Air Compressors

The Compressed air system (I assume it is for machine) - does not only have the above, it does have a desiccant too.

In this condition, the function of the lubricator is to supply the oil vapours to the guide ways and other zones (eg clamps etc). The air mixed with the atomised as well as vapour of oil acts to supply the lubricants to these and replenish the flushed out/ drying out lubricants.

Lubrication of devices with in the machine itself that utilizes the air for power. Examples cylinders, motors, and their control valves.

Lubricators are required on all machines that consume air because sliding or rotating surfaces are subject to scoring. O-rings can stick and be torn. The only time lubrication is not wanted is in paint spraying equipment or food processing equipment.

Very much right.

In process industries, compressed airs from utility plant are of two kinds: Plant air and Instrument air.

Instrument air needs to be more purer than plant air, as not to chock/restrict the movement of finer components. For this reason, instrument air compressors are of 'non lubricated' type, means no oil in the air.

At the utility end, say an air motor, filter, regulator and lubricator are facilitated. Filter knocks of the dirts (rust from pipe), Regulator appropriates the pressure as required to that motor and Lubricator supplies oil mists along with the air (for the pupose as indicated by: Ronseto).

In most of the Lubricators, the amount of oil mist (witnessed as drops per minute) can be adjusted as required by end equipment. This is very important point to be included in 'Preventive Maintenance check list'. Over enthusiastic technicians, some times, tend to over feed this setting. This is as dangerous as under feeding. The oil in the lubricator could be spend in a shorter time and run without lube for the rest of the cycle untill it is replenished next time.

Very interesting note on your experience w/o lubrication. I'm sure it is contrary to what many recognize as "standard" practice.

When in doubt verify what the machine's designer or manufacturer wants/recommends for the compressed air supply.

Ried I don't know that I would accept anything as standard practice in an age were things become obsolete before they can make it to market. With todays metallurgy and lubricants. I would be careful about the application of past practice and outdated manuals when keeping up with technology can bring major changes to your shop floor and have a huge affect on the bottom line. J.Conway

You must have the most effient plant there is. Let me know where it is and where I can apply. I am an Industrial Mechanic with 30 years experience and I can prove and show you what lack of lubercation will do to machinery. I guess at your plant I can be like most Engineers and sit back and let the system flow. Sorry I have a lot of respect for a lot of GOOD ENGINEERS but I have had more bad ones that have come to me to solve their Industrial Problems. Not that my suggestiopns were the best or most effiecent but 90% have taken my advice. This just goes to prove ther is a lot to experience and just not schooling.

DCJ

Note that Jerrel says that lubrication is not mandatory and that lubrication then occurs at machines where it is required. (No mention of not lubricating things that require it). This is best practice. It means that your compressed air lines are filled with nothing worse than dry air and that you have good control of the quantity and quality of oil supply to machines that require it, and NO oil to machines or worse still instruments that do not.

Well said Tazman20, I agree you concern, though an engineer.

Lubrication is mandatory. OEM says, "Liquid (oil) lubricants are complimentary for materials with impregnated solid lubricants".

Carbon filled PTFE rings are used for dry air/gas services. Still 'mini lube' is recommended for longer service. I've noticed, these rings miserably failed within a quarter, when the lubricators didn't function.

I like to modify the OEM statement as, "Liquid (oil) lubricants are supplementary for materials with impregnated solid lubricants".

Tazmsn20 Yes we did have a very high efficiency throughout our facility. We looked at employees as an investment and made sure they had the knowledge and tools to do the job. Information is useless unless you share it. As to the lubrication we are talking about the house air and not the machine overall. There are many industries that can not risk contamination of the product such as food, drugs or what about the space program. Most all components used in a compressed air system are lubricated when they are assembled with a silicone base grease. This grease stays in place well and last a long time. Sure we experience failures but most can be traced to contamination from assembly or particals being drawn in through the mufflers on spool valves and cylinders or osulating shafts without boots. If its just from lack of lubrication then the component can usually be restored by re greasing with the OEM type lubricant. The life cycle of our machinery is 10 years and the majority of the components in the air system will last until rebuild time. If you are experiencing failures that leave scratching on the bores, cylinders or spools then you are probably suffering from contamination. Components that run clean for many years will have a very high gloss glazed appearance without scratching. Tazman20 maybe you can add to your knowledge base today and share it with others tomorrow. J.Conway

