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Week of 27 March 2017: Thinking new thoughts about maintenance

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There are some ways in which original capital purchases can serve to reduce maintenance costs and downtime.

Let's start in the woodyard with some thoughts about sprockets on conveyors. The driving sprocket often has twelve teeth while the driven sprocket has forty-eight. It would be a good idea to purchase the set with the smaller sprocket hardened. The logic behind this is that the smaller sprocket makes four revolutions for every one made by the larger. By hardening the smaller, both would wear out at about the same time. But why not also buy the shaft on the conveyor and the shaft on the motor in extended lengths? In this way, two sets of sprockets can be mounted on them so that when the first set of sprockets wears out, the second set can immediately be fitted with a new chain. This will cut downtime way down. It will not cost any more in stores inventory, for the second set would be in the storeroom anyway. Now it will simply be mounted in place. Both sets can then be replaced on a major outage sometime into the life of the second set, thus not jeopardizing the operation of the pulp mill. Taken a step further, a small box could be mounted near the shafts containing the replacement chain, oiled and ready to go.


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And now, let's look at the ubiquitous horizontal pump. It is nothing short of a ceremony to align a pump and motor set. Why can't pump manufacturers build their units with a design and strength to use C-Flange motors? Bolted on the ends, these motors would require no aligning. This would mean there is no danger of misalignment and early wear problems. The T-frame motor and its sloppy bolt holes, coupled with poor pump and motor base manufacturing techniques, make the current setup about as dimensionally accurate as Stonehenge (which is fairly precise, but not perfect).

And then, there are the suction roll seals. Why can't manufacturers build suction roll vacuum boxes with two sets of installed seals that can be raised and lowered from outside the roll without removing it from the press section? Think of the time and costs this would save. Yes, it would take some clever design work, but it does not seem impossible. It may even eliminate the need for some spare rolls.


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Installed spares are generally a bad idea. However, when the spare is cheap, relative to the maintenance costs or potential downtime an unplanned failure represents, installed spares can make a great deal of sense. They can free up maintenance time to do preventive and predictive work, saving big money.

How to know when installed spares make sense? Start with the big picture, analyzing planned and unplanned downtime, and maintenance labor and material costs during downtime. If the length of shutdowns is long and the labor costs are high when compared as a sum against the cost of replacement items installed, it may be time to look at the situation in depth. Carefully qualified installed spares may be very valuable.

And, of course, the less maintenance labor that is required to maintain your facility, the less likely you are to incur maintenance related accidents--a cost factor of nearly incalculable size.

Be safe and we will talk next week.


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