The hidden possibility

Published:  27 April, 2007

Stan Jackson, managing director of SPM Instrument UK, looks at the financial benefits of condition monitoring.

The trend in British industry has been towards larger companies operated by less people. Machines have as far as possible replaced human labour. Operating large plants with a relatively small workforce must necessarily also shift the focus of management. This approach in industry is commonly described by the term "Asset management”. Maintaining the technical life of the machine past its economical life has a positive effect on the final economic results of the asset. However traditional management takes a fairly narrow view. It works by departments, trying to make each part of the ongoing activities as efficient as possible. Quite often, this does not produce the optimal total result, because “improvements” in one sector can actually have greater negative effects on other activities.

For example, the incentives for the purchasing department to lower purchase prices can result in cheap products, spare parts that don't fit, break, generate higher energy costs, are difficult to maintain, reduce reliability etc. The savings in one department therefore increases the costs in others so the overall profit is reduced.

Budgeted maintenance costs are usually only the tip of the iceberg. The real costs, often in the form of indirect costs, are hidden, or turn up in some other part of the organisation.

 

Where does CM fit in?

Condition monitoring of rotating machines has been used for more than 30 years. The technical developments in form of instrumentation and software have been significant during this time. These handheld instruments have become much smaller and more powerful analytical tools supported by user-friendly software. But this is not very good on its own. The condition monitoring effort must also fit into an overall reliability commitment to enable it to work.

Reliability has to be supported by a maintenance policy and strategy, so the entire organization can focus on 'the correct thing to do". The benefits of the CBM programme are recognized when the results from the measurements actually are used to support the correct maintenance activity.

This support of reliability and maintainability starts with correct design and procurement. The Purchasing Department must work from a Life Cycle Cost (LCC) approach and the products they buy should be of such quality and design that they are easy to maintain and have the ability to be Condition Monitored. The machines that are purchased can be fitted with adapters or permanently installed transducers for measurements with portable instruments or with online systems for even better protection. The condition monitoring can then easily be instigated from the start. Retrofit often takes longer and can sometimes be technically very difficult, or sometimes even impossible to do.

 

Traditional strategy for maintenance

In a traditional maintenance strategy the resources are to a large extent used to open up machines that are in good condition, it is difficult to make changes. There is simply no time; the resources are organized for,

1) Cleaning and lubrication.  

2) Time based overhauls

3) Redundancies are designed into the process

4) Corrective work

Everybody is working very hard driven by unnecessary planned stops, breakdowns, and unplanned stops. The management is chasing ways to cut maintenance costs because the company is not profitable enough. No one knows how to calculate the contribution from maintenance.

To introduce condition monitoring in a company with this culture nearly always fails. If the programme starts it will normally be short lived, the resources for doing condition monitoring are needed to do “more important work - like overhauling machines”.

 

Reliability driven maintenance

All successful companies implement condition monitoring as part of a maintenance strategy that supports the activity. The management must allow for a change of priorities in the maintenance work. The implementation is critical and it is important that everybody realises what the new priorities are and why they are made. The maintenance resources in the organisation must now be focused on the activities that drive the reliability of the plant:

1) Design out the repetitive problems

2) Increase the lifetime of the machines

3) Condition monitoring during normal operation

4) Condition monitoring during planned stops

5) Time based

6) Redundancies

7) Corrective

 

The condition-monitoring programme becomes absolutely necessary, as the pre-warning time of developing machine problems is vital for the strategy. The maintenance work is carried out during planned stops and all unplanned activities must be considered as problems that have to be prevented from occurring again. The unnecessary overhauls and breakdowns are eliminated so the labour hours can be freed to work on improving the quality of the machines. Condition monitoring is also used to identify the root-cause of the problem so the right corrections or design changes can be made. In a world-class performing company there must always be time for improvements in machine design and procedures. Always asking if you are doing the right thing, according to the strategy. This strategy becomes a positive spiral that feeds on itself with, far fewer breakdowns, less spare part consumption, better planning of needed man hours, increased safety, better environment, improved reliability and reduced Energy consumption. When a full cultural change has been made only 20% of the work is actually spent on the traditional maintenance work.