Because raw air consists of various small as well as large particles which can cause harm to our consuming machine.Thats why we are using filter.To control the fuel flow(air) regulator is used

rajeshbhanushali123 We had a large filter inside every drop at each machine. Even though we had extremely dry air the major contamination found in the filters was rust from the iron piping but this would take many years to have an effect on the pressure. The product we made could not be contaminated with any lubricants due to being consumed by the customers. Compressed air was a major component in producing the product and came in direct contact with the product. The compressed air being dry and clean allowed most of the components to last the life cycle of the machine (10 years) without lubricators. J. Conway

I can't comment on air-driven machines, but as an instrumentation and control systems engineer, what's needed for instrumentation is dry air, WITHOUT lubrication.

DZ

Hello vanuta,

I have not known of 'lubrication' in air-lines.

I suppose there may be a need in very hot and or dry situations. But usually the machine powered by the compressed air has its own greasing point/s or possibly uses 'frictionless bearings'?

Hope this helps.

Take care

If the compressed air is used to create motion in a mechanism, such as an air cylinder, there needs to be some lubrication to keep the seals moist. The piston and rod will have seals. If they are dry they may overheat, leak or burn out. That would apply to large air cylinders on front end loaders for example, all the down to small solenoid valve actuators.

Hope this helps. www.vacuumandlowpressure.com

Howard Tring

Vacuum and Low Pressure Consulting. PA USA

Very stimulating discussion. I think this proves that 1) compressed air is used in many different applications within the industrial sector, 2) some systems require lubrication, especially those that use the compressed air internal to the device only and that have rotating metallic parts that will overheat, score, or "lock up" without the use of a lubricant, 3) there are many applications where lubrication in the compressed are is a big NO-NO, and 4) we all have some experience with compressed air and our opinions are prejudiced by our own experiences, but not by the universal truth that all systems are different.

Hence, Vanuta, there are many reasons why lubricators are use in compressed air lines, and many reasons why they are not used. Best case is to check the operating instructions on the end equipment and if external compressed air lubrication is recommended, use it, and if it isn't, then don't complicate the issues by installing a lubricator that may introduce oil mist where it is not wanted, or needed. FYI, the equipment my company sells uses compressed air for valve pulsing and we always specify clean, dry compressed air without lubrication because it fouls the equipment.

YesMAM Well said, J.Conway

I would have to agree with YESYEN's answer since most petroleum, chemical and petro-chemical complexes spent a lot of money in providing very clean and dry instrument air systems. The plant air system was designed to supply clean and dry air. Lubricators were provided at the machinery that required it. After all, you wouldn't want to use a air nozzle to blow off an area for cleaning and leave an oil spray on the surface. Such connections were provided before a lubricator but after the regulator-filter point. For stations where rotating, vibrating or recipocating tools were used a lubricator is very necessary, as was pointed out, otherwise the vanes, rings, bearings, etc. wouldn't last very long.

My Trumpf CNC punch only want dry clean air, no lub.

Always check manufacturer requirement for compressed air. You need to know if lub is needed and what type.

The answer is too obvious. The lubricator is needed to lubricate. This only applies, though, when the machine actually needs lubrication. In some cases it does not. We manufactured thousands of attaching machines for textile industries over my 32 years at Eastlex Machine Corporation. Each and every air powered machine got a small storage tank, a regulator, a filter and a lubricator. Many times there was a problem with the machines that had their lubricators opened up too far. The excess oil in the air would wash the grease right off the O-rings in the valves. The valves would stick and the machines would malfunction. So, it was not only important to have a lubricator but it was also very important to have it adjusted right. The machines generally worked very well for a good long while without the lubricators being turned on at all. Periodic regreasing was always a necessary maintenance operation but getting the oil mix right helped prolong that time period and also helped the O-rings to last longer. Also, using a thicker oil was helpful to prevent washing the grease away but if I recall, anything above 50 weight would not work very well in the lubricator. Each type of machine has it's own need or lack of it as far as the lubricator is concerned.

