Getting the best from your investment

13 November, 2007

In the drive to optimise their processes, leading manufacturers and processors investing in new industrial vacuum equipment and those running existing systems, need to consider the following issues to ensure they get the best from their investment: performance, running costs and contamination. Those that are analysing these issues seriously are making significant gains in quality and efficiency.

Recognising the critical performance factors and understanding how they impact on the process is key to optimising the vacuum system specification. For example, in a chemical processing application, it may be health and safety legislative issues which determine the choice of pump. Many processors whose equipment has traditionally been specified to the T4 temperature rating of 135ÞC have had to make compromises in vacuum pump speed and efficiency in order to meet ATEX regulations. In fact, T4 is an over-specification for most multipurpose chemical processing applications and users may find that other temperature classifications specified under the new rules will allow them to meet the regulations with more efficient vacuum pumps.

In other applications, the critical factors may be accuracy of the vacuum pressure, the way the system is controlled or integrated into other control equipment, or it may be environmental factors such as noise or heat generated by the system.

The traditional solution is not always the best one. When Edwards supplied equipment for the world's largest mechanically pumped vacuum degassing facility at the ORI Martin steelworks in Brescia, Italy, it was not traditional steam ejector technology that they recommended, but a 'dry' pumping system.

This solution uses less energy than the traditional alternative, avoiding the issues of disposal of contaminated waste water and oil, and, crucially in this built up area, offered quieter operation.

The issue of running costs is increasingly being taken into account by manufacturers and processors making capital purchases. The key factors affecting the running costs of a vacuum system include energy consumption and maintenance. Modern vacuum pumps are either oil-lubricated or 'dry', that is they have no oil in the swept volume.

Choice of pumps

Many vacuum pumps in laboratory, processing and manufacturing applications, are oil-sealed pumps. Manufacturers of these pumps ensure their products achieve maximum throughput with low base pressures, but for the user to achieve optimum performance, the choice and use of lubricating oil – a vital and yet often overlooked component – must be carefully considered.

Every company has the responsibility to manage its lubricants effectively and to recognise the impact of lubrication on the environment.

Selecting the correct grade of oil ensures that the pump will provide the performance it was originally designed for. Monitoring the oil and changing it regularly will keep the pump running, and will prevent expensive repairs and inconvenient, unplanned stoppages.

Dry pumps are, by definition, cheaper to run than oil-sealed pumps. There is no oil consumption, no requirement for the pump to be taken off line for frequent oil changes and no waste oil which must be disposed of in accordance with local environmental regulations

Also, dry pumps tend to be more energy efficient than their oil-sealed counterparts. There is no risk of contaminating the process with oil, or the oil with fine particles from the process, which can cause a gradual loss of pumping performance in oil-sealed pumps.

Cleanliness is key

The effect of the vacuum system on the cleanliness (or lack of it) of the process is increasingly being appreciated in the process industries, and in many processes, cleanliness is key to optimising output.

In practice, this is a complicated issue because each application is different, and the needs of each process specific. In general terms contamination of the process, known as 'process-poisoning', may be caused by ingress of dust or water vapour into the system, or the presence of unwanted gases such as air, nitrogen, hydrogen, oxygen and others.

Manufacturers do not always realise that quality problems may be related to contamination in the vacuum process. Recipe-based processes are particularly vulnerable to these types of problems because operators are not usually trained to recognise vacuum-related problems, or how to remedy them.

Consideration of life cycle costs associated with key equipment is an essential element in the drive to optimise production efficiency. Edwards is helping its customers make process gains as a direct result of vacuum pump system optimisation.