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How to size the perfect decentralised flow valve

In large, complex plants a one-dimensional automation concept simply won’t cut it these days. Every part of the process, down to machine level, now has its own specific requirements. This is where an intelligent combination of automation concepts can truly provide the ultimate productivity and efficiency, especially decentralised valves and Proportional-Integral-Derivative (PID) controllers.

Decentralised automation involves using intelligent decentralised flow valves for all your production processes – providing maximum flexibility and process control. By integrating automation functions directly, via intelligent decentralised valves, you can completely eliminate the problems associated with centralised systems.

As such, you can minimise your plant’s cables and compressed air lines. Furthermore, by integrating an AS interface as a fieldbus interface, all that you will need for the power supply, feedback and communications is a two-wire connection, interfacing the PLC with up to 62 valves.

The benefits of installing decentralised valves are clear to see. But how do you then size the perfect decentralised valve for your flow control application? We’re glad you asked! Because we have the ideal solution. Read on to find out more.

How to size decentralised valves

Appropriate valve sizing is crucial, particularly in the case of a pressure reducing valve. Labouring under the misapprehension that sourcing the correct valve size is as easy as matching your chosen valve to the line size, particularly in relief valve or pressure reduction applications, can invariably lead to the specification of a valve that is too large for the application. Or else a valve that provides sub-standard performance.

However, you needn’t rely on guesswork to size your decentralised valve correctly. Here at Bürkert, we’ve developed a handy process valve selection and sizing tool to make your valve selection process easier and smoother than ever before. Our sizing tool enables you to calculate the flow coefficient Kv or Cv, flow or pressure drop for media from a large database and will match your operating conditions with a suitable valve model and size.

It’s as easy as that!

Benefits of a PID controller explained

As a means of further enhancing your decentralised valve processes, PID controllers can be an excellent addition to any closed loop operations. As the name suggests, PID controllers oversee proportional, integral and derivative control. As such, they manipulate various process variables, such as pressure, flow and temperature, to name but a few.

The feedback signal from the plant is compared with a set point or reference signal u(t) and the corresponding error signal e(t) is fed to the PID algorithm. According to its proportional, integral and derivative control calculations, the PID controller generates a combined response or controlled output, which is then applied to the plant’s control devices – including decentralised flow valves.

The Bürkert Type 8793 digital process controller features a PID controller which, apart from position control, can also be used to implement the aforementioned process control parameters by means of cascade control. Operated with a 128 x 64 dot matrix graphics display and a 4-key keypad, the Type 8793 enables you to calculate the position set-point value of the valve from the process set-point value and the actual process value via the control parameters.

The process controller is equipped with diagnostic functions to monitor the operating conditions of the decentralised valve, enabling you to programme your planned maintenance and optimise your plant availability. The pilot valve system can be used for single and double acting actuators. While the Type 8793 also benefits from a defined safety feature in case of failure of the electrical or pneumatic power, as well as an impressive air capacity range with pressure supply up to 7 bar.

For more information about sizing decentralised valves for your application, or about the Bürkert Type 8793 digital process controller, please contact our sales team today on +44 (0) 1285 648 720 or email sales.uk@burkert.com to discuss your specific requirements.

Type 8793

Digital electropneumatic Process Controller SideControl

Type 8793
  • Compact and robust design
  • Start-up via the TUNE function of the positioner and process controller
  • Integrated diagnostic functions for valve monitoring
  • Dynamic actuating system with no air consumption in controlled state
  • EtherNet/IP, PROFINET, Modbus TCP, PROFIBUS DP-V1 or Bürkert system bus (büS)