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Avoiding the Death Spiral: Keeping your compressors safe from lubricant break down
Posted on February 02, 2015
The Synthetic Lubricant “Death Spiral”, Or...
How To Prevent Oil From Destroying Your Rotary Screw Compressor...
AND Avoid Spending Too Much Money On Oil In The Process!
Protecting yourself from these problems is EASY with a good Oil Analysis Program.
The inside of a rotary screw air compressor is a tough place for oil to remain stable. It’s one of the few mechanical environments where oxygen, heat and moisture are continuously combined. In order to withstand these harsh conditions, synthetic compressor lubricants contain many complex additives including Barium, which prevents the formation of acid. Any new synthetic lubricant is nearly acid-free and, by industry standard, has an extremely low Total Acid Number (TAN). This is because its Barium content is high (usually 350 –400 ppm). But as the lubricant accumulates hours, its Barium content and other additives slowly become depleted. As this happens, acids begin to build up, causing the lubricant’s TAN to rise. These acids are derivatives of sulfuric acid, and they attack the inside of your compressor, eating away at its metal components. When a lubricant’s TAN hits 2, it’s time to change it. The most common practice is to change compressor oil at regular intervals based on either time or hours so that the lubricant’s TAN never reaches a dangerous level. This seems logical, right? WRONG!
Changing Your Compressor Lubricant Based On A Set Time Schedule Or Hours Of Operation Can Actually Shorten Its Life!
pressor oil is to DRAIN it, not FLUSH it out completely. But when old compressor lubricant is simply drained, about 10% of it stays in the compressor –in the oil lines, in the oil cooler, and in the bottom of the sump. This remaining oil CONTAMINATES the new oil – and that’s where the problem starts! Here’s what happens: Let’s say a company schedules its compressor oil changes every 12 months/8,000 hours, and the lubricant’s TAN measures 2.5 at the first oil change. The new lubricant’s TAN is 0, but this oil only accounts for 90% of the total oil in the compressor – the other 10% is the old oil with a TAN of 2.5. Therefore, the actual TAN of the “new” lubricant at the start of its second cycle is .25, not 0! This means a TAN mark of 2.5 will be reached sooner (probably at 10 months/6,667 hours) and it may hit 4.0 by the time the next scheduled oil change is due. Once again, 10% of the old oil is left behind, and in the third cycle the TAN hits 2.5 in only 8 months/5,333 hours. By the time the next scheduled oil change takes place, the TAN could easily be 15, and the next time it could be much higher! This progressive, vicious cycle is known as the Synthetic Lubricant “Death Spiral”. Over the years, we’ve found that TANs of 13 – 20 are not uncommon, and we’ve even seen them as high as 30! Customers often wonder how TANs can get so high even though they change their lubricants on a regular basis – until they learn about the “Death Spiral”. When TANs reach such high levels, big trouble starts because serious corrosion of the compressor’s internal components is occurring. This results in premature air/oil separator blockage, oil filter blockage, control devices working improperly due to the sludge and varnish build-up, and ultimately, air end failure.
OIL ANALYSIS: The Easiest, Most Effective Way To Avoid The “Death Spiral” – AND Reveal Other Problems That Can Cause Compressor Failure!
Establishing an Oil Analysis Program is the only way to be 100% sure that your compressor lubricant’s TAN never gets above 2. If you have oil samples regularly tested in a laboratory by compressor experts, you’ll know exactly when to change your lubricant so that dangerously high acid levels never occur! You’ll also be able to anticipate and avoid other performance-related problems because trends in the results will become evident after several samples are analyzed. Trends are the best indicators of the unfavorable –and often unseen –conditions that cause poor compressor performance and premature failures. But with regular oil analysis test results in hand, you can determine what steps need to be taken in order to improve operating conditions and maintain peak compressor performance.
Simply put, Oil Analysis is a powerful longterm management tool that takes the guesswork out of lubricant maintenance!
AN EXTRA ADDED BENEFIT: You’ll NEVER Waste Money By Discarding Oil That’s Still Good!
There are times when changing your oil according to a regular schedule actually results in removing lubricant that still has an acceptable TAN. The only way to know if oil is still good is to analyze it shortly before the scheduled oil change. Otherwise, you may be literally throwing money down the drain! A consistent Oil Analysis Program can save your company a lot of money by helping to prevent compressor failures. Add to those savings the money you won’t spend on premature oil changes!
Please Take Advantage Of Our FREE OIL ANALYSIS PROGRAM!