All most 100 years ago compressed air began replacing steam as a common motive force. Without the wetness of steam compressed air was a problem. State of the art became filters to take out junk and condensate, regulators to control the pressure and lubricators to reduce friction.

Today that is an archaic and wasteful practise that hasn't had enough innovation to remember how to spell it. Each component of what is often referred to as FRL (Filter/Regulator/Lubricator) causes a pressure drop that is often redundant. This is a no brain approach to useful compressed air. Some reports say 40% or more of all compressed air is lost to excess pressure drop. If the archaic FRL is a good thing it kills with kindness.

We suggest centralized Filtration, and Lubrication and Drying if you prefer for compressed air that is clean and lubricious. Regulate if you must but know that over compressing and regulating down is a very wasteful practise.

If you ask me how would my answer be commercializing?

"We suggest centralized Filtration, and Lubrication and Drying if you prefer for compressed air that is clean and lubricious. Regulate if you must but know that over compressing and regulating down is a very wasteful practise."

Tom, ordinarily I agree with all you say on compressed air. (Great minds think alike?) But I disagree with central plant lubrication. Lubricants come in wide varieties, and should be specific for the application. If this was not true, why take out the compressor's oil in the compressed air and then re-inject air at the air tool?

I do agree that most compressed air systems are over-sized for too much pressure in the compressor room and under-sized with large pressure drops in the distribution piping and end-user. On a per plant basis, thousand of $$$ are not even noticed in energy waste due to wasted use of pressure.

But I disagree with central plant lubrication. Lubricants come in wide varieties, and should be specific for the application.

Reid

Possibly "Centralized AREA Lubrication" would be better terminology. A typical wood products plant often uses a single "airline lurication oil ie Texaco Rhando (SP?) 35" in 99% of the "drip oilers" (coloquial term for ubiquitos aerosol lubricators of ancient paradigm that have a 'drip rate sight glass'.) The Oilers fill all the 7 oz. bowls on the drip oilers on a frequency that keeps the bowls from running dry with their standard airline oil.

If the cost of an Oiler's salary and administrative cost, is $40,000 per year central AREA lubrication could free one or more Oilers to spend their time doing something more productive and less tedious. Also keep them off ladders away from dangerous machinery in motion.

Of course there are these places where we can't have any oil. A coalescing filter will handle that and still save $100,000.

Is lubricantion required for most valves, cylinders, air tools and pneumatic devices? Squeaky Clean Dry air with good grease applied to components at assembly may provide half life or less. If lubrication doesn't make mechanical devices run better and last longer I could save a bundle on automotive oil changes

Innovation - "Get 'er done!"

I'll buy the "area lubrication" argument. I am seeing a few pieces of equipment with central lube systems instead of several "lube cups" that simplify the "oiler's" job.

While excessive pressure drops in a compressed air system are truly a wasteful practice many plants increase the system pressure to increase the storage capacity in terms of SCF and therefore make more air available. At a higher pressure, the drops through the system should be smaller due to the passage of smaller volumes in ACFM ( Boyle's Law ), while the SCFM delivered at the higher pressure gives more usable capacity. Also since many systems were initially set up with positive displacement compressors you could then save a bit of horsepower by lowering the discharge pressure (system pressure), however many of the larger recip systems have been replaced by centrifugal multi-stage compressors and these have impellers more designed for given volumes and lowering the pressure might increase the volume and horsepower requirements more than throttling back on the curve by increasing the discharge pressure. I haven't really looked at one of those curves in a while so I could be wrong on that. Anyone know?

Spinco

The least expensive and most efficient use of compressed air would be to over size all plumbing and components. Then drop the pressure at the compressor. The pressure loss in turbulent air becomes almost nil at lower flow velocity with laminar flow.

