I. Differences in Structure and Installation Method
Flange-type probes: These probes utilize a flange connection structure, rigidly fixing the sensor flange to a standard flange (such as DN25PN1.6) on the pipeline or equipment using bolts. The mounting surface is flat, requiring a sealing gasket for media isolation. They are suitable for high-pressure, high-temperature, and high-vibration environments. Structurally, they typically feature an integral metal housing, with the hot end extending into the media and a junction box pre-installed at the cold end. They offer high overall rigidity and strong resistance to deformation.
Threaded probes: These probes are screwed directly into the pre-drilled threaded holes in the equipment via standard threaded interfaces (such as M12×1.5, M20×1.5, G1/2), achieving a seal through thread engagement and a sealing ring. They feature a compact structure, customizable probe length, and require no additional flanges for installation, making them easy to operate and suitable for medium- and low-pressure, conventional industrial pipeline applications. Some models support ferrule adjustment for easy control of insertion depth.
The core difference between the two lies in their connection mechanism: the flange type uses "face contact + bolt fastening", while the threaded type uses "line contact + screw-in locking".
II. Applicable Working Conditions and Industry Applications
|
Application scenarios |
Flange type probe |
Threaded probe |
|
Pressure Level |
≥1.6MPa, suitable for steam, high-pressure oil circuits, and reaction vessels. |
≤1.6MPa, suitable for water, gas, and ordinary liquid pipelines. |
|
Temperature environment |
-200℃ ~ 850℃ (high temperature resistant material) |
-200℃ ~ 500℃ (mainstream range) |
|
Vibration environment |
Extremely strong vibration resistance, suitable for large machinery and boilers. |
Good vibration resistance, but requires anti-loosening design under long-term high vibration. |
|
Industry Applications |
Petrochemical, nuclear power, metallurgy, and thermal power boilers |
Machinery manufacturing, food and pharmaceutical, HVAC, power auxiliary equipment |
|
Maintenance frequency |
Disassembly is complex, and it is mostly used for long-term fixed installation. |
Easy to disassemble and replace, suitable for regular calibration or replacement. |
Flange type is the first choice for safety redundancy design of high-voltage systems, while threaded type is the mainstream economical and universal solution.
III. Performance Parameters and Selection Considerations
Accuracy class: Both conform to the IEC 60751 standard, commonly classified as Class A (±0.15℃) and Class B (±0.30℃), with no essential difference.
Thermal response time: Threaded type has a faster response time (e.g., 3s~10s) due to its lightweight structure, while flange type has a slightly slower response time (10s~40s) due to the thermal inertia of the flange.
Protection rating: Threaded products are widely available, with common ratings from IP65 to IP68, supporting corrosion protection (316L stainless steel) and explosion protection (Ex d IIC T6); flanged products are mostly customized for engineering projects, and the protection rating depends on the flange sealing design.
Wiring method: Both three-wire (mainstream industrial) and four-wire (high-precision laboratory) are supported. Two-wire is only applicable to high resistance models such as PT1000.
IV. Supporting Evidence from Market Product Examples
Typical threaded products:
Ruiwen PT100 Fixed Thread Resistance Temperature Detector: Supports M12×1.5 thread, measurement range -50~500℃, thermal response ≤40s, and customizable 4~20mA output.
Shanghai Yinxi fixed thread temperature sensor: thread specifications cover M6~M12, probe diameter φ6mm, protection level IP65, suitable for industrial sites.
Hankai FBWZPK-231AC: Supports M20×1.5 threads, temperature resistant design, suitable for power and chemical industries.
Flange type product characteristics:
Most flange type products on the market are customized for engineering projects, such as BD-JBF-PT100-A-DN25PN1.6. The flange specifications match the pipeline standards. There are no standardized retail products. They need to be purchased through industrial instrument suppliers.
V. Installation and Maintenance Recommendations
Flange type installation:
Ensure the flange faces are parallel and undamaged;
Use high-temperature resistant graphite gaskets;
Tighten the bolts evenly diagonally to avoid uneven loading;
Test the seal after installation to prevent leakage.
Threaded mounting:
Clean impurities from inside the threaded hole;
Apply thermal grease to improve heat conduction;
Tightening torque should be controlled between 15 and 20 N·m to avoid thread stripping.
Anti-loosening shims can be added for use in vibrating environments.
Selection rule: "Use flanges for high pressure, choose threads for low pressure; choose flanges for heavy vibration, choose threads for easy replacement."
