— A Practical Guide for Engineers, EPCs, and Plant Operators

In steel smelting, chemical production, engine testing, power generation, and countless other industrial processes, high temperatures are not an exception—they are the norm-11. Selecting the right pressure transmitter for these conditions is not just about finding a device that can survive the heat. It is about ensuring measurement accuracy, process safety, and long-term reliability in environments where a single failure can mean costly downtime or a safety incident.

This guide covers the key challenges of high-temperature pressure measurement, the critical selection criteria, and the practical solutions—from sensor technology to cooling methods—that ensure reliable performance.

1. Why High Temperatures Are a Problem for Pressure Transmitters

High temperatures affect pressure transmitters in multiple ways, compromising both accuracy and reliability:

Most electronic transmitters are suitable for ambient conditions ranging from lows of -20 to -40°C to highs of 60 to 85°C—but not all, particularly those with special filling materials-. Once process media temperatures exceed approximately 100°C, you need to start considering protective solutions-.

The key principle: The transmitter body must be kept at near-ambient temperature-. Do not expose the pressure transmitter body to high temperatures—the maximum temperature it can withstand is typically 85°C-. Your job is to bridge the gap between the hot process and the cool transmitter.

2. Critical Selection Parameters

2.1 Temperature Range: Know Both Numbers

When selecting a high-temperature pressure transmitter, you must consider two separate temperature specifications-2:

Key rule: The transmitter's "operating temperature range" and "process media temperature range" must both have upper limits higher than the maximum field temperature-11. Different high-temperature pressure transmitters offer different temperature compensation ranges, so selection should be based on the specific operating temperature-1-7.

2.2 Pressure Range

The first step in selecting any pressure transmitter is determining the measurement range-1-7. The range should be based on the actual application to ensure full coverage of expected pressure variations-:

• Too small: The transmitter may be damaged by overpressure-1-7

• Too large: Measurement accuracy may be reduced-1-7

A good rule of thumb is to select a range that places your normal working pressure at 50% to 90% of the transmitter's full scale-.

2.3 Accuracy Class

Higher accuracy classes deliver more precise measurements—but at a higher cost-1-7. Common industrial accuracy classes include 0.1%, 0.2%, and 0.5%-1-7:

Thermal error is additive: The static accuracy (at reference temperature) plus the thermal error introduced by high temperatures is the total possible error for the measurement-20. Always check the temperature coefficient (TC Zero, TC Span) in the datasheet—it directly reflects the instrument's compensation performance-11.

2.4 Wetted Materials

The materials used in the transmitter directly affect corrosion resistance and service life-1-7:

In environments with corrosive media, transmitters made of corrosion-resistant materials should be selected to ensure long-term reliability-1-7. Special consideration must be made for harsh media such as acids, hydrogen, salt water, and ammonia-2.

2.5 Sensing Technology

Different sensing technologies offer different high-temperature performance:

High-temperature pressure transmitters often use a diaphragm-sealed piezoresistive measuring cell-7. The process pressure is transmitted through a stainless-steel diaphragm into a temperature-resistant filling fluid, separating the media from sensitive electronics-7.

3. Four Ways to Handle High Process Temperatures

When your process media temperature exceeds the transmitter's limit, you have four primary options:

3.1 Remote Seal (Diaphragm Seal) System

How it works: A remote diaphragm seal is connected to the transmitter via a capillary tube filled with silicone oil. The seal isolates the transmitter from the hot process media, transmitting only pressure-11.

Best for: Viscous, corrosive, or extremely hot media where the transmitter cannot be mounted near the process.

Considerations:

• Remote seals are the most common and effective way to protect instruments from corrosive substances-

• For high-temperature differential pressure (DP) applications, specialised filling media and remote diaphragm structures achieve separate measurement of hot and cold zones-

• Changes in ambient temperature can affect accuracy and response time; keep the capillary as short as possible-

Tiankang offering: Tiankang remote seal pressure and differential pressure transmitters are available with high-temperature silicone oil filling, suitable for process temperatures up to 400°C.

3.2 Temperature Stand-Off (Cooling Element)

How it works: A short length of tubing between the process connection and the transmitter dissipates heat into the atmosphere before it reaches the transmitter-2.

Best for: Applications where a special high-temperature transmitter would be expensive and a stand-off provides sufficient cooling-20.

