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Insulating Joint
Mar 05, 2018

The insulation joint is the general description of pipeline joints featured by sealing performance and strength capability required by buried steel pipeline and the insulating property required by electrical corrosion. It is used for cathode protection of long pipeline for gas and oil supply so as to insulate each section of pipeline.

It consists of special-shaped bushing, connecting ring, cylinder, insulation board, insulation ring, seal stuffing, seal ring, short nipple and thermal shrinkage anticorrosive sleeve.

It clasps and fixes the insulation board and seal ring into the barrel through extrusion welding. After assembling, the inner objects shall be fixed on relevant position. The insulation joint is in good condition under soil pressure, specified pipeline operation pressure and factory or field hydraulic test. The potted component leans against the insulating plate tightly in the joint, which has everlasting elasticity. In addition, both sides of the potted component touch directly the naked surface of metal without moving, keeping the compactness of joint.

1 Shot Piece-1  2Connection Ring   3Insulating Flange   4 Cylinder Liner  5Insulating Plate

 6U-Shape Seal ring 7 Seal Packing 8 Shot Piece-2  9Inner Anticorrosive Layer  10Anticorrosive Thermal Shrinkable Sleeve


a. Good insulating property: 1000V megger test insulation resistance ≥25MΩ, breakdown voltage ≥6KV;

b.     Long life time: The same life time and strength as the pipeline;

c.      High strength: pressure test≥1.5PN(design pressure);

d.     Allowable temperature: -40100;

e.      Applicable medium: oil, gas, water, chemical materials and coal water mixture, etc;

f. Installation position: horizontal, buried and overhead;

g. Criteria for design: ASME B31.8; ASME B 31.4

h. Design specifications: ASME BPV Code VIII Div.I

Features of Materials

The materials of the product meet the following requirements:

Insulating materials: Laminar composite material of high strength epoxy resin and glass fire: ASTM D709 G11;

Bending strength: longitudinal direction ≥390MPa, cross direction≥290MPa;

Pulling strength: longitudinal direction ≥340MPa, cross direction≥240MPa;

Compression strength: ≥340MPa; Hygroscopicity: ≤30mg;

Water logging resistance≥5×108Ω; Breakdown voltage ≥35KV;

Composite steel: 20、16Mn  NB/T47008;ASTM A694 F52、F60、F65、F70、F85。

ASTM A694 F65;

Nozzle stub: 20#、16Mn  GB8163;Q345R GB713-2008;

L245、L360、L415、L450、L485 GB/T 9711.2-1999

X85、X80、X70、X65、X60、X56、X52     API SPEC.5L。

Sealing materials: O-shape or U-shape seal ring, fluorine rubber and nitrile-butadiene rubber conform to ASTM D2000;

Filling material: cold curing resin;

Insulating painting: imported liquid epoxy resin;

Anticorrosion materials: thermal shrinkage anticorrosion material. 

Features of Product

The factors that will affect the seal of insulating joint are as follows: 

1). Appropriate sealing gasket (reasonable geometry shape);

2). Simultaneous seal between the metal surface of insulating joint and the insulation ring;

3). Avoid multiple seal rings.

The U-shape seal structure of the insulating joints produced by our company fully meets the above requirements and has the following same advantages as the insulation with O-shape and rectangular seal ring: 

1). Prevent from medium leakage under high pressure;

2). The large medium flow distance before short circuit can withstand high internal pressure;

3). Simultaneous seal between steel, steel and steel and insulation ring;

4). The sealing performance remains unchanged even in occasional long bending or flexural stress.