Waukesha U2 Pump Assembly with By-Pass and Pressure Relief Valve

Cleaning in place (CIP) is a now commonplace in almost all food, beverage, and pharmaceutical production plants. The highest standards of plant hygiene are an essential prerequisite for the production of any product made for human consumption. The Society of Dairy Technology defines CIP as:

The cleaning of complete items of plant or pipeline circuits without dismantling or opening of the equipment and with little or no manual involvement on the part of the operator. The process involves the jetting or spraying of surfaces or circulation of cleaning solutions through the plant under conditions of increased turbulence and flow velocity.

That being said, some pieces of equipment are harder to create “increased turbulence and flow velocity” through. One of those pieces of equipment is the ECP style PD pump.

Why is this? A lot of it has to do with a general conflict of purpose.  Sanitary ECP pumps must have close clearances for good pumping performance (low slip). These close clearances create problems for CIP chemicals that require full access to all product contact surfaces. Close clearances restrict access of cleaning solutions to certain product contact surfaces and prevent adequate cleaning, especially with “hard to clean” products and products with small particulates, such as small seeds and stringy meat.
Sanitary PD pumps are also generally run slower than their centrifugal counterparts. This is great for thick, viscous products that require a high level of torque, but often prevent the pump that handles your tomato paste from propelling your cleaning solution at the requisite 5 ft/second velocity.  This is why sanitary PD pumps are not generally used for a CIP supply pump. In many circumstances, it just isn’t practical to ramp up rotary pump speed to clean the rest of the system.

How can we combat these roadblocks? The first thing we need to address is pump design. Waukesha offers “CIP versions” of the Universal 2 pump. This includes perforated rotors that allow passages for cleaning solutions and a flat body profile to allow full draining when mounted in the vertical position. We also need to operate the pump during CIP to promote scrubbing and turbulence.

Certain system design considerations must also be taken in to account to allow for effective cleaning of a sanitary PD pump. First, you need to be able to create differential pressure across the pump to obtain more flow through close clearance areas. We can do that using a W68 Waukesha throttling valve that can be alternately pulsed providing pressure for pump cleaning and flow for line and system cleaning.

Even with the pressure differential, the sanitary PD pump can act as a dam, preventing effective cleaning of equipment downstream. This makes the use of a bypass loop essential. One way to accomplish this is with a removable jumper around the pump that utilizes an orifice to create differential pressure. By throttling the bypass flow, the inlet pressure is higher than the discharge.  Another way to accomplish this is with the use of a permanent jumper to create both a pressure relief and CIP bypass leg. With the use of a W63  Waukesha valve at the inlet of the pump, we have a pressure relief valve during production. During CIP, the valve is opened to bypass excess CIP. A second valve, a W68 valve, is then used to provide backpressure during CIP. This combination is a zero dead leg solution to pressure relief and bypass.

To conclude, good cleaning is the result of sanitary pump design, CIP program, and system installation and design. The pump design provides access for cleaning solutions to all product contact surfaces, but the CIP program and installation must also be adequate to ensure cleaning. Before you select your next sanitary pump, take these factors into consideration and ensure both effective product handling and system cleanability.
Holland Applied Technologies