How to choose a thermocouple junction box? What are the differences between splash-proof, waterproof and plug-in types?

1. Core elements of thermocouple junction box selection
Environmental requirements
Humidity and corrosion: If there is water mist, oil or corrosive gas on site, waterproof (IP65/IP66) or corrosion-resistant materials (such as stainless steel, cast aluminum) junction boxes should be selected
Explosion-proof requirements: Explosion-proof junction boxes should be selected in hazardous areas such as chemical industry and oil fields, and their sealing and materials should comply with Ex explosion-proof certification
Temperature range: In high temperature environments (such as metallurgical industry), junction boxes made of high temperature resistant materials (such as nickel-based alloys or ceramic sheaths) should be selected to avoid melting of the sealing ring
Protection level standard
IP protection level: Splashproof type is usually IP44 (splashproof), waterproof type is IP65/IP66 (high pressure water spray or immersion), plug-in type generally has a lower protection level (below IP54) due to interface structure limitations
NEMA standard: Splashproof type corresponds to NEMA 3R, waterproof type corresponds to NEMA 4X (waterproof and corrosion resistant), industrial applications need to refer to international standards to match protection level

Installation and maintenance requirements
Quick disassembly and assembly scenarios: Plug-in junction boxes use standardized connectors and are suitable for equipment that needs to be frequently replaced or repaired (such as laboratory instruments)

Sealing requirements: The waterproof type needs to tighten the sealing ring (such as silicone or fluororubber) through threads to ensure long-term sealing; the splash-proof type relies on gaskets and buckle designs

2. Selection process and practical suggestions
Clear working parameters, measure temperature range, medium corrosiveness, mechanical vibration intensity, etc.
Matching installation method
Fixed: Flange or thread fixation is suitable for pipes or containers, and the insertion depth needs to be calculated (≥8-10 times the outer diameter of the protective tube)
Movable: Armored thermocouples with plug-in junction boxes are suitable for detection equipment that needs to be frequently moved

3. Verification and testing
Sealing test: Perform a water pressure test on the waterproof junction box (such as 0.5MPa water pressure spray for 5 minutes) to observe whether there is water seepage inside
Insulation test: Insulation resistance ≥100MΩ·m at room temperature (when length＞1m), and GB/T 30429 standard must be met at high temperature