Take the plunge

Jon Lawson

Jan Sprakel explains how plunger pumps with new drive technology enable high pressures to be produced efficiently

Pumps are one area of process technology that is ripe for technical development.

Responding to the need for progress, one pump expert has fundamentally revised the mechanical powertrain of its triplex plunger pumps for pressures up to 3,500 bar.

In combination with an appropriate variable speed control, in particular, these new pumps allow considerable gains in efficiency and energy savings to be achieved.

The ‘classical’ design of Kamat plunger pumps, with their undivided pump housing, has stood the test of time in many different high-pressure technology applications (up to 3,500 bar). They have also been adapted in various ways to meet the different requirements of users.

As positive displacement machines, these pumps also offer a very high degree of efficiency.

For this reason, they open up new areas of application beyond the usual target branches of industry, such as mining, water jet and surface technology. In chemical and process engineering, for example, plunger pumps are increasingly substituting centrifugal pumps and make it possible to achieve some considerable energy savings, starting already in the 80 to 100 bar pressure range.

Plunger pumps are also increasingly being used in areas that were previously occupied by expensive diaphragm pumps.

Users in these areas are placing higher demands on the quiet operation of high-pressure pumps. This requirement was difficult to achieve with the existing drive concept used in Kamat pumps, because the crankshaft – which moves the plunger via crossheads – had to be asymmetrical, to fit it into the undivided housing.  As a consequence of this asymmetry, a lot of vibration and a high noise level were produced, making it difficult to decouple the damping elements.

This explains why Kamat decided to re-design the transmission. The objective was to achieve a reduction in noise and - at the same time - values at least as good as for all other characteristics of the previously tried and tested concept in the past, such as the ease of servicing, durability and energy efficiency.

New transmission from its own production

This goal was achieved using a bisected housing, where a symmetrically balanced crankshaft is responsible for the power transmission between the gearbox and the plungers. A newly designed double helical gearing also contributes to the increased running smoothness of the pumps. All component parts are produced in-house.

The new construction has been successively rolled out over the past few years in the form of the triplex pump programme, with power ratings ranging from 80 to 800 kW. This also forms the basis for the drive construction of the quintuplex pumps, which the company has now developed ready for serial production, enabling considerable cost savings for users of large volume flow pumps.

The mechanical part of the drive system creates the prerequisites needed for the variable speed control of the pumps. The large-dimensioned crossheads are part of the construction details of the power transmissions, which exerts a lower surface pressure. They allow excellent hydrodynamic lubrication of the pump transmission where most of the load arises, even at low speeds, i.e. low rotational speed.

For this reason, a Kamat plunger pump can work with full rod force at rotational speeds ranging from 10 to 100%. It is therefore able to adapt very well to the volume flow required at the time.

The control makes the difference

These pumps can now be used as the appropriate basis for setting up a highly efficient regulation system. If two high pressure pumps are used, the speed of the master pump is controlled via a frequency converter.

As soon as the demand exceeds the delivery capacity of the master, the basic load is taken over by a slave pump. Thus, a single speed-controlled pump will suffice and at the same time cover a very large range to be regulated, which represents a quite considerable cost advantage.

Another very important factor is the type of regulation, more specifically achieving appropriate control of the flow rate. Bypass valves are used here as a standard solution, which work using a ‘black and white’ technique and either guide 100% of the flow rate to the consumer or to the tank. In practice, this can be achieved three times in 10 seconds and - considering the high pressures and high flow rates - places a very considerable stress on the entire system: almost like an endurance test for pump, piping, valves and tank.

Kamat is able to control variable pumping stations far more elegantly via a pressure sensor and a frequency converter. The bypass valve does not have to be able to switch over to adjust to the rate of flow. This has been shown to reduce wear and tear by about 90%, which considerably reduces costs and increases the availability of these pumps.

Designed for rough operating conditions

Other characteristics of these plunger pumps include their ability to operate horizontally and vertically.

The ductile cast iron housings can be used for a wide temperature range and the user can expect a long service life, even under extreme environmental conditions. All models comply with common international pump standards and are optionally available in an ATEX version. They are also suitable for pumping corrosive, abrasive and volatile fluids.

With this range of properties, the new drive concept offers customers clear advantages in terms of efficiency, service life, servicing, total cost of ownership and, of course, noise level.

These benefits are increasingly being valued in the process technology sector.

The pumps can be used, for example, in high-pressure homogenisation (up to 3,500 bar), in gas washers, to remove deposits using water under pressure and in reverse osmosis systems, and in this case distinctly lower pump-related operating costs – thanks to the principle they use of high efficiency, as well as their extremely robust construction and very good controllability.

Jan Sprakel, is managing director of Kamat.

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