Pick The Perfect Industrial Air Compressor

Industrial air compressors have improved in many ways in the last several decades.  Over the years, compressor OEMs have integrated a multitude of features to increase efficiency, improve serviceability and enhance user interface with compressed air equipment.

However, in spite of these improvements, the primary technologies utilized for air compression have remained mostly the same since the late 1960s.  A few key types of industrial air compressor technologies dominate the marketplace, and each have characteristics that make them ideal for certain applications and environments.

Before purchasing a new industrial air compressor, end users should become familiar with these technologies and their respective benefits.  By educating themselves before making a final purchase decision, they can be sure to select a compressor capable of reliably and efficiently meeting their needs for years to come.

 

Industrial air compressors can be divided into two primary types based on their theory of operation:

Positive Displacement compressors trap air molecules in a confined space (known as a compression chamber), then mechanically reduce the volume of the space.  When volume is decreased, pressure is increased.  Many types of industrial air compressors employ the principle of positive displacement.

Dynamic compressors increase air pressure in a different way.  These machines use high speed impellers to accelerate air molecules to rapid velocity.  The direction of the fast-moving air stream is then quickly changed in a device called a diffuser.  This rapid change in direction causes the air molecules to bunch together – increasing pressure in the industrial air compressor.

Positive Displacement Compression

Reciprocating Compressors

Reciprocating compressors have been a staple of small commercial and industrial air compressor systems for decades.  This old and familiar technology uses pistons and cylinders to create a compression chamber for positive displacement.  The steady thumping sound of reciprocating compressors can be heard in small manufacturing and automotive repair shops around the world.

Despite their familiar technology and relatively low cost, reciprocating compressors are naturally limited in a few important areas.  For example, reciprocating compressors are not widely available in sizes above 30hp (100cfm).  Therefore, applications requiring larger capacities often require rotary screw or centrifugal compressor technology.  Moreover, the cylinders and pistons in reciprocating compressors are subject to heavy wear – causing decreased capacity and increased oil carryover over time.  The noisy operation of reciprocating compressor is also a limiting factor, as end users must install them away from offices or other spaces where high noise is disruptive.

In spite of these limitations, reciprocating compressors can be a good fit for many light or intermittent compressed air applications.  Talk to your local compressed air expert to determine if a reciprocating compressor makes sense for your facility.

 

Rotary Screw Compressors

Rotary screw compressors have been widely used in commercial and industrial applications since the 1960s.  They are robust and durable machines that can be deployed in a variety of applications and environments.   Because of their versatility, rotary screw compressors are some of the most common in the market today.

Rotary screw compressors are positive displacement machines.  Their compression chamber contains two rotors (or “screws”) that each have several lobes.  When the two rotors are turned, their lobes interlock to create air pockets.  The volume of these air pockets is progressively decreased as they travel through the compression chamber – causing pressure to increase.

Rotary screw compressors are known for smooth, reliable operation in almost any application or environment.  They are available in a wide range of capacities (5-600hp+) and deliver a steady supply of compressed air that is free from pulsation.  Additionally, rotary screw compressors are designed for high duty cycles at full load capacity.  They can operate at their maximum discharge capacity for long periods of time without risk of excess wear or damage.

Rotary screw compressors can be equipped with several control options to enhance efficiency at part load.  Additionally, they are available in oil-flooded or oil-free configurations.

The incredible versatility of rotary screw compressors makes them an easy choice for many industrial compressed air applications.  If you think a rotary screw compressor might be a good fit for your next project, call your trusted compressed air specialist for a professional recommendation.

Scroll Compressors

Scroll compressors are a relative newcomer to the commercial compressor landscape.  However, their quiet operation and oil-free compression technology has made them increasingly popular for laboratories and medical applications.

Scroll technology has been widely used in refrigeration systems for years.  These positive displacement machines contain two interlocking scrolls.  The orbiting scroll rotates around the fixed scroll in a circular motion.  In this way, progressively shrinking pockets of air are carried through the compression chamber – increasing pressure along the way.  The air is then discharged at final pressure into the system of the industrial air compressor.

Scroll compressors are limited in size, so larger machines usually contain several scroll pumps combined into a single unit.  However, despite their comparatively small capacities, scroll compressors emit very low operating noise.  The average scroll compressor is as quiet as a common household refrigerator.  Because of this, these machines are a great solution for labs and office spaces where noisy industrial machines are not practical.

Additionally, scroll compressors contain no lubricant in their compression chamber.  This oil-free design makes them a safe choice for medical and lab projects where compressed air quality is critical.

 

Dynamic Compressors

Centrifugal Compressors

Centrifugal compressors are capable of delivering extremely large volumes of oil-free compressed air.  This particular dynamic industrial air compressor uses one or more sets of impellers to impart velocity to incoming air molecules.  The high-velocity air stream is then passed through a diffuser, which quickly changes the direction of travel – causing the air molecules to bunch together, thus increasing pressure.

Centrifugal compressors are used primarily in applications where air demand is extremely high.  Major automotive plants, refineries, beverage bottle production and large-scale manufacturing facilities often use centrifugal compressors to supply their compressed air needs.

Because of their large drivers (up to 10,000hp+), high rotational speeds and dynamic compression technology, centrifugal compressors carry a different set of considerations than positive displacement machines.  Careful planning and engineering must be conducted when selecting a new centrifugal industrial air compressor. However, in applications where large and steady volumes of compressed air are required, centrifugal compressors are often the most efficient and practical long-term solution.

 

End users should consult their trusted compressed air expert for a detailed system analysis before purchasing a new air compressor.  Each technology offers unique characteristics that can benefit specific applications.  However, with a proper planning and a little knowledge, buyers can be sure they make the right choice.

