Contracting Quotations in Compressed Air/Vacuum Technology Compressed Air/Vacuum Technology — Requirements Dictate System Design

Editor: Sonja Beyer

Despite their fundamental differences, compressed air and vacuum technology do have some things in common: expensive technology is required in order to generate high or low pressures. Variable-speed drives are the technology of choice for compressors and vacuum pumps alike in order to keep operating costs in check. The demand for contracting quotations is also increasing.

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Production of vacuum pumping stations at Pfeiffer Vacuum (Picture: Pfeiffer Vacuum)
Production of vacuum pumping stations at Pfeiffer Vacuum (Picture: Pfeiffer Vacuum)

In industry, compressed air is taken from a socket outlet like electricity — and is therefore a much valued source of energy in many production processes. For example, about 62,000 compressed air systems are installed in Germany alone. And precisely because compressed air is so safe and easy to use, many operators do not keep a very watchful eye on the costs incurred by its use. A great deal of money literally vanishes into thin air through leakage, with loss rates tending towards 15 percent as a general rule — although the figure can be as high as 70 percent.

All the big names in the industry are now offering compressed air audits. The aims of such audits are to detect leaks, diagnose incorrectly dimensioned lines, and to identify instances where the generation of compressed air is not tailored to the specific application. The first step on the way to energy efficiency in the generation and distribution of compressed air is to analyze the present situation and identify the actual requirements. Once all the data are available, it is possible to work out what level of investment is needed. A study commissioned by the European Union showed potential energy savings of between five and 50 percent with compressed air systems. Moreover, most of the measures aimed at improving efficiency had payback periods of less than two years and would therefore be a very attractive economic prospect for the companies in question.

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Optimized Compressed Air Management

The maximum possible energy efficiency of each individual component in the compressed air system may be a necessary precondition to optimizing the system as a whole, but is still a totally inadequate way of achieving this end.

With the exception of continual process engineering sequences, the profile of requirements obtained by analysis usually shows variations. It can then make sense to work with regulated-speed compressors. It is also advisable to use a primary control with larger systems. The advantage of this is that several compressors can be synchronized and operated at one station. The performance under load can then be made more efficient, e.g. by distributing (splitting) the load across several compressors of different sizes.

The Delcos XL developed by CompAir is an integrated touch screen controller which has been custom-designed for the L 30 - L 132 range of fixed-speed and regulated-speed compressors. It displays detailed statistics, including network pressure and average weekly flow rate, in the form of on-screen trend diagrams and graphs. By analyzing these trends it is possible to set precise parameters for the compressor.

A central compressed air station can be advantageous for the operator unless extremely long lines argue in favor of a decentralized supply system. If compressors can be combined there are more benefits to be reaped than just simplifying service and maintenance. The primary by-product of the compression process is heat, therefore a waste heat recovery system can reduce energy costs further. According to Kaeser, up to 96 percent of the energy supplied to the compressor can be recovered as waste heat and used for a second time (e.g. for heating purposes).

Boge demonstrates how efficient a system of this type can be: three compressors with a rated output of 632 kW are installed at a catalyst manufacturer. The thermal output which can be recovered and fed into the heating system is 757 kW. Is this the perpetual motion machine at long last? Not quite! The fact that more thermal output is recovered than is supplied in electricity is due to the intelligent use of the heat generated by the condensation of the air humidity intake in the compressed air after-cooler. This heat is available free of charge, as it were, in addition to the heat of compression.

Variable Costs to Replace Fixed Costs

More and more companies are exploiting the possibility of generating compressed air with a new and energy-efficient system without tying up capital.

Ultra Air is also in the business of customizing these systems: after analyzing the customer’s situation, load profiles and estimated compressed air requirements, the company designs compressed air stations for their specific applications. As they work on the systems, the engineers consult a database containing the full range of compressors and the accessory components made by all the leading manufacturers along with their respective performance data.

