Materials Technology

UNAFLEX expansion joints are made from a combination of materials that have been used for many decades, and others developed more recently in response to technological advancement and demands of consumers.

All materials used to make UNAFLEX expansion joints undergo a battery of tests and control procedures which replicate actual conditions under which the expansion joint must operate. The materials are tested in the following areas:

  • Flexibility
  • Temperature resistance
  • Chemical resistance
  • Mechanical strength
  • Heat Convection
  • Recovery rate after compression
  • Tensile strength
  • Abrasive and tear strength

Materials and Application Technology Combined to Provide the Best Possible Engineering Support

Experience and technology enables UNAFLEX to provide its customers with the very best engineering and technical support.

We are able to:

  • Document design with detailed construction drawings, measurements and instructional drawings along with information on relevant specifications for other components.
  • Provide the best materials based on operating conditions
  • Design for optimum survivability
  • Protect plant ductwork and operating systems from vibrations and thermal stress

Expansion Joint Material Specifications

Utilized for Metal, Rubber, PTFE and Fabric Expansion Joints

PTFE | Kevlar | Stainless Steel | Carbon Steel | Inconel | Hastelloy | Monel | Neoprene

UNAFLEX standard bellows material is A/SA240 321ss. Other materials available to UNAFLEX to manufacture bellows are:

  • A/SA240 304ss
  • A/SA240 304Lss
  • A/SA240 316ss
  • A/SA240 316Lss
  • A/SA240 310S
  • B/SB443 Alloy 625 (Inconel® 625)
  • B/SB168 Alloy 600 (Inconel® 600)
  • B/SB575 Alloy C276 (Hastelloy® C276)
  • B/SB575 Alloy C22 (Hastelloy® C22)
  • B/SB127 Alloy 400 (Monel® 400)
  • B/SB409 Alloy 800
  • Duplex Alloy 2205
  • Hastelloy® X
  • Nickel 200
  • Alloy 20
  • AL6XN

UNAFLEX welders are qualified in accordance with ASME Section IX latest edition (available as required). We stock various types of bellows materials, flanges, plates, pipe and threaded rods for fast response and delivery times.

PTFE

Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene that finds numerous applications. PTFE is a fluorocarbon solid, as it is a high-molecular-weight compound consisting wholly of carbon and fluorine. PTFE is hydrophobic: neither water nor water-containing substances wet PTFE. PTFE has one of the lowest coefficients of friction against any solid. It is very non-reactive, partly because of the strength of carbon–fluorine bonds, and so it is often used in containers and pipework for reactive and corrosive chemicals.

Kevlar®

Kevlar® is the registered trademark for a para-aramid synthetic fiber developed at DuPont in 1965. Typically it is spun into ropes or fabric sheets that can be used as such or as an ingredient in composite material components. Currently, Kevlar® has many applications because of its high tensile strength-to-weight ratio; by this measure it is 5 times stronger than steel on an equal weight basis. When used as a woven material, it is suitable for mooring lines and other underwater applications.

Stainless Steel

In metallurgy, stainless steel is defined as a steel alloy with a minimum of 10.5 or 11% chromium content by mass. Stainless steel does not stain, corrode, or rust as easily as ordinary steel, but is not stain-proof.

Carbon Steel

Carbon steel, also called plain-carbon steel, is steel where the main interstitial alloying constituent is carbon. The American Iron and Steel Institute (AISI) defines carbon steel as: "Steel is considered to be carbon steel when no minimum content is specified or required for chromium, cobalt, molybdenum, nickel, niobium, titanium, tungsten, vanadium or zirconium, or any other element to be added to obtain a desired alloying effect.

Carbon steel is used in the manufacture of tools and dies, where the finished product needs to be very hard and wear-resistant. The more the carbon content in steel, the better will be its ability to be hardened using heat and quenching.

Inconel®

Inconel® is a registered trademark of Special Metals Corporation that refers to a family of austenitic nickel-chromium-based super alloys. Inconel® alloys are typically used in high temperature applications.

