Process control design – do not let ATEX restrict your plans

Jon Lawson

There are more options than you would think to increase process control and efficiency in a potentially explosive atmosphere by using the latest valves, controllers and panel built solutions

Manufacturers have developed a huge range of products and systems that can be combined and integrated to produce bespoke process control systems. However, when the application involves operating in potentially explosive atmospheres, designers could be forgiven for thinking that the choice of design might be restricted.

The task of designing process control systems that meet DSEAR, ATEX and other similar standards requires considerable levels of expertise and competence in order to deliver a suitably compliant process that meets the demands of the application. The primary concern in such conditions is safety and often this may need to be maintained at the expense of performance.

The path of least resistance

In terms of the individual components, manufacturers spend considerable amounts of time and effort in producing products that are certified for use in particular applications under specific conditions. In situations where the requirement is simply for a replacement part, it is a relatively easy task to ensure continued compliance with the regulations.

However, when there is a more wide ranging project, such as modifying an existing control system or building a completely new one, the task of delivering a fully certified installation is more complex and requires a wide range of skills and expertise. In such situations it is important to select partners that understand process control design with the ability to deliver bespoke solutions using the latest technology that is certified to the standards in force locally.

As one of the leading manufacturers of control and measuring systems for fluids and gases, Bürkert Fluid Control Systems has over 25 years’ experience in delivering solutions for hazardous areas to a wide range of industries and applications. The development of ATEX and IECEx certified versions of its industry leading components as well as complete control systems has been supported by the establishment of a centre of competence in Menden, Germany.

Taking a right turn on product selection

At the operational end, the ELEMENT valve controllers were initially designed to operate Bürkert’s CLASSIC range of process valves and they are now rapidly becoming the global standard for process control, setting the benchmark for the major manufacturers. Having already been developed to control 3rd party process valves, the latest improvements include ATEX and IECEx approvals for operation in Zones 2/22 and 1/21 where potentially explosive atmospheres may exist.

Similarly, with such a wide variety of applications, the use of quarter turn valves has become widespread, but it is very important to ensure that the selection process is carried out carefully so as to avoid poor performance or incompatible equipment. Development of this commonly used valve actuator includes the Type 3004 actuator, which is classified as ATEX II 2 GD Ex d II B T6 and rated to IP67 and therefore suitable for installation in areas classified as Zone 1.

Further enhancements can be made using servo-assisted pneumatic valves, such as the Type 6519, which can be installed individually or in manifolds and can be used to control double or single acting actuators. Available in EEx m and EEx i versions, they provide a high flow rate capacity and reduced power consumption, which is often an important factor, especially in larger installations, where the cumulative power consumption of a process control system can be significant.

Centralised versus decentralised control options

However, the benefits of these individual components can only be properly appreciated when they are brought together within a comprehensive design structure that maximises their benefits. This can be accomplished with the AirLINE Ex 8650 which is one of the only electro-pneumatic automation systems designed for installation in Zone 1.

This system is particularly suited to decentralised process control tasks concerning fine chemicals, pharmaceuticals, cosmetics and oil & gas; it can be used for example to automate the filling of potentially volatile solvents, alcohol or lacquers. In these application areas, the system is unique, as it is the only compact electro-pneumatic automation solution allowing integration of EEx ia rated pneumatic valves without additional wiring.

Systems such as this can only really deliver the expectations of the client if they are conceived, designed and manufactured by a single, dedicated team with the experience to appreciate the fine detail involved.

The bespoke system design route

When there is a requirement, but not a product or solution to fit it yet, then custom built is still an available route. By creating the Systemhaus concept, Bürkert provides experienced teams of designers, project managers and engineers who work together to produce innovative solutions. The Dortmund Systemhaus for example maintains a very high level of expertise specific to delivering control cabinets for installations for potentially explosive atmospheres.

From initial concept to on-site commissioning, a dedicated team is assigned to each project to ensure both continuity and understanding of project requirements are maintained. Due to the multiple competencies within each team, it is possible to design compact, integrated solutions that often contain both electrical and pneumatic circuits and even fluidic connections as well. In this way it is possible to deliver a single control cabinet, minimising space requirements as well as all the equipment that will deliver the process control itself, which reduces commissioning time and improves final delivery.

In conclusion – you have options

Clearly, the overriding concept for process control within zoned areas is that of safety, but in today’s market it is now possible to design and deliver efficient and compact systems to rival standard applications. The key is to understand the application and know that the product offering isn’t as restricted as you might think to deliver a control solution that will conform to the current standards.

The AirLINE EX 8650 system provides a solution for a retrofit project in a whiskey distillery. It offers substantial reductions in cabinet space, wiring, documentation and validation; thereby reducing complexity and costs. The 8650 combines EEx ia classed solenoid valves with modules from the Siemens ET 200iSP system and Fieldbus communications, providing the client with a complete ATEX certified unit for use in zone 1/21.

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