Control Panel Fabrication:
Complete Guide
for Oil & Gas (2026)

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What Is Control Panel Fabrication?

Control panel fabrication is the engineering, assembly, and testing process of building custom electrical enclosures that house the control equipment for industrial machinery and processes. In oil and gas, control panels manage everything from wellhead pressure shutdowns to compressor motor starters to pipeline SCADA communications. The panel is the physical interface between field instruments, PLCs, and the operators who monitor production.

Unlike off-the-shelf electrical equipment, industrial control panels are custom-built to each application's specific I/O count, voltage requirements, communication protocols, environmental rating, and hazardous location classification. A panel fabricator takes an engineering design - or develops one from scratch - and produces a complete, tested unit ready for field installation.

Types of Control Panels

• Motor Control Centers (MCC): Large assemblies housing multiple motor starters, variable frequency drives (VFDs), and disconnect switches. Common in compressor stations and processing facilities. Typically built to NEMA 12 or NEMA 4X ratings.
• PLC Control Panels: Enclosures housing a programmable logic controller, I/O modules, power supply, and communication interfaces. The most common panel type in oil and gas wellhead and compressor automation. Can range from a compact 24×24 enclosure to a large 72×72 free-standing cabinet.
• SCADA Panels: Panels housing RTUs or PLCs with cellular, radio, or Ethernet communication modules for remote monitoring. Often deployed at tank batteries, pipeline block valve stations, and well pads. See our SCADA panel design guide for detailed component breakdowns.
• Remote Terminal Unit (RTU) Panels: Compact panels designed specifically for data acquisition and telemetry at remote sites. Often solar-powered with battery backup for off-grid installations.
• Junction Boxes: Smaller enclosures that consolidate field wiring from multiple instruments before routing to the main control panel. Essential for reducing conduit runs on large well pads.
• Hazardous Location Panels: Panels built to Class 1 Division 1 or Division 2 ratings for use in areas where flammable gases may be present. Require special enclosure designs, purge and pressurization systems, and NEC Article 500-compliant component selection. See our oilfield control panel guide for more on hazardous location ratings.

UL 508A Certification Explained

UL 508A is the Underwriters Laboratories standard that governs the construction of industrial control panels in the United States. Understanding this certification is essential before purchasing any control panel for oil and gas operations.

What UL 508A Means

UL 508A establishes specific requirements for how industrial control panels must be designed and built - covering component selection, wire sizing, short circuit current ratings (SCCR), spacing between components, and required markings. A panel built to UL 508A standards has been constructed by a certified shop under a documented quality program and is subject to periodic inspections by UL field representatives. The UL label on the panel door indicates compliance. For a complete breakdown of UL 508A requirements, see our UL 508A certification guide.

Why It Matters for Oil and Gas

Most oil and gas operators, EPC contractors, and insurance carriers require UL 508A listed panels on all new installations. A non-UL panel may be cheaper upfront but creates significant liability exposure: if a non-UL panel causes a fire or arc flash incident, the operator may face insurance claim denials, OSHA penalties, and civil liability for using non-compliant equipment. Many lease operating companies (LOEs) in the Permian Basin now specify UL 508A as a minimum requirement in their vendor qualification documents.

UL Listed vs. Non-UL Panels

A non-UL panel might look identical to a UL listed panel from the outside but differs in critical ways: components may not be rated for the actual fault current available at the installation, wire sizing may not meet NEC minimums, and the enclosure may not be rated for the environmental conditions present. When you see a UL label on a control panel, it means the fabrication shop has an active UL 508A program number, employs a Program Manager who oversees compliance, and allows periodic UL follow-up inspections of the shop.

Insurance and Liability Implications

Operators who install non-UL panels risk policy exclusions under their property and liability insurance. Many operators are unaware that their insurance policies include clauses requiring electrical equipment to meet applicable UL standards. A $3,000 savings on a non-UL panel is not worth the potential exposure when a non-compliant panel is involved in an incident at a well site.

Key Components in Oil & Gas Control Panels

Understanding the components inside a control panel helps operators evaluate quotes, spec panels correctly, and communicate with fabricators about what they need.