In Womak Fluid Power Data Book (Feb 1998) page 28 for a single stage compressor to compress 1 SCFM to 80 psig = .160 HP. To compress 1 SCFM from 0 to 120 = .196 HP

It is common to visit a compressor room with one or more compressors struggling to send 120 psig air to the plant only to find that in the production area 80 psig is maximum available pressure. For 1000 SCFM that is a continuous waste of 36 HP.

In most cases saving by using small components and storing compressed air in a receiver at a high pressure are both stinkin thinkin which has been Grandfathered in.

I don't dispute your rationale , however, I would point out that there are probably a lot more compressed air systems that had increased demands put on it (more capacity requirements, more equipment placed in service) years after installation then systems that were properly sized originally as far as piping and sufficient number of work stations, equipment etc. so that the lowest discharge pressure possible could be maintained. Therefore increasing discharge pressure is often the most economical route as opposed to replacing all your piping. The increased utility cost would be spread out over some years as opposed to a significant capital cost up front.

Also most pressure drop calculations are based more on continuous flow numbers whereas most real systems do not operate on a constant flow basis since many of the uses are more of an intermitten flow application and the actual volumes at a given time are no where near a design criteria. Other than that you are right in that it is better to oversize your utility piping systems during construction to allow for future additions. Some places even maintain a second high pressure system with a separate compressor just to handle a few specific requirements.

I am on Tom's side for this one. Higher compressor pressures require higher horsepowers, which require money.

Get rid of the air receiver, install oversize piping, and have lower operating costs. The volume of air in the oversized distribution piping can be used as your receiver.

Years ago, I worked in a locomotive factory. Shop air system was a nominal 100 psi, but there was a secondary 180 psi system in a small building for specialized testing. No need to operate every thing at a high pressure that is only needed in a small area. Design the system to the right size for better efficiency.

I would think twice about the complete lack of air receivers in any pneumatic system. Receivers are primarily there to allow for surges and to prevent significant loss of pressure in the system at times of increased demand. It would require extremely large piping to do the same and the cost factor would be far higher than the use of receivers. I have never seen a plant air system designed in your manner. I really don't think I ever will.

Spinco

You have to get out more. Many Rotary compressors run up to set pressure (90 psig) and unload as required to hold that pressure. They add air only as required to meet demand while holding set pressure. The compressor motor never shuts off and free wheels when no air is required. I can take you to a plethora of plants (one in mind with a 250 and 350 HP) that have seperate refridgerant dryers and then tee into a common header that goes through the exterior wall into the plant. The compressor delivers constant pressure from no load to maximum flow and a receiver does not provide a benefit of stored air at higher pressure.

The recips that pumped pressure up to the high pressure switch and cut off the motor which was turned on again by the low pressure switch. The receiver stored air to extend the time between the motor being on and off. These are inefficient, hard on the electrical motor and going extinct in large plants.

You find reciprocating compressors in 5, 10, 15 HP "gas station" applications but the real world has moved on to rotary compressors and don't need a central receiver unless they want enough air stored for orderly shut down in the event of a power failure or for minor cooling.

As far as "getting out more" I have a feeling that I was out there before you were even born. I saw the end of the era of IR XLE, Joy, Worthington and other recip compressors being king and was specifying and buying Elliott PAPs, IR's Centacs and the Dresser-Clark centrifugal plant air packages. Those packages started off in the 125 HP range and now run upwards of 3000 HP. The use of suction vane controls allowed the turn-down in capacity with centrifugal compressors while not suffering huge efficiency losses. As far as rotaries they were just coming up as contenders in the late 60's early 70's. The manufacturers were still trying to achieve decent seal life without excessive lubrication requirements. They had not yet really tried to compete in the NL market against the IR or Joy non-lubed or mini-lubed recip compressors for Instrument Air applications. In the chemical plant, petro-chemical & petroleum refinery construction field we did not give them much credence due to lack of track record, limited capacity and excessive maintenance requirements.

