PTFE Expansion Bellows

Ethylene's Flexijoint expansion bellows have a proven record worldwide of handling the CPI's most corrosive pipe stress problems. They are formed from isostatically molded, FDA approved, virgin PTFE resin to guarantee product purity and uniform thickness.

Ethylene Flexijoint®

Actual Flexijoint Cross-Section

Actual Flexijoint Cross-Section

Ethylene Flexijoint PTFE expansion joints are flexible connectors and tremor barriers designed to compensate for misalignment, absorb expansion and contraction, and isolate vibration and shock in process piping, tanks and pumps. They also offer a low spring rate to protect stress sensitive FRP, glass or graphite equipment.

Flexijoints are available in sizes 1/2" to 42" and from 2 to 12 convolutions for maximum movement.

Flexijoint has almost universal chemical inertness, high and low temperature resistance, invulnerability to ozone and sunlight, outstanding flex life, and low acoustical impedance (sound dampening properties).

Flexijoint® Distinctive Features

  • Pure 100% Virgin PTFE Resin

    The unmatched performance of Flexijoint is due to its exclusive Fluoroforming™ process, a development of Ethylene. The Fluoroforming™ process employs only high molecular weight resin to utilize pure PTFE with no pigments or additives which might contaminate contacting fluids by leaching out, or to be vulnerable to blistering. In addition, high molecular weight with tightly controlled crystallinity, inherent in the Ethylene Fluoroforming™ process, results in lower permeation rates, outstanding flex-life and maximum tensile strength. Competitors which use paste extruded resin are NOT using Pure PTFE. They must mix a hydrocarbon such as Isopar™ to facilitate PTFE paste extruding.

  • Uniform Wall Thickness
    Uniform Wall Thickness

    Ethylene’s exclusive Fluorforming™ process guarantees multiple convolution walls of constant uniform thickness for any size. This relationship of heavy wall and geometry is one of the basic reasons for the outstanding performance of Flexijoints. Deep convolutions allow increased axial travel and also reduce the force necessary to produce movement or lateral misalignment. As a result, Flexijoints have a longer service life when compared to conventional blow molded or stretch molded expansion joints which introduce stress points and exhibit alarming thinning of the convolution wall and root. Note: Blow-molding is sometimes referred to as “contour” molding by some manufacturers.

  • T-Band™ Root & Sidewall Support
    T-Band Root & Sidewall Support

    Flexijoint T-Band™ reinforcement on the outside of the convolutions supports the convolution root and sidewall for improved service life and increased safety in high pressure applications. As pressure and temperature increase, the sidewall of the PTFE convolutions conform to the contour of the T-Band, improving stability under pressure.

  • T-Band™ Protection From Over Compression
    T-Band Protection From Over Compression

    Flexijoint T-Band™ metal reinforcement on the outside of the convolutions not only contributes to the pressure rating of the Flexijoint but also limits the total axial movement in compression. The shoulders of the T-Band™ are designed to butt when maximum compression limit has been reached to provide protection from excessive compression for improved safety and increased service life.

  • LimitLinks™ Protection From Over Expansion
    LimitLinks Protection From Over Expansion

    LimitLinks™ consist of stainless steel cables conforming to MIL-C5424 - the government specification for Aircraft Cable, at the ends of which stainless steel ball-shaped terminals are swaged. The opposite ends of each LimitLink™ are firmly anchored in the Flexijoint flanges in a manner which limits over expansion of the Flexijoint, but also leaves the terminals free to swivel as the flanges change position relative to each other during their adjustment to angular misalignment, parallel misalignment, purely axial motion or a combination of all three.

  • LimitLinks™ & T-Band™ Additional Benefits
    LimitLinks & T-Bands Additional Benefits

    LimitLinks provide easy installation even when the mating flange bolts don’t align. They also won’t get in the way and they never need to be removed for installation unlike competitors' LimitBolt designed expansion joints which may void warranties.

    T-Bands cover approximately 75% of the outside of the convolution when not compressed to provide protection from external damage such as falling tools or weld splatter.

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Download Flexijoint Brochure

Download Engineering Guide

Download Standard Specifications


  • Diameters from 1/2” through 42”
  • 2 through 12 convolutions
  • 150, 300 Class ANSI, J-bolt and other flanging available
  • Full vacuum with Vacuband support rings

Quick Selection Guide



How to Order

Ordering Instructions

Flexijoint® With Durcor®-62™

Durcor-62 Flange

Advanced Composite Technology

Durcor®-62™ Flanges are manufactured by PureFlex® Inc. from a proprietary advanced fiber-reinforced composite. Durcor®-62™ has tensile and compressive strengths that rival steel along with outstanding impact resistance that is unmatched in the industry. Its reinforcing fibers are long and interlocked; this interlocked reinforcement system transfers loads throughout the fiber matrix, making Durcor®-62™ Flanges virtually indestructible. The strength of Durcor®-62™ enables the Flange to maintain CLASS 150 rating and ANSI B16.5 dimensions. And allows it to be installed in any type of piping system without the need for special considerations. Durcor®-62™ Flanges excel in temperatures from (-)60°F to 300°F and has only .001" of thermal expansion across its full temperature range.

