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Flexible Piping Systems

Engineering Design Standard RX3000

Expansion Joints of TEFLON®


Table of Contents References
  • EJDM2002 - Expansion Joint Design Manual
  • WWW.PTFEFLEXJOINTS.COM
  • DuPont TEFLON® Manual
  • Engineering Standard RX0001

Expansion Joints of TEFLON®


1.0 PURPOSE

The purpose of this document is to provide general specification information for the transferring of chemicals utilizing expansion joints of TEFLON®.

2.0 SCOPE

2.1 This standard describes guidelines to choose expansion joints of TEFLON®. In addition, this specification recommends additional procedures for selecting qualified manufacturers and appropriate distribution outlined in Engineering Standard RX0001.
2.2 See Engineering Standard RX0001, "Flexible Products Specification and Reliability Improvement" for general guidelines for expansion joints of TEFLON®.
2.3 If an expansion joint is used as a permanent installation, then a documented design analysis should be completed.

3.0 DEFINITIONS

3.1 Components - flanges, hardware, grommets, and bellows.
3.2 Bellows - molded PTFE component including reinforcing rings.
3.3 Limit Rod - bolt component restricting overextension and misalignment.

4.0 HOW TO USE THIS SPECIFICATION

4.1 EJDM 2002 lists various expansion joint styles. A specification sheet (example 1) for each standard style of expansion joint, provides:
  • Nominal Size
  • Neutral Length
  • Maximum Axial Travel
  • Maximum Misalignment
  • Maximum Angular Deflection
  • Spring Rates
  • Materials of Construction
  • Weight
  • Part Number
4.2 Additionally, the EJDM 2002 provides a pressure rating chart (example 2) for all styles of expansion joints of TEFLON®.

Example 1: Specification Sheet

Example 2: Non-Shock Pressure vs. Temperature

5.0 IMPORTANT DESIGN CONSIDERATIONS

The use of the "Expansion Joint of TEFLON® Application Guide" should be used in the design of standard or special applications when possible. This document will request specific information that allows experts to recommend an expansion joint of TEFLON® to decrease risk and increase life expectancy. This guide can be done electronically on the Resistoflex expansion joint web site "Ask the EJ Doctor" section.

5.1 LINER MATERIALS - Testing information in EJDM 2002 reflects the use of TEFLON® PTFE, DuPont T-62 expansion joint bellows. Any resin other than DuPont T-62 will affect the flex life, permeation rates, and overall life of the expansion joint (see DuPont TEFLON® test data). All expansion joints MUST call out the base resin material, not just PTFE or FEP to insure the specificity within the broad family of fluoropolymers.
5.2 TEMPERATURE - Plastics have a tendency to lose strength as the working temperature increases. Non-Shock working pressure at Temperature example is shown above (example 2) and present in EJDM 2002.
5.3 APPLICATION - A careful consideration must be taken on the working conditions of the expansion joint. If the expansion joint application is a shock situation or contains two or more movements, it could change the capabilities of the expansion joint. A general rule for two or more movements is 50% of the rated movement values.
5.4 MEDIA - The bellows is the only wetted part of an expansion joint of TEFLON®. Atmosphere conditions may require available limit rod and flange options such as stainless steel or Kynar® coating if the standard carbon steel hardware and painted ductile iron flanges are not acceptable. All expansion joints of TEFLON® should require a safety shield or wrap.
5.5 PRESSURE-VACUUM - The pressure and vacuum rating coupled with temperature and movement usually determines which expansion joint can be used. If standard expansion joints will not meet the required design specifications, additional expansion joint options such as super heavy-duty liner, internal vacuum rings, and stainless steel housings should be used.
5.6 TESTING

100% PIECE TESTING   Each final production piece must pass the following testing:
  • Hydro Test - To ensure final product is free from defects 100% of finished expansion joints shall be proof tested hydrostatically at 1-1/2 times their ambient temperature pressure rating with any leakage resulting in cause for rejection.
  • Roll Test - Before molded in to convoluted form each expansion joint should be roll tested by compressing liner to 50% of its diameter in two different planes to force cracks or other faults. Any non-conformance or premature fault shall result in cause for rejection.
PRODUCT PERFORMANCE TESTING   Expansion joints of TEFLON® shall be capable of passing qualification tests designed to demonstrate the joint's ability to withstand severe operating conditions. Once an expansion joint design has passed qualification testing, re-testing is not required. The expansion joint manufacturer shall make joint qualification test reports available upon request. Qualification testing is as follows:

Flex Life Test   Subject hose to destructive flex life test to determine allowable operating pressure and proof test pressure.
  • One expansion joint of each size shall be installed at neutral length on flex tester.
  • Flex joint at 50% of the maximum allowable compression and extension at specified pressure and temperature.
  • Pressurize unit to failure at 100°F.
  • Record burst pressure.
  • Unit shall be certified to 100,000 cycles while still retaining full pressure capability.
  • One cycle shall be defined as neutral-compression-neutral-extension-neutral.
NOTE: Allowable operating pressure is also known as "rated working pressure" and "working pressure".
Static Testing   Subject representative expansion joint of TEFLON® to static test. Test Stages shown in figure 1:

Figure 2: Static Testing

6.0 QUALITY DOCUMENTATION

Manufacturer's design, engineering, manufacturing, sales, and service shall be certified to ISO 9001 and AS9000.

Document revised August 2003
This document may be used and reproduced only with permission of Resistoflex.
The information contained herein is provided only as a guide for the use of Resistoflex products and does not constitute an express warranty of any kind. Resistoflex specifically disclaims the implied warranty of merchantability and fitness for a particular purpose.

Confidential

TEFLON® is a trademark of DuPont. Only DuPont makes TEFLON®


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