Some years ago, AxFlow Poland was approached by fruit and jam concentrates producer Zentis, to provide pumps for a test mixing station at the University of Olsztyn. The purpose of the test facility was to check mixing conditions, pump speed and the sizes of various fruits and two pumps for dosing fruit and yoghurt were supplied by AxFlow to the University's Food Processing Faculty.
The pumps supplied for the Zentis mixing stations were the Waukesha Universal II models and in the intervening period, this pump type has become standard on all Zentis fruit yoghurt mixing stations. "The size and capacity of a mixing station varies according to the packaging machines installed in the dairies, but the most common size offers a capacity of 1000-6000kg of finished product per hour," reports AxFlow Product Manager Tomasz Jasinski. "Each mixing station contains two Waukesha Universal II pumps, one for yoghurt and one for fruit. Typically, the fruit pump has a capability to handle between 50 and 1500kg/r at 10000cPS and the yoghurt pumps have the capability to handle 750 – 5700kg/hr at 100cPS."
In order to prevent damage to the fruit, the 18Universal II pump is normally specified and run at speeds between 7 and 70rpm, depending on the dosing requirements. For pumping yoghurt, the preferred pumps are the 30Universal II and the 40Universal II, and these are run at speeds between 250 and 300rpm. Typically, pressures do not exceed 4 bar, but in certain special cases where high pressure buffer tanks are required, the preferred choice is the 45Universal II pump. All the Universal II pumps are of the standard construction with TC/SC faces, FKM Elastomers, flat body profile and have a maximum temperature tolerance of 104ºC.
The Waukesha Universal is a rotary piston pump that employs an operating principle known as the external circumferential piston (ECP). In this design the arc-shaped rotary pistons, or rotor wings, travel in annular-shaped cylinders machined in the pump body. The resulting long sealing path reduces slippage and produces a smooth product flow without destructive pulses or pressure peaks, and without the need for valves or complex parts.
However, unlike progressing cavity and rotary lobe pumps, the Universal pump is not adversely affected by varying or viscous products even with large particles that may settle in the pump. Because the rotors of the Universal Series ECP pump produce a scooping action, they do not squeeze and compact the medium being pumped.
The Waukesha Universal ECP is ideally suited to the dairy products industry because it can handle sensitive materials without causing any damage to the pumped product. It combines a very gentle, pulse-free pumping action with the high suction capacity necessary for allowing the thicker liquids to be drawn into the pump without any separation of the ingredients. The pump uses double '0' ring self-lubricating sealing system for all applications, which allows high vacuum to be developed on the inlet side.
Manufactured from stainless steel and suitable for CIP cleaning, the pump's close clearances allow the pumping of water against back pressures, whilst its simple design enables operators to completely strip it down for inspection in situ without the need to remove connecting pipework. Where high viscosity fluids and solids are involved, the large fluid cavities of the rotors, together with the large easy-entry anti-cavitation ports enable efficient pumping.
The success that Zentis has enjoyed through its association with AxFlow and the Waukesha UII pumps has not gone unnoticed as more recently this pump type has been applied for a new line of mixing stations for fruit, cottage cheese and high fat cream. Where these mixing stations differ from those dedicated to fruit yoghurt is that higher pressures are required to handle the high viscosity of the cottage cheese.
Initially Zentis looked at using progressive cavity and lobe pumps for the cream, but trials showed poor results. Using the 30 Universal II, the parameters of the final product and level of control were in the range acceptable to the customer.
"To dose cream at high pressure we have to increase the pump speed to compensate for the slip associate with low viscosity," says Tomasz Jasinski. "However, we have to limit the speed to 150rpm in order to avoid making butter in the pump. Should butter be produced, then all clearances are closed and we are able to achieve the flow required, but in that situation the user encounters other problems. These include changes in the final fat content and unstable dosing because it is necessary to flush out the butter from the clearances."
As a result of working in close collaboration with Zentis in equipment trials and demonstrating that Waukesha Universal II pumps provide the best possible solution for these applications, AxFlow Poland has now provided pumps for Zentis mixing stations that are in use all over the world.