In your plethora of plants did you run across any where during loss of power (and resulting loss of instrument air supply) would result in disaster due to the failure of the instrument air to allow an orderly shut of a complete petroleum complex? I did. In the that case we had an electric motor PAP unit with a stand-by steam turbine driven PAP unit that was designed to automatically start on power failure. Obviously, that was not the unit to have any electrical control valves, drain valves or any other item to inhibit the reliable safe start-up of the turbine. All instrumentation was pneumatic as were all the safety controls on the distillation towers and hydro-cracker and cat-cracker unit pressure vessels.

And , or yes, we did have receivers on that instrument air system designed to provide a certain minimum of capacity to allow the stand-by to come up to speed and take over and God forbid it didn't, to allow enough capacity for critical safety functions to occur.

And or yes, that system was tested during one of the big blackouts we had in the 70's and that plant had an orderly shutdown with no casulties, human or otherwise.

I am not sure that Tom Kreher's suggestion for centralized FRL would always be best. If you lubricate at a central point your lubricant may condense in the piping before it reaches the point of use, unless there is a steady flow all the time. We know that water vapor from the air that is compressed will condense in the piping in the long term cause rusting in iron piping. There is also a need for clean and dry instrument air in some applications. I think that Vanuta has received many comments now and there is not just one answer. Some operations need lubricated air, some need clean/dry air. I suggest checking the web for Compressed Air magazine. They have many good articles on plant air systems and how to reduce wasted energy. I saw an ad from one company that offers aluminum piping now with special connectors. This is lightweight, easier to install and less prone to rusting. You would still need to angle the lines and have drip legs to drain condensate, and in large plants use a ring main to equalize the pressure around the plant, but it is a step towards modern design.

I'm with Howard on this. Saving on maintenance effort by centralizing FRL is great, but only if it doesn't undermine function.

Case in point: pneumatics controls don't like even tiny pieces of anything getting into them. And that goes double for precision pneumatics such as valves that have tiny ports or nozzles inside for force-balance, etc. Even a tiny speck of grit or something could affect a nozzle/port's function and mess up the valve. Same goes for lower-precision valves ... seals can degrade and spools can gum up.

An example: pipe and valve threads are often sealed by using teflon tape. Pieces of tape can (and do) fleck off and find their way downstream. If there's no FRL (OK, just F) to catch those, they can wind up anywhere; and if that 'anywhere' has valves, etc., then that's bad news.

By the way, I recommend that teflon tape be avoided for pneumatics and hydraulics. We've had better results when we used pipe-joint paste ('pipe dope').

Cheers!

DZ

DZ

You guys made "centralized FRL" out of whole cloth. I said centralized lubrication. If you use a good F after the compressor and keep your teflon tape under control where will the bad juju come from? Dirt has a hard time entering a pressurized pipe. If you have sensitive pneumatic controls use good coalescing filtration for that dedicated supply. If the inside of the plumbing has a protective layer of lubricant rust will not grow and migrate as an abrasive.

Now suppose you could seed the compressed air with a colloidal dispersion of nano particles of lubricant that resist settling? The electrical charge that perpetuates Brownian Motion helps motivate those nanos. Turbulence and velocity cause coalescing in the small passages of valves, tools, cylinders and just critical surfaces (upper cylinder lubrication) are coated with a thin layer of lubricious marvel.

We are talking innovation here, a departure from FRL. We will have enough trouble with the guys who sell FRL's resisting the demise of the cash cow.

Don't say what if it doesn't work. Allow that it might because it does.

oops!

didn't log in for #30

My best advise is: you need a source of clean dry oil-free air at all times, under your control, under all pressure and flow conditions, and under all atmospheric weather conditions.

You then treat the air at the point of use, at the machine, or collectively at a group of machines, at an appropriate pressure, with a lubricant (if required) specifically to suit the machines requirements, where (in my specialised field of respiratory protection) oil is a definite 'no no' in breathing air.

Saving money by compromising on quality and equipment, by undersizing compressors, receivers, filters, dryers, pipes etc is false economy.

To my knowledge, no engineer has ever been sacked for doing the job properly.

Hello horace40,

Very good advice! You wrote precisely what I was about to!