PLCs - Allen-Bradley and Siemens

The PLC is the brain of the control panel - executing the automation logic, processing inputs from field sensors, and controlling outputs to valves, motors, and alarms. Allen-Bradley CompactLogix and ControlLogix dominate North American oil and gas. Siemens S7-1200 and S7-1500 are common in international operations and increasingly in domestic midstream. See our Allen-Bradley PLC programming guide and Siemens PLC programming guide for platform comparisons.

HMIs and Operator Interfaces

Local HMIs (Human-Machine Interfaces) provide operators at the panel with a graphical display of process values, alarm status, and control buttons. Allen-Bradley PanelView Plus and Siemens SIMATIC TP series are common choices. For remote sites with cloud SCADA, local HMIs are sometimes omitted in favor of tablet-based monitoring through the cloud platform.

Power Supplies and Transformers

Control panels require clean, regulated DC power for PLCs and instruments. Control power transformers step down incoming AC voltage (typically 480V or 120V) to 24VDC. Mean Well and Phoenix Contact DIN rail power supplies are common choices. Battery-backed UPS modules are added for critical panels where power interruption could cause safety issues.

Circuit Breakers and Fuses

Overcurrent protection devices protect wiring and components from fault currents. The UL 508A standard specifies the required interrupting capacity (SCCR) based on the available fault current at the installation point. Allen-Bradley 140M and Siemens 3RV series motor circuit protectors are widely used in oil and gas panels.

Terminal Blocks and Wiring

Field wiring from sensors, transmitters, and actuators terminates on DIN rail-mounted terminal blocks inside the panel. Phoenix Contact and Wago are dominant terminal block suppliers. Wire sizing, color coding, and labeling must comply with NEC requirements and the fabricator's UL 508A program requirements. Proper wire management - including cable trays, wire ducts, and strain relief - is a mark of quality fabrication.

Relays and Contactors

Relay logic controls discrete outputs: switching signals between PLCs and field devices, providing isolation between different voltage levels, and implementing emergency shutdown (ESD) circuits. IDEC, Phoenix Contact, and Allen-Bradley Bulletin 700 relays are common. Contactors handle higher-current motor loads and are typically Allen-Bradley 100-C or Siemens 3RT series.

Instrumentation Inputs (4–20mA, RTD)

Analog input modules in the PLC receive 4–20mA signals from pressure transmitters, flow meters, and level sensors. RTD (Resistance Temperature Detector) inputs measure temperatures from wellhead components and compressor bearings. Proper shielding of analog signal wiring prevents noise interference from nearby motor loads - a common issue in wellhead panels.

Communication Modules (Modbus, EtherNet/IP)

Communication modules enable the panel PLC to talk to SCADA systems, RTUs, and cloud platforms. Allen-Bradley PLCs communicate natively via EtherNet/IP. Modbus TCP/RTU gateways convert between protocols for legacy SCADA systems. Cellular communication modules (Teltonika RUT956, Sierra Wireless) connect remote panels to cloud SCADA platforms like Merobix over 4G LTE.

The Control Panel Fabrication Process

Understanding the fabrication process helps operators set realistic timelines and know when to engage a fabricator in a project's development cycle.

1. Design and Engineering

Fabrication begins with an engineering design package: one-line electrical drawings, panel layout drawings, I/O lists, terminal block schedules, and a component BOM. For custom panels, the fabricator's engineers develop this package from the operator's process description and control narrative. For repeat panel designs, existing drawings are modified. Engineering typically takes 1–3 weeks depending on complexity.

2. Bill of Materials (BOM) and Procurement

Once the design is approved, a complete BOM is generated and components are ordered. Lead times on PLC hardware, communication modules, and enclosures can run 4–12 weeks for certain items - particularly Allen-Bradley CompactLogix CPUs and Siemens modules during supply chain constraints. Communicating your in-service date early allows the fabricator to identify long-lead items and order them immediately.

3. Fabrication and Wiring

Physical fabrication involves mounting DIN rails, cable trays, and components inside the enclosure; routing and terminating wire runs; installing conduit knockouts; and applying labels and markings. Quality fabricators use computer-aided wire cutting and labeling systems to eliminate manual errors. Each wire is labeled at both ends with the wire number from the engineering drawings.

