ISL - Isolated Systems Limited

Industrial Noise Vibration &
Thermal Management Solutions




ISOFLEX Fabric Expansion Compensators


“Isoflex” Expansion Compensators:

  • “Isoflex Expansion Compensators”, (E.X.J.), are designed to provide: Protection of ductwork and other hardware from the effects of thermal expansion absorb expansion, vibration and when specified, installation misalignment.  Minimise transmitted loads to the Turbine outlet flange and by their very construction, E.X.J.’s also offer excellent acoustic properties.
  • Primarily designed for applications with increased operating temperatures, over and above those accommodated by both our single ply Flexible Connections and higher rated Multi-Layer Seals. – These applications include Gas Turbine Exhaust Systems.
  • E.X.J.’s are similar in construction to ISL Multi-Layer Seals but can feature higher temperature rated materials and wire mesh in their standard construction, which provide the following design features, necessary for the arduous operating conditions associated with G.T. Exhaust Systems:
  • Mechanical Strength
  • Protection from buffeting
  • Protection from high velocity gasses
  • Maintains “bulbous shape further promoting expansion compensation.
  • Standard construction E.X.J. can operate up to +550°C. as standard, (depending on specific seal construction)
  • Operating Temperatures up to +1000°C. can be accommodated with the inclusion of an Insulation Bolster* See Note.
  • E.X.J.’s can be supplied as “fabrics only” for installation onto existing steelwork or with supporting steelwork “carriers” – this is effectively a “cassette” design ready for installation between Gas Turbine outlet flange and the Exhaust Ductwork.
  • If the steel carriers are to be supplied, Gas Turbine and Exhaust Ductwork materials of construction must be stated.
  • Steelwork carriers can be manufactured to ASME IX or BSEN 1011-1:2009 standards.


Steel carriers can be supplied in the following arrangements:

  • “Hot To Hot” – Used on the majority of Gas Turbine Exhaust Systems where heat recovery or personnel protection are not required. – No internal steel carrier insulation is fitted.
  • “Hot To Cold” – Typically employed directly on the Exhaust outlet of a Gas Turbine. – Steel Carrier Internal insulation is fitted “downstream only due to extreme buffeting upstream.
  • “Cold To Cold” – Steel carrier is insulated on both upstream and downstream ends providing maximum heat retention for use by waste heat recovery systems.
  • Available in the following standard geometries:
  • “Circular Flat Flanged” (C.F.F.) - Circular with “plain ends” suitable for “Jubilee Clip” type installation.
  • “Rectangular Flat Flanged” (R.F.F.) - Square / rectangular with “plain ends” suitable for backing flat installation.
  • “Circular Angle Flanged” (C.A.F.) - Circular with flanged ends at 90 degrees to the body suitable for steel backing flanges. ** See Note
  • “Rectangular Angle Flanged” (R.A.F.) - Square or rectangular with flanged ends at 90 degrees to the body suitable for steel backing flanges. ** See Note.
  • Can also be manufactured as tapering and / or transitioning from circular to rectangular geometries.
  • Can be supplied pre-punched to match clients existing ductwork flanges or “plain flanges” for drilling during installation, where specific hole centres are unknown.
  • Fire rated construction available for specific applications.
  • All related steelwork can be specified, designed and manufactured in-house, including:
  • Steel Backing Flats / Flanges, Steel Inner sleeves to protect the Flexible Connection from abrasive particles or high velocity gasses / buffeting.



* Insulation Bolsters comprise of additional layers of High Temperature Insulation Wool, encased by High Temperature Woven Glass Fabric and further protected by a layer of wire mesh.

The woven Glass Fabric can vary from 12mm thick to 150mm thick and the wire mesh can be constructed from either 304 Stainless Steel, 316 Stainless Steel or Incoloy depending on the maximum operating temperature.

*Due to potential issues with heat build-up in the corners of angular flanged Multi Layer Seal arrangements, operating temperature are limited to +550°C.  For operating conditions in excess of +550°C. Flat Flanged geometry must be specified.


"FM-3-LS" Reference Table:

Plies Construction Temp (Max) Pressure (Max) Application
  1. Silicone Coated G/F
  2. PTFE Foil
  3. Woven G/F
  4. 25.4mm Insulation Wool
  5. Woven G/F
  6. Incoloy Mesh
+600°C 1400mm WG Light Acid Attack

Notes on additional “over-Insulation” on Gas Turbine Expansion Joints

NOTE: Whilst it is common to insulate the Gas Turbine for reasons of personnel protection or heat recovery, standard construction E.X.J.’s must never be insulated or over-clad, as the relatively low temperature rated outer plies, (Silicone coated glassfabric and PTFE Foils layers), will be damaged.

On installations where it is necessary to insulate over the expansion joint – this can be accommodated using a special construction Expansion Compensator, type: SFM-3-LS, which replaces these low temperature rated layers with a more robust construction, summarised below.


Standard "FM-3-LS" Construction Special "SFM-3-LS" Construction (Suitable for over-cladding)
  1. Silicone Coated G/F
  2. PTFE Foil
  3. Woven G/F
  4. 25.4mm Insulation Wool
  5. Woven G/F
  6. Incoloy
  1. Stainless Steel Mesh
  2. Woven G/F
  3. Stainless Steel Foil
  4. Woven G/F
  5. Stainless Steel Foil
  6. Woven G/F
  7. 12.5mm Insulation Wool
  8. 12.5mm Insulation Wool
  9. Woven G/F
  10. Incoloy Mesh

T3 Rated Shrouds:

In certain hazardous area installations it is necessary to limit the surface temperature of any “hot” steelwork to prevent accidental ignition of ambient gas. ISL Expansion Joints, supplied in the special “SFM-3-LS” construction, detailed above, can be provided with a T3 rated Shroud effectively insulating the hot carrier steelwork from the ambient air.