GA to you Sir.

Take care.

Horace I have no doubt there are plants and places where the air should be primarily pristine with a little lubricant added just to those places that don't thrive on pristine.

Boeing in No. Washington state has need of personal protection wear that includes breathing air. They use seperate and distinct fittings and connectors for the breathing air supply to prevent dufus from plugging into the industrial air supply that lifts that barge and totes that bail.

Anyone using plain industrial air for breathing air would be better off to play Russian Roultte. Oil is easy to remove down to .01 ppm. Better than you are breathing right now. However breathing air must have monitors for carbon monoxide and noxious gases that are not removed with filtration and other hazardous substances that may be ingested by the compressor intake. Leaving the oil out of industrial air does not make it breathable.

I may as well ask why putting compressors, dryes ect. at the point of use is almost never done. OK I'll answer. It would horribly inefficient, cumbersome and in need of constant service and maintenance. Which is my point about the benefits of central lubrication as well.

If you are working with clean room environment or computer electronics which are protected from dust, dirt, fumes, smoke, oil mist, personal methane etc. a specialized approach is in order.

Factorys that process and package foods may require food grade lubricant, for incidental contact with food. Foundries, Saw Mills, Paper Mills, Machining, Marine and the ilk lubricate most of their industrial air with a single air line lubricant.

They may run a seperate 20 psig "Clean Dry" instrument air supply.

Your "point of use" lubrication concept was invented in 1926 by a Mechanical Engineer named Carl A. Norgren. It was brilliant and served a great need in it's time.

This is 2009 and everything that was done in 1926 from Model A cars to Wringer Washing machines have disappeared or morphed into marvels. Incandescent lights, telephone and telegraph have been replaced by personal communciations, home entertainment and lite beer, radical changes. Strange names like Ipod, GPS, MP3, Mac, PC and foot prints on the moon tell an amazing tale of innovation and progress. There are compressors and vacuum pumps in cars, boats airplanes etc.

One area that is woefully lacking in updates, innovations and progress is "standard practises" for compressed air and especially point of use lubrication.

Minds and dirty diapers should be changed frequently.

JohnDG Your research on this topic places irrefutable manufacturers specifications on the table for all to see. Maybe some will pursue this further and facilitate changes that can have a significant impact on machine efficiency and production quality. If nothing else after reading all of the responses to the OP the facts should be self-evident about the need to opening ones mind to current practices or even establishing ones own when one has reason to believe that advancements in technology has brought about superior materials and or methods since the time their opinions and practices were formed. When your daily output counts are in the billions per machine per shift any thing that effects the cost of an individual item has a rather large impact on the bottom line. When one is paid to be abreast of technology but instead relies on the experience of those before them or around them to establish ones own perspective then those responsible for each machine that fails to maintain or exceed daily shift production quotas due to a false or errant perspective should be considered the same as grand larcenist. I have had to deal with supervisors and managers that due to fear of losing their jobs began asking what past practice had been before giving a reply when confronted. They felt safe in this approach but it was detrimental to production. According to past practice I don't do answers like this. Its a long post and I'm sticking to it . J.Conway .

Hello JohnDG,

Good little piece of detail here. Well found!

GA to you Sir.

Take care

Hi JohnDG

Good answer so I gave you a GA vote. To lubricate or not. That is the question. (Somebody famous used one like that.) In practise we see air driven devices with good lubrication last at least twice as long and some times have double digit life. Non-Lube most often means "Pre-packed with grease, no added lubrication required". Or with less spin "This product will work until the initial grease becomes ineffective."

The manufacturers of pneumatic products understand that good lubrication requires attention, effort and expense. Catalogs and advertising that specifies "Non-Lube" or Lubrication Optional" is very appealing to those who hope for a short cut.

On the other hand the ASME, NFPA, IFPS and similar manufacturing, fluid power and motion control non-profit organizations tend to suggest lubrication as a norm from past experience.

To declare that all applications should have or not have lubrication is not a credible position. In general non-lube is easier while properly lubricated applications operate more consistently, longer with less down time.

Tom