXIMUS ADVANTAGE™ Any Chiller- Any Problem- Any Part- Any Refrigerant- Anywhere.

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Boxed, shell and tube chiller condenser being lifted into a building with a crane

Chiller Condensers

Shell & Tube

One of the chiller condensers of a row of four, 2 MW centrifs we look after had deteriorated over a long period of time. We had carried out tube cleaning and noticed that it had been extensively repaired in the past. There were a lot of damaged tubes that had been blanked off. This had reduced the useful surface area for heat exchange to occur. The chiller was experiencing a ‘discharge limiting’ condition which was causing it to back off to 54% capacity.

Air Cooled

Because of the difficulty to remove and replace the condenser from the plant room, the customer had explored the possibility of air cooled condensers. His idea was to fit the discharge and liquid piping up the side of the building and into the plant room. After considering this possibility, we decided to advise him against using air cooled condensers because it would take two, 16 fan ‘V’ types. This would have a footprint too big for the available space. We decided to use a crane to lift out the old condenser, then lift in the new one.

Pump Out

The old condenser was valved off from the rest of the system and the refrigerant was pumped into an 800 kg recovery vessel. This was one of 2 vessels in the plant room that had been there since the chiller was new.

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Lift Out for Chiller Condensers

The pipework was unbolted and the ancillaries removed. When it came to unbolting the condenser, some of the bolts were seized due to a long period of rusting. Some of them came loose by heating them with oxy-acetylene, the others were ground off with an angle grinder. We used a specialist lifting company to shift the condenser from the plant room and out to the lifting bay. They then attached slings to one end, manoeuvred that end of the condenser to the outside of the building, then attached slings to the other end. Rather them than me! Quite a dangerous operation, but it had been assessed when composing their Risk Assessment Method Statement. The condenser was lifted onto the back of an articulated truck and taken to a scrap yard for recycling. There was quite a lot of copper inside- so our customer got quite a good weigh in!

Lift In for Chiller Condensers

The new condenser, in the photo, was kept in its packaging during the lift up, so as to protect it from damage. Once it was in the building and near to the plant room, it was removed from the box and shifted the rest of the way with dollies. There was some difficulty getting it into its final location. This was because the old steelwork had to be cut back with a blow torch to make the new condenser fit. Also, with limited room and no gantry crane, the lifting company had their work cut out to manoeuvre it. Eventually, it was in location and we decided to call it a day.

Adapting the Pipework

This particular condenser was selected because it was similar in dimensions to the old one. The positioning of the refrigerant and water system pipework was similar too. That said, it was not an exact match. We called an industrial plumbing and welding company in to make the changes we needed. They measured up and built adaptors to bolt in between the condenser and the water system pipework. They cut back the new condenser discharge connection and welded a new flange on. This was so it could be bolted onto the existing discharge elbow from the chiller. The liquid pipe connection on the new condenser was in the same location, but came with a different thread. Therefore, this too was cut back and an adaptor fitting was welded into place.

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Ancillaries

The fittings on the new condenser were BSP and the fittings on the chiller were Flare. We carry an extensive range of fittings that go between BSP and Flare. We can go from male to female, female to male, male to male and female to female. We can step up and step down in size too. Using these fittings, we attached the high pressure switch and high pressure transducer. The wires for the liquid and discharge temperature sensors were extended. This was so they could reach the location of the pockets that were built into the new condenser. Then, we used a special heat transfer paste to get a good transmission of heat in between the sensors and the pockets.

F-gas Pressure Test

We then carried out a strength test and a pressure test in accordance with F-gas guidelines. This was witnessed at the beginning and at the end by the customer. A satisfactory outcome was achieved, so on to the next phase of the job…

Dehydration of Chiller Condensers

We needed to dehydrate the system and remove the nitrogen that was used in the pressure test. This is because nitrogen is a non condensable which will affect system performance. Our powerful vacuum pump was set up, then we left it running overnight. A 1.5 Torr vacuum was achieved, which was the same pressure as when the Torr gauge was fitted directly on to the vacuum pump.

Open the Valves and Test

After removing the vacuum pump, the recovered refrigerant was pumped back in, then the discharge and liquid valves were opened back up. Then, our engineer had a good look round for leaks. I know it had just been pressure tested, but we think it’s always a good idea to check again. This done, the water system pumps were started and the water temperature showed at 23°C on the controller. The set point for the chilled water was 6°C so this warm water was helpful as it gave us plenty of load to carry out the testing. The chiller went through a timer and then started up. It loaded steadily up to 100% with no dramatics- splendid!

