Adrienne Houston explores the common causes of failure for carbon vanes and the steps end users can take to ensure correct operation
One of the main facets of a rotary vane vacuum pump are the carbon impeller blades that rotate inside the pump casing, creating the pressure differential between the contact area and chamber to push gases in or out of the device. Ensuring the reliability of these blades is therefore paramount to avoid costly downtime and damage to pump efficiency.
The operating temperature of a vacuum pump has a great effect on vacuum, flow and power. When operating at a higher vacuum level, relatively little air is present in the pump to transfer heat. Therefore the heat created by friction is dissipated throughout the pump, increasing stress on the components within the device, especially the carbon blades. This can drastically reduce pump efficiency and service life while reducing the integrity of the blades, which over the long term can cause blade and pump failure.
Specifying the correct oil for an application also has a great bearing on the wear of the carbon blades. Sselecting the correct oil for operating temperature is paramount for a long service life.
Vacuum pumps can operate in a wide range of temperatures, therefore it is important to specify oils with a high viscosity rating. For operating in a wide range of temperatures, using synthetic oil represents the best choice. Such oils can reduce wear on parts during cold starts, but retain their viscosity when the pump is operating at high temperatures. This minimises the friction endured by the carbon vanes within the pump, while simultaneously keeping the temperature of the pump itself within tolerable levels. Consequently, maintenance is kept to a minimum for cost effective efficient operation.
Another common issue with regards to the protection of carbon vanes within a vacuum pump is the contamination of vapours and particulates within the pump chamber. Such contaminates can greatly damage the blades. Discolouring provides visible signs of carbon material degrading; in this example the blade has turned dark grey showing degradation. The blade will eventually fail due to wear from particles inside the pump.
The internals of a vacuum pump must be clean to allow the pump to reach a required pressure as quickly as possible. Contaminants can include residue from when the system was installed such as grease and oil; environmental contaminants such as dust and vapour that has condensed inside the chamber that is absorbed into the chamber walls. To reduce these risks, vacuum pump systems must be installed cleanly leaving no residue, and should feature rigorous filtration to deny particles access to the internals of the pump. Furthermore, the use of cooled condensers can ensure vapour is separated, limiting absorption in the pump chamber walls. By complementing a vacuum pump with required accessories, carbon blade durability is greatly increased.
The EuroVacuum Products range of blades are tough and reliable carbon vanes that have been proven to outlast OEM’s vanes. This encourages quieter operation due to the blades being specially impregnated and an isostatic graphite that gives the product its special characteristics. It is resistant to liquids and any chemically inert and non toxic gases. Due to the vanes low thermal expansion properties they offer good wear resistance.
By taking advice from a vacuum professional, end users can be sure not only of access to premium quality vacuum pumps and spares, but also all the necessary support and advice to create a complete product and service package. End users can therefore benefit from the cost effective reliable pump operation that industry demands.
Adrienne Houston is director of EuroVacuum Products Ltd.