The Benefits and Drawbacks of an Air Suspension System


he United States developed the air suspension system during World War II specifically for heavy aircraft. The original purpose of air suspension was to save weight with a compact construction. Back then, air suspension systems were also used in other aircraft and some heavy trucks to achieve a self-leveling suspension. This would ultimately result in a vehicle with an axle height independent of the weight of a vehicle's cargo.


Ultimately, the air suspension system offers several benefits and drawbacks for drivers who rely on larger trucks and vehicles to carry heavy loads.


What Is an Air Suspension System?


An air suspension system is a style of vehicle suspension that's powered by an electric pump or compressor that pumps air into flexible bellows that are typically made out of a textile-reinforced type of rubber. Additionally, Pro Car Mechanics describes air suspension as a replacement to the leaf suspension or coil spring system with airbags composed of polyurethane and rubber. A compressor inflates the bags to a certain pressure in order to behave like springs. Air suspension also differs from hydropneumatic suspension because it uses pressurized air instead of pressurized liquid.


What's the Purpose of an Air Suspension System?


In most cases, air suspension is used to achieve a smooth and constant driving quality, but in some instances, sports suspensions feature an air suspension system too. Similarly, air suspension replaces a conventional steel spring suspension in heavier vehicle applications, like trucks, tractor-trailers, passenger buses, and even passenger trains. Air suspension has also become popular in low-riding trucks like this gorgeous 1982 Dodge D200 Camper Special.


What Is Electronically Controlled Air Suspension?


According to the company now known as Dunlop Systems and Components, at the start of the 1990s, Dunlop developed and installed the Electronic Controlled Air Suspension (ECAS) system on the 1993 Range Rover Classic and again on the Range Rover P38A. The United Kingdom-based company developed the ECAS to include several key features:


Vulcanized, heavy-duty rubber air springs at each of the vehicle's wheels


An air compressor in the vehicle's trunk or under the hood of the vehicle


A storage tank for compressed air, which allows you to store air at around an average of 150 PSI


Valve blocks which direct air to the four springs from the storage reservoir through a set of solenoids, valves, and o-rings


ECAS computer that communicates between the vehicle's main computer to calculate where to direct air pressure


Air pipes connecting from the storage tank to the air springs that channel the flow of air throughout the suspension system


A desiccant-filled drier canister to keep the internal recesses of the system dry



The electronically controlled air suspension also features height sensors that are based on sensing resistance in contact with the terrain on all four of the vehicle's corners to provide height reference for all corners. Additionally, further advancements are beginning to feature some Electronic Control Units (ECUs) that are able to fit under the vehicle's floorboard, making air suspension more widely featured in everyday driving.


The Benefits and Drawbacks of Air Suspension Systems


According to Future Marketing Insights, the total value of the air suspension market at the end of 2017 was around $4.3 million. So whether it's a manual or electronic air suspension system, the benefits can greatly improve the ride of the vehicle. Take a look of some of the benefits of air suspension:


More driver comfort due to the reduction in noise, harshness, and vibration on the road that can cause driver discomfort and fatigue


Less wear and tear on the suspension system due to reduced harshness and vibration of heavy-duty driving


Trailers last longer with air suspension because the system components don't take on as much vibration


Front air suspenions reduce the tendency of short wheelbase trucks to bounce over rougher roads and terrain when the vehicle is empty


Air suspension improves the ride height based on the load weight and a vehicle's speed


Higher corner speeds due to air suspension being better suited to the surface of the road



Air suspension increases the transport capabilities of trucks and trailers by providing a better grip that levels the entire suspension. An air suspension system can also be adjusted for feel, so drivers can choose between a softer feel for highway cruising or a harder ride for improved handling on more demanding roads.


In the case of hauling heavy loads, air suspension offers more consistency and keeps all wheels even. The air suspension system keeps trucks level from side to side, especially in cases where cargo is difficult to level. This results in reduced body roll when turning corners and curves.


