WearFlex (R) Telescopic Seals

Wearflex® telescopic seals are designed to compensate for large axial tube movements (100-350 mm) at high temperatures whilst maintaining a seal preventing air ingress into the furnace. They are manufactured using pre-fabricated stainless steel half pipe sections, and insulated on the inside to ensure good thermal insulation and personnel protection.

Design properties of telescopic seal

Telescopic Seal during Hot & Cold Position


  • Seals top section of reformer furnaces / process heaters / boilers where tubes penetrate the roof.
  • Utilized in the chemical and petrochemical industry.
  • Prevents cold air ingress into the radiant section.


Features :

  • Made of insulated stainless steel half-pipe sections.
  • Absorbs large axial movements up to 350 mm.
  • Quick and easy installation.
  • Air tight seals.
  • Prefabricated.


Telescopic Seals vs Conventional Method

Telescopic Seals are used when tubes have a large expansion in the axial direction only.

Telescopic Seals compensate for the large axial movements whilst retaining the seal on the roof penetration as well as continuing to insulate the expanded tube sections preventing additional radiant heat loss.

Conventional methods usually utilise insulation blankets wrapped around the tube.

This method is ineffective when tubes have large expansion in the axial direction as the insulation blankets are unable to expand proportionately resulting in radiant heat loss from the exposed sections of tubes. Gaps are also exposed at the furnace roof allowing for air ingress.

Expanded reformer tube (hot condition) with Installed Telescopic Seals. All exposed tube surfaces remain insulated and the gap between the tube and roof plate is effectively sealed.

Sections of reformer tubes protruding through the furnace roof allowing excessive radiant heat loss to the environment and allowing ambient air ingress into the furnace through the roof gaps.

How Telescopic Seals are designed and installed?

Firstly, some details are taken into account such as :

  • Process temperature
  • Required cold face temperature
  • Diameter of tubes
  • Minimum and maximum movement of tubes

The data are then used to design & fabricate Telescopic Seals in our factories and shipped to our clients.

Telescopic Seals installation how to, step by step:

  • It is installed at pigtail connection and on top of the steel roof.
  • The upper set of two half-pipe sections (fixed around each tube) moves like a telescope over the lower set (fixed at the roof casing plate).

* Installation within 5-10 minutes.
* Using a screwdriver & stainless steel jubilee clips.

Telescopic Seal during hot and cold position

Key Benefits

  • Prevent cold ingress air through the existing gaps resulting in improved furnace efficiency of reformer furnaces / process heaters / boilers.
  • Compensate axial movements up to 350 mm.
  • Easy and quick installation.
  • High temperature resistant
  • Reduce the possibility of tube damage due to rapid quenching.
  • Block radiant heat loss on exposed tube surfaces.
  • Cost effective with very fast payback on investments.
  • Personnel safety enhancement.

Telescopic Seals installed on roof of furnace