Gas-Compressor Solution Reduces the Pains of Proprietary Systems

Shale Gas Growth Fuels a New Kind of Project

The U.S. is already the world’s top shale gas producer, and production is only expected to grow – from 37 billion cubic feet per day (Bcf/d) in 2015 to 79 Bcf/d by 2040.

Energy Control Technologies (ECT), an OEM member in the Rockwell Automation PartnerNetwork^™ program, is one of the companies helping drive this relatively recent energy boom. The Iowa-based company designs, builds and supports turbomachinery-plant control systems for oil and gas production. Its anti-surge and performance-control solutions are used in applications ranging from gas production and offshore platforms to refining and pipelines.

One company recently selected ECT to develop the turbomachinery control for gas compressors at a new, U.S.-based LNG pretreatment facility. While ECT has decades of experience developing systems for oil and gas operations, this customer’s project presented a new challenge: deliver the turbomachinery control platform in an open and integrated solution instead of using the traditional proprietary-systems, or “black-box” approach.

High-Availability Turbomachinery

ECT was tasked with developing a turbomachinery control system for two trains, each with three parallel compressors. Because the operations will be expected to run continuously for years at a time, a redundant architecture was essential to ensure a backup system would take over and reduce the likelihood of downtime should a failure occur.

The turbomachinery itself required a SIL 2-rated hardware platform for the compressor controls. The auxiliary systems required a SIL 3-rated hardware platform for the motor cooling, lube oil and seal gas skids, and overall management of all system trips, interlocks and permissives. Finally, the project required condition monitoring of the vibration and bearing temperatures for all the equipment.

This project also needed to integrate the six compressor control systems with a single motor soft start system. To meet this unique requirement, ECT provided an additional redundant PLC to manage the sequencing and interlocks necessary for all six of the compressors’ electric motors to share a single LCI soft starter.

Traditionally, developing a high-availability, turbomachinery control platform of this magnitude required combining multiple proprietary systems from different vendors. But that approach comes with a number of inherent challenges.

“The different systems often don’t natively talk to each other, which makes integration more challenging and time consuming,” said Tom Stoll, senior project engineer for ECT. “Also, piecing together different proprietary systems can make life more difficult for end users in several ways. It requires maintenance technicians to learn and be able to service a wider range of systems, or outsource maintenance to multiple vendors. It requires operators to learn and work with different HMIs. And it requires companies to purchase and manage more spare parts.”

ECT’s customer wanted to avoid these challenges altogether by relying on a single vendor to combine all of these systems into a single integrated solution using open-architecture, industry-standard technology.

Designing an Integrated Alternative

Delivering an easy-to-use system with this breadth of scope meant that ECT needed to use an automation technology that leverages open-architecture standards.

The company found just that in the modern PlantPAx^®DCS from Rockwell Automation. The PlantPAx technology is based on open-communications standards and can serve as a common automation platform by connecting process, discrete, power, information and safety control.

For the turbomachinery applications, ECT used the PlantPAx system to provide a SIL 2-rated platform for compressor control. The hardware leverages add-on instruction capabilities and delivers execution speeds that are equal to or better than proprietary systems. ECT also incorporated its patented, state-of-the-art, surge-control software, which uses algorithms to help detect and prevent potentially damaging surges in the compressor.  Integrated HMI software from Rockwell Automation was used for the operator interfaces.

“We also incorporated load-sharing as another critical application in the turbomachinery control system,” Stoll said. “The compressors work together to maintain a constant discharge pressure for the compressor network. Load-sharing also allows the customer to bring individual machines on-line or off-line to accommodate changing demands without disturbing the overall process.”

For the auxiliary systems, ECT used the AADvance^® fault-tolerant control system from Rockwell Automation to provide a SIL 3-rated hardware platform for sequencing and process control for the auxiliary skids, and for system trips.

“If the lube-oil system quits or if cooling is lost on the motor, the AADvance platform can trip the system and stop it before damage occurs,” Stoll said.

As part of the integration of the turbomachinery, auxiliary control and condition monitoring systems, the open-platform solution also provides a single connection to the plant distributed control system (DCS) via Modbus/TCP.