Monthly Archives: October 2020

Chilling plant maintenance of grey machines with red warning signs

Chilling Plant Maintenance

We at Maximus Chillers carry out chilling plant maintenance in factories and facilities around the UK and overseas.

HFC Refrigerants

HFC (hydrofluorocarbon) chiller refrigerants were developed to be chlorine free. For a while they were seen to be the great new thing until the GWP (global warming potential) of the refrigerants became more of a concern. The release of these refrigerants from leaking systems dramatically increases the green house effect and so trapping more heat in the atmosphere. For this reason, F-gas regulations are phasing them down to 21% by 2030. Because of the 650kg charge in the chillers in the photo, we carry out leak testing at one month intervals. Where a leak is identified with this refrigerant, the system can be pumped out using the push/ pull method. There are no refrigerant system shut off valves available to allow the systems to be pumped down.

Chilling Plant Maintenance using Leak Detectors

We employ HFC refrigerant leak detectors to identify any leaks around the system. On systems of this size, there may be more than one leak, with a large leak alerting the attention of the engineer and the smaller leaks found subsequently. Our leak detectors are sent off periodically to be calibrated with the internal replaceable components upgraded as necessary.

Static Leak Detectors

Static leak detectors are available for each machine to catch any leaks as soon as they happen- before the one month intervals. This reduces the amount of refrigerant leaking to atmosphere and so adding to global warming. These leak detectors are bump tested on each visit to ensure reliability with replacements available on site, should one of them fail.

Chilling Plant Maintenance for One World

The above measures are essential with this kind of refrigerant in the interests of the environment. Basic checks now, protect the future of the planet. We only have one world, so we need to look after it as best we can. You can rest assured that you are in safe hands with how we handle this range of refrigerants.

0161 370 7193

service@maximuschillers.com

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Shell and Tube Chiller Condensers

During the maintenance, we assess the subcooling values under part and full load to diagnose the efficiency of the shell and tube condensers. This kind of condenser is very popular with larger chillers in the UK. They are not sensitive to different weather conditions as the heat rejected into the condenser water system is pumped into the cooling towers outside of the plant room.

Chilling Plant Maintenance of Copper Pipework

The nest of pipes inside the shell are constructed using copper. This is because of the excellent heat transferring properties of this metal. On other sites where the refrigerant is ammonia for example, stainless steel is used as ammonia corrodes copper and most other metals and alloys. Thorough maintenance of the pipework is carried out on each visit.

Water System Maintenance

The water loop is inspected at various test points around the system with our range of test equipment. Where there are readings that are starting to go beyond nominal conditions, we carry out adjustment to bring them back into line. If the water system is behaving abnormally, this will in turn affect the efficiency of the condenser. In extreme circumstances, a system failure can occur causing a potential loss of production. Effective maintenance from Maximus Chillers has evolved over time to prevent this from happening in the first place. Each time we encounter a new issue, a thorough investigative process is carried out, the solution is arrived at and this is added into the routine.

Air Bleed Ports during Chilling Plant Maintenance

Air can be pulled into the condenser from the cooling towers outside. This can sit on top of the water in the condenser and so prevent the heat exchange of latent heat from the refrigerant and into the water. An air lock in the condenser amounts to that portion of the heat exchanger from not being in use. This dramatically affects the efficiency of the plant. We carry out checks to each condenser and bleed any air on each visit to ensure the best running conditions of the plant.

0161 370 7193

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Refrigerant System Standing Pressure

One of the ways to assess the condition of the refrigerant is the standing pressure. Only during factory shut down are all the chillers off for long enough for the system pressures to stabilize and so have a consistent standing pressure around the system. The pressure readings can be taken and added into our software to determine the composition and purity of the refrigerant and the presence of non condensables. Where the refrigerant is found to be in poor condition, maintenance can be arranged to rectify the issue.

Coefficient of Performance

The coefficient of performance is the cooling effect compared to the amount of electricity used. In an inefficient system, a small amount of cooling is achieved relative to a large amount of electricity used. In this age of environmental concerns, we carry out extensive measures and adjustments to improve the COP. Not only is an efficient plant cheaper to run, it is better for the environment too.

Control Panels

The control panels for the chillers in the photo are defunct. That is to say- the component parts are no longer manufactured. I am sure there is the odd circuit board rolling around on a shelf somewhere, but we fit state of the art controls. Our supplier builds bespoke panels exactly suited to each particular machine. They are plug and play with associated sensors, transducers and vane loading actuators supplied. The panel is fixed next to the chiller, wired in and ready to go. All settings come as default, so just the odd one needs to be modified. The panel can be easily integrated into the existing remote start stop and variable speed drives.

Related Articles:
Air Cooled Chiller Planned Maintenance

Water Chiller Maintenance

Process Chiller Maintenance Visit

Chilled Water System Maintenance

Centrifugal Chiller Maintenance

Industrial Chiller Maintenance

Air Cooled Chiller Condenser Maintenance

Glycol Chiller Maintenance

To read more about shell and tube chiller condensers hit the Tag at the top of the page.

For further reading on Hydrofluorocarbon Refrigerants | Click Here


Maximus Chillers sign outside our chiller maintenance company office

Chiller Maintenance Company

Chiller Diagnosis

One of the most important parts of a chiller maintenance company is the diagnosis. If this is done wrong, the wrong parts are ordered and the return job goes wrong.

News Article No.7

For us at Maximus Chillers, it is imperative that we get the diagnosis right, so the return job goes easy. On a maintenance visit, a detailed Tick Sheet is completed with all the necessary readings and adjustments.

