Uniting the forces of air movement

Vacuum pumps and air compressors are vital parts of a myriad of engineering processes. Historically, vacuum pump equipment has been overlooked in comparison to its ‘twin’. However, there is a new trend that couples this equipment together, according to Mark Taylor, product manager at Atlas Copco Compressors:

Due to the technical similarities between the operating principles of compressors and vacuum pump screw technology, there is a growing trend within a number of companies that views the two processes as relative opposites.

Rough vacuum technique is often viewed as being ‘less sophisticated’ than compressed air technique, and vacuum pumps have often been either ignored or serviced by non-specialists. Realising such arguments as the cost of unplanned downtime, many people are coming around to the idea that having both compressors and vacuum pumps serviced by an air movement specialist is essential.

However, as yet, this is not the general practice. Within a broad spectrum of relevant applications, the essential presence of a modern compressor is not matched by its vacuum pump equivalent in terms of equipment age, operating principle and energy efficiency.

One of the reasons for this is the ubiquity of compressors in comparison to vacuum pumps. It is estimated that on average there is one vacuum pump for every three compressors installed on a typical production site.

What’s more, there are many questionable tales regarding neglected and un-serviced traditional vacuum pumps being located in remote areas of some production sites; with these machines operating at minimum performance levels and representing an uneconomic burden on energy consumption.

Yet, surprisingly, in such cases these pumps may well be under-performing within a production environment equipped with state-of-the-art compressors operating far more efficiently and located at the actual point of use.

Efficient, on-site vacuum in the operating pressure range 0.5 mbar(a) to 500 mbar(a), such as that provided by Atlas Copco’s GV range, is produced by oil-sealed rotary screw systems whereby two screw elements rotate at slow speeds, enabling the pump to run at a sound level as low as 69 dB(A).

Such silent operation allows installation close to the point of use; provides the added benefit of minimum pipework connections and gives a corresponding reduction in pressure drop energy losses.

There is also close parallel between the relative size, rating and configuration of the latest vacuum pumps and those of screw compressors. Although vacuum pumps operate at a comparatively lower differential pressure and therefore require a smaller motor than their counterparts, electrical energy consumption represents 50 to 80% of the lifetime costs of both types of equipment. 

In the past this cost component of vacuum pump operation may have been considered to be inconsequential, it is significant that pumps incorporating screw technology now fall within the boundaries of the BCAS uniformity of energy reporting initiative ? a yardstick which does not necessarily apply to other types of vacuum drive systems.

The commonality of motors, drive trains and components argues strongly in favour of maintenance programmes designed to cope equally effectively with compressors and vacuum pumps from the same manufacturer or service provider.

Most compressed air users would agree that to get the best return from their capital investment, the monitoring, measuring and management of compressor installations is essential if optimum control, improved productivity and energy efficiency is to be achieved.

Conducting energy audits is seen as the definitive approach to identifying trends, establishing how well a system is performing, and installing energy-efficient solutions where needed. This cost-saving approach applies equally well to the new generation of screw technology vacuum pumps.

Applying simple non-intrusive air audit data logging techniques to vacuum pump systems can help establish a true indication of a system’s air use and, ultimately, help to identify any wastage factors such as leakage and pressure drops.

These monitoring techniques have been applied to a considerable number of diverse applications throughout industry and as a result of implementing these energy-efficient measures, it is not uncommon for operating cost savings of as much as 40% to be realised.

Therefore, it seems clear that by looking at all air movement demands collectively, whether for compressed air or vacuum applications, plant operators can realise considerable improvement in terms of cost and energy-efficiency, plant uptime and system integrity. What is more, the rapid advance in energy-saving technologies suggests even greater productivity benefits for the future.