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Posted
Just wanted to take a minute and see what everyone is doing for a maintenance schedule. We currently are using generic pm scheduleds with mixed results. We have pump and valve rebuilds done at preset intervals. Sometimes it seems like we are throwing away parts with no wear, especially if the line hasn't ran in a few months. I'm starting to toy with the idea of doing timed predictive maintenance. For example... Have our plc's keep track of valve cycles, and motor runtimes to get the most of our equipment. So I'm looking for any feedback.... Good bad or ugly.. Thanks
Posted
For any rotating equipment, our shop provides scheduled balance testing. The results I have seen from our repair division are that the customers who use this properly avoid the larger catastrophic failures places that do not test get. You have to think of it not as just balance testing because you get a record of the rotating equipments noise levels across the spectrum, and over time you can see if that changes it is a red flag to pull it and repair. It is the noise equivelent of megger testing motors, you wait to see if the readings change over time, and when they do you know you have a problem. Your local tech would probably recommend a schedule for this testing, and not all equipment needs the same frequency of testing. Lower rpm devices will have less wear and not fail as badly when a component goes bad, coupled devices will have less side load on bearings and just make noise instead of being pulled off center when failing, these can give you warning before they are expensive repairs. High rpm stuff can fail pretty quick. A 2 pole motor can go in a day if the bearing heats up from something as simple as too much grease. A pump can get some gook on the impeller and be out of balance and tear itself up, or not be catastrophic but begin to leak just the same. For the valves, counting cycles is a good idea, and most manufacturers will provide a failure rate you can use to determine when you want to pm them.
Posted
Predictive/Preventive Maintenance is part science, part experience and part black magic. There is no one system that will fit everyone or even every piece of equipment. I suggest that you get a good software package that allows for as much flexibility as you you can afford. Add hour meters and counters to the controllers of every and all pieces that have moving parts. Begin inputting data based on use, cost of down time and cost of maintenance (or age). You are correct that time alone will waste some money but it is better than nothing if unscheduled down time is the enemy. This is one area that needs to be micro-managed to get the best results. contacting manufacturers of the equipment and the parts used on the equipment, such as gear boxes, motors, cylinders, anything with moving parts, to get recommendations is a good place to start. This data needs to be integrated with each other and with how you use the equipment, this is where experience comes in. One needs to look at where and what is used at or near its capacity and what is under utilized in order to get the most out of your predictive maintenance schedules. It takes a lot of boring work and data collection to get a good system that pays for its self but can be worth the efforts if you can get the needed cooperation from manufacturing. :)
Posted
If the valves are proportional modulating valves with smart positioners, the buried diagnostics in a HART smart positioner can be used to determine whether a valve is a likely prospect for re-build. The people who run commodity product on paper machines 24-7 where the profit is 21 minutes out of a 24 hour day use valve positioner diagnostics in just such a fashion -to minimize the relatively scarce labor during a scheduled outage. A given machine might have 36 valves on it, but only 14 might show enough cycling to warrant a rebuild during an outage. Every hour saved on an outage is money in the bank. Some use an asset management software program that reads and categorizes the HART diagnostics. Others use a HART handheld to read the data and fill in a spreadsheet from which they make their determinations. The 20 manual pages related to diagnostics for a Siemens positioner is attached so you can have a look see at they kind of data collected. I presume other brands have similar functions, but Siemens is the only one I'm familiar with. Siemens PS2 positioner diagnostics.pdf
Posted
Can't believe I am typing this, thought the book was another "Program duJour" when the boss asked me tor read it, but Terry Wireman's Maintenance Strategy Series Volume 1 Preventative Maintenance is an excellent read on the subject. ISBN 978-083113300-9. Probably my favorite line in the whole book is "If attempts are made to deploy advanced techniques before the organization is mature enough ..... THEY WILL FAIL" Capital Letters I added for emphasis.

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