Hygienic Pumps Variable-Speed Hygienic Pumps in the Food & Pharma Industry Boost Process Reliability

Many industrial users are aware that variable-speed pumps, which automatically react to variations in demand, save a substantial amount of energy. It is less well known that pumps with electronic control enhance hygiene and improve process efficiency in the food and pharma industry.

Related Vendors

Maag Pump Systems AG

Donadon SDD Srl

ProMinent GmbH

Grundfos GmbH

Throttle or bypass valves are often used to regulate pressure and flow rates on hygienic pumps in the food & pharma industry. This is not the most energy efficient solution, and there are also hygiene and cleaning considerations which raise doubts about the effectiveness of this control strategy. Any flow control devices which are deployed to adjust the operating point (restrictors, flaps or throttle valves) place unnecessary stress on delicate products and make cleaning more difficult.

As a general rule, any additional apparatus which is used to control the pressure and flow rate of a centrifugal pump presents a potential biological hazard which has to be addressed when the production system is cleaned. High shear forces generated by greater rotational speeds may damage the product. Last but not least, more energy (i.e. heat) is transferred to the medium than necessary, and this is always undesirable due to the risk of microbial contamination.

Continuous electronic speed control avoids these problems. The best answer is a frequency converter which is built into the pump drive, such as the solution which Grundfos-Hilge offers on the majority of its pumps. This cost-effective, user-friendly, distributed design can be more easily tailored to the application than an external frequency converter. Simplified wiring and the elimination of a control cabinet reduce installation complexity. The pump drive can be configured to suit the user’s requirements, and it is ready to go as soon as it is wired up.

There is no need for additional controller setup. The performance and functionality of variable speed pumps are verified and documented. Connectivity to higher level control systems using analogue or digital interface technology is another advantage. Profibus-DP, Modbus-RTU and LONWorks modules will soon be available to support digital data bus communications.

Variable-speed drives enhance process reliability

Designing bus connectivity into the pump drive provides parameterization and data transfer functionality which supports centralized monitoring, control and visualization/recording of pump operating data. This information can then be used for intelligent integration of the pump into the production system to optimize the process flow.

• Protect delicate products: tailoring pump operation to match typical and actual system operating conditions minimizes degradation of delicate media.
• Reduce wear: detecting cavitation, pressure surges, overload, etc. and modifying the program sequence accordingly provides a means of avoiding these problems (thus reducing pump and system wear).
• Save energy: intelligent design reduces energy costs, and hydraulic energy is used more efficiently.
• Determine the optimum maintenance intervals: regular maintenance on high-wear parts in a centrifugal pump reduces susceptibility to failure and increases pump service life.

Standardization is a feature which system suppliers will appreciate. The pump as a component can be classified into (kW) performance ranges to support a variety of machine performance ratings. It is no longer absolutely necessary to define the exact operating point. Pump pressure and flow can be adjusted to match the system characteristic curve during installation. The pump manufacture can perform basic company or customer specific configuration or initial set up to reduce installation effort. Variable-speed pumps also have an advantage during the cleaning cycle in the food & pharma industry. Pumps running at maximum speed deliver sufficient volume flow for CIP.

Practical example 1: filtration systems

Pressure differential tends to increase over time on filtration systems, and this parameter normally gives an indication of filter degradation. If the volume flow must be maintained at a constant level, a flow meter is installed to detect the actual state, and pump speed is increased as necessary to compensate for rising counter pressure. The pumps can also compensate for changes on the suction side, for example when the medium is supplied from another tank with a different suction head.

Engineers select a centrifugal pump which can cope with maximum demand, but the pump runs in the partial-load range during virtually the entire filtration process. Without a frequency converter, regulation would have to be provided by throttle or bypass valves. Pumps without electronic control operate at the full rated speed, placing unnecessary stress on the medium. Shear forces are generated in the pump and the throttle valve, degrading both product quality and filter performance. Heat energy is also induced into the medium, high noise levels make the working environment less pleasant and correct dosage of filtration agents becomes more problematic (reduced filter service life). (See next page to read about Practical example 2: applications with discharge points.)

Practical example 2: applications with discharge points

Demineralized water systems normally have multiple discharge points. It is unlikely but not impossible that all taps will be opened at once. The minimum volume flow, which depends on the pipe cross-section and flow rate, must be added to the maximum discharge volume to prevent the risk of microbial contamination in the return flow. Pressure-controlled pumps can detect circulation, partial discharge and full discharge states and continuously regulate hydraulic output. A pressure sensor indirectly detects the flow rate in the return line. As the discharge rate varies, no more energy is applied than is necessary to pump the medium. Unregulated pumps have excessive hydraulic output which is ultimately converted into heat. Besides wasting useful energy, heat can cause problems at the biological level, and heat exchangers may be needed in the circuit to alleviate these problems.

Optimal solution: variable-speed high efficiency motors

The Grundfos range of electronic pumps is based on the MGE motor (Motor Grundfos Electronic) which the company developed and now produces in house. The variable speed motor, which is based on the EFF1 high-efficiency motor, has a built-in frequency converter and a PI regulator with specific pump functions. The pump, motor, frequency converter, sensor, application software and regulator are guaranteed to work flawlessly together, because they all come from the same source.

Grundfos has updated its 11–22 kW MGE motors, and the range now extends from 0.37 kW (single phase) to 22 kW (3 phase). These motors will be available on Hilge sterile and hygienic pumps in the 11–22 kW range starting in the spring of 2009. A number of new features will be added to the existing functions and control options. To cite two examples for large e-pumps (11–22 kW), the pumps have a built-in heating unit which prevents condensation from forming in the motor when it is not running. The pumps also feature a motor bearing monitoring function.

Compared to pumps with a separate frequency converter, e-pumps with an MGE motor offer the following advantages:

• full system integration;
• fully assembled unit delivered ready to install; as easy to install as fixed-speed standard motors;
• very rugged design, because no additional cooling fan is needed for the frequency converter;
• low cabling costs—no shielded cable and no additional filter between the frequency converter and the motor;
• compact design, no control cabinet/switch room or wall space requirements;
• fully compatible components—one product, one supplier and the expertise of a single professional partner.

In practical application, MGE motors have the advantage that an electrician can access the software and make modifications which may necessary for another controller. Also, the drives are very quiet because the clock frequency is outside of the audible range. The motor is protected against splashing water (which is of course an important consideration in the food & pharma industry).

MGE motors are available on the Hilge range of hygienic and sterile pumps (e.g. Euro Hygia, Contra and Maxa), the traditional range of Grundfos multi-stage CR, MTR and SPK pumps, single-stage TP pumps and single-stage NB and NK standard end-suction pumps. If an integrated frequency converter is not suitable for the application, the Grundfos CUE series offers an external frequency converter solution in the 0.55–250 kW range for wall (IP 54) or control (IP 20) cabinet installation.

Summary: Frequency converters turn pump drives rated at up to 22 kW into intelligent, adaptive pumping systems, which offer a number of user benefits. They help improve hygiene in the food & pharma industry, and they also enhance process reliability. Automatic speed control in the pump drive minimizes energy transfer to the medium (saving money and preventing product degradation). The elimination of flow control elements (restrictors, flaps and throttle valves) on the pump pressure side reduces product degradation to an absolute minimum. Pumps with frequency control also reduce wear and increase reliability and service life by avoiding pressure surges and cavitation effects which lead to material fatigue.

S. Gögl is Beverage/Industrial Division Sales Manager and Markus Reichling is Bus Communications/Controls Product Manager at Grundfos GmbH, Erkrath/Germany.

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