Properly Servicing Your Rotary Screw Air Compressor: A Complete Guide

rstom036
Jul 30
5 min read

Rotary screw air compressors are essential machines across countless industries, from automotive repair shops to manufacturing plants and construction sites. Their reliability, efficiency, and continuous-duty capabilities make them indispensable in environments requiring steady and powerful air supply. However, like any mechanical system, rotary screw compressors require regular and thorough maintenance to function optimally and avoid unexpected breakdowns or costly repairs.

Proper servicing of a rotary screw air compressor involves several critical steps, including changing air and oil filters, replacing the air/oil separator, checking and changing the rotary screw oil, inspecting and adjusting belts, checking voltage and electrical components, and conducting general system inspections. This essay provides a comprehensive, step-by-step guide for maintaining your rotary screw air compressor to extend its lifespan, improve efficiency, and ensure safe operation.

I. Importance of Regular Maintenance

Before diving into the procedures, it’s crucial to understand why regular maintenance is necessary. Routine servicing of a rotary screw air compressor:

Prevents unscheduled downtime and expensive repairs
Improves energy efficiency and performance
Extends the lifespan of the machine
Maintains air quality by preventing oil carryover or contamination
Ensures operator safety by avoiding electrical or mechanical hazards

Failing to perform timely maintenance can lead to catastrophic component failures, increased operating costs, and compromised productivity.

II. Safety Precautions Before Servicing

Safety first—always follow these steps before beginning any maintenance:

Shut down the compressor using the manufacturer's recommended shutdown procedure.
Isolate electrical power by turning off the main breaker or disconnect switch.
Depressurize the system by opening the drain valve on the air tank or system outlet.
Allow the unit to cool—rotary screw compressors and their oil can become extremely hot during operation.
Use PPE (Personal Protective Equipment) such as gloves, safety glasses, and work boots.

Never work on a pressurized or energized compressor.

III. Replacing Filters

A. Air Filter

Purpose: The air intake filter prevents dust and debris from entering the compressor and damaging internal components.

How to Replace:

Locate the air intake filter housing.
Open or unscrew the cover.
Remove the old filter element.
Clean the housing with a dry cloth or compressed air (from another clean air source).
Insert a new filter element and reseal the housing.

Frequency: Every 1,000 to 2,000 hours, or more frequently in dusty environments.

B. Oil Filter

Purpose: The oil filter removes impurities and particulates from the compressor oil before it circulates through the system.

How to Replace:

Locate the oil filter (usually a spin-on type).
Place a drain pan underneath to catch any oil spills.
Use an oil filter wrench to remove the old filter.
Lubricate the O-ring of the new filter with fresh rotary screw oil.
Spin on the new filter until the gasket contacts the base, then tighten 3/4 turn more.

Frequency: Typically every 2,000 hours or as per manufacturer recommendations.

C. Air/Oil Separator

Purpose: The air/oil separator removes oil mist from the compressed air before it exits the compressor, keeping oil in the system and air clean.

How to Replace:

Remove the top cover or access panel to access the separator tank.
Disconnect the lines going to the separator.
Unscrew or unbolt the separator element from the tank lid.
Carefully lift out the old separator.
Install the new separator using a new gasket or O-ring if required.
Reassemble the system and reconnect the lines.

Frequency: Every 4,000 to 8,000 hours depending on usage and oil carryover rates.

IV. Changing the Rotary Screw Oil

A. Importance of Proper Oil Change

Rotary screw compressors use oil not only for lubrication but also for sealing and cooling. Over time, oil degrades due to heat, oxidation, and contamination.

B. Steps to Change the Oil

Warm the compressor slightly to thin the oil (but make sure it’s not too hot).
Locate the oil drain plug or valve at the bottom of the oil sump or separator tank.
Place a suitable container beneath the drain point.
Open the drain and allow all oil to flow out.
Close the drain securely.
Remove the fill plug and fill the system with the appropriate rotary screw compressor oil to the recommended level.
Replace the fill cap.

