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Jointing Technology
KRAH MISR provides trained engineers to supervice the installation and welding. All Krah pipes are produced automatically with a socket and spigot, which are adaptable to the following kinds of jointing techniques:

Integrated electro fusion It is important to choose the most suitable and permanent joint tecnique. The welding with the help of electro fusion has been a common method in the market for years. Above all because this jointing technique is very favourable, simple and secure, which has caused Krah to develop this technique for big pipes according to DVS2207-1. A fusion wire is included into the socket of the pipe. After putting the socket and spigot of the two pipes, that shall be connected, together, the wire is heated with the help of a special fusion device whereby the two pipe ends (the socket and the spigot) are welded together. This jointing technique allows pipes to be installed in such a short period of time never achieved before. With only one welding device it is possible to install a pipeline of 72m with a diameter of 1200mm inbetween 8 hours.

Integrated electro fusion socket

DN / ID [mm] voltage [V] time [sec.] nos. welding devices
300 15 780 1
400 18 840 1
500 20 900 1
600 24 1020 1
700 25 1080 1
800 33 1020 1
900 39 720 1
1000 40 1080 1
1100 41 1200 1

DN / ID [mm] voltage [V] time [sec.] nos. welding devices
1200 43 1260 1
1300 46 1320 1
1400 28 1020 2
1500 32 1020 2
1600 33 1080 2
1700 34 1200 2
1800 40 1900 2
1900 38 1100 2
2000 39 1200 2
2300 44 1380 2
Average welding parameters for larger diameters on request

Welding proceduren Generally the electro fusion socket and the spigot are already prepared for the welding and the welding wire is included into the socket before delivery. After the basic justification of the pipes the plastic foil, which serves as protection, is removed. The connection of the welding wire should be at the top of the pipes The pipe is justified, the inside support ring necessary for pipes which are larger than 800mm, is put into the right position and the outer tensile band is tightened. Now the wire ends can be connected to the welding device. The pipe contains a barcode, which includes all necessary information for the welding. After having finished the welding a certain cooling time which depends on several factors, has to be respected. The result is a permanently and longitudinally strong superior joint of two pipes.

Software The welding device has the capacity to record any individual welding. These welding records are saved in the device and can be read out by the computer. The software which is needed for this is called (Krahcode). With this software two things can be done: On one hand the data of the welding device can be read and administrated and on the other hand the barcodes for the welding of the pipes can be made.

Traceability Information uploaded on to the electro fusion device can be used to trace back specific product batches. The barcode is added to the fittings as well as to the pipes and contains information about pipe history, product type, pipeline components etc.

Electro fusion socket incl. welding device and barcode

V seam extrusion welding
The pipes and fittings are jointed with the help of an extrusion welding extruder. The outside of the ends are chamfered. Thus a welding seam is produced which looks like “V” . The welding has to be done according to DVS 2207 part 4.
Extrusion welding
The pipes and / or fittings which shall be connected are jointed by a socket and spigot joint. Thus the two pipe ends are connected with the help of an extrusion welding device. The jointing method can be carried out inside or/and outside of the pipe. This jointing is most suitable for low-pressure gravity pipes and manholes.

Heat element butt welding
The pipes and fittings are jointed with the help of a heating element butt welding machine. The ends of the pipes and fittings are butt-welded. This kind of jointing method is only recommended for pipes and fittings with a maximum wall thickness of 150mm and with diameters from DN/ID 300mm to DN/ID 2500mm. The welding has to be done according to DVS 2207 part 1.

Flange connection
The ends of the pipes and fittings are jointed with the help of a steel flange and a rubber gasket. Depending on the type of pipe the flange adapters are completely manufactured with the pipe, or the flanges are available as separate fitting. This kind of jointing method is mostly used for open sea discharge application and for tank connections. The greatest advantage of this connection is the facility of disjointing.

Gasket connection
Our system has solid plain socket and spigot, with an integrated EPDM sealing. The minimum wall thicknesses of the spigot is according to EN134763- table 7 and in addition the ring stiffness of the socket plus the ring stiffness of the spigot is higher than the ring stiffness of the pipe.


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