Is Your Compressor Maintenance Keeping Up with The Times?

The compressed air experts at CAGI (Compressed Air & Gas Institute) warn users that “the methods, tools and quality of maintenance used in the past are no longer adequate in a contemporary production environment.”  CAGI’s warning begs a very important question.  Has your compressor maintenance kept up with the times and are your methods, tools, and quality of maintenance still adequate in today’s competitive environment? If your company is still following “preventative maintenance” practices, then the answer is NO!

What are the best maintenance practices and tools available to insure maximum reliability of your oil-injected rotary screw air compressors?  To answer this question and more, it’s helpful to provide some historical context to see how industrial maintenance has evolved over the half-century in response to the changing demands and developing technologies of the times.

Reactive Maintenance (run-to-failure)

The earliest industrial maintenance dates back before World War II when manufacturing and competition were relatively sparce and demands on equipment maintenance were minimal.  In those days, rotating equipment was much less complex, and generally slower speed, heavier-duty, and inherently more reliable.  At that time, maintenance technologies and tools were rather limited, and maintenance was mainly “reactive”, with components getting repaired or replaced after they had failed.

This “run-to-failure” approach did nothing to prevent or predict failures, and often led to catastrophic breakdowns that resulted in extended downtime and lost production.  This was problematic and before long manufacturers recognized the need to find a better way to maintain their plant’s equipment.

Preventative Maintenance (time-based / replacement-centered)

After WWII manufacturing began to explode worldwide.  New industries were born, and new competitors and technologies emerged to increase pressures on plant maintenance departments.  At the same time, machinery was now being built to operate at higher speeds using smaller and lighter components, making them more prone to failure.  And while plant management’s intolerance for downtime grew, so did the need for a new maintenance strategy to help improve reliability and keep critical equipment up and running.  As a result, a new type of “preventative” maintenance was developed and quickly became the standard practice of the post war era.

In basic terms, preventative maintenance (PM) is a time-based “replacement-centered” strategy where components are regularly replaced at fixed time intervals, whether needed or not.  By design, this practice wastes considerable time and money by indiscriminately replacing items that still have ample useful life remaining.

The practice of regularly replacing oil and parts based on time in service, while ignoring their actual condition and root causes of failure, proved expensive, time-consuming, and parts and labor intensive. With growing concerns over the environment and worker health and safety, PMs’ excessive parts consumption, waste generation, and frequent exposure to dangerous equipment created new challenges for plant maintenance personnel.

Reliability Centered Maintenance (proactive, predictive, condition-based)

In the 1960s the airline industry was reeling from a series of reliability-related accidents and skyrocketing maintenance costs that impacted their bottom line.  To put these problems in perspective, aviation accident rates were on the order of 60 accidents per million takeoffs. And Boeing’s 747 aircraft averaged an astounding 2,000,000 man-hours of maintenance for every 20,000 hours of flying time, or about 100 man-hours of maintenance on the ground for every revenue producing hour in the air.

To address the issues of poor reliability and high maintenance cost, the airlines teamed up with the FAA and established a task force to investigate more effective strategies and techniques.  They first performed failure analyses on the aircrafts most critical components.  One of their key findings was that only about 11% of all component failures were related to their time in service.  This finding undermined the core assumption driving most “time-based” PMs and led the task force to look for more “reliability-centered” maintenance practices.

In 1978 the airline task force published its report entitled, “Reliability Centered Maintenance” (RCM).  As the name implies, RCM focuses on reliability, safety, and economics to determine the best practice for maximizing reliability at the lowest possible cost.  Unlike PM’s oversimplified “time-based” approach, RCM is a targeted strategy that looks at the specific causes of failures and then uses the best available  methods to proactively prevent them.

By the early 1980s, the airlines had transitioned away from their costly and ineffective PMs and had fully embraced RCM.  The success of RCM was quickly realized with a reduction in accidents per million takeoffs from 60 down to less than 15, or more than a 75% increase in reliability.  Even more impressive was the 97% reduction in labor costs from 2,000,000 man-hours down to 66,000, or only 3.3 man-hours of maintenance for every hour of flight time (down from 100).  Soon, other industries took notice and began applying the airline’s RCM strategies to their plants’ most critical equipment.

The Root Causes of High Compressor Maintenance Costs

To determine the best RCM strategies for rotary screw air compressors, it’s necessary to first identify the components driving poor reliability and high maintenance costs, and then determine each of their root causes of failure. The most frequently replaced and costly components are the compressor’s oil, air-oil separators, air and oil filters, bearings, shaft seals, and coolers.  Performing a failure analysis on each  reveal that their failure modes most often share one common thing – they are all oil-related.

Often referred to as the “life-blood” of the compressor, rotary screw air compressor oils are critical to the compressor’s performance, reliability, and maintenance costs.  These oils are specially formulated to perform a number of vital functions (lubricate, cool, seal, clean, and protect) and deliver satisfactory life in one of the most aggressive environments imaginable.  The constant onslaught of aeration, contamination, oxidation, and additive depletion degrades the oil’s properties and performance, produces acids, and increases internal corrosion, wear, and fouling – the root causes responsible for most compressor maintenance. Both reactive and preventative types of maintenance ignore these root causes allowing them to progress unimpeded to harm the oil and every component it contacts.  Fortunately, by focusing on the oil and incorporating 21st century proactive reliability-centered maintenance best practices, compressor users are able to mitigate the root causes of oil degradation, wear, corrosion, and fouling, improve reliability, and reduce maintenance frequency and cost.

