Product category:
Pumps, Vacuum pumps
News Release from: AxFlow | Subject: Wilden Pumps for paint
Edited by the Processingtalk Editorial
Team on 29 September 2005
Pumps for use in the paint and resin
industry
Transferring paint, resins and solvents can be a difficult process in respect of preventing leakage of the pumped medium and the effects that solids contained within the medium can have on the pump
Transferring paint, resins and solvents can prove to be a difficult process in respect of preventing leakage of the pumped medium and the effects that solids contained within the medium can have on the components of the pump Leakage to atmosphere creates both potential hazardous and environmentally dangerous conditions
This article was originally published on Processingtalk on 2 Nov 2004 at 8.00am (UK)
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Component wear and possible blockage reduces the working life of the pump, increases maintenance costs and lost production due to down time.
Of the many pump types that can be considered for transferring fluids in the paint and resin industry, the air operated double diaphragm positive displacement pump can be described as ticking most boxes.
This type of pump can transfer anything and everything and is suitable for operation in the most hazardous and difficult conditions.
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It can transfer heavy, abrasive liquids and slurries equally as efficiently and effectively as fluids that can be damaged by high shear forces.
The other key factor in its employment is that because air operation is intrinsically safe by design, the pump can be used in hazardous areas where ATEX compliance or certification is required.
One of the leading manufacturers of air operated double diaphragm positive displacement pumps is Wilden, which has a high international presence within the paints and resins industry.
"Two of the main factors that contribute to the success of the Wilden pump in these industries are its shear sensitivity and ability to react to viscosity changes," says Peter Carfrae, Wilden Product Manager at AxFlow: "The Wilden pump is now offered with both clamp band or bolted construction to give a choice of containment builds.
When running, the dynamic components that come into contact with the fluid are the two diaphragms which are connected by a common shaft, the two inlet valve balls and the two discharge valve balls.
The diaphragms act as a separation membrane between the compressed air supply and the fluid.
Driving the diaphragms with compressed air, rather than the shaft, balances the load on the diaphragm which removes mechanical stress and therefore extends diaphragm life.
The valve balls open and close on the valve seats to direct the flow.
The absence of close fitting parts allows solids to pass through the pump without harm, whilst abrasive and viscous products can be pumped without any damage to the fluid characteristics.
Furthermore, the pump can run dry, self-prime and 'deadhead' without any adverse implications.
The primary wearing part of this pump type is the diaphragm, so it is essential that the correct type of material is specified for the media to be transferred in order to attain long working life and reduce maintenance costs.
Rubber (Neoprene, Buna, Nordel, Viton) diaphragms are moulded with natural rubber and manmade additives to increase the diaphragm chemical resistance and/or flexing characteristics.
A nylon fabric mesh is positioned within the rubber diaphragms during the moulding process to strengthen the diaphragm while dispersing stress.
Thermoplastic (Polyurethane, Santoprene and Wilflex) diaphragms are manufactured by moulding manmade compounds into net shaped parts.
These thermoplastic diaphragms have inherent tensile strength and do not need fabric reinforcement.
In addition, reducing the stress to which the diaphragm is subjected will contribute to long diaphragm life.
In the case of the Wilden pump, the diaphragm is moulded in an 'operational' shape, such that stress concentration is minimised throughout its entire stroke length.
In contrast, traditional and dome-shaped diaphragms reform as the pump operates, which induces high stress levels in the rubber and fabric from which the diaphragm is constructed.
By far the most commonly used Wilden pumps within the paints and resins industry are the P4 Metal and P8 metal models, both being available with the wetted housing in a choice of Aluminium, Cast iron, Stainless Steel and Hastelloy.
The range of duties for which these pumps can be used is considerable.
Where the transfer of pigmented non-emulsion paint and resins has been an expensive problem due to the fluid constantly leaking from the existing pump, the Wilden P8 has proved to be an effective solution.
In one plant a transportable P8 unit, operating for periods of between 4 and 6 hours daily, has eliminated leakage and pump downtime.
Elsewhere, in a plant historically relying on manual transfer and gravity flow in containers, eight Wilden P8 pumps have provided the resources to streamline operations and expand production.
Polypropylene pumps with Teflon elastomer were supplied for the corrosive epoxy paint applications and aluminium units with Buna elastomer were selected for the less aggressive latex paint transfer.
Waste product disposal is another area where this type of pump comes into its own.
When a US based paint company needed to replace a constantly leaking gear pump used for transferring water based waste latex for disposal, the Wilden P8 was specified.
In addition the leakage problem, the latex was forming solids called "skins" which caused the gear pump to fail.
The Wilden P8 offered the capability to pass solids up to 35mm in diameter and maintain a flow of 200lpm.
The same manufacturer also turned to the P8 to assist in transferring the water based latex paint from bulk tanks into gallon cans on the assembly line.
Here the problem for the existing gear pumps was that they were unable to pass the grinding medium occasionally present in the paint.
This grinding medium, in the form of small metal balls, unleashed major maintenance issues on the tight tolerance gear pumps.
For the paints and resins industry, the Wilden air operated double diaphragm pump offers significant benefits over gear pumps.
With applications including pre-process, process and waste disposal it is ideally suited for the cost-effective transfer of heavy, abrasive, abrasive and viscous fluids without incurring damage to the fluid characteristics. Request a free brochure from AxFlow ...
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