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Rotary screw air compressors are one of the simpler designed and relatively easy to maintain compressors on the market. This brings them to be one of the most popular designs on the market as they can be used for all operations.

If a rotary screw air compressor is well maintained, they are capable of providing thousands of hours of excellent performance. This article will provide you with all the sort of things you should be regularly checking on your rotary screw air compressor.

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Rotary Screw Air Compressor Maintenance Tips

Rotary screw air compressors are built to last for several years of professional quality operations. That said, all air compressors do have their limits and wish to be inspected on a periodic basis to ensure optimal performance for the duration of their lifespan.

A rotary screw air compressor consists of several key internal components that would gradually wear over time if you don’t give them their due and timely inspections. The key parts are the airend and the drive train, which respectively pressurize the now compressed air and drive the mechanisms of the compressor. 

It’s also important to examine the motor and filters on a periodic basis and replace the lubricants when necessary.

Rotary Screw Compressor Airends Maintenance

Of all the components that comprise rotary screw air compressors, the airend is probably the most crucial because this is where the pressurization of air takes place. While an airend can generally last for a minimum of 40,000 hours, it can malfunction before its time if not properly maintained. An airend may be damaged by extreme system heat, dirty fluid, or contamination.

To prevent the development of damaging conditions in the compressor, you must inspect the airend on a periodic basis. It is generally recommended to check for the following issues during each inspection of the airend in your rotary screw air compressor:

  • Overheating
  • Condensation
  • Corrosion
  • Improper Lubrication
  • Vibrations
  • Incorerect Control Adjustment
  • Oil Seal Leaks
  • Bearing Noise
  • Over-Pressure

Overheating

While the airend is typically designed to withstand its share of heat, system issues can sometimes push the temperature beyond the acceptable threshold. The internal components should be monitored along with the heat level on a regular basis to ensure they’re not fielding too much heat.

Improper lubrication

An air end, like any internal moving mechanism, may wear down if it doesn’t have sufficient lubrication. Excess heat will be generated when friction occurs between poorly lubricated metal parts, and this will lead to a chain of problems.

Condensation

Condensation can spread throughout the internal components and cause system problems if you do not drain daily. Condensation can also be an issue if the air compressor lacks sufficient ventilation, especially when operating in extreme weather conditions.

Corrosion

If corrosion or rust develops on the airend or any adjacent component of the screw compressor, the compressor evidently has not been sufficiently maintained, lubricated, and drained. Corrosion will form when the surfaces of metal parts absorb moisture or face internalized friction due to inadequate lubrication.

Over-pressure

The internal parts will lose their ability to function as normal if too much pressure is being used. If the compressor begins to grind and overheat due to lack of lubricants then the airend could be forced to overexert itself.

Incorrect Control Adjustment

In some cases, an airend will wear out at an accelerated pace due to improper compressor settings. Therefore, operators who oversee this area should all be trained in the proper settings of a given air compressor and monitor these settings on a daily basis.

Vibrations

If a rotary compressor begins to make unusual vibrations, the internal parts are probably enduring excessive strain. Strange vibrations should serve as a serious red flag that the compressor needs to be shut off and further inspected for other issues.

Oil Seal Leaks

If the oil leaks, the air compressor will be drained of the fluid that the mechanisms need to be able to operate properly. Oil leaks will lead to mechanical friction and system overheating. If you spot an oil leak, it is crucial that you shut off the compressor and inspect the issue immediately.

Bearing Noise

Just as with vibrations, strange and unusual noises from an air compressor should serve as a red flag that something is wrong with the internal mechanisms. In a rotary screw air compressor, an unusual noise will typically be the result of worn airend bearings.

You should pay particular attention to oil leaks and strange noises from the motor bearings as these are the two main indicators of imminent problems with an air compressor.

Rotary Screw Compressor Drive Train Maintenance

In a rotary screw air compressor, the drive train is the component that guides the motion of the internal mechanisms. Therefore, for the compressor to function at optimum performance, the drive train to fun must have correct alignment at all times.

When you inspect the drive train, you should specifically check for the following symptoms:

  • Poor alignment
  • Insuffcient lubrication
  • Improper belt tension
  • Worn belt

Poor Alignment

If the drive train is misaligned, it will not be able to drive the motion of the screw compressor with consistency. A poorly aligned drive train will undoubtedly cause system stress that could eventually lead to premature failure of the motor bearings.

