Reliability-Centered Maintenance of a Daiken Split Air Conditioning System - Report Example

Report Reliability-centred Maintenance of a Daiken Split air conditioning system Table of Contents Page List of tables 2 Introduction 3 Operating context 3 Working Principle 4 Main parts of the split air conditioning system 4 Most common problem 5 Primary and Secondary functions of the split air conditioning system 5 RCM information 7 Proactive and reactive maintenance tasks 7 RCM Decision 9 RCM Decision Analysis 9 Consequences 10 Conclusion 11 Appendix 1 12 Appendix 2 14 References 15 List of Tables and Charts RCM 11 worksheet RCM Decision Analysis Introduction This paper uses Reliability-centred Maintenance 2 (RCM 11) to analyse the operations of a Daiken 12000 BTU split air conditioning system which has a primary function of providing cool air at 26 degrees Celsius. It operates at a temperature differential of between 8 and 11 degrees Celsius at a comfortable noise level. According to Mutual Consultants Ltd (2009), Reliability-centred Maintenance (RCM) which is based on the principle of preserving the functions of the equipment to which it is applied has demonstrated the ability to deliver optimum maintenance for all kinds of assets. RCM covers both the risk of physical and operational failure and considers events that could reasonably cause an asset to cease performing any of its desired functions (Mutual Consultants Ltd 2009). Proper maintenance of assets while important for both households and businesses is fundamental to the operating efficiency of businesses. The failure of a critical asset can have devastating consequences for a business if it cannot be repaired or replaced quickly. In order to ensure that adequate maintenance takes place a maintenance program needs to be implemented for all equipment in use. This program should be capable of predicting the degradation or failure of an equipment before it happens. An RCM program can lead to increased operating performance, reduced maintenance costs and reduced energy bills (Chimack et al n.d.). 2.0 Operating context ‘RCM is a maintenance perspective in an operational context’ and so understanding the goals and needs of the organisation is fundamental in the development of a maintenance strategy to optimise business outcomes in the context of the goals of the business (August 1999). The asset that is being analysed is a Daiken split air conditioning system which is located in an office of 54 square metres. It provides cool air at a temperature differential (TD) of between 8 and 11oC and as a secondary function helps to eliminate or reduce unwanted particulate or gaseous substances from the air being supplied to the office. The office operates six (6) days per week at an average of seven (7) hours per day providing customer service to internet users and students doing research. On average about five to seven customers are being served at any one time and approximately 36 in any one day. The air conditioner is switched on and off using a remote control when the temperature gets too cold. The room temperature normally gets cold when only one or two customers are in the office. However, it is normally set at a temperature gauge of 26oC. It is flushed once every three (3) months and the air filter is also cleaned by the office staff. The air conditioner is only serviced by a trained technician in reaction to a fault that causes it to malfunction. In addition to its primary function of providing cool air at low noise levels it also removes dust and other particles from the air. 2.1 Working principle Airconditioning-and-heating.com (n.d.), the air conditioning system circulates a compressed gas refrigerant in a closed “split” system to cool and condition inside air in order to make its occupants comfortable. This refrigerant has to be re-cooled and condensed, and the air outside is generally the medium that is used to facilitate this process. Split airconditioning.com (n.d.) also states that the air conditioning system also controls the purity of the air by reducing or eliminating unwanted particulate or gaseous matter from the air being supplied to the office. 2.2 Main parts of the air conditioning system The main parts of the air conditioning system are the compressor and the condenser which are located outdoors and the evaporator coil and expansion valve which are located indoors. The compressor helps to maintain a determined level of pressure in the evaporator. It does so by extracting vapour as soon as it is formed. If liquid get in the compressor it will prevent it from functioning efficiently. The condenser consists of a number of tubes that are filled with refrigerant. It eliminates heat from the refrigerant using air so that it can change the superheated vapour that is discharged from the compressor. The condenser pulls air through the condenser coil so that the heat can be dispersed into the environment (Airconditioning-and-heating.net n.d.). Any excess heat escapes outside. The fan which is connected to the condenser uses the air outside to cool the refrigerant before it is re-circulated into the system. The evaporator is a tube that is filled with refrigerant. It removes heat and moisture from the office by changing liquid refrigerant into vapour. An evaporator blower circulates cool air in the space. The evaporator is located indoors. The expansion valve controls the flow and pressure of the refrigerant. The liquid refrigerant passes through the expansion valve after it leaves the condenser in its cooled state. 