Maintenance: How is it used?

Preventive maintenance is very expensive. It adds a tremendous cost to systems that cannot be allowed to fail. It is an important part of military systems, like ships, planes, weapon systems, etc. If it must not fail. it will cost you. One way around it may be to weigh the costs between preventative maintenance and redundant systems. In the case of a failure, that part can be isolated and the system continues working while the failed part is repaired/replaced. This is already done in piping systems. A valve can be bypassed while it is being repaired/replaced.

The purpose of maintenance to keep the operational cost to the minimum. Without a maintenance plan, operational cost would soar, the production plans would go haywire, quality would suffer.

The maintenance system would depend on the criticality of equipment and the stakes. Preventive maintenance would become essential in aeroplanes even though costly. In simple manufacturing machines, simple breakdown maintenance could be an answer. These decisions depend on what is at stake, but without any maintenance plan, the operations would suffer badly.

Even with the best preventive maintenance, machines break down. If break down is not an option, then standby equipment must be available until the breakdown can be repaired. Depending on the complexity of your equipment and its operation, this could replace preventive maintenance.

The short answer is. It depends on how much you are willing to spend and how important machine uptime is to you and your operation.

Anything that is life critical either to persons or company should require a hot back up that is monitored for condition and is ready to go at a moments notice. These systems usually switch over automatically and quite often have a cold back up in reserve. This is the most expensive solution as it requires three times the equipment and three and a half times the labor to maintain. This is standard operating procedure in industries such as Nuclear, Petroleum, and Chemical to name a few that simply can't afford any equipment failure to take a critical line or system down.

Systems that are important but not critical can have a cold back up system that is usually manually switched over and the faulty unit is repaired while the back up system is used. Many systems are designed this way but again, it requires twice the equipment and two and a half times the labor to maintain.

Most equipment lives in the realm of fix it when it fails. (FIWIF) That is to say, when a piece of machinery goes down, a crash crew of maintenance people come in and repair the equipment as quickly as possible. Although common, this is a risky way of doing business. It relies heavily on competent maintenance crews, and the availability of spare parts, stocked, and readily available. Cost cutting and Lean Manufacturing quite often reduce spare parts stocked in house, to a point were a quick repair is not possible. Even our suppliers avoid stocking inventory. Production crews are idle when these repairs are carried out and so efficiencies drop.

Preventative Maintenance (PM) can reduce downtime but it won't eliminate it. It is however, a very useful tool in assessing a machines condition and replacing parts found to be failing. This is where most industry is now.

Predictive Preventative Maintenance (PPM) requires a data set that is usually not available. Most companies simply don't keep track of what fails, for what reason and how often. What is needed is a monitored PM system with the data logged and used to generate the PPM work orders. This must be bought into by upper management, as access to the equipment for repair work has to be scheduled into the line, and production people resist this. PPM orders will also allow enough lead time to bring repair parts in, so they need not be stocked in house. I believe industry needs to move in this direction. Will it happen? Probably not, as payback is not immediate. Until the engineering side of the factory starts having more control and the finance people are kept out of plant maintenance we are in trouble.

Elroy