Monolithic Insulating Joints

What are the Monolithic Insulating Joints?

Monolithic Insulating Joint is a metal-insulated, non-seamable, prefabricated construction

with or without a spark gap to ensure electrical discontinuity of the pipeline in which it is installed.


Use of a Monolithic Insulating Joint

  • Underground and aboveground transmission and distribution pipelines,
  • Existing and under construction facilities,
  • In front and behind gas reduction stations,
  • Aboveground and underground gas and crude oil storage facilities,
  • Tanks and installations for liquid and gaseous fuels.

Mechanical properties

  • Monolithic Insulating Joints bodies are made as welded structures from thick metal sheets (carbon or low alloy structural steel),
  • Results of measurements and tests are included in documentation enclosed with our products.

Electrical properties

  • The quality is guaranteed by the use of high-class insulating materials,
  • The use of exchangeable spark gaps,
  • No sparking or breakdown during the electrical test with alternating voltage of 5 kV (50 Hz) for 1 min. (test performed before and after hydrostatic test),
  • Resistance of Monolithic Insulating Joints above 1GΩ at 1kV in the dry state,
  • No breakdown at a voltage of 15 ÷ 25 kV (depending on requirements) when checking external insulation coating with holiday testing.


  • Standard according to WUDT-UC-WO-0, PN-EN 13480-3 and ASME VIII Div. 1
  • Additional values such as bending moment and bursting forces can be imposed by customer,

  • Necessary parameter for calculation is the working pressure.


  • Pipe use for welding according to

    PN-EN ISO 3183, PN-EN 10028, DIN 1626, API Spec 5L, ASTM A53 and other,

  • Steel elements (rings) made of sheet metal, metallurgical rings and forgings according to PN-EN 10028,
  • Insilating materials are laminated epoxy boards according to PN-EN 60893 and DIN 7735

Welding and non-destructive testing

  • The steel elements of the Monolithic Insulating Joints are joined together by MAG welding in accordance with approved procedures by an independent certification body,
  • The welds are examined using non-destructive methods: VT (visual testing), PT (penetrant testing) and UT (ultrasonic testing) by 2nd level specialists holding competence certificates issued by the Welding Institute.

Applied exterior coatings

  • Polyurethane coatings according to EN 10290,
  • Heatshrinkable coatings acc. to PN-EN 12068, “CANUSA” “REIHEM”.
  • Paint coatings (epoxy) acc. to PN-EN 12944.

Internal coatings used

  • Paint coatings (epoxy) acc. to PN-EN 12944, PN-EN 10301.


  • Construction, dimensions, materials,
  • Hydrostatic strength test with pressure 1.5xMOP (maximum working pressure),
  • Pneumatic tightness test at a pressure of 6 bar,
  • Electrical test with 5kV/50Hz alternating voltage for 1 minute (no sparking),
  • Resistance above 1GΩ at 1 kV DC.

Scope of performance

  • It is possible to supply Monolithic Insulating Joints with increased working parameters, i.e. working pressure up to 420 bar (ANSI 2500), working temperature -50°C ÷ 180°C,
  • additionally with internal, external spark gap or with adjustment for external spark gap.

Product datasheet

Manual of transportation, storage, assembly and use of Monolithic Insulating Joints

Product gallery

We provide solutions for the gas and oil industry

If you have any questionsplease contact us

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