Powering your air compressor by an industrial engine can be done by various means. Choosing the way you power your compressor should be decided by a number of factors. Space, existing components and systems, weight and your engine options are all variables to consider. In this article we talk about the most common found in the market today.
Engine Mounted FEAD Belt Drive
Auxiliary components are commonly mounted directly to the engine and driven from a serpentine or V belt. This is termed “Front End Accessory Drive” (FEAD) and is often used to drive alternators, generators, air conditioning compressors, water pumps, cooling fans etc. Air compressors can also be driven via FEAD belt off the front of an engine. This can be in line with the existing belt system or by adding another pulley to the crankshaft and designing another belt system. The driven and driving pulley diameters can be customized to provide the required compressor output at a given engine speed. Belt drives will also provide some damping of potentially damaging torque pulses. The compressor can be driven via a clutch or fixed pulley depending on whether it is desirable to be able to completely stop the compressor while the engine is running. A custom bracket will likely be needed to mount to the engine to support the compressor and if equipped, the secondary belt system components such as the idler(s) and tensioner.
Frame Mounted Belt Drive
To simplify the design of a bracket to mount the compressor it can be mounted to the base frame instead of directly to the engine. The belt is still driven off a pulley mounted to the engine’s crankshaft. Generally, a V belt will be used instead of a serpentine belt as it is better able to handle misalignment and variations in tension due to the changes in positioning between the engine and compressor under operating conditions, especially if the engine is not hard mounted to the frame.
Auxiliary Port Direct Drive
Many industrial diesel engines and some gasoline engines come equipped with an auxiliary PTO port used to power bolt-on accessories. These ports are usually part of the front or rear engine cover and are driven via the crankshaft/camshaft/fuel pump gear-train. Auxiliary ports come in various configurations usually conforming to an industry standard. The connection to the drivetrain is generally either a splined port or direct gear mount. Over or under drive ratios may also be available via bolt-on adaptors. Although traditionally small reciprocating compressors are driven by these auxiliary ports there is a growing number of higher volume rotary screw compressor designs taking advantage of this PTO drive method.
Flywheel Direct Drive
A common method of power to an air compressor is to drive it through a coupling directly off of the flywheel. Commonly used industrial couplings are designed to dampen vibration and torque spikes while often allowing some misalignment between the engine and compressor. To generate the high RPM required for rotary screw compressor operation a speed increasing gearbox is commonly used.
Flywheel Belt Drive
Much the same as the FEAD drive listed above, a pulley and belt configuration can be connected to the flywheel to power your compressor. The main advantage to using a belt driven from the flywheel is that there are generally fewer components to work around which typically makes designing the bracket and belt system simpler.
While not directly mounted to the engine, the use of an engine-driven hydraulic motor to power an air compressor is not uncommon. If the engine or equipment is using hydraulic power for other functions, adding hydraulic power to run a compressor can be a convenient option. This method is less efficient compared to the direct drive methods discussed above. It may require additional hydraulic cooling capacity and will burn more fuel for a given compressor output. This method does allow more positional flexibility between the engine and compressor which can be helpful if there is limited space on or around the engine.
Like the hydraulic drive above, using electric power generated by the engine is another way of producing air power. While the availability of sufficient power to produce large air volumes is unlikely, small electric driven compressors can be used when air flow and duty cycle are very low.
Ultimately choosing a drive method for your compressor comes down to your unique situation, air compressor requirements, and equipment available to you. The choice of how best to drive your air compressor system is best discussed with the members of the application team of your engine distributor and compressor manufacturer.
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