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① Insulating joints. Pipeline insulating joints come in various types such as flange type, integral type (buried), and union type. In recent years, the developed integral buried insulating joints feature a monolithic structure, direct burial, and high insulation performance, overcoming the drawbacks of insulating flanges such as poor sealing performance, assembly affecting insulation quality, inability to be buried, and external flanges being prone to dust accumulation. They are ideal insulating connection devices for pipelines.

Locations where insulating connections need to be installed include:

a. Connection points between pipelines and wells, stations, or storage facilities;

b. Boundaries of equipment ownership along the pipeline;

c. Connection points between branch pipelines and main pipelines;

d. Junctions between pipelines of different materials, new and old pipelines, and pipelines with and without anti-corrosion coatings;

e. Both ends of large crossing sections (such as rivers or roads);

f. Sections affected by stray current interference;

g. Boundaries where different cathodic protection methods are applied.

② Insulating supports and insulating pads. When pipelines pass through walls or cross highways or railways using casing pipes, electrical insulation between the pipeline and the casing is required, typically achieved with insulating supports or insulating pads.

Pipelines should be electrically insulated from support frames, pipe bridges, tunnel pipes, piles, and reinforcing steel in concrete. If insulating joints are already installed at both ends of a pipe section, insulating the above-ground pipe section from the buried pipeline, then the pipeline can be directly mounted on support frames without additional electrical insulation.

③ Other electrical insulation. When pipelines cross rivers using weight blocks, fixed anchors, or concrete weight coatings, the pipeline should be electrically insulated from the reinforcing steel in the concrete, and the original anti-corrosion coating of the pipeline must not be damaged during installation.

Pipelines should maintain electrical insulation from all encountered metal structures.

(2) Longitudinal electrical continuity of pipelines.

For non-welded pipeline connections, welded jumper wires should be used to ensure the longitudinal electrical continuity of the protected pipeline, facilitating current flow. For prestressed concrete pipelines, when applying cathodic protection, the longitudinal reinforcement of each pipe section should be connected end-to-end with jumpers to ensure the longitudinal conduction of cathodic protection current. Sometimes, a parallel cable can be laid, with each prestressed pipe section connected to it, to achieve electrical continuity. For long-distance pipelines, insulating facilities are installed at the inlet and outlet of stations. To ensure the pipeline's overall electrical continuity, jumper connections are generally made for electrical continuity. However, in cases where cathodic protection interference occurs, to limit the extent of interference on the pipeline, jumper connections at the station inlet and outlet can be omitted. In such cases, multiple constant potential rectifiers can be used to protect the pipelines entering and exiting the station separately.

Pei Yingying  1862587  9268