Walkers Nonsuch of Stoke–on–Trent has installed six Waukesha Universal 1 Series rotary piston pumps from AxFlow to replace rotary lobe pumps that were plagued by mechanical seal failures.

The company has been making traditional toffees for more than 100 years and exports its confectionery to more than 35 countries.

Walkers Nonsuch switched to the Waukesha pumps after consulting AxFlow, the UK distributor for the pump brand, about the sealing problems that it was experiencing with the existing rotary lobe pumps. “There were two reasons why the Waukesha pumps were selected, the first being down to efficiency of the design and the second was the elimination of replacing mechanical seals,” said production director, Edward Walker.

“It was costing us around £2,000.00 every time seals needed replacing. The attraction of the Waukesha pump is that it contains a self-lubricating double ‘O’ ring seal, so the problem of costly mechanical seal failures is eliminated. In reality, the initial outlay on a new pump can be recovered in around a couple of years.”

The Waukesha Universal 1 Series 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 that may settle in the pump. Because the rotors produce a scooping action, they do not squeeze and compact the medium being pumped.

The Waukesha Universal 1 pump is ideally suited to confectionery manufacturing because it can handle both thick and thin fluids 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 thick mix 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, while 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. Maximum service life can be achieved even under severe operating conditions where fluids are non-lubricating or abrasive because there is no contact between the bearings and the pumped fluid, nor is there sliding or rolling contact and rotor-to-rotor contact.

According to Edward Walker, it is now about two years since the first of the Waukesha pumps was installed and following on from the success of the pump the other five units have been installed as required. Should there be a need to shut one of the Waukesha pumps down, it can be quickly removed and flushed out in a very short period of time in situ.

“When you are making up to as much as 40 tons of toffees a week and having to satisfy orders from customers from all over the world, minimising downtime is a key issue,” commented Edward Walker. “The removal of the old pumps and their replacement with Waukesha Universal 1 Series pumps has removed the uncertainty and costs of mechanical seal failure, and at the same time is contributing to efficiency.”