I have a "husky" air compressor that I'm attempting to rebuild as I found the internals to be very dirty. I mostly started working on this because it wouldn't run anymore and found the culprit to be a faulty switch. But before I found the switch to be at fault, I took apart the compressor assembly and found a lot of dirt due to there not being a filter on the intake. So anyway I have the piston out and I cleaned up the piston, the ring and the cylinder with rubbing alcohol, removed some particulate matter and I'm done. So now I'm wondering, what kind of oil should I put in here to lubricate it?This is technically a maintenance free air compressor, so I don't exactly know what the difference between an "oil" and "oil free" air compressor is except that the prior you don't have to add oil. Do they for the most part use the same oil? Can I just use 5w-30 motor oil in place of the compressor oil?I've fully reassembled the air compressor and I tested it up to 5 psi, seemed to run smoothly. However I don't have any air tools so I didn't feel comfortable in bringing the compressor to 100psi and or doing continuous testing so I don't know at this time whether or not it will hold up.Now that I've tackled that project, onto the next one. I have a Diehard battery booster, portable power and compressor. http://www.sears.com/shc/s/p__1...&blockType=G15 Well one day when I was inflating the tires of my truck, I hooked it up and left it alone for several hours (forgot about it) and the compressor stopped working. Everything else worked on it except the compressor and so, after further visual inspection and finding some oil on the bottom of the unit, I concluded that the compressor had seized. Since I really only needed the compressor that comes with this unit, it has been useless to me since it stopped working in . So flash forward to today when I "completed" (we'll see!) work on a broken air compressor, I felt like I had the ability to tackle this looming project of mine. Alright, so I took the unit apart, took out the compressor assembly and I was able to confirm my suspicions, the compressor was completely seized. So I took the compressor apart and I found a bunch of metal shavings on top of the piston and inside of the cylinder.Alright, so this is the real crux of the problem, something that might affect BOTH compressors. The Designs of BOTH air compressors are almost identical, the difference on this second air compressor that I've found is that it's covered in oil on the outside (leaked). I think the reason why my compressor failed is because it got too hot and all the oil left the compressor, causing it to seize. I didn't find evidence of any oil actually on the first compressor but this second one looks like it has oil like I would expect it to. Keep in mind that the first compressor wasn't having any problems, it was just that since I was already in there, I figured I'd clean things up and attempt to bring it to "like new" condition.So now I'm wondering, how should I lubricate this compressor and what should I do? Maybe this is an older design that uses oil and has no teflon coating on the cylinder walls, therefore that's the reason why it failed? That maybe I could clean things up and try applying that same teflon stuff myself? I'm not really sure what to do now.
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One of the benefits touted for oil-free air compressors is reduced maintenance. While there are differences in what oil-free and oil-injected compressors need, neither type will provide reliable operation with no maintenance at all. What&#;s more, while oil-free compressors may need less frequent attention it might be argued that they need overhauling more often.
Here we&#;ll discuss the maintenance and repairs needed by oil-free compressors, and how this differs from oil-injected designs. First, though, it is important to be clear about what &#;oil-free&#; means and why it can be important.
Every air compressor is a pump, the two most common types being piston and rotary screw. In a piston compressor, also called a reciprocating compressor, a piston moves up and down in a cylinder. Air is drawn in on the downstroke and compressed on the upstroke. In a rotary screw design, compression is performed by a meshed pair of helical screws that suck air in and squeeze it into a reducing volume.
In both of these designs, oil is injected into the compression chamber. Its main function is to seal the gap between the piston ring and cylinder wall or screw tips and housing. In addition, it provides lubrication and takes away heat.
As air moves through the compressor some of this oil becomes entrained. A separator after the compressor pulls out most of this oil, leaving a very small amount that is carried into the air distribution network. This may sometimes appear as a buildup on the exhaust ports of air-powered tools and equipment.
In some industries, it is essential that compressed air used in production is completely free of contaminants. Food and beverage and medical industries are the main examples. Arguably, compressed air can be filtered to the required purity, but many compressor purchasers in these industries prefer to buy a compressor that has been designed so it will not put oil into the air.
The oil-free designation does not mean the compressor runs without lubricating oil. What it means is that no oil is introduced into the air compression chamber. Achieving this means the piston or screws need a different means of sealing and lubrication.
Reciprocating compressors, use PTFE (Teflon) seals between piston and bore. Rotary screw compressors have special sealing elements or materials applied to the screw tips. In both designs, these materials seal and lubricate motion, although there is nothing to take away heat.
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The principal difference between oil-free and oil-injected compressor maintenance is that the former has no oil to check and replace. In addition, the oil separator is eliminated. However, and this is a critical point, any gearbox and driving engine will still be lubricated and that will need periodic maintenance. In addition, bearings will need greasing, if the compressor is designed that way.
Routine maintenance should address:
Furthermore, as oil-free compressors have no oil to take away the heat of compression, thermal protection takes on greater importance. Always ensure external surfaces, especially fins, are kept clean for efficient heat radiation and conduction.
Providing an oil-free compressor is maintained in accordance with the manufacturer&#;s recommendations, it should run trouble-free for a long time. However, the seals will wear and eventually need replacement. For many compressors, this can be between 2,000 and 8,000 hours of operation, depending on how the equipment is used. Some oil-free compressors will go longer, depending on the design and type of sealing material used.
A particular issue is temperature. If allowed to run too hot, thermal expansion can result in increased rates of seal wear. Cleaning and regular intake air filter changes will help prevent excessive temperatures.
Seal replacement is a big job that will take the compressor offline for several hours. It&#;s best done before performance has deteriorated to a point where the compressor can no longer make the required pressure or runs excessively.
Other common repairs relate to the controls and valves. As with oil-injected compressors, these can give incorrect readings or fail to work as they should. In particular, a faulty unloader valve can make a compressor hard to start due to the additional force needed to move the piston against the pressurized air.
An oil-free air compressor that&#;s maintained according to the manufacturer&#;s recommendations should prove as reliable as its oil-injected equivalent. However, the materials used for sealing instead of oil should be considered as consumables that need periodic replacement. While this period could be a year or more depending on how the compressor is used, it is a substantial repair that the oil-injected type will not need.
The flipside of seal replacement is that there is no need for periodic oil and filter replacement. Depending on how the compressor is operated and the cost of having it down, this may help justify the cost differential between oil-free and oil-injected air compressors.
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