Compressed air might be out of sight and out of mind but when it breaks down, or doesn’t work properly, then the maintenance manager is under pressure to resume normal service.
There are a range of maintenance areas that need to be given attention in a traditional compressor and these include the checking of filters, monitoring for over-heating, leaks, water residue and keeping the right pressure:
Filters – Just as a car’s service covers checking its oil and filters, so the same can be said of an air compressor. The oil and filters must not only be checked, but changed regularly to ensure optimum operation.
Each compressor will have specific service interval timings which are indicated in the manufacturer’s manual, however as some compressors operate in dusty work spaces, frequent checking is essential.
Bearings and other components, such as the oil separator, can be severely affected by dust and dirt particles and these can prevent shorten the life of the equipment
Hot under the collar – Air compressors are particularly prone to over-heating. In addition, they also create a significant amount of heat whilst in operation, which needs to be removed.
If the compressor runs for too long near the boundary of its warning temperature for even a limited time, then it can cause severe damage to the entire system.
Monitoring the compressor’s operating temperature and identifying any temperature problems as early as possible is vital to its long-term health.
Leaks – However small a leak in the compressed air system, it shouldn’t be ignored. In fact, in many applications, a leak can account for up to 30% of the total operational cost of the compressor.
Common areas for leaks are connection joints like valves, unions, couplings, fittings, etc. As well as wasting energy and money, these leaks can also result in lost pressure, potentially reducing the end use product’s performance.
So, it is worth fixing leaks as soon as they are identified, to minimise time and cost losses.
Water – Water and air compressors don’t mix well, and this means that the maintenance teamhas to be vigilant when it comes to monitoring the dryers and condensate drains.
As well as damaging the compressor, tools and the end product, pipe components within the compressor can be particularly affected. Regular checks for water in the compressed air line are quick yet vital.
Set the pressure – By setting the pressure of the compressor at the level that is actually needed, rather than at a higher rate ‘just in case’, helps the maintenance team keep the system in balance and ensures that energy is conserved and money saved.
Oil-free - Another area that can be an issue for maintenance managers is that oil suspended in the air can create maintenance problems.
Although many air compressors rely on oil injection to seal their compression cavities and remove heat from the air supply, the potential
With an oil-free compressor, the air is compressed entirely via the action of rotary screws (two meshing helical screws, known as rotors).
In other words, it is a ‘dry running unit’ whose compression chamber is not lubricated and whose screws operate contact free. This means there is no oil to contaminate the compressed air.
Oil-free compressors can use a variety of basic designs and operating principles. A high proportion are positive displacement compressors, which create pressure by volume reduction.
Rotary screw compressors, pull air into the compressor and ‘squeeze’ it by rotating elements in the compression chamber to a defined pressure.
Piston compressors use a reciprocating piston to compress the air and other compressors use a dynamic compression approach, generating pressure by accelerating the incoming air to high speeds.
Cost-effective oil-free compressors
One of the issues with oil-free compressors is that traditionally, the maintenance costs associated with operating them have been typically higher than oil-injected compressors, preventing wide scale uptake of oil-free.
However, the latest oil-free compressor technology, such as the High-Speed Turbo (HST) from BOGE, has lower maintenance costs than both oil-free and oil-injected compressors.
This means the industry now has access to the most effective way of producing oil-free compressed air, at a cost estimated to be 30% less than previously possible with screw compressors.
Latest technology compressors are 50% smaller and lighter than traditional oil-free machines. They are also quieter - typically 63dBA for the 55kW unit, as opposed to 80dBA for a raditional screw compressor.
High speed turbo compressors use an impeller driven at very high speeds. They contain no oil, which removes the need for oil changes or oil filter replacements, as well as eliminating the risk of contaminating products (whether that’s food, medical supplies, packaging, etc.).
On top of this, there are no gears in the machine and fewer components to change overall; in fact, they have only one moving part, ensuring ease of maintenance from day one.
Another advancement in compressor technology are air bearings. At the heart of the compressor are two compact permanent magnet (PM), high-speed motors each having a central rotor suspended on self-stabilising air foil bearings.
Two precision balanced titanium impellors of different sizes and blade arrangements are mounted at each end of each rotor. At rotational speeds typically in excess of 100,000rpm, air is drawn in via an intake funnel and a specially designed spiral casing to be boosted in three stages to reach operating pressures quickly and efficiently, with minimal energy losses thanks to the frictionless air bearing configuration.
Indeed, the air bearing is a novel feature, it is virtually maintenance free, unlike magnetic bearings, which are widely used in other types of turbo compressor. Magnetic bearings also require a power back-up device to be fitted to protect them in the event of a mains power failure.
Other operating efficiencies are derived from the impellor, diffuser and spiral casing design, which effectively reduces air pressure on the intake side.
This has the effect of sucking fresh air through the motor, eliminating the need for a separate fan cooling motor and control unit.
The inherently highly efficient PM motors are also inverter controlled enabling supply to be matched precisely and instantaneously to the demand.
Precision high speed turbo technology, linked with the use of advanced electronic control systems, has created a new generation of oil-free, Class 0 compressors that offer companies throughout the food and beverage, electrical and pharmaceutical sectors the potential to improve the quality, productivity and reliability of their production processes, while simultaneously reducing operating costs.
The reliability of compressors has steadily improved over the last decade, however thanks to innovations such as this next generation compressor, routine maintenance has become even easier for maintenance teams.