Reducing the cost of oil free air

As most oil free compressor users are aware the major cost of ownership of oil free compressors is the replacement of the oil free air ends at the recommended 40,000-to-50,000-hour run period.

Refurbishing reasons

When you consider that a typical oil free screw compressor has a life of 20 to 30 years the lifetime cost of replacing your air ends at these recommended intervals is very high, particularly if you have only one choice the manufacturers OEM air end.
Replacing your oil free air end at these hours ensures that the original performance remains intact. Ignoring replacement of the air end and allowing your compressor to run until 80,000 hours or longer can be quite costly in wasted energy.

Why ?

Nearly all screw type oil free air ends rely on a special coating on the rotors, body casting and seal areas. As this coating starts to degrade several losses of performance situations can occur.

Oil & air leakage from the ‘tell-tale’ seal areas resulting in a marked performance decrease.
Further performance decrease as the rotor and casting coating is worn away.
Past 50,000 hours to 80,000 hours the performance loss can be as much as 30% if all of the above occurs at once.

How can this occur?

There are several reasons why the air end performance decreases.

Air intake contamination allowing material to wear away the rotor and rotor housing coating.
Frequent stop starts.
Timing slip (the rotors are separated by timing gears that are an interference fit on the male and female rotors, these can move over time allowing the rotors to collide)
High operating temperatures and high humidity
Poor cooling media air and water causing higher than normal air end temperature conditions.
High salt content environments which can attack certain manufacturers coatings leading to premature coating loss.
Bearing failure (using SPM monitoring bearing degradation can be predicted)
Seal failure – Seal failure occurs when the coating applied to the rotating shafts wears beyond its limits.
Head loss (the distance between the rotors and housing) due to wearing of the coating.

How can we reduce the cost of replacing air ends at 40,000 - 50,000 hours?

Whilst the OEMs don’t agree with refurbishing oil free air ends several specialist companies around the World have perfected the refurbishment of oil free air ends over many years.

If your compressors oil free air ends are stopped at 40,000 to 50,000 hours in a normal operating environment the likelihood of refurbishing your original air ends to a perfectly acceptable re-useable condition is very high. In fact, in 90% of cases your air end requires merely overhauling and a new coating applied to the rotors, seals areas and housing along with new bearings, seals and occasionally new timing gears.

These specialist companies test each oil free air end on specially designed compressor test rigs to ensure that the performance of the refurbished product falls within tolerances agreed with the customer. On average the performance achieved is within 5% of the claimed performance by the OEM for a new air end.

Why would a customer accept 5% less performance from a refurbished oil free air end?

When you consider the typical cost of a refurbished air end (around 50% less than a new OEM air end) customers with multiple oil free compressors can easily justify the 5% lower performance when compared to a new OEM air end price.
The alternative could be to do nothing? and allow your oil free compressor to run until the air end ultimately fails, the resulting decreasing performance as your air end runs 50,000 to 80,000 + hours could be as much as 30% in wasted energy for the reasons explained. This point justifies a refurbished air end operating at circa 5% less performance over the very same 50,000-to-80,000-hour operation period.
Some oil free compressor owners have fifty even a hundred or more oil free screw compressors installed in their numerous factories around the globe. The accumulated saving of using the original refurbished oil free air ends twice across your compressor fleet is very attractive when you multiply the reduced cost of refurbished products.
The environmental impact of a buying new air ends is much higher than refurbishing your original installed air ends.

Refurbishing your original air ends is a green solution

What if our original air ends are beyond economical repair..

Should your original air ends not meet the performance required then other alternatives such as a Ztechnique NEW oil free air ends can be purchased at significant savings when compared to original manufacturer prices.

Summary

The manufacturers bank on exchanging your oil free air ends every 40,000 to 50,000 hours due to the significant revenue this generates. We believe that refurbishing is a viable alternative to simply throwing away your oil free air end, particularly after just 40,000 or 50,000 hours when a window of opportunity to lower your oil free maintenance costs is available and at low risk to the customer*.

Customers that have changed to using oil free air ends twice with Ztechnique include Air Liquide, Ball Packaging, Can Pack, InBev to name a few.

Ztechnique recommendations to maximise your oil free compressors performance.

We suggest maximising your oil free air end life by installing additional primary air filtration that can minimise the number of particles entering the oil free element compression chambers. After tearing down many oil free air ends we have found everything from varnish to aluminium dust (Example the canning industry) that contributes to premature failure of the air end coating. Installing primary filtration is a very low cost compared to frequent air end replacements.
Always draw your compressors cooling air from outside the building and ensure the source air isn’t being contaminated by material that could damage the compressor.
Water quality is key to longevity of many of the oil free compressors components, air end jackets, oil, intercooler and aftercoolers require treated water in order to extend the life of the coolers.
Regular service is paramount to ensuring oil free compressors remain efficient.

A business case we consulted recently resulted in installing a plate heat exchanger closed circuit loop cooling system just before the air compressors.

The existing primary cooling open tower cooling system was heavily contaminating the compressor coolers causing poor performance and frequent high replacement cooler costs.

The compressor and air dryer coolers had to be replaced every few years at a cost more than £50,000 pounds per compressor. The heat exchanger, pump module and expansion vessel cost merely £15,000 pounds saving the customer down time and replacement cooler costs for years into the future.

If you require further information about our company and our services, please contact us.

Airtec Filtration Ltd
Manor Street
St Helens
Merseyside
WA93AX

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