Tips Industrial Air Compressor Maintenance-Maintenance Cruz
What does your business want out of your air compressor?
What does your business want out of your air compressor?
- To deliver air reliably
- To run with efficiency
- To last a long time
- To deliver with relatively low maintenance cost
And there may be more considerations like component futures. Are the components at the end of their life phase and new technologies are right around the corner. It is something to be considered, but you can not always control this due to time constraints. It is a consideration because you would like to avoid having your motor control electronics become obsolete a year after you purchase a new unit.
Another consideration would be proper sizing with room for expansion or capacity to accommodate future needs. The adage that "more is always better than not enough" is true about equipment in general. Allowing extra capacity will increase the longevity of a compressor by allowing it to run at a lighter duty relieving some wear and tear. Compressor manufacturers have performance curves that show the optimum run conditions where the unit attains its highest efficiency for the dollar as well as optimum longevity of the equipment. It is very important to pay attention to these curves and configure your system to deliver in these optimum zones, adding another compressor in order to keep the units running within prescribed parameters is a consideration.
Running any facility without redundancy is asking for trouble, unless of course your plant can be without compressed air for an extended period or temporary means are readily at hand. For the most part having a redundant compressor at the ready is the prudent path. The extra equipment allows for better and more frequent maintenance. Cycling compressors to run and rest is a great way to achieve very long life and also insure that both compressors are ready to run at all times while spreading the load.
Most compressors these days have drive control systems that meter motor speed to only deliver what is needed. These units can be programmed and linked to follow each other and run a balanced program for efficiency and longevity. They can run in a master slave configuration or alternating lead-follow regimen.
There are actually a lot of different ways to make compressed air. Reciprocating (piston type), rotary vane (sliding seals in an eccentric housing), roots blower ( rotating lobe), dual screw, but they all have one thing in common, very tight tolerances. In order to move air efficiently you must have a very tight seal usually without actual contact. The vane pump and the reciprocating units have seals that make contact with the housings and friction is controlled with lubrication or even water. Vane pumps can be used to create vacuum and compressed air and many use water in the housing to create an airtight seal between the vanes and the housing, these units can create high vacuum due to this tight seal.
Any way you slice it, air compressors are highly technical and internal failures many times are catastrophic. This is one area of your maintenance plan that must be, to use a pun, airtight. If you neglect your air compressors the results will be very costly indeed. Vibration analysis and oil analysis are a must with compressors to give you insight when you need to take action to prevent catastrophic failure or replacement. Compressor manufacturers always offer services plans and they are always very expensive, but they should be considered carefully. You have to ask yourself if your team is really up to the task of caring for your compressors and if you want that responsibility.
You can also divide the maintaining tasks into those your team can handle and those that the service technicians should address. I would recommend the full service plan and analysis with the burden being with the compressor company if there is a major break down. If your people make a mistake with this equipment the total responsibility will be with your company. Compressor companies have no problem with replacing a compressor as they make their money on the proprietary expensive parts and they want to keep their brand in your building.
There are careful decisions to be made where you have to evaluate the recommendations of the manufacturer, engineers, and other professionals related to compressors. Undersized systems do not provide cost effective efficiency or longevity. Oversized system may be much more expense than you need to spend and also may be running outside the optimum efficiencies. Having a very accurate plan for present capacity and future capacity requirements is the first step in the decision process. How big does your compressor room need to be to accommodate future needs? How should you arrange your compressor room now so it provides airflow, access, and space for expansion without having to reset existing equipment in order to add more units? Pipe sizing, accumulation sizing, valve placement, branch stubs, and isolation means should be considered.
Air delivery is simple and complex at the sametime and the deeper you go the more complex it becomes. This is where having the clearest view of present requirements and future requirements is the most crucial. Granted, it is a real luxury to actually have this information as many future plans are just dashed outlines on a drawing, but there are instances where you have sufficient knowledge to make some preparations.
We Can Do it, Right?
