Electric actuation enhancements

Safe and reliable field device functionality is of crucial importance to ensure ongoing and economical operation in process technology. As a result of corrosion, devices can rapidly become extremely costly to remedy and repair - added to this, associated system downtime is an on cost that makes the issue an essential design consideration.

In light of increased environmental demands for production facilities, AUMA addressed its existing coating method for its actuator components. After an extensive evaluation, the company spearheaded an initiative to implement a two-layer powder coating of housing parts. A major investment of several million Euros was made to develop a powder coating facility for the company’s actuator housings.

A paradigm shift saw the company move from wet painting completed devices to powder coating individual housing parts prior to assembly. This is of significant advantage to plant operators as the corrosion protection coating remains intact, even when the device housing is repeatedly opened during installation, commissioning or maintenance.

The actuator manufacturer emphasises that corrosion protection is not limited to powder coating. Some outer elements of an actuation device are not appropriate for this procedure – for example, control and display elements, name plates, screws and the handwheel shaft are made of materials such as stainless steel, or are protected via the application of different coatings. If different materials are combined, under certain conditions, corrosion can appear at joints. In order to avoid so-called ‘contact corrosion’, extensive tests were performed to eliminate unfavourable material combinations.

Safety first

AUMA recognises that, when devices are used in safety critical applications, it is particularly important that they function correctly in the event of an emergency.

Standard AC .2 integral controls offer complex control functions, sophisticated diagnostics and an easy-to-use interface. AUMA’s recently developed AC .2 controls in SIL version have successfully passed certification by TÜV Nord. SA .2 actuators equipped with these controls are now certified for safety relevant applications for SIL 2 or, in case of redundant system architecture, for SIL 3. An additional PCB, the so-called SIL module, is integrated into the otherwise unchanged controls to execute the safety functions.

During normal operation, customers may use the comprehensive standard functionalities of the AC .2 controls. In the event of an emergency, the standard logic is by-passed and the safety function executed via the SIL module.

Challenging Criteria

As part of its advancements to address the needs of challenging actuation installations, earlier this year AUMA announced a new explosion proof version part-turn actuator. Designed for butterfly and ball valve automation, the SQEx .2 replaces the company’s established SG .1 range. Enhancements set to expand process control applications for AUMA include a significant increase in torque range, sophisticated diagnostics and asset management functionality.

A new actuator size in the SQEx .2 series more than doubles the torque range offered by AUMA’s predecessor product: this is a significant expansion now covering 50Nm to 2400Nm.

Advanced features and benefits include adoption over a wider torque range without the need for a gearbox – this provides a more compact and cost effective actuation solution. Sophisticated diagnostics and asset management enhancements include additional temperature and vibration sensors. For enhanced positioning accuracy, and an increased number of permissible starts per hour, an SQREx version for modulating duty is also available from AUMA.

Commissioning and operation of SQEx actuators are identical to the SAEx .2 multi-turn range. Both ranges are available with simple AMExC or micro-controller operated ACExC integral controls – controls are therefore interchangeable and, at plants where both product series are installed, on-site device management is simplified.

With a focus on engineered solutions and significant R&D investment, AUMA has a strong reputation for technical advancements in the field of modular electric actuators. The company, which is celebrating the 50th year, has a global network of subsidiaries and distributors; it is represented in the UK by AUMA Actuators.