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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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Large air cooled brown chiller with test equipment during planned preventative chiller maintenance

Planned Preventative Chiller Maintenance

Featuring planned preventative chiller maintenance, which is part of a series of longer, in depth articles.

News Article No.2

This time concentrating on the checks, adjustments and diagnosis our engineer carries out while on site. We can extend the life of your plant and reduce energy costs- just with the effect of our maintenance. As well as completing a detailed checklist, which is sent to your office in PDF form, our engineer carries out extensive F-gas leak testing.

Planned Preventative Maintenance of Chiller Controls

The first part of the maintenance is carried out to the controls of the redundant systems. This is because all the pressures and temperatures should be reading the same. If not, this is an opportunity for:

Sensor Calibration

Before calibrating a sensor that is reading out, our engineer carries out a diagnosis to assess the serviceability of the sensor. With NTP (negative temperature coefficient) and PTC (positive temperature coefficient) sensors, the resistance is taken at a given temperature, which is then compared with a chart. With pressure transducers the 0-5vdc feedback signal is analysed to see if it is within the allowable tolerance. Once this diagnosis is complete and the sensor is deemed to be in good working order, our engineer will then calibrate the sensor. A password is entered into the PLC (programmable logic controller) to gain access to the service menu. From here, he can select the particular sensor, then offset it by the required amount. A lot of controls are not linear, that is to say, a sensor reading 2°C high being reduced by 2°C may not calibrate correctly. An amount of trial and error is often required. Also, monitoring the sensor against a digital thermometer at various temperatures is carried out.

Program Settings and Timers

Each program setting and timer in the various menu levels is checked against the previous maintenance checklist. Sometimes these are changed accidentally by the onsite engineer when looking for something else- it is easily done.

Planned Preventative Chiller Maintenance of Safety Chain

Each component on the safety chain is manually tripped or the fault condition is replicated to cause the device to trip. This part of the PPM (planned preventative maintenance) is essential to ensure the safety chain protects the chiller during a fault condition. Compressor failure or evaporator freeze up can occur with dramatic cost implications. We routinely prevent small problems, such as a faulty switch, becoming big problems.

Planned Preventative Chiller Maintenance of Wiring

Each wire on the chiller is checked for tightness including the fans (on air cooled chillers) This includes the compressor motor connectors and compressor contactor contacts. Loose line wiring will cause breaker and fuse faults. Loose control wiring will cause error messages and chiller faults. This is a call out in between visits that can be eliminated. With the effect of our maintenance, any chiller becomes more reliable and has lower energy costs.

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After the above stop checks are carried out, system run checks are carried out:

Superheat

Using R134a refrigerant as an example, the refrigerant pressure will be 1.9 bar at 0°C This refrigerant is in the HFC (hydrofluorocarbon) family- a commonly used refrigerant. If the refrigerant vapour returning to the compressor is excessively superheated- this is a sign of system issues. Here are some of the causes for a high superheat condition:

Refrigerant Shortage

Not enough latent heat being absorbed by the refrigerant in the evaporator. This allows the refrigerant to carry on superheating with the available heat load. Refrigerant leak testing is required to identify any leaks. The history of maintenance checklists can be consulted to see if the issue has been deteriorating over several visits.

Expansion Valve Failure

A thermostatic expansion valve operates with a higher superheat value, whereby an electronic expansion valve has a much closer control. In either case, our engineer will be accustomed to the nominal readings.

Thermostatic Expansion Valves

This type of valve is operated with a power element and orifice. A bulb is clamped onto the suction pipe which is connected to the power element via a capillary tube. The power element is pressurised with the same refrigerant as in the chiller. Some of this refrigerant is in its liquid phase, so with an increase in temperature, there is a corresponding increase in pressure. This pressure acts against the diaphragm and so pushes the orifice open. The orifice allows more refrigerant through the valve. When load conditions change and there is a reduction in heat load, the reverse happens- the orifice closes and reduces the amount of refrigerant through the valve. When the power element looses its charge- the orifice shuts down causing a high superheat condition. A low pressure trip out can also occur.

Electronic Expansion Valves

This type of valve uses sensors on the liquid and vapour sides of the evaporator, or a transducer and sensor vapour side of the evaporator. This is so the program can work out the superheat value. If the sensors are faulty, the valve will not operate correctly and a high superheat condition may occur. If the step motor or driver have failed- replacement parts are required.

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Subcooling

This is the measurement of the refrigerant condition in the condenser. Air cooled condensers are particularly popular in the UK as the ambient conditions make them very efficient. Shell and tube condensers are used on lager systems- these are cooled down using a water tower. When there is a refrigerant shortage, the liquid does not stay in the condenser long enough for it to subcool sufficiently. Some of the refrigerant stays in its vapour phase. With not enough latent being rejected in the condenser- the chiller’s COP (coefficient of performance) will be reduced. This means high energy consumption relative to the refrigeration effect of the chiller. This condition can be remedied with a scheduled visit from one of our team.