The resources can be allocated to maintain the asset value of the plant and the reliability improved at an even lower cost; the profits go up.

 

Using condition monitoring to its potential

The most difficult challenge is to create a structure where condition monitoring is part of the maintenance strategy. Once done the next challenge arises, to use CM to its potential. Even companies that are considered successful very seldom follow up the economical effect of the programme or look for ways to develop the programme to cover the entire plant even if the potential for earning more money is there. To become successful it is important to evaluate the economical contribution of condition monitoring on a regular basis. Only then will the foundation for the programme be allowed to expand and cover the entire plant.

These are some examples of key performance indicators that can be followed to measure the effect:

• Maintenance cost/Asset value

• Condition monitoring hours/ Total hours of work

• Time based hours/ Total hours of work

• Hired labour hours/ Total hours of work

• Total hours unplanned repair/ Total repair time

• Average shock pulse and vibration levels

• Stock of spare parts/Asset value

• No. of purchase orders of spare parts

• No. of withdrawals from stock

• Waiting time

 

Case study from industry

Let us compare with some other key performance indicators from industry. This study was made at a Swedish paper mill in Hallstavik, Sweden and an example how the contribution from the programme can be analysed. The mill produces 785.000 tons of paper per year. The key performance indicators were selected as:

1) No. of machines included in CBM (condition based maintenance)

2) No. of measuring points per inspector

3) Pre warning time

 

Result:

1) In total there are 8 inspectors that cover 16,000 measuring points at the mill. The applications consist of some 800 rolls and 4000 auxiliary machines in the plant.

2) In total this makes an average of 2000 points/ inspector.

3) In order to evaluate the pre warning time from the first detection of faults to the time when the component was changed. The database covering 6200 measuring points was analyzed. It consisted of 2300 machines and covered the period of 6 years. The selection of the machines that were studied consisted of:

• 103 pumps

• 1070 el. motors

• 74 fans

 

The average pre-warning time from detection to corrective activity is 69 days and 95% were changed within the period of 59 to 78 days. The differences in pre warning time for the various applications can also be seen in the enclosed graph fig 2. The pre-warning time on electrical motors, pumps and fans are similar for most industries, according to our experience.

During this period there were no catastrophic failures on the equipment that was included in the programme, so all incidents/faults could be detected and failures avoided. The number of rotating machines can run close to 1000 units on a large factory so it is important to set up the programme in a cost effective way where one person could handle the entire plant.

 

Select a CBM strategy that works

The results from the condition-monitoring programme must be easily understood by a number of key persons that not are experts in understanding what the data means. This is the first and most important consideration to make. When the condition monitoring activity only involves complicated vibration analysis the programme will never take off. It takes several years of daily measurements to become an expert on your own machines with this technique. Great care should instead be made to see that the software and instrumentation could give clear evaluated answers in easily understood form, like green, yellow and red trends.

The study from industry shows that the vast majority of the readings are good. 75% are in good condition 20% on observation and only 5% actually show risk for potential failure. To determine that a machine is good must be fast and accurate, don’t spend expensive time analysing good machines; it is a waste of time. This sounds like an unnecessary statement because it is so obvious. Never the less many companies have fallen into the trap to do full analysis on everything.

 

Outsourcing vibration analysis

Some companies have also been contracting condition-monitoring specialists that do a few regular inspections per year. This approach does not replace the CBM programme on plant. Random tests cannot ever exchange routine measurements where some machines have to be followed up daily if any damage is developing. If the specialist not can be available on short notice and spend the required time from case to case, it is not condition based maintenance but rather ‘trouble shooting for special events.’

 

Summary

Industry has a huge opportunity to increase profits when implementing Condition Monitoring. There are however strategic considerations to make when introducing CM. Condition monitoring has in the past been introduced on several hundred sites sometimes with limited or no success at all. In most of these cases the condition-monitoring tool has been purchased without considering the necessary change of the organisation and the need for an organised knowledge transfer.

The maintenance strategy has to support the CM activity and the results from the programme must be used to change the priority in the maintenance work. The instrumentation and software should be selected to carry out front line CM and more complicated analyses should be implemented as second line only.

For further information please visit: www.spminstrument.co.uk

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