Insufficient Lubrication

Lubrication provides the internal mechanisms with smoothness and consistency as they move. If the lubricants are old or spoiled, the drive train is liable to friction within the compressor, which will ultimately lead to more problems.

Improper belt tension

The tension of the belt is crucial to the moving operations of a rotary screw air compressor. If the tension is weak, the compressor may become inefficient as it’ll have to overwork to maintain an even pace.

Worn Belt

For the drive train to move at its correct speed, the belt must be in optimal working condition. The belt won’t have sufficient tension if it becomes worn or frayed. You should check for frayed ends and crack every time you inspect the belt tension.

Overall, it is generally recommended that the drive train should be inspected every other month to ensure that the belt remains intact and properly adjusted. while also monitoring the lubricant to ensure it maintains proper viscosity.

Rotary Screw Compressor Motor Maintenance

To ensure proper motor health with your screw air compressor, you must make sure that the operating area is sufficiently ventilated during usage hours. To prevent overloading, keep track of the ampere draw.

Most importantly, make sure that the motor bearings are properly lubricated during each inspection. Some of the biggest problems with rotary air compressor motors result from the following problems:

Insufficient Grease

The motor is deprived of necessary lubrication if grease is not adequately applied to the bearings. This can lead to friction between metal parts that will cause the system to overwork itself and generate excess heat in the process.

Hardened Grease

In colder working environments, grease can harden and lose its proper viscosity. This will deny the internal mechanisms of the lubrication needed for parts to run smoothly. In worst-case scenarios, grease can freeze in subzero temperatures and become sludgy when temperatures rise back to normal.

Melted Grease

In hot working environments, grease can lose its viscosity in the opposite way and become ineffective as a lubricant because it is too runny. Under intense heat, grease can melt away and leave the metal parts of the motor unprotected. Grease will melt even more easily if it lacks proper viscosity for the application at hand.

Wrong Grease

Specific machines and working environments call for a specific type of lubrication. If you lubricate your air compressor with the grease of the wrong grade, it won’t offer the necessary protection against internalized mechanical friction, especially not under extreme temperatures.

Mixed Greases

Greases are not designed to be mixed with one another. When you apply a new coat of grease, remnants of the last application of grease should be thoroughly wiped away from the parts in question. The old grease could have acidic elements that might contaminate the new grease and heavily impact its effectiveness.

Over-Greased Parts

If the bearings of the motor are over-greased, it could render them incapable of moving properly because the grease would function more as a coat of molasses than an actual lubricant. To keep your bearings running smoothly, you must make sure that fresh applications of lubricant go neither below nor above the recommended amount.

Without the right grade of grease in proper proportions, the metal bearings of a rotary compressor are left to grind against one another with every revolution of the motor.

Filters

In addition to the air/oil separator, a rotary screw air compressor will typically contain two other filters — oil filters and inlet filters. Each of these filters must be inspected on a periodic basis to ensure optimal filtration and to prevent the spread of dirt and oily mist throughout the compressor’s system.

Ideally, you should check the inlet filters after every 2,000 hours of operation. You should inspect the fluid filters every 1,000 hours. Filter maintenance helps to spare the system of the following problems:

  • Airend wear
  • Oil contamination
  • Component contamination
  • Reduced air quality
  • System overheating

Airend Wear

A dirty filter can have many significant effects on the airend. The dirt from a clogged filter will be able to pass through an air compressor and diminish the quality of the pressurized air heading to your applications. A dirty filter also deprives the system of proper ventilation.

Oil Contamination

Poor filtration can dirty up the oil and grease within an air compressor, reducing the quality of lubrication and making the compressed air system more vulnerable to breakdowns.

Component Contamination

As unfiltered dirt and oil spread to other parts of the air compressor, problems are liable to occur with other components as dust collects on oily and moisture-laden surfaces.

Reduced Air Quality

Poor filtration has a detrimental effect on the quality of end-point applications because the outbound compressed air is rendered dusty, oily, and watery. An air compressor could lose its ability to fulfill its purposes if its filters are allowed to accumulate dirt.

System Overheating

When an air compressor lacks sufficient inlet filtration, system overheating could result from the accumulation of air-bound particles. The service life between each round of maintenance will shorten the hotter the mechanisms become.