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Further reading on the subject of preventive maintenance on Wikipedia


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 when you have high water system temperature:

Small Chiller Maintenance Checklist

Low Pressure

If the chiller 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 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 like 'suction limiting' This is the controller preventing the compressor from loading up, so as to prevent a low pressure trip out. 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™

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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 overhead gantry crane and specialist equipment to hand- Maximus Chillers completes the picture. We have a lift and shift team who are skilled at getting the compressor out of the most awkward locations. A variety of lifting equipment is used, including 3 phase electric hoists and trollies. Our team do this kind of work all the time, so they are accustomed to overcoming all the difficulties and obstacles.

Screw

Screw compressors are remanufactured on the bench. With compressed air and bearing tools- our skilled technicians are seasoned in high tolerance measurements. The bearing clearance and shaft run out are accurately measured and adjusted. This means that the useful life of the compressor is extended, often to beyond the lifespan of the chiller.

Scroll

We have a range of off the shelf Copeland compressors for a fast lead time on process chiller repairs. These can be sent to site on the day using our fast door to door supply chain. We have all the sizes of compressor available. The pipework and mountings can be adapted too. This means that if your compressor is a different make with a longer lead time- our compressor will be fitted and adapted to your machine- fast!

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. This is done free of charge and ensures that the new condenser will fit easily into the old chiller. The exact subcooling requirement of the old condenser is taken into account which is duplicated on to the new condenser. This means a like for like swap can take place even when the old condenser is obsolete.

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. We have these condensers built to order by our bespoke manufacturer. They are shipped to site on an overnight delivery, so we can get straight down to work in the morning. We therefore minimise downtime in the swap out of this part.

Chiller Parts Supplier of Evaporators

Shell and tube are 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 and into the refrigerant. This is latent heat as the liquid refrigerant boils off into a vapour. Where the heat exchange does not greatly improve after cleaning, we recommend replacing this part.

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Vibration Eliminators

We have all of the sizes of anacondas on the shelf in our stores. This saves on the delivery time to site when your process is off due to the chiller. Maximus Chillers will get you up and running- fast! We can also fit flexible vibration hoses which achieve the same result as anacondas. Whereas two anacondas are fitted vertically and horizontally, only one, long vibration hose is needed.

Chiller Parts Supplier of Flushing Agent

When things go wrong, we stock a solvent based flushing agent which is blown through the system using nitrogen. The waste product is caught on the far end in drums that come with the kit. This is then returned to the suppliers for recycling.

Refrigerant Economizers

These are another term for a subcooler. If the refrigerant is further subcooled after the condenser- the system will run more efficiently. This part usually takes the form of a plate heat exchanger with an expansion valve providing the refrigeration effect needed to further subcool the remaining liquid.

Chiller Parts Supplier of 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 on site. Then we can get your chiller up and running with the correct readings in the controls. This will assist your onsite maintenance engineers in giving us useful readings when we are in communications over the phone.

Chiller Parts Supplier of Ammonia and HFC Refrigerant

A full selection of refrigerants are available including: anhydrous ammonia, R407c, R134a and R410a. These refrigerants come in small 12kg, midi 26kg, large 56kg and bomb 800kg sizes. Our vehicles are equipped with tail lifts and lifting gear to facilitate delivery. We can therefore arrange the delivery and collection of refrigerant at your site, free of charge, anywhere in the UK. For our overseas customers, we arrange the transportation from the local suppliers.

Chiller Parts Supplier of Oil

Low, medium and high viscosity oils in 5ltr cans and 20ltr drums are ready for shipping from our storage area. It is critical to select the correct grade of compressor oil as bearing wear and reduced service life will result. We take regular samples of this oil to see if things are starting to go wrong in the compressor. We can then nip these problems in the bud, giving you dramatic savings.

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

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Engineer carrying out process chiller service with yellow and black cylinder

Process Chiller Service

Maximus Chillers has just carried out process chiller service to a flooded evaporator. The refrigerant seal on a four bolt, flanged coupling had been found to be leaking liquid refrigerant. There was no possibility to valve off that section of the machine, as the flooded evaporator is the storage vessel for all of the charge of the system in its liquid phase.

Refrigerant Recovery during Process Chiller Service

Our high capacity refrigerant recovery unit was set up next to the machine to carry out the task. 55 kg of refrigerant was recovered in a short time into our recovery cylinder. This refrigerant was collected for recycling after the job was completed.

