Introduction
Oil and gas temperature measurements range from pipeline and compressor monitoring to separation, storage and refinery process control. The measuring point may combine pressure, flow, vibration, corrosive media and a classified electrical area.
The sensing element is only one part of the design. Thermowell calculations, wetted materials, process connections, transmitter configuration, cable entries and the site's hazardous-area requirements must be reviewed as a complete measurement loop.
Process Context
Upstream duties can include wellheads, separators and produced-fluid systems. Midstream points include pipelines, metering systems and compressor stations. Refineries add columns, reactors, heat exchangers, tanks and steam utilities.
Some locations are electrically classified because flammable material may be present. The applicable protection concept, equipment marking, temperature class, gas group and installation method must come from the site's area classification and engineering requirements.
Selection Guidance
Where a thermowell forms part of the pressure boundary, select its material, construction, insertion length, connection and profile from the process design conditions. Sour-service material requirements and any ISO 15156 review must be confirmed by the responsible materials engineer.
Pt100 RTDs suit many moderate-temperature measurements, while Type K or N thermocouples are considered for higher-temperature duties. The connection head, transmitter, glands and barriers must all match the protection concept specified for the installed loop.
Recommended Sensors
Heavy-Duty Flanged Thermowell Assemblies
Solid-machined thermowells with full-penetration welded flanges, engineered to withstand pipeline pressures and high-velocity flow.
Multi-Point Reactor Profilers
Complex arrays of thermocouples routed through a single nozzle, designed to map the 3D temperature profile inside a catalytic cracking unit.
Assemblies for Classified-Area Designs
Sensor, head and transmitter configurations selected against the site's required protection concept and equipment approvals.
Installation Considerations
Thermowells exposed to significant process flow may require a mechanical evaluation, including wake-frequency analysis where applicable. The review should use the actual fluid properties, velocity, pressure, temperature and proposed thermowell geometry.
Classified-area integrity depends on the complete installed loop, not just the sensor. Connection heads, transmitters, barriers, cable glands, seals, wiring and grounding must follow the approved design and local installation requirements.
Key Benefits
- Supports process monitoring across upstream, midstream and refinery duties.
- Matches sensing technology and wetted materials to the measurement point.
- Integrates temperature measurement with the site's classified-area design.
- Reduces thermowell risk through appropriate mechanical review.
Specifications
| Parameter | Typical Specification |
|---|---|
| Standard Process Range | -50°C to 400°C (Pt100 RTD) |
| Refinery / Reactor Range | 400°C to 1200°C (Type K or N Thermocouple) |
| Thermowell Construction | Solid-drilled bar stock, Flanged or RTJ connections |
| Sour Service Review | Wetted materials assessed against process conditions and applicable ISO 15156 requirements |
| Electrical Safety | Protection concept and approved components selected from the site's area classification |
Frequently Asked Questions
Does the temperature sensor come with a hazardous area certification?
Approval cannot be inferred from the sensor description alone. The required protection concept and equipment markings must be specified, and every component in the installed loop must be verified against the site's area classification.
What is NACE compliance?
ISO 15156, historically associated with NACE MR0175, addresses material selection for equipment used in hydrogen-sulfide-containing oil and gas environments. Applicability depends on the material, environment, stress and project specification.
Why use an RTD for custody transfer?
Metering systems often use RTDs because they provide stable, repeatable measurement over moderate temperature ranges. The complete metering design, calibration and applicable standard determine whether a sensor is suitable for custody-transfer service.
How do you measure temperature in a highly viscous fluid?
Viscous fluids require a robust thermowell to withstand the drag force. Furthermore, a longer immersion length or a stepped thermowell design is often used to ensure the sensor reaches past the slow-moving boundary layer to measure the core fluid.
References
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