Automation for modern compliance and reporting in additive processing
03/05/2012 - Automation solutions increase efficiency and repeatability in hygienic processing systems - which are subject to ever-increasing levels of compliance and reporting - for food, beverage, dairy, sodas, meats processing. Chris Hoey
In the production of food and beverage additives such as concentrates and flavours, excellent process hygiene plays a key role.
This is enforced in Australian and New Zealand by stringent specifications and governmental regulations aimed at protecting consumers, with many companies working to HACCP.
Companies operating in the competitive global market are also forced to make production processes as efficient as possible.
Combined, this has led to an increased demand for automation solutions at the process level. However, process owners are increasingly finding that conventional centralised process automation incapable of meeting ever-stronger industry requirements.
Intelligent process valves with integrated automation functions offer a viable and efficient alternative, driving efficiency and delivering the reporting capability necessary for HACCP and other compliance standards in modern processing environments.
In the field of process valves, conventional automation solutions including control cabinets with valve terminals, I/O systems and fieldbus interfaces normally require costly hose connections and wiring. Valves are connected to the central control unit through a large number of long control air lines and discrete feedback connections.
In addition to high planning and installation cost, such solutions are not entirely without problems as regards hygiene.
A recently upgraded plant for fruit juice concentrate and other basic food and beverage ingredients demonstrated a better way: the new facility includes intelligent process valves from the fluid technology specialist Bürkert.
These valves are used by the drink manufacturer across the entire production area, with the company opting for automation by means of decentralised control head solutions with ASi communication.
In addition to hygienic seat valves and butterfly valves controlling the product flow, all on-off valves of the auxiliary circuits for water, steam, sterile air and cleaning are also automated in a decentralised manner by means of intelligent valves.
In contrast to control cabinet-based automation concepts, the only tasks left to the central process control system in Bürkert's decentralised solutions are control and status monitoring.
At field level, pneumatically operated process valves are used. These can be equipped with all required top-works, including pilot valves with manual actuation, electrical feedback units and optical status indicators, fieldbus interfaces and even positioners and process controllers.
Less cabling – greater transparency
Decentralised automation of the control system for production and auxiliary processes proved extremely reliable at the plant, so the company rolled the concept out to new plant sections being installed for an extension of production facilities.
Today, the raw product intake unit, homogenisation and pasteurisation stations plus raw product distribution system featuring valve nodes are equipped with intelligent process valves from Bürkert.
Angle seat and diaphragm valves control the flow of cleaning media, including acid, alkaline and water as well as the steam and sterile air supply. All drivers are equipped with an ELEMENT control head with integrated automation functions plus ASi for communication via fieldbus.
Thanks to the integration of the field bus interface, the advantages of decentralised automation can be utilised to the full. All that is required for power supply, feedback and communication is a two-wire line connecting the PLC with up to 62 valves.
Each process valve is individually connected to the main compressed air supply line installed in the field, whereby these connections are kept as short as possible.
This reduces the number and length of hose and wire connections as well as the number of required control cabinets to a minimum.
Some of the plant components are extremely compact in design and highly automated, which means that there are less lines and hoses. Super-bright LED valve status indicators, that can be clearly seen from across the plant floor, further enhance process transparency.
The status of each individual valve can thus be checked on site even from a distance. As the process valves can be manually operated through the pilot valves at the control head, the operation of the machine is made even simpler.
Hygienic, compact and safe
The units consisting of a valve actuator and a control head are manufactured according to the EHEDG guidelines for hygienic design and easy cleaning. In addition, they feature the high IP protection required for the actual application and are made exclusively of detergent-proof materials.
The IP protection is therefore not affected by long-term use under conditions of high air humidity or by frequent cleaning with aggressive chemicals. This is of great advantage, especially to valve nodes, as there is often a problem of detergent solution or water escaping through the leakage valves, requiring frequent cleaning of the outside for hygiene reasons.
The design of the entire production facility is aimed at achieving trouble-free operation and minimising maintenance while prolonging the machine's service life and ensuring that it retains its value. High reliability, availability and durability of the process valves thereby play a key role.
In Bürkert valve systems, this is achieved by means of an integrated control air inlet to the actuator chambers that ensures that the spring chamber of the pneumatic driver is supplied only with clean control air. Moisture, dust and contaminants in the ambient air cannot enter the actuator units.
This in turn effectively prevents contamination of the piston seals and corrosion of the drive springs by cleaning solutions. There is also no risk of moisture from the spring chamber entering the feedback module or the control head along the spindle extension.
While this design significantly prolongs the service life of the driver, it also enhances the hygiene of the process. As product cannot enter the driver, both the spreading of germs and contamination of the driver by mould are effectively prevented.
The risk of pores produced in the spring chamber being ejected into the ambient air at each switching process, which is a common problem with conventional valves, is thus eliminated.
The actuator 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 a change in temperature or rinsing with cold water. Should the pressure after several switching processes increase above a set limit, the integrated pressure-relief valve automatically releases pressure from the housing.
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.
Extension of a tried and tested standardised concept
"For the extension of the plant, we were able to pursue the decentralised automation concept across the entire system, using our intelligent valve systems," Chris Hoey, managing director at Bürkert said.
"As the operating and maintenance staff were already familiar with the fieldbus system and the connecting and wiring concept, the new plant sections could be commissioned without any difficulties.
"To sum up, the practical integration at field level of automation functions in the pneumatic drivers of the process valves allows for a high degree of automation at minimum costs and ensures excellent transparency."
Thanks to the modular design of the valve systems, customised automation solutions can be devised easily and quickly. This is not least due to the fact that Bürkert offers not only process valves, but also digital electro-pneumatic positioners and process controllers that can be combined in the same manner to provide complete control valve systems.
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