The decentralised alternative for steam control valves

New Food editor Helen Difford spoke to Bürkert Fluid Control Systems’ Steam Segment Manager and New Food blogger Greg Sutcliffe regarding Bürkert’s new ELEMENT range of process control valves.

Greg, Bürkert are introducing a new range of intelligent process valves to the food and beverage market. What industry needs do these valves meet that others may not?

“Hygiene plays a key role in the production of food and beverages in the process and plant area. With companies who compete in the global markets being forced to make production processes as economical as possible, there is an increased demand for automation solutions at the process level. Intelligent process valves with integrated automation functions offer a more viable and efficient alternative to the conventional approach of centralised automation. With a decentralised system, only control and status monitoring are handled by the central process control system. At the field level, pneumatically operated process valves are used and can be equipped with automation components such as pilot valves with manual actuation, electrical feedback units and optical status indicators, field bus interfaces and even positioners and process controllers.”

New Foodworks closely together with the EHEDG (European Hygienic Engineering Design Group). Has the new range been designed with EHEDG guidelines in mind?

“The simple answer is yes! The valve systems themselves have been designed in accordance to the EHEDG guidelines for hygienic design and easy cleaning. They also feature the high IP protection required for the actual applications and are made exclusively from detergent-proof materials, which prevents it from being affected by long-term use in ambient conditions with high air humidity or frequent wash-down cleaning with aggressive chemicals and high temperatures. When you compare them to conventional automation solutions, these features mark real progress for improved hygiene.”

How hygienic, easy and safe are the valves to install?

“The valves require only minimum space and can be easily installed in the pipeline system of the plant. Since they are made with extremely resistant materials, they’re easy to clean and provide maximum availability, thanks to excellent functional safety. This is achieved by the integration of the control air supply to the actuator chambers, which ensures that the spring chamber of the pneumatic actuator is supplied only with pure and clean control air. This prevents moisture, dust and contaminants in the ambient air from entering the actuator units, which in turn effectively prevents contamination of the piston seals and corrosion of the drive springs caused by cleaning solutions entering the housing. There is also no risk of moisture from the spring chamber entering the feedback module or the control head along the spindle extension. Not only does this significantly prolong the service life of the actuator, it also enhances the hygiene of the process. As product can’t enter the spring chamber, both the spreading of the germs and contamination of the inside of the actuator by mould is effectively prevented. This means that there is no risk of fungal spores produced in the spring chamber being ejected into the ambient air at each switching process, which is a common problem with conventional actuator design.

The control unit housing is flushed with control air at each switching process as some control air is fed through the pilot valve. This means that, upon switching, a small volume of control air enters the housing. This process takes less than 10 milliseconds. As a result, a slight overpressure is built up in the housing, further improving its IP protection and preventing the penetration of humid air, for example in the event of changes in temperature or rinsing with cold water. The integrated pressure-relief valve ensures that the pressure in the housing is automatically reduced, if it reaches a value of approx. 0.5 bar, which can be the case after several switching processes. Through this combination of control air inlet and release, a constant overpressure is maintained inside the housing, while a certain volume of air is regularly replaced. This ensures that no condensate can build up inside the housing. In a similar manner, digital electropneumatic positioners and process controllers can also be upgraded to complete control valve systems. The control valves thereby meet the same stringent hygiene standards as the process valves and come with air supply to the spring chambers as standard.”

How viable are the new range of process controls for the food and beverage industry?

“Decentralised automation systems have become a viable alternative to control cabinet systems with the development of practical solutions that integrate automation functions into pneumatic actuators of process valves. They allow food and beverage manufacturers to reconcile the commercial necessity for a high degree of automation of production with hygiene and safety. The modular structure of systems based on intelligent process valves ensures that they can be adapted according to the actual situation and application, whereby such optimised solutions are always based on high-quality, tried and tested components with a long service life.”

And specifically for steam applications, what features have Bürkert included to make life easier?

“Our steam experience drives us find solutions to meet the application realities. In providing practical solutions for the steam applications we face, we have introduced some cute features to set us apart.

Each globe valve body is offered with at least three valve trim set options. These parabolic trims provide the user the choice and flexibility to change the trim at a later date if the process conditions change, but also allow you to fit ‘line-sized’ control valves with reduced trims, reducing the work needed on site during the valve installation.

Saturated dry steam is in itself not especially abrasion, but this assumes a 100 per cent dryness fraction, meaning no condensate present. Our control valves are made from cast 316L stainless steel, which not only sits very well in a food and beverage environment, maintaining a great long lasting exterior look, but it offers greater shock resistance to impact from water hammer.

Another big issue that valve users face is the problem of ‘wire-draw’, the action of condensate cutting a groove through the valve trim, particularly prevalent when the plug and seat spend long periods together. Bürkert offer as standard the ‘Cut Off’ function, an adjustable automatic closing function if the valve position is less than 10 per cent open, for example.

With a steam application in a food and beverage plant, the three things you will find for sure are humidity, heat and product. Our Element process and control valves are constructed from clean stainless steel and temperature resistance PPS, durable and tough enough to live in this demanding world. The internal routing of the air channels and stroke position feedback means that we avoid the clunky and cumbersome external linkages, connections and sliders found in more conventional general purpose control valves, thus removing as much as possible, places where product can sit and attract unwanted attention!”