I make it sound like air compressor maintenance is totally beyond the scope of the maintenance department. There are departments with qualified personnel that can handle precision machine maintenance down to internal repair, but this has been very rare in my experience and generally only one person who had the kind of training required in the department. If you build a program around the highly technical end of compressor maintenance and over time your personnel change, you may end up in a situation where people who really have no businesses working on your equipment in that capacity are trying to accomplish highly technical repairs with guesswork, not good.
I have seen plenty of technicians that have gone to manufacturer training and still have no real clue what they are doing, you must be very careful with this. The big disconnect is that compressor technicians work on compressors everyday and receive ongoing and updated training on a regular basis as where your technicians perform the highly technical aspects of compressor maintenance twice a year with general maintenance in between.
What's New and Is It Better?
It comes back to the original question, What does your business want out of your air compressor? This question is more complicated than just delivering air and reliability when you take into account the other points I have described. I had mentioned vibration analysis before and wanted to add a note.
The newer speed controlled units modulate to maintain delivery pressure. A side effect of speeding and slowing a motor is bearing collisions that can cause premature bearing failure. The bearings are rotating at a high rate and your controller starts to ramp down essentially putting the brakes on. The bearings want to continue forward while the shaft is slowing down so the bearings are constantly racking back and forth in the bearing cage, this causes premature bearing failure. Much of this collision is generally absorbed by the lubrication but not all. Many new machines have incorporated vibration sensors near these bearings due to this issue. These sensors are tied into the processing unit with limits that will shutdown the unit when reached to avoid major failure.This is an unfortunate by-product of the efficiency scheme.
Lastly is lubrication and all that needs to be said here is follow the manufacturers recommendations. If there is a choice between synthetic or petroleum based lubricants I opt for synthetic as the performance is usually much much better. Synthetic is usually expensive, but the longevity of the lubricant is usually much longer. Again this is a call that should be made through manufacture recommendations and specific requirements of your factory, like food grade only.
Lubrication is the lifeblood of our machines, an area not to be neglected. I think that is a given, yet still many maintenance systems have poor or inadequate lubrication schedules. Air compressors, out of all your equipment, is the first place ensure complete lubrication attention and scheduled work. That is not to say that there is not other items of equal importance in your factory, they too will need stringent adherence to scheduled lube work. Compressors are just unforgiving when neglected, they tend to have major catastrophic failures and even very serious fires. A gearbox on your conveyor has a little forgiveness if left unattended and a minimal chance to ignite, by no means am I endorsing neglect, just pointing that they are at different priority levels. A gearbox generally gives some warning be the presents of a leak or rise in temperature giving some time to address the issue. A compressor, on the other hand, can expel all of it's lubrication in seconds if a line or joint bursts leaving metal to metal contact at very high RPM.
Most newer compressors have plenty of safeties and sensors to prevent this kind of situation, the main being oil temperature limits. Even at that, your compressor has been losing a small amount of lube through the air/oil separator over time. Now you have been running on the lower end of your oil capacity. This will work less oil harder and hotter causing the lubrication break down to increase significantly. This is the most common source of premature wear and tear with compressors. Your basic maintenance and annual work are adequate, but that slight leak may be put off until a scheduled PM. This maybe okay, if the lube is constantly monitored and refilled, but easily overlooked and maybe a very costly mistake.
Never miss the scheduled oil change on a compressor. That is the best advice I can give, the lube has done its job and the lubrication package has been breaking down since it was poured in X amount of running hours ago. It may still look like good oil, but its not and must be changed out or the big issues are coming.
Get that old oil looked at. Send a sample to be tested and see what is in there. Oil testing is valuable and mostly you see exactly what you expect, metal particles. The size and amount of the particles give good insight into what the inside of your compressor looks like. It also tells you if that lube is doing the job it is supposed to be doing. Break in oil analysis is very important as well and most compressor manufacturers include this in first service as a warranty item and maybe included in the six month service. Regardless, regular oil sampling should be done and not just on your compressors.
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