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Home>>Pipefittings knowledge>>Insulating Joint
The Insulating Joints is a new generation developed product to resolve use problems of old insulating flange. It is the essential pressure component necessary for steel pipeline cathodic protection system, broadly applicable to steel pipeline cathodic protection systems. Yochoic company's insulating connectors adopts a unique design based on referencing foreign latest product structure to overcome problems of inadequate rigidity, prone to leak, unable to be buried under ground, short service life, etc. The insulating connectors have realized buried parts maintenance-free function and allow a service life matching the pipelines.

Technical Characteristics:

Pressure Grade:1.0MPa~40MPa
Service Life:same as the service life of pipeline
Ambient Temperature:-30°C~90°C
Applicable Medium: oil, gas, water, chemical feed, mineral slurry

Quality Requirement:

Insulating Resistance value≥10MΩ @DC1000V, Maximum voltage:≥3KV
Insulating Intensity: no breakdown or arc for one minute @2500V 50Hz
Hydraulic Pressure testing pressure: 1.5 times of desingned pressure
Air-tight Testing Pressure: equivalent to designed pressure
Non-destructive Testing: All the butt-connectors are 100% ray-detected according to JB4730-94; other pressure welding seams are 100% magnetic power detected. Groove: adopt API 5L standard

Quality Requirement:

This Product adopt's material satisfy below request
Insulanting Material: hign strength epoxy resin and fiberglas stratification composite material
Bends Intensity: Lengthways≥390MPa Side direction≥290MPa
Pulls Stretch Intensity: Lengthways≥340MPa Side direction ≥240MPa
Compressive Intensity:≥390MPa Water-absorbing≤30mg
Scaks in water behind resistance≥5x108Ω Breakdown resistance≥35KV
Assemblies steel: 16Mn JB4726; ASTM A694 F52 F60
Short pipe 20# 16Mn GB8163-99 X70 X65 X56 X52 X46 API SPEC.5L
Sealing Material: O shape or U shape gland ring: Rubber fluorine, Jing base butadiene rubber, According ASTM D2000
Lining Material: Cold solid colophony
Insulating Paint: Imports liquid epoxy resin
Anti-corrosin Insulating Material: two-component solvent-free epoxy coating, anti-corrosion thermal contraction bushing. Practical application
  1. on existing objects, and during building,
  2. on gas pipings, water line and liquid fuel pipings,
  3. before and over distribution gas stations,
  4. in systems storerooms oil and gassy mines,
  5. on gasholders and liquid fuel tanks,
  6. under and overground building.

Mechanical properties
• bodies of insulating joints are made as welding construction of steel plates (from constructional carbon steel or low-alloy steel),
• results of ivestigations and tests are in documentation enclosed to ours products.

Electrical properties
• using high class insulating materials is graduate high quality,
• using exchangeable spark gaps,

  1. lack of sparking and breakdowns during erectrical test at alternating voltage 5kV (50 Hz) in timel min. (test are made before and after hydrostatic test),
  2. insulating joint's resistance above 5 MO at voltage 1 kV in dry condition,
  3. lack of brakedown at voltage 15 25 kV during control of leaktightness insulating coat connection external spark gap - insulating joint.


  1. calculations are carried out according to WUDT-UC-WO-0 and PN-EN 13480-3,,
  2. additional value of bending moment and tensile forces might be dictated by customer,
  3. necessary parameter to carry out calculations is giving operating pressure.

• used pipes to welding according to PN-EN 10208, DIN 1626, API Spec 5L, ASTM A53 and others,
• (rings) steel elements are performed from metal plate and die forging wg PN-EN 10028,
• 0-nng seal is nitryl, fluoride or silicone rubber, that is ageing resitance and resistnce in common use medium,
• laminating. epoxide plates are insulating materials according to PN-EN 60893 and DIN 7735.

Welding and non-destructive tests

  1. steel elements of insulating joint are connected by MIG-welding according to approved procedures by independent certificate organisation,
  2. carried out fusion welds are testing non-destructive methods: VT (visual test), PT (dye penetration test) and UT (ultrasonic test) through specialists who have competence certificate of Welding Technology Institute.

Using external coating
• polyurethane caoating according to PN-EN 10290,
• termo-shrinkable coating according to PN-EN 12068, XANUSA" ,,REIHEM"
• paint coating (epoxides) according to PN-EN 12944.
Using internal coating (lining)
• paint coating (epoxides) according to PN-EN 12944, PN-EN 10301
Tests • construction, dimensions, materials,
• hydrostatic strenght test for l,5xMOP pressure (maximum operating pressure),
• pneumatic leakproof test for pressure - 6 bar,
• electrical test at alternating voltage 5kV / 50 Hz in time 1 min. (sparking - not give rise),
• resistance above 5Mf2 at constant voltage 1 kV.

The range of execution
• working parameters of insulating joints that are shown in table below, apply to standard carrying out.
• there is an opportunity of providing insulating joints by increasing working parameters, which means:
working pressure to 420 bar (ANSI 2500), working temperature -50'C ^ 160*C,
• additional carrying out with internal spark gap or adaptation for external spark gap.

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