Predictive vs Preventive Maintenance
Which Maintenance Approach is right for me?
This article will look at predictive vs preventive maintenance and try to explain what each approach is and how they compare to one another. I hope at the end of the article you will be able to make a decision as to which approach your company should be looking at to ensure that you get the best from your equipment and machines.
The aim of any maintenance program is to prevent any unplanned downtime of your production equipment that interrupts your normal production schedules and threatens your ability to meet customer demands.
Unreliable equipment causes your company to need to invest in having excesive amounts of work in progress and finished goods stocks to try to cushion your production processes and customers from the effects of any breakdowns. This stock comes at great expense to your company and requires not only cash to fund it but space to store it, equipment and personnel to move it and presents the opportunity for many quality problems.
A Maintenance program of some description is therefore required to try to minimize any unplanned downtime of your equipment and machines.
Preventive or preventative maintenance is what most people recognize as being "maintenance". We take action to repair and maintain a machine before any breakdown occurs; the most recognisable form of preventive maintenance that most people can relate to is your car;
For our car before we start a journey we check (or should check) our oil levels and coolant levels to ensure that they are at the right levels for the operation of our car. Failure to do so could lead to us having a breakdown during our journey.
We also conduct regular maintenance, we will change our oil every 8,000 miles or whenever the manufacturer informs us is the correct interval and will also do other changes such as changing the timing belt after 50,000 miles. We do this because we know that these things tend to wear out after a period of time and if they break the costs of the repairs will be far greater than the costs of making replacements before they break.
The machines and equipment we have in our company are no different, we need to ensure that we maintain them in a good condition and undertake maintenance at the periods suggested by the machines manufacturers or at periods that history has told us are going to ensure that we prevent any possible failure.
It is far better to schedule planned maintenance of our machines than risk them breaking when we needed them the most or in a way that causes expensive additional damage to the machine.
Infrared Thermal Imaging
Predictive Maintenance Video
Predictive maintenance has a slightly different approach to preventative maintenance, it seeks to identify when a failure is going to occur so that we can make whatever repairs are required before the breakdown actually happens.
Predictive maintenance would not just automatically change a component after a set period of time, it seeks to monitor the various aspects of the machines performance to identify when components are beginning to wear and are starting to approach their failure points. It uses a number of different techniques such as;
- Vibration Analysis
- Thermal (Infrared) Imaging
- Oil Analysis
- Sonic and Ultrasonic Monitoring
- Process Monitoring
- Crack Detection
These methods and others allow a skilled technician to be able to predict when a failure is going to occur giving enough time to schedule maintenance and prevent a more catastrophic breakdown.
In the past many companies have seen the maintenance department and the act of doing maintenance as an expense rather than as an investment to reduce costs in the long term. Some only running machines until they failed with the subsequent costs and delays to their manufacturing.
Most people today however recognize that a few dollars spent up front on maintenance can save many hundreds of dollars later on when machines fail and you cannot meet your customer needs. Which would you rather do? Spend a hundred dollars on replacing your timing belt or risk even greater damage and more expensive repairs if it fails plus the need to have a replacement vehicle whilst it is being repaired?
So now that most people agree that we have to spend money on maintenance the question becomes when is the most effective point to do that maintenance and spend the money? This is where the difference between Preventive and predictive maintenance come into play.
Use Predictive or Preventive Maintenance?
Preventive or Predictive Maintenance
From Preventive to Predictive Maintenance
Predictive or Preventative Maintenance?
Preventative or Preventive Maintenance requires you to do maintenance at a set intervals whether the machine actually needs the work or not. For instance, most garages and manufacturers tell you to change your motor oil every 6000 to 10000 miles depending on the model; but what if you have been driving like a madman over rough terain for those miles and you used the cheapest brand of oil or alternatively if you are the most careful of drivers and used the most expensive highest quality oil?
The period of time or number of machine cycles does not always take into account the actual load put on the machine and of course there is always that chance factor thrown in by our friend variation - sometimes something will want to fail after a short time, other times it will go on and on many times past its expected lifetime. We therefore often change something long before we really need to do so; thus we add unnecessary costs.
Being able to better predict when something will fail therefore is a more efficient way to decide when to undertake any maintenance work. This is where the predictive maintenance techniques come into play, they enable you to run a machine until it starts to show the symptoms of an impending failure enabling you to get the most cost effective use of the components.
HOWEVER, using predictive maintenance will cost you money; you need trained personnel and diagnostic equipment to monitor your machines and this is of course is an additional cost. You need to decide if you can save more money by investing in predictive maintenance or if your additional savings will be less than the investment in predictive techniques.
If you only have a few machines then it will probably be best to stick with the preventive maintenance model as the savings from a predictive maintenance program are unlikely to be significant. If however you have a host of expensive machines then you are in the perfect situation to either train someone internally in predictive maintenance techniques or to hire in a predictive maintenance company to do the inspections for you on a regular basis.
TPM Video Introduction
Total Productive Maintenance
Within Lean Manufacturing you need to build on your maintenance through something called Total Productive maintenance (TPM), this involves everyone in the company in your maintenance efforts and seeks to make your maintenance as cost effective and efficient as it possibly can be whilst focusing on supplying the customer. Preventative and predictive maintenance techniques are an integral part of TPM and should be implemented within this framework to gain the greatest benefits.
Within TPM you should aim to ensure that your equipment is maintained in the most efficient manner possible whilst ensuring that you fully meet your customer's needs. This will almost certainly lead to operators conducting basic maintenance checks and even some aspects of preventive maintenance whilst your maintenance experts will look at the cost effectiveness and other benefits of using predictive maintenance techniques.
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