2.3 Most common problem with the air conditioning unit The most common problem with the split air conditioning system is that they start leaking water or refrigerant. The outlet in the gutter tray gets blocked and water starts to accumulate. As a consequence of this problem the air conditioner will start leaking. According to Split Air Conditioning (n.d.), the most dangerous case is when this leak is in the refrigerant line. In extreme circumstances a leak in the refrigerant line can also cause an explosion. 2.4 Primary and Secondary Functions The primary function of the split air conditioning system is to provide a cool environment in the office (26oC) and at a TD of between 8 and 11oC. It also assists in the efficient operation of the computers and the printer. If it gets too warm the computers especially will breakdown. The secondary function includes the elimination dust and other particles from the environment. This function of the air conditioning unit can be assessed using ESCAPES which is the acronym for environmental integrity; safety/structural integrity; control/containment/comfort; appearance; protection; economy/efficiency and superfluous functions. Environmental integrity - The air conditioning system is environmentally safe unless a leak develops which causes the refrigerant to leak onto the roof where condenser and compressor is located or on the ground outside the office. This can be hazardous to humans. With proper maintenance and constant monitoring the environmental integrity of the system will be maintained. Safety/ Structural integrity – The equipment is kept in a safe place out of the way of customers and staff. It is properly affixed to the wall and the roof and should not fall off under normal circumstances. Control/Containment/Comfort – The unit comes with a remote control which is used to set and control the temperature at the required levels. The thermostat allows the motor to turn on and off to maintain the temperature based on the settings made by the operator. Appearance – The air conditioning system fits normally with the aesthetics of the office and will not have a negative impact on how the customers view the business and its services. It appears to be in good condition. Protection – Both the indoor and outdoor components of the air condition is protected by hard casings in such a way as to make the system operational as well as to protect it from damage. Economy/efficiency – Both the indoor and outdoor component is placed at a location where it can be operated efficiently and so does not use more than the required level of energy to function properly. Superfluous functions – The air conditioner not only remove dust and other particulates from the office space. 3.0 RCM Information This analysis provides information relating to the operation of the evaporator in the split level conditioning unit. According to Moubray (1997) RCM analysis involves an assessment of how the air conditioner can fail based on the context in which it is being operated. The RCM worksheet in Appendix 1 indicates the function of the asset and specifically the evaporator which is the provision of cool air for the occupants of the office at 26oC and with a temperature differential (TD) of between 8 and 11oC. If this does not take place then the air conditioner and especially the evaporator which is the component that is being assessed would have failed to function properly. There are several ways in which the evaporator can lose its function and this is defined as ‘functional failure’ as shown in column 2 of the RCM worksheet in Appendix 1. The column labelled ‘failure mode’ provides an indication of the root cause of the problem while the failure effects column provides information on how the business operation is affected and how the problem can be dealt with (Moubray 1997). 4.0 Proactive and reactive maintenance task According to Chimack et al (n.d.), RCM has some elements that share some similarity with predictive maintenance. However, it is somewhat different in the sense that it ranks equipment by importance and the probability of failure from the degradation caused by various mechanisms. In this same breath Chimack et al (n.d) indicates that the components of the air conditioning system which is considered in this paper can be ranked according to their importance as part of the system and the probability of failure. RCM also takes into consideration the availability of both financial and personnel resources with the aim of optimizing their use (Chimack et al n.d.). RCM can lead to a reduction in costs by instituting the most cost effective maintenance programme. The elimination of unnecessary maintenance will also assist greatly in lowering costs. Chimack et al (n.d.) also states that cost is one of the greatest disadvantages with RCM which has a significant start up cost involving the use of both training and equipment. Proactive maintenance which is the same as preventive maintenance is the performance of inspection and or servicing that has been scheduled in advance. Hinchcliffe (2003) indicates that there are four basic factors behind the decisions to carry out preventive maintenance. They are to mitigate failure occurrence; to detect the onset of a failure; to discover a hidden failure; and to do nothing. It involves taking the necessary steps to ensure that maintenance critical components are done before repairs or replacement of parts is deemed to be a necessity. It is synonymous with preventative maintenance which seeks to prevent common problems by scheduling regular maintenance programs. According to Chimack et al. (n.d.) reactive maintenance involves operating the equipment until it fails to function, with no plans for maintenance. In this scenario maintenance only occurs when the equipment cannot function or does not function as it should. It is also described as corrective maintenance. Regular servicing will prevent most of the failure functions outlined in Appendix 1. The refrigerant line will be checked for any leaks and to ensure that an adequate amount of refrigerant is in the system. This will prevent it from cooling below normal temperature. This will also help the air conditioning system to effectively remove dust and other particulates in the environment. Regular servicing will also include cleaning the evaporator coils and other areas of the system. A burnt circuit board or a damaged capacitor cannot be prevented because of obvious limitations and so corrective maintenance will be the only solution to these problems. 