Tools for the 21st Century

When rotary screw compressors were first introduced in the 1960s, maintenance tools and technologies were not what they are today.  Many of the basic tools we currently take for granted, like computers, CMMS software, oil analysis, and fluid conditioning, were nonexistent when these air compressor maintenance manuals were first written.  Fortunately, we’re not in the 60s anymore and compressor users are not limited to the tools of last century.

Oil Analysis

At the top of the list of today’s most valuable maintenance tools is oil analysis.  If you’re not regularly sampling your rotary screw compressors’ oil, you definitely should be.  Routine oil analysis is easy, inexpensive, and provides vital information that guides users to perform much more targeted, efficient, and cost-effective maintenance.  When used properly, oil analysis serves as the foundation upon which other maintenance best practices can be applied.

Commercial oil analysis first came on the scene in the 1970s and was used primarily to allow users to monitor the oil’s  in-service condition and optimize their oil change intervals.  By simply switching from meaningless “time-based” oil changes to data-driven “condition-based” changes, users are able to change their oil only when needed, and significantly reduce their oil change frequency, oil consumption, and waste oil handling and disposal.

Oil analysis also provides users with critical information on the oil’s contaminant and additive levels.  Too many contaminants or too few of the oil’s protective additives can have catastrophic consequences to the compressor’s oil and internals.  But like a blood test for your compressor, oil analysis can flag these issues early and direct maintenance personnel to perform corrective actions to prevent these contaminant and additive related failures.

Compressor Oil Purifiers

Oil analysis also exposes a major vulnerability of oil-injected rotary screw air compressors to oxidation and contamination.  Unlike most rotating equipment, rotary screw compressors have a unique “forced-contamination” design, where harmful vapors (oxygen, water vapor, acid-gases) and solids are continuously ingested, forced into the oil, and  thoroughly mixed at elevated pressures and temperatures. This design creates an extreme oxidative and contaminant-rich environment that accelerates oxidation, acid production, additive depletion, oil degradation, corrosion, wear, and fouling.

To address these problems, compressor oil purifiers were developed to help rid the oil of harmful contaminants and increase protection of the oil and compressor internals.  Today’s compressor oil purifiers are simple “filter-like” devices that combine acid adsorption with ultra-fine filtration to proactively remove damaging acids and ultra-fine solids from the oil.  Just as the body’s kidneys continuously remove toxins from your blood to keep it healthy and protect vital organs, compressor oil purifiers continuously remove acids and solids to maintain oil health and protect compressor internals.

Combining oil purification with oil analysis and condition-based oil changes, compressor users can typically increase their oil service life up to 5 times the OEMs’ artificial change interval and reduce oil changes, consumption, and disposal by 80%.  Purifying the oil and keeping acids and solids to a minimum also reduces fouling of the compressor’s air-oil separators and increases their life (up to 2 years), while reducing pressure drop and energy consumption.

Additive Restoration

Oil analysis also enables users to address another leading cause of high compressor maintenance costs – the constant depletion of the oil’s protective additives.  All of today’s rotary screw air compressor fluids rely heavily on oxidation and corrosion inhibiting additives to increase protection and extend the oil’s useful life.  Unfortunately, these additives naturally deplete while in service and their rate of depletion constantly accelerates with increased temperature and exposure to air (oxygen and water vapor) and contaminants – the exact conditions created inside the compressor.

Fortunately, there is an easy fix to additive depletion.  With routine oil analysis users can easily monitor their oil’s additive levels and maintain them as needed using preblended compressor oil additive concentrates. These concentrates contain the exact same additives used in the original oil and are formulated to be periodically added in small doses to restore additives to their healthy “new oil” levels.

By focusing on the oil and combining oil analysis, oil purification and additive restoration, compressor users can safely and easily increase their oil life up to 10 time, and slash their oil changes, consumption, and waste oil disposal by more than 90%.

Summary & Conclusions

Rotary screw air compressor users would be wise to heed the warnings of the compressor experts at CAGI and update/upgrade their maintenance tools and practices.  Borrowing a page from the airlines, compressor users can benefit greatly by replacing the OEMs’ obsolete “replacement-centered” preventative maintenance with more proactive and cost-effective “reliability-centered” practices.  Rotary screw users will save significant time and money using current best practices like oil analysis, oil purification, and additive restoration.  These simple tools are proven to improve compressor reliability and cut costs by reducing maintenance frequency, oil and parts consumption, major repairs, downtime, waste disposal, and environmental impact.

Fluid Metrics is the industry leader in compressor oil formulation, contaminant control and fluid conditioning technologies. Contact us today and let us show you how easy it is to improve your compressors’ reliability and save time and money.