Lubricants

In rotary screw air compressors, the supply of oil is crucial to the success and health of the system. Oil allows for clean and easy movement between the various parts that drive the pressurization of incoming air. In doing so, oil keeps the screw compressor cool through many hours of heavy-duty operation.

For the oil to do its job properly, you must follow a schedule and change the oil supply on a frequent basis. Sample the oil every two or three months to ensure that it retains the right color and consistency. Once the level drops, clean out the old oil and refill it. It is important not to mix old and new oils because the former could have contaminants that would infect subsequent oil supplies which will not be ideal.

Overall, you must prevent the following oil conditions from occurring in your air compressor:

  • Leaky oil
  • Runny oil
  • Mixed oil
  • Diluted oil
  • Improper oil
  • Acidic or contaminated oil

Leaky Oil

The air compressor will be deprived of vital lubrication if oil leaks. An oil leak could imply a crack in the oil compartment or a poorly fitted connecting fastener.

Runny Oil

All oils are sold at certain grades with specific viscosities. If the oil in your air compressor loses its viscosity, it will stop functioning effectively for the mechanical components inside the machine. Runny oil is about as effective as water when it comes to parts lubrication.

Mixed Oil

The oil in your air compressor must remain clean and pure. If the oil in your compressor is mixed with other grades or with older, contaminated oil, it could have significant effects on your system’s health.

Diluted Oil

In a dirty air compressor, oil can become contaminated by coming into contact with stray elements. If your system is plagued with stray dirt and dust due to poor filtration, the dirt could easily corrupt the oil.

Improper Oil

If the oil in your screw compressor is a different grade than the kind recommended in the user’s manual, your machine could have problems in the near future due to improper lubrication. This is why specific oil grades are recommended for air compressors.

Acidic or Contaminated Oil

If an oil supply is left to linger past its freshness, the oil is liable to develop acidic-like qualities, especially if it comes into contact with moisture, dirt, or rust.

Oils can last anywhere from 2,000 to 8,000 hours, but this depends on the type of operations in question. To know what kind of oil is best for the make and model of your air compressor, consult the owner’s manual or contact your manufacturer directly. Visit our Air Compressor Oil Types GUIDE – What Oil To Use In Air Compressor for more information!

Rotary Screw Air Compressor Maintenance Checklist Example

I have picked out this example of maintenance guidelines, or a checklist, provided by Eaton in their rotary screw air compressor manual!

Before getting into the maintenance checklist, Eaton provides some necessary safety steps to help protect you from hurting yourself or anyone around you!

Rotary Screw Air Compressor Maintenance Safety

It’s advised that you should disconnect, tag, and lock out the power source then release all the pressure from the system before attempting to install, service, relocate or perform any maintenance, to avoid shock and serious personal injury.

To avoid serious personal injury, when performing maintenance in an enclosure large enough to hold a man, inform others and be sure to tag and keep open any access doors. Before closing and latching access doors, make sure all persons are clear from the enclosure. You must make sure that repairs are done in a clean, dry, well lighted, and ventilated area.

Rotary screw compressors components can become very hot during operation. You should try to avoid bodily contact with hot liquids, hot surfaces, and sharp edges and corners, otherwise, burns or personal injury could be a result.

To avoid serious personal injury, be sure to relieve all system pressure then lock out power and tag the compressor to prevent unexpected movement of the unit. Never attempt to regulate or tamper with the safety valve, to avoid serious injury or death. The safety valve is designed to relieve system pressure when necessary.

Now, let’s get into the example of a rotary screw compressor maintenance schedule!

Daily Maintenance

  1. Check the oil level using the sump sight glass or dipstick. Visit our Air Compressor Oil Capacity Guide – Air Compressor Oil Levels for more information!
  2. Check safety valve for signs of rust or damage
  3. Check coolant level
  4. Drain condensate from the air receiver tank by operating the tank drain located at bottom of the air receiver tank. Visit our How Often To Drain Air Compressor Tank guide to learn more!