5.0 RCM Decision The decision on what maintenance procedures to follow will depend on whether the problems can be prevented by proactive maintenance. If the functional failure affect a protective or redundant device then proactive maintenance is necessary as a means of finding failures before they occur. The RCM decision analysis diagram in Appendix 2 explains this. If the failure involve significant safety, environmental or operations risk as with a refrigerant leak it will need to be fixed. If a trained operator cannot resolve the problem then one will need to determine if the failure can be detected by monitoring the condition of the unit and if so condition based monitoring (CBM) should be instituted. If not then a determination should be made of whether the failure relates to wear and tear of component parts. If so then one should determine the time it takes to reach that stage and put in place a scheduled or time based maintenance programme. If not then it is important to determine whether a cost effective corrective (reactive) maintenance program exist wherein the air conditioning system or the particular component should be allowed to run until it fails. If not then the design of the air conditioning unit may need to be assessed further in order to determine what changes may be made. 5.1 RCM Decision Analysis The RCM decision analysis sheet shows what decisions will be made in order to have the air conditioner function effectively. This analysis is shown in Appendix 2. There are certain functional failures in the air conditioning system which it is more economical to address proactively because they are either condition based or time based. Others will not be identified until they occur and so are neither time based nor condition based. If the capacitor becomes damaged by the stroke of lightening the operator will not find this problem until the air conditioning unit stops functioning. Tests can be carried out to determine if the capacitor needs to be replaced 6.0 Consequences In its current operational capacity the air conditioning system provides cool air at 26 degrees Celsius and a temperature differential of between 8 and 11oC at a moderate noise level. It fails to provide that function when it does not cool at all; when it cools at temperature above and below the required level; when it blows hot air; when it becomes noisy; and when it only cools a section of the office area. These failures result in additional operational cost which are not been budgeted for. According to Brignall (2006), a 12000 BTU air conditioning unit cost 12 pence per hour to operate a few years ago. If we assume that the cost remains the same this means that if it is operating efficiently it will cost approximately £4.2 per week in terms of electricity cost to operate. These failures will result in increased costs to the business in terms of additional labour hours and the replacement of parts. Some of these costs can be prevented if problems are detected earlier. Therefore the common refrigerant leak problem can be identified and prevented by carrying out timely checks and ensuring proper installation of the unit. Failures which can affect the environment result in poor air quality which will not be tolerated by customers and staff. Dust particles can cause health problems and result in customers taking out law suits against the company. Some of these problems can be prevented if proper and scheduled maintenance procedures are followed based on the user manual as well as based on proactive maintenance procedures. RCM analysis provides this kind of opportunity. 7.0 Conclusion RCM is a very costly exercise in terms of both the financial and personnel resources that are necessary to carry out the tasks associated with this maintenance procedure. However, it serves the function of reducing the number of function failures associated with the use of a split air conditioning system while requiring regular servicing does not require any sophisticated proactive maintenance strategies to operate efficiently and effectively. While time based maintenance is required for servicing relating to flushing, cleaning of air filters and coils, other parts of the system will be affected by wear and tear. Components affected by wear and tear can be replaced as soon as the condition warrants it. These replacements can ideally be done during regular maintenance. In addition to that there are some aspects of the air conditioning system that will be allowed to run to failure. According to Chimack et al (n.d.) proactive maintenance involves a time based or a machine- run time based schedule. Maintenance in this scenario is scheduled in order to detect or reduce the degradation of specific components in the air conditioning system. This can help to lengthen the life of the components and the system while allowing for savings of unnecessary labour cost which normally occur when a component does not function efficiently or stops functioning altogether. Proactive maintenance will prevent damage to various components of the air conditioning system. Because maintenance occurs whether