The use of Emerson and GE (now part of Emerson) PLCs in oil & gas is a perfect case study of how control technologies are applied based on the specific segment and criticality of the operation. It's crucial to understand that GE's Intelligent Platforms business (including PLCs and PACs) was acquired by Emerson in 2019 and is now integrated as part of Emerson's machine and discrete automation portfolio.
Here is a detailed breakdown of how these platforms are deployed across the oil & gas value chain.
Core Philosophy: The Right Tool for the Right Job
In oil & gas, control systems are stratified by criticality, complexity, and geographic scope:
1. Distributed Control System (DCS): For complex, continuous, plant-wide control (e.g., a refinery crude unit, LNG liquefaction train).
2. Programmable Logic Controller (PLC) / Programmable Automation Controller (PAC): For discrete, skid-based, or remote/standalone control (e.g., a compressor package, a wellhead, a fire & gas system).
3. Safety Instrumented System (SIS): For separate, dedicated safety shutdown functions.
Emerson provides solutions at all three levels, but its PLCs/PACs serve specific, vital niches.
Emerson's PLC/PAC Portfolio in Oil & Gas
Emerson now offers two main lineages of PLC/PAC products relevant to O&G:
Emerson PACSystems (formerly GE RX3i & RX7i): The workhorse PACs for high-performance control.
Emerson PACMotion: For advanced motion control (less common in upstream O&G).
Emerson VersaMax & Series 90-30: Rugged, smaller PLCs for remote applications.
Emerson ControlEdge™ PLC: A newer, IIoT-native PLC designed for remote operations.
Primary Use Cases & Applications:
A. Upstream (Exploration & Production)
Wellhead Control & Methanation Units (WMUs):PLCs (VersaMax, ControlEdge) autonomously control individual or clusters of wells, managing chokes, valves, and safety shutdowns. They communicate via satellite or cellular to a central SCADA.
Compressor & Pump Control Skids: Reciprocating or centrifugal compressor packages are often controlled by a PACSystems RX3i due to its high reliability and ability to handle complex sequencing and safety interlocks.
Chemical Injection Skids: PLCs precisely control the injection of inhibitors, scale preventers, or methanol into flow lines.
Fire & Gas (F&G) and Emergency Shutdown (ESD) Systems:
PACSystems are often used for process shutdown (PSD)
systems, while a dedicated SIS (like Emerson's DeltaV SIS) handles higher-integrity safety functions. For less critical facilities, a high-integrity PLC configuration may serve as the ESD.
Remote Telemetry Units (RTUs):The ControlEdge PLC is designed for this, acting as a ruggedized RTU/PLC hybrid for gathering field data from tanks, pipelines, and wells and enabling remote control.
B. Midstream (Transportation & Storage)
Pipeline Pump/Compressor Station Control:PACSystems are frequently the controller of choice for standalone stations, managing pumps, valves, flow calculations (AGA), and local HMI.
Valve Automation & Sectionalizing: PLCs control large block valves and sectionalizing valves along pipelines.
LNG Liquefaction Train Auxiliaries: While the main liquefaction process is controlled by a DCS (Emerson's DeltaV), numerous supporting systems (utilities, refrigerant storage, loading arms) are controlled by PLCs (PACSystems).
Tank Farm Automation: PLCs manage tank levels, valve sequencing for transfers, and vapor recovery units.
C. Downstream (Refining & Petrochemical)
Package Unit Control:Refineries are filled with vendor-supplied packages (air compressors, water treatment, boiler feedwater). These skids are almost universally controlled by Emerson or competitor PLCs (e.g., PACSystems), which then interface with the plant-wide DCS.
Blending Systems: PLCs are ideal for the discrete logic and fast control needed for in-line product or additive blending.
Loading Rack & Terminal Automation: PLCs control the precise loading of trucks and railcars, managing valves, meters, and safety interlocks.
2. Why Emerson/GE PLCs are Prevalent in These Applications
Ruggedness & Wide Temperature Ranges:They are designed to operate in harsh environments (-40°C to 70°C) found in remote locations.
High Reliability & Deterministic Performance: Critical for safety interlocks and equipment protection.
Strong Networking & Protocol Support: Native support for Ethernet/IP, Modbus TCP, and, historically, Genius Bus (a robust, deterministic fieldbus still heavily used in legacy GE systems). This allows easy integration with turbine controls (GE), variable frequency drives, and other skid components.
Legacy Installed Base: The GE legacy created a massive installed base. There is a vast pool
Tsuen Wan,HONG KONG