Even with the benefits of an air suspension system, Driving Tests New Zealand suggests several drawbacks. Some of these disadvantages that so and so reports include:


The initial costs of purchasing and installing an air suspension system — air suspension can also sometimes reach three times the cost in repairs as a leaf suspension system over 10 years' time


Fuel overheads for running compressors for occasionally pumping air to the correct pressure


Fuel efficiency can suffer from the heavier weight of rear air suspensions over the weight of leaf suspension


An air suspension system's vulnerability to air leaks can result in malfunctions



Some of the drawbacks of air suspension systems are because of some of the mechanical issues they can be vulnerable to. Several of the common issues with air suspension systems that can require repair include:


Rust or moisture damage from the inside that can lead to the air struts or bags to malfunction


Failure of the air suspension tubing connecting the air struts or bags to the air system


Air fitting failure resulting from initial fitting or infrequent use


Compressor burn out due to air leaks in the springs or air struts from the compressor constantly engaging to maintain the proper air pressure



Even with these common mechanical problems, the benefits can far outweigh the drawbacks.


Understanding Compressors


Compressors are mechanical devices used to increase pressure in a variety of compressible fluids, or gases, the most common of these being air. Compressors are used throughout industry to provide shop or instrument air; to power air tools, paint sprayers, and abrasive blast equipment; to phase shift refrigerants for air conditioning and refrigeration; to propel gas through pipelines; etc. As with pumps, compressors are divided into centrifugal (or dynamic or kinetic) and positive-displacement types; but where pumps are predominately represented by centrifugal varieties, compressors are more often of the positive- displacement type. They can range in size from the fits-in-a-glovebox unit that inflates tires to the giant reciprocating or turbocompressor machines found in pipeline service. Positive-displacement compressors can be further broken out into reciprocating types, where the piston style predominates, and rotary types such as the helical screw and rotary vane.



In this guide, we will use both of the terms compressors and air compressors to refer mainly to air compressors, and in a few specialized cases will speak to more specific gases for which compressors are used.


Types of Air Compressor


Compressors may be characterized in several different ways, but are commonly divided into types based on the functional method used to generate the compressed air or gas. In the sections below, we outline and present the common compressor types. The types covered include:




Piston




Diaphragm




Helical Screw




Sliding vane




Scroll




Rotary Lobe




Centrifugal




Axial




Due to the nature of the compressor designs, a market also exists for the rebuilding of air compressors, and reconditioned air compressors may be available as an option over a newly purchased compressor.


Piston Compressors


Piston compressors, or reciprocating compressors, rely on the reciprocating action of one or more pistons to compress gas within a cylinder (or cylinders) and discharge it through valving into high pressure receiving tanks. In many instances, the tank and compressor are mounted in a common frame or skid as a so-called packaged unit. While the major application of piston compressors is providing compressed air as an energy source, piston compressors are also used by pipeline operators for natural gas transmission. Piston compressors are generally selected on the pressure required (psi) and the flow rate (scfm). A typical plant-air system provides compressed air in the 90-110 psi range, with volumes anywhere from 30 to 2500 cfm; these ranges are generally attainable through commercial, off-the-shelf units. Plant-air systems can be sized around a single unit or can be based on multiple smaller units which are spaced throughout the plant.


To achieve higher air pressures than can be provided by a single stage compressor, two-stage units are available. Compressed air entering the second stage normally passes through an intercooler beforehand to eliminate some of the heat generated during the first-stage cycle.


Speaking of heat, many piston compressors are designed to operate within a duty cycle, rather than continuously. Such cycles allow heat generated during the operation to dissipate, in many instances, through air-cooled fins.


Piston compressors are available as both oil-lubricated and oil-free designs. For some applications which require oil-free air of the highest quality, other designs are better suited.


Diaphragm Compressors


A somewhat specialized reciprocating design, the diaphragm compressor uses a motor-mounted concentric that oscillates a flexible disc which alternately expands and contracts the volume of the compression chamber. Much like a diaphragm pump, the drive is sealed from the process fluid by the flexible disc, and thus there is no possibility of lubricant coming into contact with any gas. Diaphragm air compressors are relatively low capacity machines that have applications where very clean air is required, as in many laboratory and medical settings.



Helical Screw Compressors


Helical-screw compressors are rotary compressor machines known for their capacity to operate on 100% duty cycle, making them good choices for trailerable applications such as construction or road building. Using geared, meshing male and female rotors, these units pull gas in at the drive end, compress it as the rotors form a cell and the gas travels their length axially, and discharge the compressed gas through a discharge port on the non-drive end of the compressor casing. The rotary screw compressor action makes it quieter than a reciprocating compressor owing to reduced vibration. Another advantage of the screw compressor over piston types is the discharge air is free of pulsations. These units can be oil- or water- lubricated, or they can be designed to make oil-free air. These designs can meet the demands of critical oil-free service.