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As a standard, the joints we use for temperatures up to 130 °C are self-shrinking and have an inner adhesive layer. The intermediate ring is either foamed directly on site, or the joint is supplied with a segmental intermediate ring (crescents made of PUR foam). The joints for temperatures 130 - 300 °C are standardly supplied as self-shrinking with an inner adhesive layer and a second waterproof lock (shrink sleeve).

1. Working conditions

The joints must be installed in such a way as to ensure good access for sealing the joints with shrink foil by heating. Therefore, the pipe must either be lined at the point of the joint, or a trench must be dug in the excavation below it so that there is a space of at least 25 cm from the casing pipe at the point of the joint. If the joints are assembled in rainy weather, the assembly site must be covered, e.g. with a tent, tarpaulin, etc., to keep the joint dry throughout the assembly. The pipeline can be welded solely by a welder that has passed the state certification exam, and the welded joint coefficient should be V = 08 without root defects. Welding work also includes finishing, i.e., the cutting off and the adjustment of the segment of the service pipe. The shrink sleeve must be fitted to the pipe before the pipe is welded. Installation of the joints is only carried out after pressure or X-ray tests have been performed. Piping along the pipeline is laid out according to a layout scheme, where each component of the pipeline is precisely designated. The method and symbolism of the designation are clearly discernible from the legend in the attached drawing. After finishing the welding work, it is necessary to fix in the anchors with concrete. The bottom of the foundation joint at the anchor must be deepened so that the cross-section of the horizontal axis of the system is at the centre of the block. Multiple-pipe distribution systems (e.g., central heating and domestic hot water) and cases where there is no anchor on some of the pipes are handled at the spot of the anchor, so that the axial movement of the unanchored pipe is not restricted even without the anchor (e.g., by wrapping with cardboard, which allows the lengthwise dilatation of the pipe through the body of the anchor even after the anchor is fixed by concrete). Directional routing of the piping in the concrete blocks in front of the compensator is also handled in the same way. Concrete blocks serving as anchors and guides shall be set into the overgrown terrain. Pressure tests can be started no earlier than 10 days after the completion of the concreting of the anchors. After the pressure tests are successfully completed, the joints can be assembled. Thorough the compaction of the pipe backfill material at a minimum of 150 mm above the top of the pipe is very important for the proper operation of the system. Green warning foil shall be placed on each pipe so that it extends at least 50 mm across the diameter of the pipe on each side.

2. Pipe preparation prior to joints installation

The surface of the steel pipes is factory-protected with anti-corrosion coating and does not need to be cleaned separately. Before installing the joints, all wet foam must be removed from the ends of the pipes by hollowing them out to a depth of a min. of 2 cm. The inner surface of the joints casing must be clean, free of any dirt, soil, or grease deposits that could be transferred to the surface of the casing pipe during the casing installation process. The surface of the ends of the casing pipes must be degreased with e.g. acetone or benzine and roughened with sandpaper at the place of the installation of the shrink sleeve in a width of at least 15 cm so that a matte surface is achieved and the surface is degraded, or the greasy layer is removed. It is advisable to do this roughening after the shrink-sleeve has been pushed into the joint to prevent the casing pipe from clogging again when the shrink sleeve is pushed in. For the welding of service pipes, regulations and principles for the installation of water or steam pipes apply.

3. Installation of joints with shrink sleeve

(can only be performed by trained personnel)

  • before welding the service pipes, a shrink sleeve is placed onto one end of the casing
  • the surface of the service pipe and weld must be cleaned and dried
  • for joints from 150 °C to 300 °C, the following guidelines apply:
  • measure the moisture content of the pipe before removing the cap, if the pipe is wet, the pipe part should be dried with a propane butane flame
  • around the end of the casing pipe, cut the foam perpendicularly in a length of 25 mm and remove the protective cap with PUR foam, taking care not to damage the alarm wires or its casing, if applicable
  • thread a longitudinally slit aluminium hose onto the pipe at the joint, stretch it along the length of the joint and fasten it with adhesive tape
  • wrap 1 layer of fibreglass (“KOBEMAT“) onto the prepared aluminium hose and fasten with adhesive tape
  • stack the individual sections all around the circumference so that they fit tightly on the ”KOBEMAT“ fibreglass (the mineral wool sections must be protected from moisture), and tighten with foil, and finish by securely tightening with adhesive tape at the opposite pipe locks
  • The shrink sleeve is pulled over the joint, the protective cover is removed and one flush hole with d = 22 mm is drilled (for joints with a diameter greater than 400, the hole is 25 mm). The shrink sleeve is centred so that its centre is directly over the weld.
  • Tightening and sealing of the ends of the slide is achieved by heating both ends evenly (over a length of approx. 80 mm) with a weak propane flame. The two ends of the shrink sleeve are heated until they are firmly shrunk and perfectly bonded to the casing.
  • After the shrunken ends have cooled down (below 40 °C!), the joint is foamed. After the foam has cured, it is necessary to check that the foam has not been pushed between the shrink sleeve and the casing at both ends of the shrink sleeve. This shall check the tightness of the joint - if it has oozed out, it is necessary to reassemble the joint.
  • The surface of the casing, on which the shrink foil will sit, is cleaned with technical alcohol, roughened with sandpaper, and the residues from sanding are removed.
  • The prepared surface is activated by heating with a propane butane flame to a temperature of 60 °C.
  • After heating and checking if the correct temperature of the surfaces is complete, the shrink foil is placed on it and shrunken with a flame.
  • After the assembly of the joint is completed, it is very important to check whether the adhesive is pressed out all around the shrink foil at both ends, which is proof of the correct shrinkage of the shrink sleeve.
  • The foaming holes are cleaned and sealed with plugs using a polyfusion welder. Protruding ends are cut off, and the surface is aligned.
  • Blind spots and the surrounding surface are degreased with technical alcohol, roughened and heated to 60 °C.
  • Circular foil (FOPS) is attached to the prepared surface and a second waterproof lock is applied in the form of a shrink sleeve.
  • Each delivery of joint material is provided with detailed instructions.

4. Foaming of joints

smrst spojAfter shrinking and closing the joint, drill a filling hole and perform the actual foaming of the joint. PUR foam is supplied for each joint separately (both components must be mixed together in a larger container). Immediately after mixing, the mixture must be poured through the drilled hole into the clutch housing. When the joint is foamed, the surface temperature of the sheath must be between 15 °C and 45 °C. If the temperature is not within these limits, it must be reached either by shielding the joint from the sun or by heating it with a gentle flame in winter. The temperature of the PUR foam components must be maintained between 15 °C and 25 °C. After pouring the mixture, wait until the foam reaches the filling or venting hole, at which point the hole is closed with the supplied plug. After the foam reaction is complete (approx. 20 min.), the plug is covered and sealed with a cap (e.g. FOPS) applied in the same way as the shrink foil is assembled, or the plug is replaced with a welding plug. The foam must not leak under the shrink sleeve during foaming.