or not it is necessary it becomes a labour intensive effort. However, it may result in necessary repair work especially when small leaks are detected. Appendix 1 – RCM II Worksheet RCM II Worksheet Asset: Split air conditioning system Component: Evaporator Function Functional Failure Failure Modes Failure Effects 1. Provide cool air at between 8 and 11 degrees Celsius above room temperature with little noise A. Not able to cool at all B. Blows hot air C. One section of the office is cool and other sections are warm D. Cools at a TD of less than 7 degrees Celsius E. Cools at a TD of 13 degrees Celsius F. Loud noise from the evaporator blower/motor 1(a). The refrigerant has leaked out completely 1(b). The circuit board has gone bad 1(c). The capacitor has burnt out 2. The evaporator motor has stopped working 3. The evaporator blower has stopped working 4(a). Not enough refrigerant in the line 4(b). Dirty or blocked evaporator coils 4(c). Some of the fins on the evaporator has been damaged 5. The thermostat is not working 6. The blower is to close to the evaporator 1(a). There are signs of refrigerant on the roof. It has a foul smell and poses a health hazard. If the room is not cool enough customers will not purchase our services and so the business will lose income. It will take two days to be repaired. Refrigerant leaks could cause an explosion which can damage the building and its equipment. The line will have to be repaired or replaced to prevent further leakage. 1(b) Customers will be lost and the circuit board will have to be replaced. This will result in a total downtime of two (2) days. 1(c) The evaporator cannot function. No electric charge is being received by the evaporator. The capacitor will have to be replaced. This will result in one day downtime. 2. There is no sound coming from the evaporator motor. The office will be hot and uncomfortable and so customers will go somewhere else with their business. This will result in lost income for the business. The motor will have to be replaced. 3. The evaporator blower is not spinning and so the air is not circulating. The fan will have to be fixed or replaced and this problem will take a day to be resolved. There will be a loss of customers for one day and staff will not be able to complete orders on time. This will affect the reputation of the business. 4(a). The room is not cooling sufficiently even when the switch is set at temperatures below 26 degrees Celsius. The business will not be able to accommodate more than two customers at a time. This will result in a reduction in income for at least half a day. The technician will have to be called in to check refrigerant level and add some more. 4(b). The air coming from the air conditioner is reduced and so the room cannot accommodate the usual number of customers. Business will be lost until the evaporator is cleaned. 4(c). The office is not been cooled at the set temperature and therefore cannot accommodate the number of customers it usually does without becoming uncomfortable for its occupants. 5. The office is very cold and so customers do not stay as long as they usually do. The staff cannot function efficiently. Revenue will be reduced for one before the thermostat is repaired or replaced. 6. The office is noisy and customers are easily annoyed and will therefore cut their time short. This will result in a decrease in revenue which will continue until the problem is fixed on day 2. 2. Reduce or eliminate dust particles from the room A. Dust can be seen in the office 1. The evaporator coil is dirty 1. Dust particles are being blown around the office. It affects customers, especially those with sinus problems. It is making the staff sick. The equipment will be out for four hours to enable cleaning. Worksheet format adapted from Eerens, E.W.J (n.d.) Appendix 2 – RCM Decision Analysis RCM Decision Template adapted from Eerens, E.W.J (n.d.) References AirConditioning-and-Heating.com. (2011). How air conditioners work: Components and functions of AC units. Retrieved from: http://www.airconditioning-and-heating.com/how-acs-work.php. Last accessed 29 Jul 2011 August, J. (1999). Applied Reliability-centered Maintenance. USA: PennWell. Brignall, M (2006) Air Conditioning. The Guardian 22 Jul 2006. Retrieved from: http://www.guardian.co.uk/money/2006/jul/22/electronicgoods.shopping. Last accessed 3rd Jul 2011 Chimack, M., Walker, C., Miller, R., Aardsma, J., Novosel, D. (n.d.). National Center for Energy Management and Building Technologies Task 10: Energy Reduction Through Practical Scheduled Maintenance - Subtask 10.1 Literature Review. Retrieved from: http://www.ncembt.org/downloads/NCEMBT-051231-1.pdf. Last accessed 15th Jul 2011 Eerens, E.W.J. (n.d.). RCM Analysis, Information and Decision Worksheets. Retrieved from: http://members.dcsi.net.au/eercons/RCMAnalysisSheets.pdf. Last accessed 4th Jul 2011 Energy Savers. (n.d.). Common Problems With Air Conditioners. Retrieved from: http://www.energysavers.gov/your_home/space_heating_cooling/index.cfm/mytopic=12400. Last accessed 18th Jul 2011 Moubray, J. (1997) Reliability Centered Maintenance. 2nd ed. USA: Independent Press Inc. Mutual Consultants Ltd (2009). PAS 55-1: Asset Management: Part 1 Specification for the optimised management of physical assets and RCM. Retrieved from: http://www.mutualconsultants.co.uk/ebooks/pas55rcm/files/pas-55%20and%20rcm.pdf. Last accessed 3rd Jul 2011 Smith, A.M. & Hinchcliffe, G.R. (2003). RCM: Gateway to World Class Maintenance. USA: Elsevier Butterworth Heinemann Split Air Conditioning. (n.d.). Troubleshooting for Split Air Conditioners. Retrieved from: http://www.splitairconditioning.net/troubleshooting-split-air-conditioners. Last accessed 11th Jul 2011 Read More