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Chapter 10
Summary Material selection lubrication cleaning working discipline
Material selection lubrication cleaning working discipline are all items to give ample attention in vacuum-based science and industry. The selection of materials must always be preconditioned by their suitability to give a ‘proper’ vacuum. Outgassing, vapour pressure, leak tightness and corrosion resistance, thermal degradation and permeation are important characteristics to be taken in account. Depending on the specific employment of the material, other more general material properties may also play an important role. For metals there is the question of enough mechanical strength (Pressure Equipment Directive PED). In practice, many incidents of collapsing vacuum systems upon first evacuation are known. In the selection of elastomer seals, elasticity and dimensional stability are particularly important features. Under pressure, in particular at elevated temperatures, permanent deformation may occur, which also may result in leakage. In certain circumstances the wear resistance and the flexibility should be taken into account. The choice of materials can also be determined by a large number of physical circumstances. Magnetic properties, heat conductivity, thermal expansion, electric conduction in metals, electrical and thermal insulation in case of glass, ceramics and synthetics, light transmittance through viewports, light absorption in optical experiments and optical emission properties may play a role. Depending on the process circumstances chemical material properties must also be considered carefully. Finally, factors such as cost, machinability and deliverability play an important role in addition to vulnerability, reliability and security. Selection criteria for the choice of metals and alloys, glasses, creamics and synthetic materials are reviewed in detail. For the lubrication of moving parts under vacuum conditions both wet and dry lubricants are available. Motion mechanisms for application in vacuum are initially designed as being intended for use under atmospheric conditions. However, in the choice of a lubricant one must take into account the influence of a vacuum environment. The section about cleaning procedures is completely revised, adapted to the changed views in this area and more focused on complete vacuum systems.
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Contents Material selection lubrication cleaning working discipline
10.1 General considerations on the selection of materials 614
10.2 Vacuum properties of materials 615
10.3 Surface outgassing 618
10.4 Bulk outgassing 619
10.5 Measurement of outgassing rate 620
10.6 Permeability 622
10.7 Vapour pressure of materials 625
10.8 Decomposition of materials 630
10.9 Summary of outgassing phenomena 632
10.10 Specific selection criteria for metals and alloys 634
10.11 Specific selection criteria for glasses 638
10.12 Specific selection criteria for ceramics 639
10.13 Specific selection criteria for synthetic materials 641
10.14 Lubrication in vacuum 646
10.14.1 Dry lubrication 647
10.14.2 Wet lubrication 648
10.15 Cleaning procedures 649
10.15.1 Bulk outgassing 649
10.15.2 The ‘physical’ surface 649
10.15.3 Surface contamination 650
10.15.4 Adsorbed gases and vapours 653
10.16 General rules for working with vacuum systems 655
10.16.1 What’s clean should be kept clean 655
10.16.2 Pumping procedures 656
10.16.3 Operating errors and malfunctions 657
