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Pneumatic conveying pumps for sale

Any pneumatic conveying system, complete with valves and filters connected by piping to silos and hoppers, must be designed according to the customer’s production requirements and the conditions in which it will operate. The design must also address to the heart of the system, the component that will make the whole system work, the element responsible for moving air or gas.

Whether it is a pump or a blower, a vacuum generation system, a turbine or a compressor, the choice of this component must be made critically and carefully. Determining flow rate, final pressure and motor power is one of the main aspects that engineers must take into account when studying a new design. Let’s take a look at the criteria for selecting and sizing pumps for a pneumatic conveying system.

How does vacuum pneumatic conveying work

Essentially, it can be seen as a continuous alternation of material suction cycle and material discharge cycle. During the suction cycle the material is taken from a container and transported through pipes into a hopper: when this is full the suction cycle stops and the material is unloaded at the point where it will be used. The cycles duration can be regulated by a sensor that detects the hopper fullness or by a timer regulated according to the capacity of the system.

Why do we talk about pneumatic vacuum conveying?

Because the hopper is connected to a pump that “sucks in” the material, creating a vacuum inside the pipework. What conveys the material particles is the air flow generated to balance the pressures. The vacuum generator, be it a pump, a blower or a unit, will be chosen according to the product to be conveyed and the technology used to load that type of product.

There is a further element to consider: the filter.

It is installed inside the hopper and prevents dust and material particles from entering the pump and being discharged outside. Bag or cartridge filters protect the pump and keep the environment healthy. We said that when the material reached certain level in the container, the vacuum pump stops, the discharge valve or clapper opens and the material is discharged.

At the same time as the discharge, the filter is cleaned. This can be carried out mechanically by means of a vertical piston that moves the filter and scrapes off the residue, or through compressed air released from a special tank. Failure in filter cleaning would, over time, lead to clogging, air flow blockage and consequent stoppage of the system.

Types of vacuum pneumatic conveying

Vacuum pneumatic conveying can be divided into two main types, dense phase and fluidized phase, both requiring different pumps or blowers and sizing. One phase or the other is chosen following the designer’s experience, the intrinsic characteristics of the product and its behavior during transport. Consider, for example, the great differences between a plastic granule and a powder such as talc.

In the fluidized phase, the tube section is occupied by 15/20% of the material and the vacuum is around 20/30%, adequate for low specific weight materials. On the other hand, in dense phase the section is almost completely occupied (90/95%) and the vacuum is very high (70/80%); since the vacuum refers to air quantity, smaller section pipes are used. These macroscopic differences alone show how the maximum transport capacity of a pneumatic system is obtained with a specific air flow value: beyond this value, even if the flow increase, the transport capacity deteriorates.

The involved pressure values are fundamental to choose of pump. Calculations always refer to atmospheric pressure, which at sea level is around 1000/1013 mbar. A vacuum percentage of 70% means that the vacuum inside the line will be around 300 mbar relative to atmospheric pressure.

When to choose the dense phase and when to choose the fluidified phase

The high vacuum values involved in dense phase pneumatic conveying mean that the material is “torn” with force and travels in blocks inside the pipes. With transparent pipes, you would see blocks of material alternating with spaces of air, moving towards the hopper. This tear-off force is more suitable for materials with higher specific weight. In addition, this method ensures that the material on arrival is exactly in the same composition as it was originally.

You mean that pneumatic transport in the fluidized phase changes the material?

Exactly. In some situations this can happen. One case is the pharmaceutical sector, where substances have to be transported to compactors, i.e. automatic machines which, transform powders in pills. Obviously, these powders are not homogenous, but composed of different particles and in extremely precise doses, depending on the medicines recipes. Multi-component materials, made up of powders with different diameters, if transported in a fluidized phase, would arrive de-mixed at the hopper, first the lighter parts and then the heavier, with harmful consequences for production. Another case is the ceramics sector with mixtures for tile manufacture. If applied fluidized method, the tiles characteristics would be very different from each other.


What is the best vacuum pump?

Depending on the chosen pneumatic conveying phase, Apply suggests the best type of pump. For the dense phase, dry vane pumps or rotary claw pumps are often used. Both achieve high vacuums up to 90% with air volumes from 25 to 200 m3/h. The claw pumps do not have vanes on the impeller but two shafts where two bodies rotate, called hooks because of their shape, which compress the air without touching each other. This technological difference leads to higher costs for claw pumps, but is compensated by lower maintenance and better performance stability over time.

When a pump has graphite vanes, which rotate in contact with the chamber, graphite powder is released. As it wears away, it loses efficiency and requires more maintenance. So why use graphite? Because its powder has an essential lubricating function, that in other types of pumps is performed by oil rings. In the latter case, the vanes can be made of bakelite or stainless steel. Note that oil ring also provides vacuum seal.

Which pump should be used for the fluidized phase?

Vacuum generators are needed to guarantee a large amount of air in relation to the vacuum obtained. This is why side channel, single or dual stage blowers are almost always used. To make a comparison also in terms of energy, a blower with 3 kW power generates more or less 300 m3/h and a 20%vacuum, a vacuum pump of the same power runs on 80 m3/h with 80/90% of vacuum.

A last economic comparison concerns filters: with less air or gas flow, filters with smaller cross-sections can be installed: they cost less and also clean more quickly.

A wide range of pumps

Pneumatic conveying can be useful in so many industrial applications, in both large and small companies; a good investment to gain a competitive advantage over competitors and to optimize production. Such a wide variety of fields of use is reflected in a considerable range of available pumps, allowing to always find the optimal solution related to what you want to achieve.

Apply is a strong point of reference in the field of pump sales, thanks to our technological expertise, in-depth knowledge of the pumps available on the market and constant side-by-side work with our customers. When buying pumps for specific applications, requirements can vary considerably. The main factor may be energy saving, small footprint, dry pump, low cost or low noise. In all cases we offer a wide range of technologies to choose from. Whatever pump you need, we guarantee its safety, robustness and reliability.

Ancillary services

Apply can provide you with maximum support at every stage of the pump life cycle. Our engineers can study your requirements and advise you on the types of pumps that will meet your needs. Our sales staff will be on hand to make a cost-effective and competitive offer, taking into account individual cases.

On request, our technicians will arrange for the pump to be assembled on site, to be integrated with other machines, whether for pneumatic transport or not, and also for various function tests. For a truly all-round service that frees you from any worry, our company is also prepared to offer you a comprehensive after-sales service. We are able to take care of all the necessary maintenance, scheduled and unscheduled, both on pumps sold by us and on those sold by third parties.

Apply’s mobile workshops guarantee a rapid response, nationwide and for any problem that may arise. We also offer our customers a pump rental service, which is useful, for example, for temporary increases in production, to quickly solve serious breakdowns in your pumps or for those who do not wish to invest in purchase.