There are two different types of maintenance or aftercare:
Reactive Maintenance, often called 'Traditional Maintenance'. A traditional maintenance regime involves a programme of planned site checks by engineering specialists, where a series of performance health checks are carried out and immediate adjustments are made to correct any issues. This means high maintenance costs due to the number of site visits and also a greater margin for error
Proactive Maintenance, also known as 'Condition Based Monitoring'. With this type of preventative maintenance, the reliability and optimal efficiency of the refrigeration plant is constantly monitored in order to advert and prevent any potential system failure, and therefore reducing your business operating costs; Typically, savings are about 20% of the total operating costs.
This type of proactive maintenance involves the use of remote monitoring, data collection 24/7, analysis of data and generation of task list, including:
Vibration analysis, when performed by a qualified technician, can predict failure of compressor components and can even often predict when the failure will occur.
The objective of vibration monitoring is to identify noise or vibration in an operating compressor. Items that must be analysed are: imbalance of rotating parts, misalignment of couplings and bearings, bentor cracked shafts, worn speed increaser gears, worn or damaged antifriction bearings, or worn or damaged sleeve bearings on the compressor and motor, hydraulic forces, rubbing forces, and electromagnetic forces.
Why Vibration Analysis?
- It reduces maintenance costs because maintenance is scheduled only when needed.
- It reduces overtime because you can predict when the machine may fail, requiring weekend and night work. Emergency repairs are reduced dramatically.
- It reduces repair costs because major repairs are practically eliminated due to a thrust bearing failure or a gear failure that may ruin the compressor.
- It reduces unplanned system, or possibly plant, downtime.
- It extends the life of the compressor.
- It increases plant safety.
- It helps control insurance costs.
There are a number of substances that can contaminate the oil within the refrigeration system. Commonly, these are water, iron, insolubles (general muck), refrigerant, and general debris.
Contaminated oil can and will cause premature failure of components within the refrigeration system, which in turn could result in a total loss of refrigeration!
Frequent checking of the oil's condition allows the maintenance engineer to address any out of specification issues and, if necessary, replace the oil, filters, control valve internals, clean strainers, etc., which will help to maintain the system at its correct operating conditions.
The F-Gas Regulations require that many refrigeration systems using F-Gases must comply with provisions that include a specified leak test programme, carried out by a suitably qualified person, and in some cases, installation of permanent leak detection equipment. We can provide these services and help you to comply with the statutory regulations.
Incorrectly aligned direct drive refrigeration compressors coupled to drive motors have caused the failure of both drive motors and compressors. Misalignment also causes the failure of the shaft seal potentially resulting in the release of refrigerant and oil. In Ammonia plants this could result in evacuation of plant rooms and loss of cooling which in turn will affect controlled temperatures and production facilities, all very good reasons why this capability is a must have for a market leader.
This can be carried out using a number of methods:
- Straight Edge.
- Dial Indicators (Clock Gauges)
Star Refrigeration use laser alignment because it is both quicker and more accurate than the other two methods using their own in house laser equipment and trained service engineers.
This service is available to all customers either within the scope of a maintenance agreement or a one off visit to resolve ongoing issues.
Consequences of misalignment
Poor alignment can lead to the following:
- Increased friction to equipment and hence
- increase in KWHr consumption
- Increased vibration and noise
- Drive motor bearing failure
- Compressor bearing failure
- Shaft seal failure
- Coupling failure
In a case study we found significant cost savings can be achieved by the accurate application of this method of alignment because of the improved reliability of equipment (less down time) and the prevention of major failures to plant and machinery through planned preventative maintenance (regular alignment checks).
The objective is to ensure the containment of the refrigerant within is system without loss, by correct design and using the properly rated equipment. Also, ensure that the system itself is operating safely and to its design specifications. Thus achieving and maintaining its operation using the minimum amount of electrical energy necessary. Operating a plant that is not correctly charged with refrigerant costs a lot more money to run and possibly not even achieving its design operating conditions.
The task would involve a regular leak-testing regime using either a hand held leak detector / soapy water / etc. and in the case of ammonia, you could use phenolphthalein / litmus leak detection paper. Refrigeration plants containing larger quantities of refrigerant, and depending upon the current regulations, would require to have a fixed refrigerant leak detection system installed, regularly serviced and maintained, to ensure its correct functionality in the event of a refrigerant leak occurring.