Weekly Maintenance

  1. Remove and clean air filters
  2. Check belt tension – the belts must be tight enough to transmit the necessary power to the compressor
  3. General unit cleaning, cleaning dust and particulates off the components

500 Hours Maintenance

  1. Change lubricating oil (after first 500 hours this is). For more information on how to do this, visit our How to Change Air Compressor Oil – Guide to Replacing Compressor Oil article!
  2. Replace oil filter
  3. Blow-out radiator
  4. Grease electric motor bearings

1000 Hours Maintenance

  1. Clean/replace air filter
  2. Inspect and lubricate suction valve

2000 Hours/6 Months Maintenance

  1. Change oil & replace oil filter
  2. Check entire compressed air system for air leakage around compressed air piping, fittings, connections, and gaskets, using soap solution and brush.
  3. Thoroughly clean oil sight glass. Visit our Air Compressor Oil Sight Glass – Oil Level Sight Glass Guide, Replacing & Reading for more information!
  4. Check & tighten all electrical connections/terminals

4000 Hours/1 Year Maintenance

  1. Clean suction valve
  2. Inspect 3 direction magnetic valve
  3. Inspect minium pressure valve
  4. Inspect motion of magnetic contactor

This checklist example mentioned checking for air leaks every 6 months or 2000 hours. Well, I would advise checking more frequently, something like:

  • Check all pressurized components for rust, cracks, or leaks. Immediately discontinue use of the equipment and relieve all system pressure if any of these problems are discovered. (Daily)
  • Inspect for air leaks. Squirt soapy water around joints during compressor operation and watch for bubbles. (Weekly)

The Importance of Proper Preventative Maintenance on Your Rotary Screw Compressor

Like all air compressor types, rotary screw designs require periodic maintenance. Thanks to the simplicity of the internal components of rotary screw compressors, maintenance is relatively easy on them. As long as you stick to the checklist, you will be rewarded with many years of optimal productivity from your machine.

The importance of proper preventative maintenance on your rotary screw compressor is because of the following 3 factors:

  1. Saving time and money
  2. Preventing emergency repairs
  3. Improving your compressor’s life expectancy

Saving Time and Money

When you stick to a proper rotary screw compressor maintenance schedule, you are going to reduce the risk of system downtime or any unexpected intervals that might occur. You will be able to spot potential problems the moment they occur, rather than allowing them to get out of hand and grow into something serious if you conduct these routine checkups.

The earlier you identify a problem, the easier and less costly it is to remedy. In a lot of situations, you will be able to rectify a problem within a few minutes of detecting it without spending money.

This scheduled maintenance will also save time in the long run. System downtime can be really costly and time-consuming. The time that a compressor remains down and inoperable is productivity lost. Even just a few hours of downtime can result in untold losses. With this regular rotary screw air compressor maintenance, you will lower the risk of costly downtime.

Preventing Emergency Repairs

One of the biggest risks of irregular maintenance schedules is that they can result in unexpected emergencies. If you only inspect your compressor at occasional, irregular intervals, you are not able to keep track of how it performs on the inside.

Even if the rotary compressor looks or seems fine from the outside and was purchased recently, there could still be internal issues that you will be liable to miss if you were to perform irregular maintenance.

In an absolute worst-case scenario, it might be that your screw compressor stops functioning. Consequently, a diagnosis could be even more time-consuming and costly. If you have consistent, periodic maintenance, you will be able to pinpoint the issues early have provided a remedy immediately.

Improving Your Compressor’s Life Expectancy

Sticking to a rotary screw air compressor maintenance schedule will allow you to extend the compressor’s life expectancy. Over the years of using the compressor, you will undoubtedly get a better return on your initial investment by inspecting the compressor on a regular basis.

As with any motorized machine, a rotary screw compressor that is well-maintained, inspected, and looked after on a strict schedule will generally last a lot longer. This routine maintenance can help you turn your initial investment in the screw compressor into an enormous return.

When the time comes that you finally go to replace the machine with a newer model, the old compressor will have likely yielded a fortune regarding its productivity, think about it!

FAQs (Frequently Asked Questions)

How do you maintain a screw compressor?

To maintain a rotary screw air compressor you should conduct regular preventative maintenance to suss out any potential problems when they’re small before they probagate into serious issues and potential downtime. To do so, you should create a schedule which includes, daily, weekly, monthly, quartely, and yearly checks.

How long should a rotary screw compressor last?

A rotary screw air compressor is predicted to provide around 60,000 – 80,000 hours before needing a rebuild, if you look after the compressor properly with a suitable preventative maintenance schedule.


If you have any questions regarding rotary screw air compressor maintenance, please leave a comment below, with a photo if applicable, so that someone can help you!