- Email: [email protected]
High-speed test at boundary conditions
FEATURE
Figure 12. The hardness change caused by chemicals on SIFEL3702 compared with FKM and FVMQ.
Figure 13. The hardness change caused by chemicals on adhesive grades of material.
Adhesive/coating and gel types can be handled in the same manner as standard silicone type materials. Regardless of the type used, the base polymer structure based on the perfluoropolyether backbone provides:
The introduction of perfluoroether elastomer provides engineers with a wide range of opportunities to improve the processing and performance of sealing, coating and bonding operations in various applications exposed to severe conditions.
• Low-temperature flexibility as low as –50°C. • High-temperature stability as high as 200°C. • Excellent resistance to a variety of fuels, additives, solvents, acids and alkalis.
Contact: Shin-Etsu Chemical Co. Ltd. 1-10 Hitomi, Matsuida-machi, Annaka-shi, Gunma, Japan, Tel: +81 27 384 5380, Fax: +81 27 384 5308, Email: [email protected], Web: www.shinetsu.jp
Figure 14. The hardness change caused by acids on a potting gel grade of perfluoropolyether.
This feature is based on a paper presented at the 5th International MERL Conference, ‘Oilfield Engineering with Polymers 2006’ organized by MERL and Rapra Technology. For copies of the Proceedings contact: MERL Wilbury Way, Hitchin, Hertfordshire SG4 0TW, UK. Tel: +44 1462 427850, Fax: +44 1462 427851, Web: www.merl-ltd.co.uk. Or contact: RAPRA Technology, Shawbury, Shrewsbury, Shropshire SY4 4NR, UK. Tel: +44 1939 250383, Fax: +44 1939 251118, Email: [email protected], Web: www.polymerconferences.com
High-speed test at boundary conditions By Bob Flitney Professor Hugh Spikes from Imperial College in London has developed a test that is designed to be applicable to the testing of lubricants with metal-to-metal bearing combinations, but the basic idea of providing boundary lubrication at a high sliding speed has some potential interest for seal material testing. The starting point for the work was a perceived requirement for a mild lubricated wear test. Environmental concerns are forcing large and very rapid changes to engine oil formulations. As new anti-wear components of engine oils are developed a reliable way of assessing the antiwear and anti-scuff effectiveness of new additives and formulations quickly and cheaply is required. Current lubricated, mild wear, tests are not up to the job. It would also be helpful to have a more ‘scientific’ mild wear test to help in research on lubricated wear. 12
Most current mild wear tests are based on pure sliding, non-conforming contact with high sliding speeds. Because of the high sliding speed, the test often operates in mixed-lubrication and is then sensitive to viscosity. The pressure is usually unrealistically high particularly at the start of the test. One potential solution is to rotate both surfaces, to give a mixed sliding and rolling wear interface. This distributes wear around contact and so there is much less change in local geometry and thus contact pressure. However it does
introduce a problem of accurate wear measurement. Wear depends on sliding distance, so to obtain sufficient wear in a reasonable time a high sliding speed is required. But a high sliding speed normally means a high entrainment speed and thus a high EHL film thickness, and so less wear. By moving the surfaces in opposite direction, contra-rotation, can produce a high sliding speed with a low entrainment speed. If two test materials are rubbed together at different speeds in opposite directions it is possible to obtain high sliding, and thus plenty of wear, in boundary lubrication conditions. The current tests have involved a ball on disk mini traction machine, as shown in Figure 1. The problem then becomes measuring the wear, which is distributed along a wear track on
Sealing Technology June 2006
FEATURE
both surfaces, in a metal-to-metal combination. The current work, which is studying metal-tometal lubricated contacts, has developed a technique using atomic emission spectroscopy with inductively coupled plasma (ICP-AES). This permits very accurate assessment of the wear particles in the oil. The results so far have demonstrated good repeatability and have been compared with alternative measurement methods. More details of the test method and results obtained can be found in Reference 1. The method of wear measurement discussed in this work is very specific to the sliding pair combination being tested. However, the basic test method provides an interesting approach as seal testing presents the same problem. It is usually very difficult to accelerate material testing without creating unrealistic loads. Increasing the speed increases the lubrication often to the benefit of the mating pair and not the test period. This paper may provide the source of ideas for some new approaches to this ever-present problem.
Reference 1. J. Fan and H. Spikes: New test for mild lubricated wear in rolling-sliding contacts. STLE
Figure 1. Diagrammatic view of the ball on disk tester used for the contra-rotating tests.
Annual Meeting, Las Vegas, Nevada, USA, May 2005.
Contact: Professor Hugh Spikes, Head of Tribology Section, Department of Mechanical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK.