The compressed air requirements must be calculated first in order to arrive at the stage where the compressed air contracting model can be developed jointly with the customer. The following questions and issues are relevant to this process:

  • Is the compressed air consumption high, average or low?
  • Given the importance of the dynamics of consumption as well, how great are the changes in consumption related to volume flow and pressure within one minute, one hour or one day?
  • What quality of compressed air is required?
  • Does the customer operate one shift or multiple shifts?

What Are the Advantages of Contracting?

The AirScan method developed by Atlas Copco takes the systems to service level, applying the rule of thumb that the standard consumption in the relevant sector of industry should be taken as a basis for calculating the compressed air consumption with a new compressed air installation.

One key argument in favor of contracting and against a company compressor plant is the issue of cost transparency, which is another point emphasized by Kaeser. Precision measuring systems guarantee that only the amount of compressed air that was actually taken out of the network will be counted. Another major advantage of contracting systems besides transparency of costs is the continual optimization of compressed air costs. Not only does Kaeser take care of the operation and maintenance of the plant, it also makes any necessary changes to suit the operating conditions and to meet the latest standards of technology at any given time.

Exactly as Much Vacuum as Necessary

Horror vacui — nature evidently has something against empty spaces. Hence the need for operators to mobilize a great deal of energy and a hefty dose of control engineering in order to maintain a constant vacuum.

These days it is possible, with the aid of regulated-speed drives and direct drives, to generate the exact amount of vacuum needed at any given time. The operating point of the application is now also subject to precision analysis and adjustment with a view to selecting the right generator or matching it exactly to the application.

The future markets for vacuum technology include renewable energy, for example, as well as medical technology, environmental technology and the electronics industry.

The iXL120 pump supplied by Edwards, for example, is a dry pump for semiconductor production. The vacuum pump is said to be the fastest in its class. The average energy consumption is apparently just 550 watts (output at 700-tonne outlet pressure). As such, the manufacturer claims that the product guarantees both high throughput and low operating costs alike. Boasting a maximum throughput of 110 m3/h, the iXL120 claims to be 22 percent faster than other pumps in its class (20-liter chamber). The pump has an optional nitrogen-free flush for processes not involving corrosive gases. There is no need to supply the pump with nitrogen with this option, thus simplifying operation and reducing operating costs.

Edwards is not the only company where energy efficiency is an important feature in vacuum pumps. Oerlikon Leybold Vacuum is also keen to emphasize that its new Dryvac screw-type pump needs 30 percent less energy than its predecessor. In addition to the improved use of energy, the company also claims that the system saves on installation space and is so quiet that people can hold a conversation while standing next to it.

Compact and Economical Pumps and Systems

More compact designs, large-scale integration, an enhanced range of functions, lower noise emissions and an increasing demand for dry-compressing systems are the trends cited by Gebr. Becker. In contrast to oil-lubricated systems, there is said to be no risk of contamination with dry-action pumps, a factor which might be of relevance in the food industry or medical technology, for example. Due to their simpler design, it is claimed that these pumps and systems can even be more economic than the oil-lubricated ones depending on the application and layout. Pumps with contactless operating mechanisms are also said to minimize wear — meaning a considerable increase in service lives.

Pfeiffer Vacuum has developed a powerful turbopump in the shape of the HiPace 60. The pump boasts high levels of economic efficiency and flexibility in all installation positions. With its improved rotor design, the pump is alleged to offer good pumping speed and high gas throughput as well as being immune to particles and dust. The manufacturer claims that the robust bearing system makes the pump ideal for heavy-duty industrial applications.

According to Busch, centralizing the vacuum supply is an economic alternative for customers who operate several vacuum pumps. Indeed, energy consumption is always substantially lower with central vacuum supply. Further advantages flagged up by the company include the higher level of operational reliability and the option of doing maintenance work during operation without the need for downtime. Due to the fact that the central vacuum system is installed outside the production area, it is also pointed out that production staff are no longer exposed to the heat and noise given off by individual vacuum pumps.

To sum up, the supply of high and low pressures is an expensive business. That makes it essential to scrutinize each individual system component in terms of its potential energy efficiency. And this does not just apply when installing new systems: it is also and especially true that a great deal can be saved with older systems in particular.

* The author is a freelance correspondent at PROCESS.

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