Tensile strength comparison
  • Tensile strength of 50,000psi per ASTM D-638 or 358 Mpa
  • Notched Izod impact strength of 30 ft. lb/inch per ASTM D-256 or 1760 J/M are achieved

Superior Performance

Durcor®-62™ vinyl ester resin backbone provides excellent protection when exposed to aggressive chemicals and hostile atmospheres such as acid sprays, bleach, salt water and high chlorides. Durcor®-62™ Flanges outperform stainless and ductile iron flanges not only in corrosive environments but non-corrosive as well. Its lightweight advantage reduces the need for heavier support structures for hanging, eliminates the need for extra equipment and personnel for pipe and fitting installation, and reduces pipe strain once installed. Durcor®-62™ Flanges are so dependable and maintenance free that we offer the industry's first 5 year, bumper to bumper warranty. Contact Ethylene or your local distributor for details.

  • Thread Strength
    Thread Strength

    Durcor®-62 provides greater than 210 Ft-lbs of thread strength. No need for Alloy Thread Inserts.

  • Materials
    • Bellows: Virgin PTFE
    • Flanges: Durcor®-62™ Advanced Composite
    • T-Bands™: Powder Coated Epoxy DI
      Option: Composite
    • LimitLinks™: 303 Stainless Conforming to
      Option: Monel

Flexijoint® PTFE Bellows


The Severe Service Expansion Joint

The unmatched performance of Flexijoint is due to its exclusive Fluoroforming™ process, a development of Ethylene™. This proprietary forming process guarantees convolution walls of uniformed thickness, maximum strength, and minimum permeability commensurate with greatest flexibility.

Ethylene also invented T-Bands™ & LimitLinks™. T-Bands™ on the outside of the convolution contributes to the pressure rating of the Flexijoint and also prevents the joint from over compressing. T-Bands™ also offer a degree of protection from falling tools or debris.

Unlike Limitbolt designed expansion joints, Limitlinks™ allow free swivel as the flanges change position relative to each other during their adjustment to angular misalignment, parallel misalignment, purely axial motion or combinations of all three.

Download Flexijoint w/Durcor®-62™


  • Lined Steel Pipe
  • Fiberglass Pipe
  • Glass Pipe
  • Pump Suction & Discharge
  • Load Cells
  • HVAC Noise Reduction
  • Expansion / Contraction
  • Misalignment
  • Reduce Vibration


  • Flanges are Strong As Steel
  • 1/2 The Weight
  • Class 150 Rated / ANSI B16.5
  • Lower cost vs. S.S Flg PTFE Bellows
  • Lower installed Cost
  • Maximum Travel - 2 to 12 convolutions
  • Size Range 1" - 12"
  • (-)60F to +300F
  • Zero Corrosion Rate inside & Out
  • 5 Year Flange warranty
  • Lower Life Cycle Cost - Guaranteed!!!


Size For Two Convolutions Each Add'L Convolution
1" 1.75 lbs .02 lbs
1 1/2" 2.50 .03
2" 3.75 .04
3" 6.25 .07
4" 8.75 1.0
6" 11.00 2.0
8" 19.00 3.0
10" 30.00 4.0
12" 42.00 5.0

Flexijoint® Styles

  • LimitBolt

    Provides resistance to rotational forces and limits lateral misalignments. Unlike competitors, the Flexijoint LimitBolt design does not require the removal of LimitBolts for installation.

  • LimitLink

    The industry standard and regarded as the most reliable PTFE expansion joint for severe services. Flexijoint with LimitLinks allow free swivel as the flanges change position relative to each other during their adjustment to angular and parallel misalignment, purely axial motion or a combination of all three. LimitLink™ also permits installation where mating pipe is not two-holed.

  • AntiSquirm™

    Each T-Band™ incorporates (3) radial spokes which rest on the Limitbolts, thereby restraining the T-Bands that hold the convolutions in balanced geometrical position. This feature will eliminate squirming or buckling effects and dramatically increase operating pressure capabilities in multi-convoluted Flexijoints.

