Control Systems

Increase the Visibility and Reliability of all Major Plant Assets

A viewpoint article by David Scheef, director of marketing for strategic business units.

Turbomachinery, essential to refining and petrochemical operations, has significant impact on plant production, maintenance and energy consumption. One of the most effective ways to improve turbomachinery performance is through the use of properly designed control systems. Control systems with optimal antisurge control and load sharing (when applicable) improve production, simplify maintenance and reduce energy consumption.

Reliability improvements. The best antisurge control algorithms prevent compressor surge and keep the machine running without unnecessary recycle – even with significant variations in process gas properties. Not all algorithms are created equal, and only the best eliminate unnecessary recycle by accurately predicting the compressor surge line and establishing a minimal offset.

Load sharing algorithms distribute flow loading optimally at the most efficient operating points among compressors operating in parallel. How the algorithm calculates the load sharing control signal is very important. In practice, the best algorithms maintain the controlling signal and load sharing functionality if the compressor crosses the surge control line.

Control development. Since the 1970s, turbomachinery controls have evolved from mechanical/hydraulic systems to microprocessor– based digital controllers. Initially, digital controllers were proprietary or “black box” solutions because commercially available controllers did not have the required speed or capability for turbomachinery control.

These proprietary systems were difficult to integrate with other plant systems. They required specialized dedicated spare parts for maintenance and additional personnel training for maintenance and operations, and unfortunately, could be unilaterally declared obsolete by the manufacturer at any time. Today, there are commercially available controllers with the speed and capability needed for turbomachinery control, eliminating these maintenance and operational issues, in addition to the added costs of “black box” controllers.

In today’s competitive environment, plant managers continuously strive to increase production and reliability. They are looking for a totally integrated control solution for all facility equipment. Using the plant’s distributive control system (DCS) provides that solution, but only a few DCS have the speed and capability necessary for turbomachinery control.

Before considering any DCS hardware for turbomachinery control, the system should be thoroughly tested with the controlling algorithm embedded to ensure a combination providing safe and precise controls for compressor operation.

New solutions. Integrating optimal antisurge control and load sharing programs into a fully capable, reliable and tested DCS controller can meet plant managers’ demands by providing precise machinery control on a single open-architecture platform for integrated control across all plant equipment, including their turbomachinery. This solution eliminates problems with multiple platforms, especially those associated with proprietary or “black box” controllers such as problematic integration, dedicated spare parts, unfamiliar hardware and programming, and personnel training.

Combining the best algorithms with proven “turbomachinery-capable DCS hardware” offers operators superior control solution as compared to proprietary or “black box” controllers. This approach can also replace obsolete turbomachinery controls with a totally integrated system. Such solutions are ideal in today’s competitive environment and for an industry seeking increased reliability of all major plant assets.

David Scheef is director of marketing for strategic business units at Dresser-Rand, which recently formed an alliance agreement with Honeywell, enabling Dresser-Rand to provide the turbomachinery-capable Honeywell Experion C300-20 controller with embedded Dresser-Rand proprietary antisurge control and load sharing algorithms. He can be reached at 713-973-5465 and dscheef@dresser-rand.com.

Reprinted in insights magazine with permission from HYDROCARBON PROCESSING, by Gulf Publishing Co., copyrighted 2013; all rights reserved.

Tags: Control and Monitoring Systems

other articles from insights issue Autumn / Winter 2013