Preamble
Due to their extraordinary properties expansion joints made with Polytetrafluoroethylene (PTFE) bellow material are used particular in applications with aggressive media and elevated temperatures. The designs as well as the operation conditions differ widely. This is the case especially for specifications concerning overall length, flange layout, diameter of support rings, movement range, guiding elements, wall thickness of the PTFE bellow and the minimal requirements of operating parameters like pressure/vacuum ratings.
This brochure provides information on standardized specifications regarding the design and operation limits and hence provides qualitative guidelines for the improvement of the operation reliability and prevention of sizing errors. The brochure is restricted to expansion joints whose bellows made of paste-extruded and sintered PTFE and contains recommendations of the Technical Guideline 12-0040 issued by the German “Interessengemeinschaft Regelwerke” (IGR).
This technical brochure is edited by the pro-K Fluoropolymergroup and was technically worked out by Robert Meyer zu Westram, SGL Group / Dr. Schnabel GmbH.
CONTENT
1 Introduction
2 Function of Expansion Joints
3 Design features
3.1 General
3.2 PTFE bellow manufacturing technology and design related properties
3.2.1 Manufacturing of bellows
3.2.2 Influence of the bellow geometry
3.3 Construction materials
3.3.1 PTFE bellow
3.3.1 Flanges
3.3.2 Support rings
4 Operation conditions
4.1 Movement absorption
4.2 Pressure/temperature related application limits
4.3 Resistance to vacuum
4.4 Load alternation
5 Dimensions and Designs
5.1 Dimensions
5.1.1 Bellow and support rings
5.2 Special designs
6 Testing
6.1 General (scope of testing)
6.2 Testing body
6.3 Test of support rings
6.4 Tests of PTFE semi-finished product (liner)
6.4.1 Density
6.4.2 Tensile strength and elongation
6.5 Tests on finished products (expansion joint)
6.5.1 Test of appearance and workmanship
6.5.2 Dimensional check
6.5.3 Test of electrical charging
6.5.4 Prototype test of PTFE-expansion joints
6.5.5 Alternating load
7 Package, storage, transport
8 Labeling
9 Operation
9.1 Intended use
9.2 Prohibited actions
9.3 Residual risks
9.4 Safety shields