  • Durcor®-62™

    Advanced composite flanges have the strength of steel with 1/2 the weight and will never corrode. ZERO CORROSION RATE! Request brochure “FlexDurcor” for more information.

  • FlexArmor®

    PTFE lined metal expansion joints provide double containment protection and higher pressure ratings. Visit the FlexArmor page for more information.

  • Hinged

    Flexijoint Hinged style expansion joints contain pivots which only allow the unit to bend in a single plane. Their hinge mechanisms are very effective at absorbing pressure — thrust and other external loads such as the weight of adjacent piping, which relieves the piping designer of having to provide additional supports and anchors as required by standard type expansion joints.

  • AnchorBase™

    AnchorBase is basically an anchor built around a LimitBolt Flexijoint. It is ready for bolting to a footing, floor, or other structural element of suitable mass. Distance from Flexijoint centerline to base bottom conforms to ANSI B16.5 for 150 lb base fittings.

  • Universal

    Flexijont Universal expansion joints consist of two bellows separated by a PTFE lined pipe spool. The primary purpose of this arrangement is to have a unit which will accept large amounts of lateral deflection and substantially reduced force (spring rate) required to cause movement.

  • Gimballed

    The Gimballed Flexijoint is basically the same as the hinge type except that instead of being limited to deflection in only a single plane, it can accept bending in any plane. It contains two sets of hinges connected to a central floating gimbal ring. Gimballed joints are the most reliable form of a flexible connector and are widely used for complex piping systems where proper anchoring & guiding may not be feasible. These flexible connectors, usually in pairs, will permit piping to float in relation to terminal points.

  • Specials

    Don’t want flanges on your expansion joints? Ethylene can provide cuffed ends for clamping directly to piping or virtually any other end connection on Flexijoints, including Tri-Clamp & Victaulic. Contact Ethylene for details.


Vacuum Ratings for Flexijoint® Bellows

The vacuum rating of a Flexijoint will decrease with increasing temperature, diameter, and number of convolutions. The table below gives the maximum working temperature for a Flexijoint operating at full vacuum.

Vacuband™ vacuum rings enable Flexijoints through 42” diameter to be rated for full vacuum at temperatures to 350°F. The Vacuband is a metal hoop inserted into the root of the convolution. Metal selection is based on the customer's specifications; materials such as Tantalum, Hastelloy®, Monel, stainless steels, Nickel and Zirconium are commonly used. Consult the factory for sizes or temperatures not listed.

Maximum Temperature (°F) for Full Vacuum Service
(without Vacubands)
*Consult Factory
Size Number of Convolutions
2 3 4 5 6 7 8 9 10 11 12
1/2 450 450 450 425 400 400 400 400 400 400 400
3/4 450 450 450 425 400 400 400 400 400 400 400
1 450 450 450 425 400 400 400 400 400 400 400
1.25 450 450 450 425 400 400 400 400 400 400 400
1.50 450 450 450 425 400 400 400 400 400 400 400
2 450 450 450 425 400 400 400 400 400 400 400
2.5 425 425 425 400 400 350 350 300 300 250 250
3 425 425 400 350 350 300 300 250 250 200 200
4 400 400 350 300 300 250 250 200 200 150 150
5 400 350 300 250 250 200 200 150 150 150 150
6 320 300 250 200 200 150 100 *CF *CF *CF *CF
8 250 200 200 150 100 *CF *CF *CF *CF *CF *CF
10 200 200 150 100 *CF *CF *CF *CF *CF *CF *CF
12 150 120 100 *CF *CF *CF *CF *CF *CF *CF *CF
14-16 120 *CF *CF *CF *CF *CF *CF *CF *CF *CF *CF
18-24 100 *CF *CF *CF *CF *CF *CF *CF *CF *CF *CF
28-42 *CF *CF *CF *CF *CF *CF *CF *CF *CF *CF *CF

Flexijoint® Weights

Example: An 8" Diameter, 5 convolution Flexijoint weighs 32 + (5-2) (3) = 41 lbs.

Note: Weights can be substantially reduced for low pressure applications.

Approximate Weight of Flexijoints®
(Pounds without packaging)
Limitlink™ Flexijoint with Two
Amount to Add
for Each Convolution
1/2 2 0.1
3/4 2 0.2
1 3 0.2
1-1/4 3 0.2
1-1/2 3 0.3
2 6 0.4
2-1/2 9 0.6
3 10 0.8
4 14 1
5 17 1
6 21 2
8 32 3
10 44 4
12 68 5
14 88 7
16 117 9
18 132 12
20 161 14
24 230 21
28 350 26
30 400 29
32 475 29
36 650 42
42 910 64