Sleeves, ensuring the energy efficiency of heating networks

During the installation process of a district heating network, the pre-insulated steel tubes are connected in the trenches by welding. The junction between two pre-insulated pipes, materialized by welding, is consequently not isolated. To protect the network and ensure its energy performance, it is necessary to isolate this part with an insulating sleeve. The sleeve serves to ensure sealing and insulation. This element, made on site, consists of a HDPE sheath (identical to pre-insulated steel pipes) and a PUR foam insulation. It is placed so as to bond the ends of the tubes and to form a continuity with the pre-insulated parts. The laying of sleeves, placed in accordance with industry standards, helps to minimize heat losses and ensures effective insulation across the entire network.

Two coexisting models of insulating sleeves

There are currently two models of sleeves:

• The heat shrinkable sleeve with collar: This is a type of conventional sleeve, the most commonly used when installing a heat network. It has 2 sealing levels.
• The heat shrinkable electrofusion sleeve: This sleeve is produced in the same manner as the heat shrinkable sleeve with collar. Its principal characteristic is that the seal is no longer provided by a sealant but by welding HDPE.

There are also three specific sleeves:

• The reduced heat shrinkable sleeve which is used to insulate a reduction.
• The end of line sleeve. This sleeve is closed on one side and is used when there is a delay in a buried network.
• The charge tapping insulation kit. It is used to insulate the network when tapping on the existing network.

Installing a double-ended sleeve

• Clean the steel tubes, protective sleeves and the sleeve with a cloth.
• Position the insulating sleeve on the tube.
• Centre the sleeve over the connection.
• Sand the pipe ends which are to be covered by the insulating sleeve using sandpaper, then wipe with a cloth soaked in solvent.
• Enable the protective tubing by preheating them with a propane-butane torch until they have a semi-matt plastic look.
• Stick the sealing strip about 5-10 mm beyond the marks.
• Partially peel off the protective film at the bottom and fold it outside.
• Put the sleeve in place in accordance with the marks and remove the protective film.
• Evenly and gently heat the insulating sleeve by moving the flame.
• Clean the area of ​​overlapping heat shrinking bands and remove the protective covering them.
• Gently heat the part covering the insulating sleeve until there is perfect adhesion of the 2 elements. Let cool.
• Drill a hole in the centre of the insulating sleeve and check for leaks.
• Pour polyurethane component into the insulating sleeve through the previously drilled hole and seal it. The sleeve temperature should be between 18 and 45 ° C.
• When foam appears in the discharge port, weld the stopper.
• Remove drips from the foam using a scraper.