4. Factory Acceptance Testing (FAT)

Before shipping, the completed panel undergoes Factory Acceptance Testing: power-on verification, I/O point checkout, PLC program download and function test, communication link verification, and UL label application by the shop's Program Manager. FAT documentation is provided to the operator as a deliverable. Operators may choose to attend FAT in person to witness testing before taking delivery.

5. Delivery and Installation Support

Completed panels are shipped on pallets with protective packaging. Most Texas-based fabricators offer field commissioning support: sending a technician to the site to assist with field wiring terminations, PLC startup, and SCADA integration. Merobix provides commissioning support for all panels we fabricate, including cloud SCADA connection and first-week monitoring to confirm stable operation.

Control Panel Costs in Texas

Panel Type	Typical Cost Range	Notes
Simple Relay Panel	$2,000 – $8,000	Basic motor control, no PLC
PLC Control Panel	$8,000 – $30,000	CompactLogix or Siemens S7, includes programming
SCADA RTU Panel	$8,000 – $25,000	RTU + cellular communication + cloud connection
Complex SCADA Panel	$30,000 – $100,000+	ControlLogix, redundant comms, hazardous location

What Affects Pricing

• Component selection: Allen-Bradley ControlLogix hardware costs 3–5x more than equivalent Siemens or Click PLC components for basic I/O applications.
• Complexity: I/O count, analog channel count, and number of communication interfaces directly drive fabrication labor hours.
• UL 508A certification: UL listed fabrication typically adds 10–20% to panel cost compared to non-UL fabrication. Worth every penny for liability protection - our UL 508A certification cost guide explains where that premium comes from.
• Lead time: Rush orders requiring accelerated engineering and overnight component shipping add 15–30% to project cost.
• Enclosure rating: NEMA 4X stainless steel enclosures for harsh environments cost significantly more than standard NEMA 12 carbon steel enclosures.

How to Choose a Panel Fabricator

UL 508A Certification

Ask for the fabricator's UL file number and verify it is current at ul.com/prodinspection. An expired or revoked UL program means the shop cannot legally apply UL labels. Never accept a panel with a UL label from a shop that cannot provide a valid UL file number.

Industry Experience

Oil and gas panel fabrication requires specific knowledge: hazardous location ratings, instrument loop wiring standards, PLC platforms common to the industry, and SCADA communication protocols. Ask for references from oil and gas operators in your region and request examples of similar panels they have built.

Lead Time and Delivery

Confirm the fabricator's current shop backlog before committing. A shop with a 16-week backlog may not work for a well coming online in 8 weeks. Get delivery commitments in writing, tied to milestone payments.

Local vs. National Fabricators

Texas-based fabricators offer faster lead times (no cross-country shipping), easier factory acceptance testing attendance, and more responsive field service. National panel houses may offer lower unit pricing for large volume orders but slower turnaround and limited local support.

Engineering Support

The best fabricators offer integrated engineering - developing the electrical design, PLC program, and SCADA integration package as a single deliverable. This eliminates coordination gaps between separate engineering and fabrication contractors and typically results in faster delivery and fewer field changes.

Merobix Panel Fabrication Services

Merobix is a Texas-based engineering company providing custom industrial control panel fabrication integrated with Allen-Bradley and Siemens PLC programming and Merobix cloud SCADA. We deliver complete automation systems - panel, program, and cloud monitoring - from a single team.

• Custom panel fabrication - panels designed, built, and FAT-tested to industrial standards
• Allen-Bradley and Siemens integration - CompactLogix, ControlLogix, S7-1200, and S7-1500 platforms
• SCADA-ready panels - every panel we build includes cellular communication and Merobix cloud SCADA integration
• Texas-based fabrication - local delivery and field commissioning across the Permian Basin, East Texas, and Mid-Continent
• Fast lead times - standard PLC panels delivered in 4–6 weeks; expedited options available

See our control panel fabrication services for a full description of our capabilities or read our UL listed panel fabrication article for more detail.

Frequently Asked Questions