David Manning-Ohren offers 10 rules to ensure that your condition monitoring techniques work for you not against you
Condition monitoring of plant is an increasingly common method of preventing failure of critical equipment and maximising uptime, but many engineers are making some basic, and costly, mistakes.
Effective maintenance management depends on the accurate forecasting and diagnosis of problems with plant and machinery. Using the wrong maintenance technique can waste time, money and resources with no effect on uptime of a pump, compressor or machine tool’s availability.
While condition monitoring can play a vital role in a maintenance programme, all-too-often its implementation is haphazard rather than strategic, targeting the wrong equipment and having little effect on productivity.
In my experience there are literally dozens of rules that an engineering maintenance team could follow when implementing a condition monitoring programme, based upon application and skillset within the team. However, if I had to pick out ten rules then these are the key ones:
Rule 1. Never use condition monitoring on its own
Condition monitoring should never be used on its own as a trending tool. For monitoring to work best it needs to be implemented in harmony with a strong maintenance strategy and repair feedback from the maintenance team or outside suppliers. Maintenance is an art not a science and a sound maintenance programme needs to take into account multiple factors, not just trends.
Rule 2. Spend your money on the most valuable asset
Not everything needs to be monitored. The key to more uptime is assessing what plant is critical and then devising a schedule that takes into account its failure or repair history and cost to a business when it is unproductive. A small motor gearbox with a replacement cost of a few hundred pounds, which can be sourced quickly and easily from a distributor, is not critical equipment and does not need monitoring.
Rule 3. Get close to your key plant and machinery
The best condition monitoring device ever invented is man. Tap into the people who are using the machine every day and notice the rattles, smells, squeaks, drips, bumps that are out of the ordinary. Every one of these will help you foresee and predict failure before it occurs. The machine operator is using the machine every day, knows its foibles and its weaknesses. Over time the operator is the one person who will detect changes in cycle times, efficiency or increased vibration which can offer clues to what is going on.
Rule 4. There is no ideal condition monitoring frequency
I’m often asked, “How often should we monitor the condition of machinery?” The answer is “I don’t know”, because it will depend on many variables from the maintenance regime, through to the quality and age of the equipment and its criticality. Frequency can only be determined once a thorough understanding of the plant and its role in production is analysed and understood.
Rule 5. Keep a vibration database
Vibration is a key part of a strong condition monitoring regime. A good vibration database will include three types of vibration reading, trend, spectrum and time waveform. Trend records the overall vibration parameter value and details the date and time of the reading. Spectrum measures the amplitude of the vibration parameter with respect to its frequency and the time waveform measures the raw vibration signature without filtering or processing. Vibration checks every 4-8 weeks is a good starting point.
Rule 6. Understand the plant and understand the operating conditions
Always walk around a site before taking any readings and switch on any machinery to ensure that it is warmed up and fully operational. A reading when a piece of plant is cold could be very different from a machine that has been running flat out for two hours. Also the speed of plant can change causing vibrations and temperatures to alter non-linearly. Base-lining with respect to speed and operating load is excellent practice.
Rule 7. Certification is better than qualification
Condition monitoring is constantly evolving. Any qualification therefore has a shelf-life and expiry date because the techniques are being constantly updated. Certification, which requires updating every five years, is therefore infinitely preferable to any qualification. If you are condition monitoring in-house you need to ensure that your key people are up-to-speed with the appropriate certificates, as well as aware of new technologies and practises.
Rule 8. If you going to outsource insist on seeing some paperwork
Due to the fact that condition monitoring is constantly evolving many maintenance teams are outsourcing to third party suppliers. There are sound reasons for doing this but before employing anyone ask to see some paperwork to ensure you are only employing the best condition monitoring experts. Plant users should insist that all engineers sent in by a service provider are qualified to ISO 18436 and abide by the British Institute of Non-Destructive Testing (BINDT) code of ethics.
Rule 9. Judge a condition monitoring provider on more than the day-rate
Condition monitoring is a specialist job but all-too-often price is the key determinant for users of plant and equipment. Typically, the cost of condition monitoring is based upon the number of machines that require monitoring multiplied by the expert’s day rate. Unfortunately, this takes no account of the type of data being taken, software being used or basic competence. Also consider the support that an organisation can offer to the condition monitoring; expertise on bearings, gearboxes, pumps and motors are essential to any condition monitoring service provider.
Rule 10. Delay failure with good maintenance
Be sure you are taking the appropriate measures to delay the failure as long as possible by doing the obvious little things like appropriate lubrication, dusting down cooling fans on motors, running a vacuum over the distribution board and cleaning the pool of oil under the machine so any new drips are noticeable. Some people call this 'preventive maintenance' but it’s just common sense.
David Manning-Ohren is an expert in condition monitoring at ERIKS UK