Example: A 6-inch length of 1/4" OD 303 stainless steel tubing can protect a transmitter from an 1100°F (593°C) pressure media-20.

Considerations:

• While some distance is recommended, too much distance can dampen dynamic response-

• The chart below shows typical stand-off lengths for different media temperatures-20:

3.3 Cooling Fins and Heat Sinks

How it works: Heat dissipation fins or cooling elements increase the surface area for natural convection cooling-10. Combined with robust housings, they ensure signal integrity at high temperatures-7.

Best for: Moderate high-temperature applications where the transmitter is mounted near but not directly on the hot process.

Considerations:

• Different lengths of散热片 (heat sinks) allow measurement of media temperatures up to 1100°C-10

• Install using mounting brackets or radiators to increase air contact area and promote natural convection cooling-11

3.4 Water Cooling Jacket

How it works: A water jacket surrounds the transmitter or sensor, circulating cooling water to maintain a safe operating temperature-10.

Best for: Extreme high-temperature applications where air cooling is insufficient.

4. Output Signal and Communication

High-temperature pressure transmitters are available with various output signal types-1-7:

Select the appropriate output signal based on the requirements of downstream equipment-1-7.

5. Installation Best Practices for High-Temperature Applications

5.1 Location Selection

5.2 Process Connection

• Use threaded or flanged connections as required-1

• For threaded connections, proper sealing is essential to prevent media leakage-1

• Ensure the pressure port aligns correctly with the pipeline or vessel port-1

5.3 Electrical Connection

• Follow the wiring diagram strictly; pay attention to power supply polarity and voltage-1

• Ensure good insulation to prevent short circuits or electrical leakage-1

• Use cable conduits or protective tubing where needed-1

5.4 External Heat Protection

6. Maintenance in High-Temperature Environments

Instruments operating in high temperatures require more frequent maintenance and calibration-11:

• Visual inspections: Check for signs of overheating (discoloured paint, warped surfaces) and seal integrity-11

• Shortened calibration intervals: Adjust calibration frequency based on service severity-11

• Performance tracking: Maintain detailed operating records to track long-term performance changes-11

• Proactive replacement: Replace components before they fail, based on service life data-11

7. Why Choose Anhui Tiankang for High-Temperature Pressure Measurement?

Anhui Tiankang (Group) Co., Ltd. has been manufacturing industrial instruments for nearly five decades. Our high-temperature pressure measurement solutions are trusted by major oil and gas companies, chemical plants, and power generation facilities worldwide.

Product portfolio for high-temperature applications:

Core advantages:

• Temperature compensation: Full-range compensation from -40°C to 85°C, temperature drift ≤0.005% FS/°C

• Wide material selection: 316L SS, Hastelloy C-276, Monel, Inconel, tantalum

• Multiple cooling solutions: Remote seals, cooling stands-off, heat sinks, and water cooling options

• Complete certifications: CCC Ex, ATEX, IECEx, SIL2/SIL3, CCS marine

• Proven track record: Long-term supplier to CNPC, Sinopec, CNOOC, and international EPC projects

8. Conclusion

Selecting pressure transmitters for high-temperature process applications requires a systematic approach:

1. Define the temperatures – Process media temperature and ambient temperature

2. Define the pressure – Normal operating pressure, maximum pressure, and potential spikes

3. Select the cooling method – Remote seal, temperature stand-off, cooling fins, or water cooling

4. Choose the right materials – Match wetted materials to the media and temperature

5. Verify accuracy and compensation – Check temperature coefficients and compensation ranges

6. Install correctly – Location, connection, and heat protection

7. Maintain proactively – Regular inspection, calibration, and performance tracking

Remember: The transmitter body must stay cool—your job is to bridge the gap between the hot process and the cool transmitter.

With nearly five decades of experience and a complete range of high-temperature pressure measurement solutions, Anhui Tiankang is your trusted partner for reliable, accurate, and durable pressure measurement in the most demanding thermal environments.

Contact Us

For high-temperature pressure transmitter selection advice, technical documentation, or project quotations, please contact:

Yin Shuangjie
International Sales Manager
📧 Email: [email protected]
📱 WhatsApp / Zalo: +86 17856068126
🌐 Website: http://www.tiankang-global.com/

Anhui Tiankang – Your partner for reliable high-temperature pressure measurement solutions.