At Air Engineering, we offer complimentary and comprehensive Lubricant Analysis Services to all of our customers because while we can certainly help you out in an emergency, we’d rather help you avoid one! Our independent laboratory testing is conducted by experienced compressor professionals and provides the following analysis:
- Total Acid Number (TAN)
- Values For 27 Individual Compounds
- Wear Metal & Moisture Content
All of these indications and values will be thoroughly analyzed and recommendations will be made accordingly. The compressor experts at Air Engineering will help you determine the most effective solution if problematic trends are discovered. We recommend that you consistently submit synthetic oil samples every 2,000 hours OR LESS*, and we’ll send you a complete kit to help you do so.
Your FREE KIT includes:
- Oil Sample Containers, With Postage-Paid Return Boxes
- Tips On How To Take Oil Samples & What Part Of The Compressor To Take Them From
- Oil Sample Forms For Documenting All Necessary Information Related To Each Submitted Sample
- An Oil Analysis Guide To Help You Better Understand Test Result Terminology
- A Troubleshooting Guide To Help You Determine The Possible Sources Of Elements Found In Each Oil Sample
*Submit Petroleum-based oil samples every 2,000 hours OR LESS!
Remember: With an Oil Analysis Program, you will never have oil in your compressor that has a dangerously high TAN or throw away oil that still has an acceptably low TAN. You’ll prevent problems while avoiding waste – and that means cost savings across the board.
Call us now and get your FREE Oil Analysis Program started today!
Collapsing Air/Oil Separators? The Separator Usually Isn’t The Problem!
I recently visited Bob, a customer that was upset because the Air/Oil Separators we were supplying for his rotary screw compressor suddenly started collapsing. Bob told me this had been going on for almost a year. He was so frustrated that he decided to get new Separators from a different supplier! I had a strong feeling that wouldn’t solve his problem though, because an Air/Oil Separator collapse is usually not an Air/Oil Separator failure. In fact, it usually means the Separator did its job!
While Bob and I were standing next to the compressor and discussing the issue, I noticed the air inlet hose looked almost new. I asked about it, and he said it had been recently replaced because they found a big crack in it. I asked Bob how long the original hose was cracked, but he wasn’t sure. I then pointed to the inlet hose and said “There’s your problem!” He looked at me as if to say “What do you mean?” So I explained...
To better understand why a Separator collapses, you need to know what goes on inside a Rotary Screw compressor: New air is brought into the compressor through its inlet hose, which is equipped with a filter designed to stop particulates such as dirt and soot from entering the system. After passing through the inlet filter, the new air is then mixed with compressor lubricant (it’s important to note that any particulates the inlet filter didn’t trap become suspended in the lubricant). Next, this air/oil mixture enters the compressor pump (or “air-end”) and gets compressed. The oil in the mixture performs two functions during this compression process: It lubricates the compressor’s bearings and also extracts heat from the air-end. But after leaving the air-end, the oil must be taken out of the compressed air stream before it is delivered into the plant. This is the function of the Air/Oil Separator.
AIR/OIL SEPARATORS: Pulling Double Duty! Located on on the discharge end of the system, this large and highly-efficient filter removes atomized oil from the compressed air stream, which flows into the separator through its outside surface area, up through the internal filtering material and then out the top and toward the plant. The Separator also removes particulates from the compressed Air/Oil mixture, and the more particulates that make it past the inlet filter and into the oil, the more particulates get trapped in the Separator. However, there is a limit to the amount of particulate a Separator can hold. If a Separator traps too much particulate, it clogs up. This greatly reduces the volume of air/oil mixture that can flow through it over a specific period of time. Eventually, the tremendous air pressure placed on the outside of the Separator will exceed its flowthrough rate, literally crushing the Separator and causing it to collapse. This was the reason for Bob’s Separator problems: The inlet hose in question was located next to the plant’s metal grinding operations – a hostile environment with massive amounts of particulate in the air. When the hose failed, all that particulate was able to COMPLETELY BYPASS the inlet filter and go directly into the compressor oil! Unfortunately, the inlet hose crack wasn’t discovered until AFTER the Separators started collapsing – but by then there was already far too much particulate in the oil (Oil Analysis done after-the-fact confirmed this). It was inevitable that the Air/Oil Separators were going to collapse. They didn’t fail though. They did the job they were designed to do (remove particulates from the compressed air/oil mixture) and kept doing so until they couldn’t any longer! Understandably, the Maintenance crew didn’t make the connection between the cracked hose and the collapsing Separators because the two problems revealed themselves at different times. If only the ruptured inlet hose had showed up first! Then the remedy would have been simple and the damage minimal: Replace the inlet hose, completely drain/flush/refill the compressor’s oil and replace only one Air/Oil Separator!