The objective is to ensure the control of Legionnaires disease within the water cooling system of evaporative condensers used in larger refrigeration plants and that they comply with the current regulations set out by the Health & Safety Executive.
The task would involve the installation of a water treatment system (installed and maintained by a qualified water treatment contractor) and could be either chemical based or using a non-chemical system. There are several different types available but Star tend use the VRTX centrifuge system if possible, which has produced excellent results on the sites that have it installed. The water treatment contractor would supply a water treatment logbook, which is filled in every month during his service visit recording all the required data. Weekly dip slides are taken either by the engineer attending site or the customer themselves with their results recorded in the logbook; this records the level of bugs within the water system and shows the level of compliance over the whole annual cycle. If however the dip slides show an increase in the contamination then other protocols can come into play (place solid biocide tablets within the condenser water pan itself). Bi-annual clean and chlorination’s of the evaporative condensers are also included within the water treatment program to ensure there is no build-up of algae which would encourage the growth of Legionella bacteria ensuring the health of the system overall.
The objective is to ensure that coolers/evaporators are clear and free from dirt/dust and/or snow/ice etc. allowing unhindered airflow giving maximum heat exchange through the coil block.
The task would involve scheduled regular cleaning of the coil block, by either our own staff or through a sub-contractor, who would supply all necessary equipment to complete the task safely. The process would include safely screening the cooler to prevent over spray of the water during the cleaning process falling down onto the customer’s product below. Star get our sub-contractor to also record before and after air flows across several areas of the cooler to prove the increase of air velocity following the cleaning process. Once complete the cooler is almost back to its original condition giving maximum design refrigeration duty.
The objective is to ensure that the evaporative condensers are being maintained within the Health & Safety guidelines, which states that, every condenser should receive a clean & chlorination service at least twice a year, (sometimes more depending upon their location), to ensure the cleanliness of the condenser is maintained at a level that will control & prevent Legionella.
The task would involve a scheduled clean & chlorination with the removal of the condensers drift eliminators (they would receive a wash down to remove dirt, algae etc.) The condenser internal walls, fans etc. will be treated with chemicals and washed down into the water pan, which would then be drained down and cleaned. Once the cleaning process is completed, the condenser would be refilled with water and hypochlorite added to carry out the disinfectant of the tower. This recirculating process can take several hours to complete within the condenser itself. Once complete the water is again drained and refilled. Once complete the condenser is returned to service.
The objective is to ensure that the ammonia refrigerant within the system is clean and free of contamination.
The task would involve the installation of an ammonia drier into the refrigeration system to absorb and control any water at a level of below 1%. If the percentage of water is greater, it has the effect of increasing the evaporating temperature within the system, resulting in achieving longer compressor running times and possibly not achieving the design duty set points. It also has the effect of introducing internal corrosion of the ammonia circuit, which could result in future refrigerant leaks. Reduces the working age of the refrigeration lubricating oil and the formation of sludge, which in turn, could block/restrict the flow of refrigerant through filters and valves thus reducing the plant efficiency even further.
The objective is to ensure that all the electric controls are photographed using an infrared camera, which shows up any hot spots within the control panel itself. Highlights where there is an issue on any piece of equipment without the need of any invasive isolation of the panel or refrigeration plant rather than waiting until the component fails, possibly resulting the shutdown of the total refrigeration system itself and resulting loss of production.
The task would normally involve an annual scheduled thermographic scan carried out by a sub-contractor. The engineer would open the live control panel and a photograph taken; this would then be checked for any issues, and if possible attended to at that time. If however, due to operational reasons, the plant cannot be switched off, then following the issuing of the annual report, the repair would be arranged at a time suitable to the customer.
- Refrigerant Quality Check (ARQ)
Refrigerant quality checks are especially important, as any water in an ammonia system, for example, can lead to severe loss of cooling capacity and rising energy costs. Water contamination of 1% or below is not something to worry about, as long as it is monitored. But for every 1% of water, your running costs go up by 1%. If left unattended, this will also lead to oils breaking down quickly and component failure, which will cause your operating costs to increase even further.
Checking the quality of the refrigerant within the refrigeration system
This procedure requires that a sample of liquid ammonia is taken and collected within a calibrated flask. The ammonia is then allowed to evaporate off with the water being left. This is then measured against the total sample taken, and the resultant figure is converted to % of water contamination. At Star, this procedure is carried out by one of Star's commissioning engineers.