Jointing methods for RC MULTIsafe® and RC MAXIprotect® PP/PE pipes -part I

Jointing methods for RC MULTIsafe® and RC MAXIprotect® PP/PE pipes -part I

Butt welding of pipes PE 100 Smart 2L and RC MULTIsafe® follows the same principles as for pipes made of PE 100. In case of pipes RC MAXIprotect® PP/PE-d with detection tape the difference consists in removing the protective jacket from the welding zone and using the butt welding machine with appropriate set of clamps, taking into consideration increased pipe diameter (due to protective jacket).

Pipes made of PE100 RC manufactured by RADPOL may be jointed with use of various methods as below:

  • butt welding in range of diameters ≥ 75 mm,
  • electrofusion welding mainly in range of diameters 25 – 110 mm,
  • mechanical connections:
    – couplings for water pipelines,
    – PE/steel transition fittings for gas pipelines,
  • flange connections (PE stub flange and metal backing ring).

The polyethylene pipeline contractor should use the jointing methods specified in the technical documentation, approved by the user of gas, water, or sewage network.

General principles

Butt welding consists in heating and melting of faces of jointed elements through their contact with the heater plate (called mirror) heated up to required temperature, and after removing the plate – connecting them to each other using appropriate pressure. Cooling of the joint should be realized in the natural way. It is forbidden to accelerate cooling by e.g. using water, ventilation, etc. The butt welding method is used to joint polyethylene pipes and fittings of the same diameter and wall thickness.

The difference in MFR (Melt Flow Ratio) of jointed elements is less important. Keep in mind that products of the same geometry (SDR), made of polyethylene of different classes (PE100 PE80), have different resistance to the internal pressure. That method should not be used for connecting pipes of wall thickness below 5 mm and diameter below 75 mm, as the misalignment to jointed elements must not exceed 10% of the wall thickness. For such small values it is virtually impossible to determine the error amount. Due to higher allowable ovality values for coiled pipes butt welding is used only for straight pipes.

Preparation of elements for welding

The welding place should be protected from negative environmental conditions, e.g. wind, too low temperature, dust, etc. In such situations take the appropriate preventive measures, e.g. use tent, increase the temperature with use of heater, etc. Butt welding should not be used in negative temperatures, but also during fog regardless the ambient temperature. After assuring proper conditions in the welder vicinity works may be realized in any weather. In order to avoid draughts in the pipes and excessive cooling of welded elements both distant ends should be plugged. Ends of element to be welded should be fixed coaxially in the welding machine, assuring the possibility of longitudinal movement of one element. Directly before welding the both ends of jointed elements should be trimmed with a trimming tool in order to remove the oxidized layer and make both pipe end faces completely planed (and parallel).

Butt welding of RC MULTIsafe® pipes is realized just like for traditional PE100 pipes, following the same parameters and welding procedures. In case of welding pipes RC MAXIprotect® PP/PE-d with detection tape it is first required to remove a piece of external jacket from the pipes ends, long enough for making a weld. Jacket removing should be realized with use of special tool designed for such purpose, available in RURGAZ offer. Maintain caution during that operation in order to avoid breaking the detection tape, located under the jacket. The tape ends with sufficient excess should be pulled from the pipes ends on both sides of the weld, and then connected by soldering or clamping and leave outside of the butt weld. The whole butt weld with tape placed on it should be secured with the heat-shrink sleeve put previously on the pipe in order to protect that place from the external conditions and mechanical damages. Displacement of external surfaces of connected elements should not exceed 0.1 of wall thickness. Ends of elements to be connected must not be damaged and must be free from contamination. In order to assure correct quality of welds pay special attention to the cleanness of tools, in particular the hot plate. Use the cleaning liquid which dissolves grease, bonds moisture, and evaporates quickly, as well as fresh, clean, absorptive, and non-dusting paper.

After preparing the pipes for welding the gap between connected elements after pressing them to each other should not exceed:

  • 0,3 mm for de < 225 mm
  • 0,5 mm for < de < 400 mm
  • 1,0 mm for de < 400 mm

Ends of connected elements should be also cleaned in the vicinity of welding zone for at least 10 cm so the contamination does not penetrate the contact surface during the technological activities. Faces of connected elements should be timed with a trimming tool just before welding. In case of contamination of faced surfaces it is sufficient to clean them with paper soaked in the cleaning liquid.