Wet running pump sets new standards

A breakthrough in the technology of wet-running pumps, Wilo Salmson Pumps has applied the principle of the permanent magnet motor, which saves a great deal of power, to pumps in which water flows continuously through the motor. The new pump, which was launched in the UK in January this year, can be used in heating and air conditioning systems. And, as Gary Wheatley, technical director at Wilo Salmson UK claimed: "The pumps can reduce power consumption by as much as 20 to 30% in comparison to conventional pumps." Wilo developed the first circulating pumps for domestic heating systems back in 1928 and is now one of the leading pump manufacturers for the global HVAC (heating, ventilation and air conditioning) market. The new pump design, Stratos, although originally intended for the HVAC market is equally suitable to other industrial applications. In fact, as Wheatley explained: "The pumps are suitable for any heating application that requires a variable demand in terms of head or flow and that delivers water at a given pressure." He cited car production, the food and beverage industry and pharmaceuticals as potential areas of interest. General manager for the business division of Big Circulators at Wilo, Dr Holger Krasmann, described the Stratos pump as: "We have now crossed the threshold to a completely new technology." The basic development, according to Krasmann, has long been pointing down this road. He said a team of Wilo engineers worked for three years in order to get the pump into series production status. Although the idea of using permanent magnets in motors is not new, applying the principle to wet-running pumps is. First, there was difficulty in transferring this principle to the heating pump, whose motor area must normally not come into contact with water. The really clever solution, said Wheatley, was a sealing system to the stator area. Although he declined to reveal to Eureka the exact method of sealing, he did say that Stratos uses a plastic aperture tube (instead of a plain metal version). The motor, rather than having a full stator, has six stator poles and four rotor poles that have field coils so the rotor is permanently excited. The water that flows through the motor has two functions: first, to lubricate the bearings and second to cool the system by dissipating heat away from it. Normally, a stainless steel can would be used to separate the rotor from the motor windings, but Wilo designed the Stratos from an advanced carbon fibre composite. The result is an obvious reduction in eddy current losses due to the non-metallic can – and hence the lower power consumption figures. Wheatley continued: "We had to think outside the box and this is where the use of 3D CAD software [Autocad from Autodesk] really helped us with the design and development of the sealing lip, 3D impeller and 3D spiral within Stratos." Krasmann made a bold statement about future opportunities for the pump on the world market: "There is no comparable product. Within a period of five to eight years, this new type of wet-running pump will replace all previous types of electronically controlled pumps. A plus for the environment and the operator."