Hastelloy®

Hastelloy® is the registered trademark name of Haynes International, Inc. The trademark is applied as the prefix name of a range of 22 different highly corrosion-resistant metal alloys loosely grouped by the metallurgical industry under the material term "super alloys" or "high-performance alloys". The predominant alloying ingredient is typically the transition metal nickel.

The primary function of the Hastelloy® super alloys is that of effective survival under high-temperature, high-stress service in a moderately to severely corrosive and/or erosion prone environment where more common and less expensive iron-based alloys would fail, including the pressure vessels of some nuclear reactors, chemical reactors, distillation equipment and pipes and valves in chemical industry.

Monel®

Monel® is a trademark of Special Metals Corporation for a series of nickel alloys, primarily composed of nickel (up to 67%) and copper, with some iron and other trace elements. It is resistant to corrosion and acids, and some alloys can withstand a fire in pure oxygen. It is commonly used in applications with highly corrosive conditions.

Rubbers/Elastomers

Rubbers or elastomers are mixed with various chemicals in order to provide the reinforcement and curing ingredients required to produce the physical properties necessary for the service conditions.

A wide choice of basic polymers (rubbers) is available, and some of these rubbers can be blended or compounded to obtain different properties.

ASTM
Designation
D1418-79

Common
Name

Composition

General Properties

NR Natural Isoprene, natural Excellent physical properties including abrasion and low temperature resistance. Poor resistance to petroleum-based fluids
IR Polyisoprene Isoprene, synthetic Similar to natural rubber
SBR SBR Styrene-butadiene Good physical properties and abrasion resistance. Poor resistance to petroleum-based fluids
CR Neoprene Chloroprene Good weathering resistance. Flame retarding. Moderate resistance to petroleum-based fluids. Good physical properties
NBR Buna N Nitrile-butadiene Excellent resistance to petroleum-based fluids. Good physical properties
IIR Butyl Isobutene-Isoprene Very good weathering resistance. Excellent dielectric properties. Low permeability to air. Good physical properties. Poor resistance to petroleum-based fluids.

EPDM


EPM

Ethylene-propylene rubbers

Ethylene-propylene-diene

Ethylene-propylene

Excellent ozone, chemical, and aging resistance. Poor resistance to petroleum-based fluids.
FPM Viton®, Flourel® Hexafluro-propylene-vinyl idene fluoride Excellent oil and air resistance at both high and low temperatures. Very good chemical resistance.
Source:
Rubber Manufacturers Association Sheet Rubber Handbook, Third Edition


Standard Belt Materials For Use in Fabric Expansion Joints

(Material code refers to Continuous Operating Temperature Limit in degrees F.) Various single layer and composite belt materials are available and are selected based on the specific application temperatures and flow media characteristics. The following is a list of UNAFLEX’s standard belt designs.

UNAFLEX utilizes the highest grades of the materials including: Elastomers, Fluoroelastomers, Fluoropolymers, Fluoroelastplastics and Metals. (Carbon & Stainless Steel, Monel®, Inconel®, and Hastelloy®) in manufacturing our products. We are a Genuine DuPont Dow Elastomers Viton® Licensed Manufacturer and supply FSA-DSJ-401-02 (ASTM-D6909-03) specified Fluoroelastomer materials. For more information or a copy of this specification, contact UNAFLEX or the Fluid Sealing Association.

Index of Terms

  • Number=Operating Temperature
  • CP=Composite
  • VI=Viton® “B” cover
  • SI=Silicon Cover
  • TA=Fluropolymer-PTFE laminated
  • FPR=Fluropolymer Cover
  • GT+Gas Turbine application design

Kevlar® is a registered trademark of DuPont, Inconel® is a registered trademark of Special Metals Corporation, Hastelloy® is a registered trademark of Haynes International, Inc., Monel® is a registered trademark of Special Metals Corporation, Neoprene® is a registered trademark of DuPont

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