Preparation Before Installation
Ensure the equipment flange specifications match the thermocouple flange, conforming to ASME B16.5 or JB/T 8622 standards, with matching nominal pressure (PN) and temperature ratings.
Inspect the flange sealing surface: It should be free of scratches, oil stains, and corrosion. The raised face or tongue-and-groove surfaces should be flat. Defective flanges are prohibited.
Select a matching gasket: Metal spiral wound gaskets (316L + flexible graphite) are used for high temperature and high pressure applications, flexible graphite gaskets for general corrosive environments, and PTFE-coated gaskets to avoid metal contamination (e.g., in pharmaceutical and semiconductor industries).
Installation and Operation Procedure
|
Step |
Operation Standard |
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1. Centering and Alignment |
Flange end face parallelism deviation ≤ 1.5‰ of the flange outer diameter, and the absolute value ≤ 2mm; axis deviation ≤ 1° |
|
2. Gasket Placement |
Place the gasket centrally on the sealing surface; avoid displacement or folding; the use of PTFE tape, silicone sealant, or ordinary rubber gaskets is strictly prohibited. |
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3. Probe Insertion |
The insertion depth of the protective tube ≥ 10–15 times the outer diameter, and not less than 75mm in high-pressure fluids; avoid the probe touching the pipe wall. |
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4. Bolt Tightening |
Use the multi-round diagonal tightening method: - First round: 10% of the target torque - Second round: 20% - Third round: 60% - Fourth round: 100% Use a torque wrench; pneumatic or manual brute force is prohibited. |
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5. Torque Reference Values |
- DN100 PN16: 80–120 N·m - DN150 PN25: 120–180 N·m - DN200 PN40: 180–250 N·m |
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6. Installation Orientation |
Vertical installation is preferred; for horizontal installation, a heat-resistant support bracket must be installed to prevent the protective tube from sagging and deforming due to its own weight. |
Wiring and Cold Junction Treatment
Polarity connection: Red wire is negative (-), yellow wire is positive (+), reverse connection is strictly prohibited.
Use K-type special compensating wire, with the shielding layer grounded at one end (control cabinet side).
Extend the cold junction to the constant temperature zone of the control cabinet (temperature ≤100℃), and enable automatic cold junction compensation (AFC) on the instrument.
Installation Prohibitions and Failure Prevention
Do not force installation if the flange is not clean or the sealing surface is damaged.
Do not tighten bolts unilaterally or non-diagonally, which may cause flange distortion and leakage.
Do not use flanges as lifting points or to bear external mechanical loads.
Do not insert the probe directly into a medium with a temperature >500℃ while it is cold (thermal shock can cause the protective tube to burst).
Do not use unshielded wires in strong electromagnetic fields (interference can cause errors of up to ±3℃).
The installation quality of fixed-flange mounted probe-type thermocouples directly determines the reliability of temperature measurement and system safety. Strict adherence to the above procedures ensures zero leakage, high accuracy, and long service life, making it the most reliable technical practice in high-pressure, large-diameter, and continuous production systems.
