Equipment for local and volumetric PWHT (heat treatment of welded joints)

Ways of heaters and thermal insulation fixing

Different methods are used for fixing heating elements and thermal insulation on the surface of pipelines and vessels.

The most common is fastening of heating elements with banding strap. Heaters are pre-fastened with elastic straps. The final fastening of heating mats is carried out with a banding strap using a special tools and clamps. In this case it is recommended to install at least three belts of banding strap on each belt of heating elements: one belt at both sides of the heating mat and one at the level of white beads at ends of heaters at the place of welding “cold end” to “hot” body.

For better fastening, we recommend to use fourth belt, fixing the zone in front of the detachable connections, as shown in the figure. It is necessary to avoid sagging which can lead to the stress state.

Fastening heating elements with banding strap

Fastening with a banding strap has a number of indisputable advantages over other types of fasteners:

  • lower price in comparison with other types of fasteners;
  • extended service life due to the use of stainless steel materials;
  • extreme simplicity and convenience in installation process;
  • thanks to the original design, the need to purchase bolts, nuts and washers, keys of various sizes is eliminated;
  • the banding tool has a long exploitation life.

In places where standard use of banding tape for fixing heating elements and thermal insulation is not possible, for example, heat treating ends of a tube sheet or a vertical surface, we offer another method of fixing heating elements: using insulation pins, that are welded to the surface with a capacitor discharge by special machines.

Fastening heating elements and thermal insulation with insulation pins

Insulating pin has a special shape that provides reliable fixation with shallow welding of metal. This technology has proven itself during heat treatment of large-diameter products. Fastening occurs through a hole in bead of heating element. After welding, the heating element is fixed with a special clip.

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