While Teflon-sheathed PTF-RTDs possess excellent chemical resistance in corrosive industrial environments, common faults are often caused by sheath damage, insulation degradation, and improper installation. Effective prevention requires a systematic approach encompassing four aspects: material selection, standardized installation, environmental control, and regular testing.
I. Optimize Structural Design to Enhance Body Protection
Adopt a double- or multi-layer sheath structure: Prioritize composite structures such as "stainless steel protective tube + integral sintered PTFE layer" or "PTFE + wear-resistant outer layer (e.g., PFA or silicon carbide)" to enhance resistance to mechanical erosion and penetration.
Select High-Temperature Resistant Alternative Materials: In operating conditions approaching 250℃, it is recommended to use PFA (perfluoroalkoxy) instead of traditional PTFE, as it offers superior thermal stability and is less prone to softening and deformation.
Ensure the Sealing Structure Matches Process Requirements: Select appropriate fixing flanges or thread specifications based on the pipe connection method to avoid inadequate sealing due to misalignment during installation.
II. Standardize Installation Operations and Avoid Human-Induced Damage
Prohibit Excessive Bending: The bending radius during installation should be ≥50mm to prevent fatigue fracture of the internal platinum wire due to stress concentration.
Control Tightening Torque: Use a torque wrench for threaded connections to avoid overtightening, which could cause sheath cracking or damage to the sealing surface.
Proper On-Site Protection: Avoid contact with sharp tools during installation to prevent scratches on the PTFE layer, affecting its corrosion resistance.
III. Optimize Operating Environment and Reduce External Risks
Control Medium Temperature: Ensure long-term operating temperature does not exceed 220℃ and short-term peak temperature does not exceed 250℃ to prevent sheath softening and aging.
Reduce Vibration Impact: Install buffer bends or fixed supports on high-vibration pumps or pipelines to reduce the impact of continuous vibration on welding points and leads.
Keep Junction Boxes Dry and Clean: Use all-plastic corrosion-resistant or stainless steel junction boxes, ensuring the sealing rings are intact to prevent moisture intrusion and terminal oxidation.
IV. Implement Regular Inspections for Early Fault Warning
Conduct Spark Testing: Scan the sheath every 6-12 months using a 12kV spark leak detector to promptly detect hidden defects such as micropores and cracks.
Measure Insulation Resistance: Regularly test the insulation resistance between the probe and the casing using a megohmmeter. The normal value should be ≥100MΩ; a value below 1MΩ requires investigation.
Check Lead Connection Status: Pay close attention to whether the terminals are loose or oxidized. Clean and retighten as necessary to ensure accurate three-wire compensation.
V. Strengthen Storage and Transportation Management
Use Three-Layer Protective Packaging: Use an "anti-static bag + cushioning foam + moisture-proof outer box" structure during transportation. The box should be marked with "Precision Instruments" and "Shockproof".
Avoid Long-Term Outdoor Storage: During storage, store in a dry, ventilated warehouse, away from strong acid and alkali environments to prevent corrosion or moisture absorption before use.
Key Reminder: The core of prevention lies in "nipping problems in the bud". Many malfunctions show no obvious signs in their early stages. Only through systematic inspections and data recording can we shift from reactive maintenance to proactive maintenance.
