Extending standby generator lifetime through maintenance

November 6th, 2014, Published in Articles: Energize, Featured: Energize

 

Standby and portable generator maintenance has become almost synonymous with achieving reliability, with the role of the maintenance professional being to maintain generation equipment at its peak operating reliability in the most cost effective manner possible. This paradigm shift has come about over the last ten years as dependence on standby generation has increased.

Equipment manufacturers make machines for really only one purpose – to make money – and customers generally buy them for that same reason. The cost of purchasing a piece of equipment tends to be relatively fixed, while the cost of operating the equipment can be highly variable. The main aim of the maintenance department is to ensure that the operating costs do not exceed income received by minimising down time and repair costs.

Maximum output is now required from minimum input and this has resulted in reliability being optimised rather than maximised. This has to be a strategic and discriminating process which considers both the cost of reliability and the consequences of unreliability. Companies which have achieved this optimisation have invested heavily in people and equipment for effective asset management. Fundamental to this is education throughout the whole company.

As technology has advanced, machines have become more complex and expensive to build. Maintenance engineering has had to develop along with the technology. From being virtually non-existent, maintenance has developed from a passive to an active philosophy. Proactive maintenance techniques now give some organisations their only edge over their competitors.

Oil analysis is both predictive and proactive and is probably the most cost effective maintenance technique available. It is not, however a panacea, it is merely a tool – a very effective one, but still only a tool. To carry the analogy further, a tool needs a tool box – there is no point in trying to implement an oil analysis programme if there is not a mature overall maintenance programme already in place.

 

49 WearCheck sampling Peter Carty and Shashay Rampersad

Fig. 1: Peter Carty and Shashay Rampersad sampling generator oil condition.

 

The evolution of maintenance philosophies

Breakdown maintenance

This involves fixing things if, and only if, they break. This was common enough 50 years ago but with the current cost of equipment, labour and downtime, it is no longer a commonly viable option; it is very cheap to implement but the consequences are dramatic. It should be pointed out, however, that all maintenance philosophies have their proper place. Each piece of equipment should be treated on its own merits and the most cost effective (optimal) combination of philosophies and techniques employed. For example, the factory manager or workshop foreman does not schedule to have all the light bulbs in the plant replaced on a calendar basis; they are replaced when they fail – this is breakdown maintenance and is the optimal strategy in this case.

Preventive maintenance

This philosophy evolved because it was soon realised that breakdown maintenance was not the best way to look after most pieces of machinery in industry. Preventive maintenance involves the servicing, overhaul and replacement of items of plant based on a scheduled time interval such as operating hours or kilometres, or on a calendar basis. This was certainly a step in the right direction, but problems arise because the “maintenance interval” is based on an average. This means a percentage of machines will fail before receiving attention and a percentage of normally functioning units will be disturbed; there is a lot to be said for the maxim “if it’s not broken, don’t fix it”.

Predictive maintenance

Predictive maintenance evolved from preventive maintenance for the reasons outlined in the previous paragraph. This is also where condition monitoring techniques come into their own, because this philosophy involves using as many non-destructive testing methods as is necessary to determine the health of a piece of equipment, then making maintenance decisions based on these results. This practice originated in the aircraft industry during the early sixties and was known as maintenance “on condition”. Predictive maintenance is a reactive technique that delivers value when early warning systems can substantially impact on the severity of a failure event. It allows the user to reduce the severity of the failure and plan activities.

Proactive maintenance

This naturally grows out of the other three philosophies and is concerned with the analysis of all maintenance and condition monitoring techniques to determine what causes failures and how these situations can be prevented in the future. Root cause failure analysis is central to proactive maintenance and it is certainly the way of the future if organisations want to become world class players. Oil analysis has one foot firmly rooted in the predictive camp, the other in the proactive camp. As its name suggests, this is a proactive technique and delivers value where the failure rate can effectively be reduced and is most productive where root cause of failure (RCFA) is identified and controlled. It allows the user to reduce failure rates and operating costs. Table 1 shows potential costs of the various philosophies.

 

Table 1

Table 1: Potential costs of the various philosophies.

 

 

 

 

 

 

 

 

 

Proactive maintenance follows the basic management precepts of ISO 9001:2000 corrective action very closely:

  • What went wrong?
  • What are we going to do to fix it right away?
  • Why did it go wrong?
  • What are we going to do to ensure it does not happen again?

The life of a generator can be extended and its reliability boosted by a well-run maintenance programme.

 

Microsoft Word - Maintenance WearCheck - editted.docx

Fig 2: Maintenance vs. breakdown costs

 

Conclusion

The secret in optimising maintenance strategies is to get the right combination of maintenance philosophies and condition monitoring techniques. In order to be cost effective you cannot run a plant on total breakdown principles, alternatively, over-maintaining equipment is not the solution either as the graph below shows. It would be wonderful if we could have a simple equation to determine the right balanced, but you will probably find that the graph is different for each piece of equipment.

Contact Steven Lara-Lee Lumley, Wear Check, Tel 031 700-5460, support@wearcheck.co.za

 

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