Stainless Steel

Our unit is made from stainless steel because this metal works well with ammonia.

Condenser for Process Chiller Service

The condenser is made from tubing which is connected to ‘u’ bends on either end. These ‘u’ bends send the condensing refrigerant back along the next tube in the opposite direction. This process, back and forth allows time for the refrigerant to condense into a liquid. Fins are pressed around the tubing to increase the surface area and help to dissipate more heat from the refrigerant. A condenser fan is fitted to suck the air through the fins and so reject the heat.

Reciprocating Compressor

A four cylinder reciprocating compressor is fitted to the unit to provide the pressure difference to pump the refrigerant into the above mentioned condenser. It has an air cooled electric motor fitted which is open drive. This is because ammonia would corrode the windings of the motor if a semi hermetic compressor were to be used. Semi hermetic meaning that the windings, stator and rotor of the motor would be internal to the system. The motor is fitted in the vertical position with the four cylinders opposing each other on the central crank shaft.

Controls for Process Chiller Service

For safety reasons controls are fitted to the unit. These include:

HP Switch

If the recovery cylinder were to become over filled, the pressure would build up to a dangerous level. The TARE and the ullage need to be calculated prior to the job to prevent this from happening. The below mentioned liquid pipes have been designed with pressure issues in mind, but somewhere on the system would be the weakest point. This would burst causing a catastrophic refrigerant leak. The whole charge of the machine and all the refrigerant in the recovery cylinder would leak to atmosphere. The HP switch is set by the engineer on site to the correct level given the ambient conditions. This takes into account the temperature of the refrigerant and the safe operating pressure of the vessel.

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Refrigerant Liquid Pipe

Steel Braided

The refrigerant in its liquid phase is pumped into the above mentioned unit down a steel braided liquid pipe. The steel braiding is to provide additional protection from the pipe being damaged on the outside. Damage like being driven over by a forklift truck, or having sharp objects coming into contact with it. Also, the braiding helps to prevent bursts when pressure builds up on the inside. This can be due to a restriction, malfunction of system components or vessel overfilling.

PTFE

The inner part of the pipe is PTFE. Other types of plastics and compounds corrode due to the toxicity of ammonia. Polytetrafluoroethylene is the chemical name for this compound, it is a fluorocarbon solid and is considered to be non reactive.

Fittings

There are various metric and imperial thread types that can be used. This depends on the fitting size on the machine and the fitting size and type going onto the recovery unit. We carry a wide range of fitting types to step down and step up in size. We can go between male to female types and use male to male and female to female where necessary. We carry adaptors to go from metric to imperial thread types.

Remote Access during Process Chiller Service

We carry an extensive stock of liquid pipes that can be connected end to end to provide remote access. We will always try to get the recovery equipment as near as possible to the plant, but when this cannot be achieved, we can arrange access up cat ladders or the side of a building. We can use our lift and shift team to arrange the hauling of all the required equipment and ancillaries to any location. Just part of what we call the MAXIMUS ADVANTAGEAny Chiller- Any Problem- Any Part- Any Refrigerant- Anywhere. Contact our office for prices for the above mentioned pipes.

Process Chiller Leak Service

The flanged coupling was unbolted and the failed refrigerant seal was removed. The new seal was fitted from our full range of sizes that we keep on the shelf in our stores. Our engineer bolted the flanged coupling back up to the correct torque setting.

Pressure Leak Test

A nitrogen pressure leak test was carried out to ensure the integrity of the system with the result being a pass.

Dehydration Process

As the system was open to atmosphere, air had got into the system which carries moisture content. The moisture and non condensables were removed down to a near perfect vacuum using one of our high capacity vacuum pumps.

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Charging of Refrigerant

The photo shows the charging of a cylinder of refrigerant into the system in its liquid phase. The cylinder has a dip tube fitted for ease of handling. Once the pressure in the system and the cylinder equalized, remaining refrigerant was drawn into the system during the operation of the plant.

Run Testing

The sight glasses and level glasses were found to be at the optimum level under the normal running conditions of the plant. As it is a flooded system, there was found to be a low superheat value. A high subcooling value was achieved with the use of a subcooler. Our engineer monitored a full cycle of an hour and a half: compressor temperatures and oil level were found to be within normal operating limits.

Remote Service Monitoring of Process Chiller

The process chiller can be remotely monitored via a data uplink through the internet. Our office continued to monitor the plant for some days as it went into seamless operation.

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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 machines 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 recips. 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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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 during Water Chiller Maintenance

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 chillers running than necessary dramatically increases energy consumption.

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