Two Ways To Protect Yourself: Over the years, I’ve seen many different problems arise for many different reasons. These problems are often oil-related (like Bob’s was) and the best way to anticipate and avoid them is with a consistent and comprehensive Oil Analysis Program – like the one we offer to all our customers free of charge (see Page 3)! The other option is to call us when even the slightest issue first comes up – we’ll take care of you right away!
Xtra Protection & Value Other Synthetic Rotary Screw Compressor Lubricants Simply Can’t Match!
XTREME10,000’s extraordinary performance provides extra insurance for your compressors between Yearly Oil Changes!
Independent tests show that Air Engineering’s XTREME 10,000TM Outperforms ALL Other Synthetic Rotary Screw Air Compressor Lubricants: X-10,000’s unique formulation improves resistance to acid build-up, oxidation and sludge/deposit formation over conventional Polyglycol, Polyalphaolefin and Ester based stocks, and we back that claim with our standard lubricant warranty! No other oil gives you as much performance, protection or value for your compressor lubricant dollar!
Conventional Synthetic Oils May PROMISE They’ll Last 8,000 Hours, But That Doesn’t GUARANTEE They Will...
Here’s why: For every 10 degrees above 190ºF that a compressor operates at, the life of the oil inside is cut in half, and so is its ability to lubricate, cool, and protect against acid formation. Even if a unit operates on only one very hot day with discharge temperatures reaching 210º (which happens often), that unit’s oil is probably only good for 2,000 hours. If this unit operates for 6,000 more hours, oxidation, sludge/deposit formation and especially acid build-up will accelerate, greatly increasing the “Death Spiral” effect AND the chances of damage or failure. X-10,000 reduces the risk of these failures, especially in extreme operating conditions!
ALL Polyglycol based lubricants (such as Sullair Sullube 32® and Ingersoll-Rand Ultra Coolant®) have a unique characteristic: They begin to smell as their TAN levels rise! This is a result of the growing acid content reacting with the polyglycol base of the lubricant. These odors can be extremely offensive, and the higher the TAN gets, the worse they become – even forcing workers out of their plants in some cases! Another common base stock is PAO, or Polyalphaolefin, and while PAO based lubricants usually do not generate any odors, acids, sludge and varnish develop within them just like any other synthetic oil. Sullair and Sullube 32 are registered trademarks of the Sullair Corporation. Ingersoll Rand and Ultra Coolant are registered trademarks of the Ingersoll Rand Corporation.
Sometimes Cleaning Can Cause Collapsing!
Occasionally, the Air/Oil Separator on an older compressor (or one with a high TAN) will collapse shortly after the unit has been flushed with a heat-activated cleaner. This happens when stubborn sludge & varnish deposits that were softened-up during the cleaning process come loose AFTER the unit has been refilled. This gunk contaminates the oil and, like too many trapped particulates, clogs the Separator until it collapses! This is yet another of the MANY reasons why collapsing occurs!
In order to prevent a premature compressor failure, units that contain lubricant with a high TAN need to be completely FLUSHED, not just drained and refilled. Flushing normally involves the following 5-steps: 1) Remove as much of the old lubricant as possible from all oil lines, the oil cooler and the bottom of the compressor sump. 2) Refill the unit with a temporary batch of new lubricant. 3) Run the compressor for a short while so the temporary batch can “flush out” the unit. 4) Drain out the temporary batch. 5) Refill the compressor as normal. To help maximize the cleansing effect of this preventative maintenance procedure, Air Engineering makes the following recommendations: Step 2: Instead of refilling the unit with new lubricant only, refill it with a “blended batch” of new lubricant and a heat activated cleaner. Step 3: Allow this mixture to circulate for 40 –60 hours at full operating temperature so the heat-activated cleaner can thoroughly dissolve the sludge and varnish deposits created by the high acid content in the old lubricant. Step 4: Drain the entire load of cleaner and lubricant while it is still warm, because if it is allowed to cool the sludge and varnish will be “released” and settle back into the compressor – defeating the purpose of this important procedure! It should be noted that while some suppliers advise using normal lubricant when flushing a compressor, we have found that lubricant alone will not clean out sludge and varnish nearly as well as a blended batch of lubricant and heat-activated cleaner.