Important: Only use oil specified by the compressor manufacturer. Synthetic oils are commonly used for high-duty cycles and longer intervals.

Frequency: Every 4,000 to 8,000 hours, though some premium oils may last up to 10,000 hours.

V. Checking Voltage and Electrical Components

Electrical issues can lead to hard starts, overheating, or shutdowns. Voltage checks should be conducted by a qualified technician or electrician.

A. Voltage Check

Ensure the unit is locked out and tagged out.
Use a multimeter to check:
- Incoming voltage at the power terminals
- Motor voltage while running (for voltage drop)
Compare readings to the nameplate values and voltage tolerance specified by the manufacturer.

Signs of Voltage Issues:

Tripped breakers
Burnt wires or terminals
Motor overheating

B. Inspecting Contactors and Relays

Open the electrical cabinet.
Check for corrosion, loose wires, and burn marks.
Clean terminals and tighten connections.
Replace worn or damaged contactors and overloads.

Frequency: Inspect quarterly or at every scheduled maintenance interval.

VI. Inspecting and Adjusting Belts

Rotary screw compressors that are belt-driven require regular belt inspections.

A. How to Inspect Belts

Remove the belt guard.
Check for cracks, fraying, or glazing on the belts.
Press down in the center of the belt span to check for proper tension (refer to manual—usually around 1/2 inch of deflection).
Look for signs of misalignment or wear on pulleys.

B. Adjusting Belts

Loosen the motor mounting bolts.
Move the motor to increase or decrease tension.
Re-tighten bolts securely after adjusting.
Replace the belt guard.

Frequency: Check every 1,000 hours and replace belts every 2,000–4,000 hours depending on condition.

VII. Additional Maintenance Steps

A. Draining Condensate

Compressors generate condensation that collects in the tank or separator.

Manual drain: Open daily if your compressor doesn’t have an automatic drain.
Automatic drain: Inspect for clogs or failures.

Neglecting condensate drainage can cause rust, water contamination in air lines, and reduced compressor performance.

B. Inspecting Hoses and Fittings

Look for leaks, cracks, or wear.
Replace any damaged hoses or fittings.
Use soapy water to detect small leaks.

C. Checking Coolers and Fans

Clean the aftercooler and intercooler fins with compressed air or a soft brush.
Ensure cooling fans are working properly and blowing adequate air.
Overheating is a major cause of premature compressor failure.

D. Checking Pressure Settings

Verify that cut-in and cut-out pressures are correct.
Ensure the pressure relief valve is functioning.
Adjust the pressure switch if necessary (refer to manual).

VIII. Keeping Maintenance Records

Detailed maintenance logs help track service intervals, identify recurring problems, and comply with manufacturer warranty conditions. Your maintenance log should include:

Date and time of service
Hours on the compressor
Parts replaced (filters, oil, etc.)
Inspection notes
Technician name or initials

IX. Manufacturer Recommendations

Always follow the OEM (Original Equipment Manufacturer) service schedule and parts list. These are based on engineering tolerances specific to your compressor’s model and design.

If unsure about oil type, service intervals, or torque specs, refer to the manual or consult a certified technician.

X. Partnering with a Professional Service Company

While many tasks can be handled in-house, complex diagnostics, electrical work, and major overhauls should be left to professional service companies.

Partnering with a local, reputable provider like H&K Pump Sales and Service—which has served the Dallas-Fort Worth area since 1972—can save time and protect your investment. Their factory-trained technicians can catch early signs of trouble and ensure compliance with warranty standards.

Conclusion

Servicing your rotary screw air compressor is not a task that should be taken lightly. With proper care—including regular filter replacements, oil changes, belt adjustments, voltage checks, and cooler inspections—your compressor can last for decades while operating at peak efficiency.

Preventative maintenance is far more cost-effective than reactive repairs. By staying on top of your service schedule and addressing small issues before they become major problems, you protect your equipment, your production, and your bottom line.

Whether you’re managing a single unit or an entire fleet of compressors, consistent and thorough maintenance will always be the key to long-term success.