An Industrial Air Compressor Maintenance Checklist: 5 Areas Your Technician Should Check

Industrial Air Compressor

In most industrial facilities, an industrial air compressor is an important utility.  It is used for power, process and control throughout all aspects of operation, and is essential for keeping production up and running.  However, unlike other utilities, compressed air is usually generated onsite with user-owned equipment.

While most companies do not produce their own electricity, heat or water, they often own and operate an on-site compressed air system.  Because this utility is vital to a facility’s operation, a thorough preventative maintenance program should be implemented to minimize unexpected downtime resulting from compressor failure.

Every industrial air compressor is configured with a few common components that must be checked and serviced regularly.  A working knowledge of the following five items will enable industrial compressed air users to better understand and maintain their equipment.

Filters

Filters are necessary components in all the mechanical systems of an industrial air compressor.  They are installed in the air circuit, lubricant circuit and control circuit to protect against contamination.   Each filter serves a unique and important purpose, and must be cleaned or replaced based on the manufacturer’s recommended intervals and environmental conditions.

Additionally, there are several filters that require regular attention when it comes to lubricated rotary screw compressors.

Air Inlet Filter:

Removes contaminants from inlet air before it enters the compressor.

Lubricant Filter:

Cleans the industrial air compressor’s lubricant – protecting precision metal parts from damage caused by solid contaminants in the oil circuit.

Air/Oil Separator:

Because lubricated rotary screw compressors operate with a flooded compression chamber, an air/oil mixture is discharged from the compressor airend.  Before usable compressed air can be discharged from the compressor package, the air and lubricant must be separated.  The air/oil separator serves this purpose, and is equipped with a replaceable coalescing filter element that should be changed regularly.

Control Line Filters: 

Many industrial air compressors are equipped with pneumatic lines for controlling and sensing various functions during unit operation.  Proper maintenance of control line filters helps to ensure the air compressor is responding appropriately to changes in system demand.

Coolers

Effective removal and dissipation of heat is an ongoing battle in every industrial air compressor.  The heat of compression must continually be expelled to prevent unsafe operating conditions and machine failure.  In light of this fact, compressor coolers must be regularly inspected and cleaned during routine maintenance.

Air-cooled rotary screw compressors are often equipped with a heat exchanger for the lubricant, and a separate exchanger (aftercooler) for the discharge air stream.  Over time, these coolers will become clogged with dust and other contaminants from the ambient environment.

Water-cooled compressors are usually configured similarly.  However, they use water as a cooling media instead of air.  Cleaning and maintaining water-cooled heat exchangers can be trickier than their air-cooled counterparts, as these units are more subject to corrosion, clogging and leaks.

Additionally, many centrifugal and multi-stage industrial air compressors include inter-stage coolers to reduce temperature between stages of compression.  These coolers must also be checked regularly to identify potential problem areas.

Lubricant

Air compressor lubricants serve a multitude of functions.  In oil-flooded compressors, lubricants are used to remove the heat of compression, seal clearances in the compression chamber, and lubricate bearings.  In compressor motors and gearboxes, separate lubricants are used to reduce friction between components for increased equipment longevity.

Regardless of their purpose, all industrial air compressor lubricants must be selected and maintained properly.  This is one of the most critical maintenance areas for operators of industrial compressed air systems.  Users that neglect to monitor and maintain the condition of their compressor lubricant can cause irreparable damage to their compressed air systems.

Regular oil sampling and analysis can turn a good compressor PM program into a great one.  By analyzing the chemical properties of a compressor’s lubricant, we can spot potential problems before they occur.  At Sullair of Houston, our standard oil sample report highlights many aspects of lubricant condition – like particle count, water content and total acid number.  This allows us to make informed and insightful recommendations to our customers about how to better maintain their equipment.  ~ George Saez, Service Manager Sullair of Houston

Controls

Controls are an often misunderstood and overlooked system in industrial air compressors.  However, their impact on the reliability, longevity and efficiency of industrial air systems cannot be understated.

In general, the controls of an industrial air compressor enable it to respond appropriately to changes in system demand.  For example, when system pressure drops, an air compressor should respond by increasing output to offset demand.  When pressure rises, an air compressor should respond by decreasing output to prevent over-pressuring the system.

There are many compressor control types available today – each with a unique set of characteristics and benefits.  However, regardless of type, all compressor control systems consist of several mechanical and electrical components that must be incorporated into the unit PM program.  Potential maintenance items include valves, solenoids, regulators, switches, transmitters, tubing, etc.   If one of these items requires service, the air compressor can operate unpredictably.

Call a trusted compressor service provider for help troubleshooting and repairing control problems.

Drains

Most industrial air compressor systems are equipped with several condensate drains.  Often, there are drains installed on compressors, filters, dryers and receiver tanks.  When functioning properly, these drain valves expel liquid water to protect downstream equipment from potential corrosion or damage.  However, if not regularly checked and maintained, a compressed air condensate drain can fail – having a detrimental impact on system performance and reliability.

A drain valve that is stuck in the open position can be a nuisance.  It creates an air leak that reduces system efficiency, or even causes overall pressure to sag.

A drain valve that is stuck in the closed position can often be more problematic – sending liquid slugs of water downstream to overwhelm dryers, filters and pneumatic equipment in the plant.

Many pneumatic control valves used in chemical process and refining applications cost thousands of dollars.  Even a small slug of water can ruin them, and replacement costs are very high.  Protecting these components from liquid water is critical – and a simple, inexpensive maintenance program for compressor condensate drains can help to prevent major failures down the road.  ~ Steve Mahaffey, Sullair of Houston