Natural Gas Distribution with Intrinsically Safe Pressure Control

• An urban gas network faced pressure fluctuations that manual regulators couldn’t safely control.

• Hazardous Zone 0 conditions made conventional electronic automation difficult and risked methane venting.

• An intrinsically safe IS-Pro™ controller enabled closed-loop, remote pressure regulation without protective housings.

• The automated system delivered stable downstream pressure, improved safety, and reduced the need for onsite adjustments.

Natural gas distribution networks are critical for ensuring reliable gas delivery to homes and businesses in urban areas. However, seasonal demand changes, refinery maintenance, and geopolitical events can all disrupt supply, leading to price fluctuations and delivery delays. To maintain timely and stable service, gas distribution centers must exercise precise control over a complex network of pressure lines.

Challenge

An East Asian energy company operating a bypass leg off the main transmission needed to maintain stable downstream pressure while complying with Zone 0 requirements. The system had to regulate feed into an urban distribution network while keeping outlet pressure stable and preventing routine methane venting during setpoint changes.

In the existing setup, a pressure regulator reduced high inlet pressure to a stable lower pressure for downstream supply. The system used a traditional two-stage approach, in which the main regulator’s dome pressure was controlled by a mechanical pilot device drawing its setpoint signal from upstream pressure. To change the setpoint, operators had to manually adjust the pilot screw or occasionally use an electric motorized adjustment. As a result, pressure control depended on frequent human intervention and introduced the risk of gas venting during adjustments.

Because the equipment was installed in a Zone 0 hazardous area, any device connected to the gas line required Zone 0 certification. Since the installation was outdoors, larger solutions such as purge cabinets or explosion-proof housings were considered impractical. To achieve fully automated, closed-loop control that eliminated manual tuning and enabled remote setpoint adjustment, the operator needed a new control strategy.

Options

Mechanical and pneumatic control

Mechanical dome-loaded regulators were capable of maintaining outlet pressure but required on-site adjustment. Adding pneumatic pilots improved response time and stability, but still demanded manual setpoint tuning, and wouldn’t offer true remote feedback. In both cases, changes to setpoint meant sending personnel into a hazardous area and, at times, venting gas during adjustment. These methods could not be implemented without undesirable venting or support real-time monitoring and control from the PLC.

Conventional electronic pressure control

Standard electronic pressure controllers could provide higher precision, data visibility, and closed-loop control of dome pressure. However, most off-the-shelf devices are not designed for direct installation in Zone 0, and the limited selection of Zone 0-rated instruments made this path difficult. To use conventional controllers in such an environment, the operator would typically need purged or explosion-proof enclosures; or relocate the electronics outside the hazardous area and run longer impulse lines and signal wiring. All of these options add cost, bulk, and maintenance complexity, and do not inherently solve venting concerns.

These constraints led the operator to consider a technology that could automate dome control without sacrificing Zone 0 safety.

Selection

To integrate automation without sacrificing reliability, the operator chose to keep the traditional mechanical pilot in parallel with the ISPC. The site had long depended on the pilot-based method and retaining it ensured that pressure control would continue uninterrupted if either system became unavailable. Under normal operation, the ISPC supplies electronically modulated load pressure to the dome for precise downstream regulation. If the ISPC were to lose power or fault to its safe state, the mechanical pilot remains in position and can assume dome control. Conversely, the ISPC can operate independently should the pilot be taken offline for maintenance. This dual-path architecture provided the automation they needed while preserving the robustness of a familiar, field-proven method.

Pre-regulators reduced the supply pressure for both pilot stages, while the pilot valves sensed downstream pressure. The ISPC then modulated the dome-loading pressure to hold the desired setpoint, continuously comparing the measured downstream pressure to its digital target and adjusting pilot pressure to stabilize the outlet.

Through an RS-485 link, the ISPC communicated with the site PLC, enabling remote monitoring and setpoint control. Its intrinsically safe design allowed installation directly in the hazardous zone without purge systems or explosion-proof housings.

Outcomes

Remote control through the PLC allowed operators to adjust pressure targets and log data through the lifetime operation of the system, helping them anticipate service, and analyze sudden changes quickly. The compact, intrinsically safe configuration simplified installation and compliance by reducing the need for protective housings and purging infrastructure.

The result was digitally automated, efficient pressure control that delivered reliable network performance under varying load conditions, while meeting the highest standards for hazardous-area operation.

• To achieve electronic control with their manual, pilot-based regulator system, operators needed an instrument capable of integrating into a hazardous, directly line-mounted environment while providing precise, automated dome pressure control.
• Zone 0 regulation made the requirements of the instrument extremely strict, limiting options to devices that could operate safely without purge systems, explosion-proof housings, or venting methane during adjustments.
• By installing an intrinsically safe IS‑Pro™ controller, the system gained closed-loop remote regulation along with a parallel mechanical backup, delivering improved safety, consistent pressure stability, and resilient redundant control.