Electrical Insulation Standards for Cathodically Protected Pipelines
Release time:
2025-09-28
Standard Technical Specifications for Electrical Insulation of Cathodically Protected Pipelines
I. Core Indicators of Insulation Performance
Insulation Resistance Requirements
The DC resistance of pipeline insulation components (such as insulated flanges and joints) shall be ≥10 MΩ; in areas with high soil resistivity, this requirement must be increased to above 100 MΩ.
Withstand Voltage Strength
The insulating material must withstand a DC withstand voltage test of over 1000 V, and the AC withstand voltage test shall be conducted in accordance with GB/T 16927.1–2011.
2. Material and Structural Requirements
Material Properties
It must exhibit chemical resistance (pH 2–12), temperature resistance (-40°C to 120°C), and UV resistance; modified polytetrafluoroethylene or epoxy composite materials are recommended.
Mechanical strength
The flange connection area must meet the axial tensile strength requirements of the pipeline (e.g., >450 MPa for API 5L X65), and the insulation layer thickness must be ≥5 mm.
3. Testing and Maintenance Standards
Detection Method
DC Resistance Test: Conducted in accordance with GB/T 3048-2015, using a 500V megohmmeter for measurement.
Polarization Potential Monitoring: After eliminating IR drop, the pipeline polarization potential should be ≤ -850 mV (CSE).
Maintenance Cycle
Inspect insulation resistance every quarter and perform AC withstand voltage tests annually; replace insulation components immediately if any abnormalities are detected.
IV. Handling Special Environments
High Soil Resistivity Areas
Employ a distributed shallow buried anode bed (with spacing of 20–50 m) in conjunction with low-resistivity backfill material (bentonite + gypsum powder).
Stray current interference
Insulated flanges must be equipped with jumper terminals and a drain device to ensure that potential fluctuations are less than 100 mV.
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West Section of Huanghai Avenue, Hai’an City, Jiangsu Province (Fenghe Co., Ltd.)