Chiller Maintenance Company Case Study

One of our engineers was on a maintenance visit recently and he found an electrical fault with a relay. An intermittent fault- so the most annoying to diagnose. The relay interlocks the compressor A1 run signal on the start contactor. The fault causing the relay to drop out was the high pressure condition. The high pressure switch was found to be in good working order with continuity back to the relay, so the relay was deemed to be not switching intermittently. The relay was changed with the available stock on site and the machine went back into seamless operation.

State of the Art Equipment

At Maximus Chillers we know that incorrect test equipment can lead to incorrect diagnosis. That’s why we have the highest quality equipment which is regularly inspected, replaced or calibrated. With a Fluke multimeter with fused leads- we diagnose the most complicated of problems. Sometimes a wiring diagram is not available, or the machine has been modified. Even wires disappearing into a conduit and ending up on the other end of the chiller can be traced and effectively diagnosed. You can rest assured that with the ongoing maintenance by Maximus Chillers- we will extend the useful life of any chiller.

Chiller Maintenance Company Technical Support Desk

For over the phone diagnosis, our contract customers enjoy the full benefit of our technical support desk. Faults are often something and nothing, or are just to do with how the machine was restarted. If we can get a chiller away over the phone, that saves us time and that saves you: the customer money too. Just part of what we call the MAXIMUS ADVANTAGE™ Any Chiller- Any Problem- Any Part- Any Refrigerant- Anywhere.

0161 370 7193

service@maximuschillers.com

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Chiller Expansion Valves

We at Maximus Chillers have a comprehensive range of expansion valves, on the shelf, in our stores at our chiller maintenance company in Droylsden, Manchester. There are three commonly used types of expansion valve used on a chiller:

Pulse Expansion Valve

This is a simple design of a solenoid coil lifting a solenoid valve and opening the diaphragm in the expansion valve. This allows the refrigerant to pass from the high side of the system into the low side. A sensor either side of the evaporator feeds back to the controls. The controls work out the length of time the valve stays open and the length of time the valve stays closed. Quite a simple idea and quite reliable from our experience too. The replacement of parts are a straight swap.

Electronic Expansion Valve

Another type of valve we stock is the electronic expansion valve. Similar to the above, this valve uses a sensor either side of the evaporator to work out the superheat. Another method of working out the superheat is a sensor and a transducer. Either way amounts to the same thing: the controls work out the difference in temperature and saturation point. The mechanical part of the valve is a step motor which winds all the way shut when the chiller starts. This is so that the controls can register step 0. As the valve opens, the controls record the amount of steps and so opens and closes for a close control of the superheat.

Thermostatic Expansion Valve

A thermostatic expansion valve is a completely mechanical and stand alone part. The pressure in the bulb increases with temperature and so forces the valve open. We have the full range of orifices for the commonly used varieties of valve on the shelf. Each orifice is used for a different application, ranging from low temperature -40° saturation, through medium temperature 0° saturation, to high temperature 20° saturation. High temperature applications include laser chillers- the secondary refrigerant cools the oscillator and the laser head.

HFC Chiller Refrigerant

HFC refrigerant is being phased down to 21% by 2030. This is in accordance with F-gas guidelines and the emission reduction measures as defined in the Kyoto Protocol. This refrigerant, however, still remains to be the most popular type amongst chillers, with new chillers coming of the production line charged with, most commonly, R407c and sometimes R410a. R134a is also a popular chiller refrigerant most commonly used in flooded centrifugal chillers. The more the phasedown starts to pinch, the more the incentive to use a lower GWP (global warming potential) drop in refrigerant. This extends the useful life of the chiller, therefore removing the need to build a new chiller, with the associated high amount of carbon emissions.

0161 370 7193

service@maximuschillers.com

Contact Form

Chiller Evaporators

Eddy current Inspections by Chiller Maintenance Company

At periodic intervals according to the maintenance schedule, the end plates are taken off the chiller evaporators and the tubes are inspected. We have calibrated eddy current instrumentation to assess the integrity of the evaporator tubing. This equipment uses electromagnetic coils to produce eddy currents, the electrical impedance is then measured. It picks up any cracks, pitting or corrosion. The conclusions are mapped onto a chart showing the tubes which are likely to fail. These tubes can be taken out of operation to prevent catastrophic system failure in the future. The system can then be pressure tested in accordance with F-gas leak testing requirements to prove the integrity of the system. Just part of the joined up forward thinking of this chiller maintenance company.

Chiller Maintenance Company Lagging

On our maintenance visits, one of a long list of checks is to check the insulation and vapour seal. If the lagging is not in place correctly, moisture from the air forms as condensation on the steel shell. This is not visible, so the condition of the steel can deteriorate dramatically over time. Where the lagging is in good condition, industry guidance states that it should not be removed to inspect. Where the lagging is in poor condition, however, it should be stripped back to the location of a good seal to inspect the integrity of the shell. For low temperature glycol or brine applications, rapid deterioration occurs as the shell is defrosting and re freezing between production cycles or defrost cycles. We heat treat the steel to remove all the moisture, then grind off any rust, before adding a two kinds of specialist paint available for sale at Maximus Chillers. We then match into the old lagging for a good join with our off the shelf varieties of lagging. The lower the temperature of the application, the greater the thickness of the lagging supplied.

Related Articles:
Air Cooled Chiller Planned Maintenance

Water Chiller Maintenance

Process Chiller Maintenance Visit

Chilled Water System Maintenance

Centrifugal Chiller Maintenance

Industrial Chiller Maintenance

Air Cooled Chiller Condenser Maintenance

Glycol Chiller Maintenance

Chilling Plant Maintenance

To read more about chiller diagnosis hit the Tag at the top of the page.

For further reading on F-gas enforcement reforms visit RAC Magazine | Click Here


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