Figure 2. Almost two-thirds of maintenance time is spent investigating “problems” that do not really exist.
In addition, because new field devices are also inherently so reliable and are connected to the host system via digital communications, when maintenance is necessary it is possible to perform as much as 80% of the required work remotely from the appropriate maintenance work station. The “Process Interface” and “Failure” problems (Figure 2) still require that a maintenance mechanic physically work on the device in the field.
Figure 3, from a presentation by Larry O’Brien of independent research firm Automation Research Corp. (ARC), Dedham, Mass., at 2004 Fieldbus Foundation General Assembly, shows how companies are presently applying the different maintenance techniques to control loops in their facilities against where they think they should be. Corrective maintenance accounts for 60% of efforts versus a target of 10%, with preventative maintenance at 30% instead of a desired 40%. Only 10% of maintenance being performed today is predictive maintenance. Obviously a gap exists and the new capabilities of digital field devices integrated with asset management tools are one way of reducing it.
ARC indicates that maintenance accounts for 40% of manufacturing cost. Related research has shown that a facility on average spends 10% of its overall maintenance budget on the automation and control system. Therefore if a site could reduce its maintenance expenses, the resulting savings would directly impact the bottom line. How can this be done?
ARC has found that 50% of maintenance is corrective (reactive). In other words, maintenance staff spends half their time involved in emergency or unplanned work. This is the most expensive form of maintenance because any equipment needed must be obtained after the request is received and, if not on hand in the warehouse or inventory, must be express ordered at a premium price. As a result, corrective maintenance is 10 times more costly than preventative maintenance — this is the main reason why most facilities now implement a preventative maintenance program.
Yet, preventative maintenance is done only 25% of the time (Figure 3). Preventative maintenance by its nature seeks to intervene prior to the expected failure date of the equipment. Vendors, to be conservative, add a small margin of error to their estimates. The facility, not wanting to be “caught” either, in many cases “shaves” a bit of time off the recommended maintenance period for insurance or to better coincide with other regular maintenance or unit turnaround/outages. However, the real difficulty with preventative maintenance is that it is time-based, instead of based on the actual condition of the equipment. Typically, 60% of preventative maintenance is unnecessary.
Figure 3. With companies now engaging primarily in corrective maintenance, there’s plenty of opportunity for improvement.
Because of this level of unnecessary work, preventative maintenance is five times more costly than predictive maintenance, which is based on the actual condition of the equipment. However to determine the actual equipment status requires the investment in diagnostic tools and software previously described.
A simple calculation based on the numbers presented shows the return on investment possible:
Assuming a facility has an annual maintenance budget of $1 million, the automation maintenance budget will be $100,000/year. Now, if 50% of this is spent on corrective maintenance instead of the target 10%, there’s a potential savings or opportunity of $40,000 difference between the actual and target as it is unlikely that it will be possible to prevent all corrective maintenance. Because few facilities are implementing predictive maintenance, we can assume that the remaining 50% or $50,000 of the maintenance budget goes for preventative maintenance, versus the target of 40%.
From the 10% difference between the actual and target levels for preventative maintenance there’s an additional maximum potential savings of $10,000. In the best possible scenario, the site reaches both industry targets of 10% corrective maintenance and 40% preventative maintenance. Let’s see what that means financially.
Moving from corrective to preventative maintenance cuts costs by a factor of 10, so the $40,000 expense would shrink to $4,000 if performed as preventative maintenance. The original $50,000 preventative maintenance budget can be reduced by $10,000. As a result the combined opportunity is $14,000/year. Converting that preventative maintenance to predictive maintenance (considering the five-fold difference) will reduce costs to $2,800. Therefore, the overall savings will be $50,000 - $2,800 = $47,200/year/million dollars of maintenance budget. These are simply average values, and each facility will have slightly different levels of maintenance activity in each category. However, the multiplier ratios will remain valid overall and could certainly be used as a first pass estimate of the maintenance savings opportunity at your facility.
Extending the gains
Of course, once the effectiveness of a predictive maintenance program has been demonstrated, efforts will be made to migrate all maintenance to the new program. The already in-place infrastructure of server and asset software will significantly lower the incremental cost of implementation.
In addition, a system with predictive maintenance tools will mean that you’re only working on the items that need to be addressed when they actually require work, thus insuring maximum operational life from your equipment. Less maintenance also translates into reduced risk and exposure to workers as well and, consequently, a safer facility.
A more reliable system isn’t only a lower cost system to operate, it is also inherently a safer system.
I have highlighted how migrating to an integrated control, operations and maintenance solution using a digital communications system can maximize the return on your capital investment while minimizing your maintenance expenditures. All that is required now is to quantify the lifecycle benefits of such a system for your facility.
Ian Verhappen is an ISA Fellow, Certified Automation Professional, adjunct professor at Tri-State University and Fort McMurray, Alberta-based Industrial Networks Director for MTL Instruments Group plc. E-mail him at firstname.lastname@example.org.