Impregnation for Dry Screw Vacuum Pumps

Impregnation for Dry Screw Vacuum Pumps

Impregnation is a process by which liquid materials such as resins and acids are soaked into a solid material to impart certain physical properties. Vacuum is a tool that increases the rate and quality at which the process is performed.

Vacuum impregnation takes place in a large batch impregnation apparatus. This apparatus is designed differently depending on the method being employed. Generally, there are three distinct methods of vacuum impregnation: wet vacuum (WI), dry vacuum (DI), and dry vacuum & pressure (DVP).

The general process of vacuum impregnation is as follows. First, the loading chamber is loaded with a batch of product. The loading chamber is then evacuated, and pressure manipulation is utilized by way of either vacuum pump or compressor to force the impregnating agent to flood the impregnation chamber. The agent is allowed to soak and penetrate into the material for a calculated extended period of time, and it is drained from the impregnation chamber. The result is a new material composite that exhibits increased quality in the specific intended aspects of the manufacturing plant.

Applications of Dry Screw Vacuum Pumps

Dry screw vacuum pumps are used for the dry vacuum methods of vacuum impregnation. This is applicable in various industries but is particularly prevalent in both the building materials industry and the food industry.

In the building materials industry, wood is commonly impregnated with various resins in order to imbue ductility, color, stress resistance, hydrophobic or dust-wicking properties. To do this, wood is first processed through a roller. This specific roller has spikes welded onto the roller so that it punctures the wood as it pushes through. The wood now has holes all throughout its breadth, which helps the impregnating agent to penetrat all the way through to the center of the wood, ensuring uniform intermolecular forces and a uniform tensile strength.

Vacuum impregnation as it relates to food products is still undergoing research. One report states the conclusions of experimentation on dewatered fruits and vegetables using vacuum impregnation. As the report states, impregnation is a useful tool for rehydrating and introducing healthy vitamins and minerals through liquid via vacuum impregnation after extended processing of the fruits and vegetables to lengthen shelf life.

Advantages of Dry Screw Vacuum Pumps

It is typically recommended that the loading chamber reach a vacuum level of approximately 23 Torr to be considered prepared for the impregnating agent flooding to occur. The average dry screw vacuum pump is able to reach up to  Torr, much higher than the former. This is partially due to the fact that the dry screw vacuum pump is designed to operate without any working fluid. This means that there is no limitation of vapor pressure to hold the vacuum level below high and ultrahigh levels.

The lack of a working fluid also translates into a lack of constant maintenance and changing, like with an oil-flooded rotary vane vacuum pump. This also means that there are no designated working fluid supply lines and no need for filtration and disposal treatment, like with a water ring vacuum pump. A dry screw vacuum pump does not have any grease inside of it that may emulsify with water and create sludge, hindering its performance or causing it to fail.

The dry screw vacuum pump is able to save much on operation costs. The dry screw does not need to run at the maximum rated RPM for vacuum impregnation applications. Thus, it lasts longer than if it were to be constantly operated at maximum recommended RPM. The dry screw vaacuum pump is designed to have a high suction capacity-to-power rating ratio, which translates to high-efficiency performance. It is also possible to configure the design with variable pitch, cutting down on both operation costs and environmental impact.

NES Company Inc. is proud to offer our NSP dry double screw vacuum pump series design. The NSP Series pumps are available with optional kits such as gas ballast kits and exhaust silencers kits for a pump that is specialized for each industry and application.

Although maintenance and repair can be quite involved with a design such as the dry screw, gas purging is easy and access to the pump chamber is widely available, making for quick and simple DIY repairs. To accelerate the simple repair process even more, NES Company Inc. offers spare parts kits for the NSP Series drys screw pumps.