Plant & Works Engineering May 2022

24 | Plant & Works Engineering www.pwemag.co.uk May 2022 Energy & Environmental Management Focus on: Boilers, Burners & Controls product with a higher cost of production. If the configuration is too small, the valve has an inadequate flow reserve, recommended to be a minimum of ten percent, and therefore cannot offer the required control reliability or flexibility. Ultimately, if the valve is too small, it might not be possible to provide the desired flow rate and achieve the required temperature change. Alternatively, if the valve size is too large, the system can face challenges maintaining the set temperature. With an over-sized valve, during heating it is nearly fully open, but to stop increasing the temperature and maintain the level, it has to be nearly fully closed. This way, an over-sized valve is too large to achieve the required precision, and temperature fluctuations result with an oscillating effect as the valve repeatedly attempts to compensate. Choosing valve type Where precision control of steam is required, a globe valve provides the greatest accuracy. While allowing a moderate flow of 13 m3/h, a globe valve ensures control accuracy to +/- 0.5 - 1.0 °C. In combination, Bürkert’s piston actuators for example, provide positional accuracy to within 0.1%, ensuring optimum control for steam and wider application types. For some applications, this level of accuracy isn’t required. For example, at a particular dairy, steam is used in cheese production. The condensate from the boiling process is used to heat a secondary water supply for a staff washroom. The required temperature is approximately 60°C, but a difference of several degrees either way is not significant. In a case like this, to save costs, a ball or butterfly valve can be used. Offering accuracy of +/- 5°C, which may be sufficient for more general temperature control purposes, a ball or butterfly valve provides full flow of 48 m3/h, which could be advantageous, depending on needs. For hygienic applications however, where it’s a requirement for the media to be separated, a diaphragm valve should always be used. Bürkert provides stainless steel valves and actuators, robust and suitable for clean-in-place (CIP) applications. In addition to the valve, the positioner, which is in-built on Bürkert valves, can also help reduce costs for steam control applications by taking load off the PLC. With a decentralised control concept, the Bürkert valve’s positioner receives the signal from the temperature transmitter and directly controls valve actuation. This way, the role of the PLC is reduced to monitoring purposes, meaning that for new applications a lower specification PLC can be used. For existing systems, the PLC’s spare processing capability can be used for additional tasks. Regardless of the valve, actuator or positioner used, to optimise efficiency and performance in steam temperature control, the application has to be specified correctly at the outset. For a food and beverage production facility, it’s vital that your valve supplier provides this service. * Kieran Bennett is Field Segment Manager, Hygienic-Food & Beverage at Bürkert E-learning Classroom based “Live” webinars On-site courses Tailored op琀ons For more informa琀on call 0121 601 6691 scan code for the training guide or email: training@bpma.org.uk Independent Pump Training from