Tel: +44 20 7594 7063, Email: [email protected], Web: www.imperial.ac.uk/me This article is based on a presentation made by Professor Spikes to the British Fluid Power Association (BFPA) Technical Committee TC 16: Fluids on 26 January 2006.
Patents Piston seal
Seal with leakage vent Applicant: Waters Investments Ltd, USA This invention discusses methods of providing a defined path to vent fluid in the event of seal failure. It is concerned with preserving the integrity of surfaces with closely controlled tolerances to prevent damage in the event of a leak. This patent is concerned
particularly with high pressure gas chromatography up to 1400 bar, but the designs shown appear to be similar to those which are standard practice on other high pressure fittings. Patent number: WO 2006/023653 Inventors: J. Angelosanto, J.A. Luongo and F.A. Rubino Publication date: 2 March 2006
Applicant/Inventor: G. Liepold (USA) This patent relates to piston seals that may be used for the transfer of sterile fluids. A plastic piston has circumferential channels that contain a ribbed plastic wiper that
seals against the cylinder bore. A number of geometries are shown. There is additionally a design that is cantilevered from the piston skirt. Patent number: WO 2006/015324 Publication date: 9 February 2006
Valve gasket with retainer Applicant: Waters Investments Ltd, USA This patent is concerned with the seals for valve components on equipment such as high pressure liquid chromatography instruments. Once a gasket has aged and creep has occurred it is susceptible to being displaced when the pressure fluctuates. Analytical instruments, in particular,
Sealing Technology June 2006
are sensitive to the rebound and pressure ripple effect, and pressure can be from 350 bar up to 1400 bar. One of the valve components will have a receiving groove to retain the gasket in position during pressure fluctuations. Patent number: WO 2006/02400 Inventors: J.A. Janiuk et al. Publication date: 2 March 2006
Examples of the piston and seal arrangement for a sterile fluid transfer device, from WO 2006/015324.
13
Figure 12. The hardness change caused by chemicals on SIFEL3702 compared with FKM and FVMQ.
Figure 13. The hardness change caused by chemicals on adhesive grades of material.
Adhesive/coating and gel types can be handled in the same manner as standard silicone type materials. Regardless of the type used, the base polymer structure based on the perfluoropolyether backbone provides:
The introduction of perfluoroether elastomer provides engineers with a wide range of opportunities to improve the processing and performance of sealing, coating and bonding operations in various applications exposed to severe conditions.
• Low-temperature flexibility as low as –50°C. • High-temperature stability as high as 200°C. • Excellent resistance to a variety of fuels, additives, solvents, acids and alkalis.
Contact: Shin-Etsu Chemical Co. Ltd. 1-10 Hitomi, Matsuida-machi, Annaka-shi, Gunma, Japan, Tel: +81 27 384 5380, Fax: +81 27 384 5308, Email: [email protected], Web: www.shinetsu.jp
Figure 14. The hardness change caused by acids on a potting gel grade of perfluoropolyether.
This feature is based on a paper presented at the 5th International MERL Conference, ‘Oilfield Engineering with Polymers 2006’ organized by MERL and Rapra Technology. For copies of the Proceedings contact: MERL Wilbury Way, Hitchin, Hertfordshire SG4 0TW, UK. Tel: +44 1462 427850, Fax: +44 1462 427851, Web: www.merl-ltd.co.uk. Or contact: RAPRA Technology, Shawbury, Shrewsbury, Shropshire SY4 4NR, UK. Tel: +44 1939 250383, Fax: +44 1939 251118, Email: [email protected], Web: www.polymerconferences.com
High-speed test at boundary conditions By Bob Flitney Professor Hugh Spikes from Imperial College in London has developed a test that is designed to be applicable to the testing of lubricants with metal-to-metal bearing combinations, but the basic idea of providing boundary lubrication at a high sliding speed has some potential interest for seal material testing. The starting point for the work was a perceived requirement for a mild lubricated wear test. Environmental concerns are forcing large and very rapid changes to engine oil formulations. As new anti-wear components of engine oils are developed a reliable way of assessing the antiwear and anti-scuff effectiveness of new additives and formulations quickly and cheaply is required. Current lubricated, mild wear, tests are not up to the job. It would also be helpful to have a more ‘scientific’ mild wear test to help in research on lubricated wear. 12
Most current mild wear tests are based on pure sliding, non-conforming contact with high sliding speeds. Because of the high sliding speed, the test often operates in mixed-lubrication and is then sensitive to viscosity. The pressure is usually unrealistically high particularly at the start of the test. One potential solution is to rotate both surfaces, to give a mixed sliding and rolling wear interface. This distributes wear around contact and so there is much less change in local geometry and thus contact pressure. However it does
introduce a problem of accurate wear measurement. Wear depends on sliding distance, so to obtain sufficient wear in a reasonable time a high sliding speed is required. But a high sliding speed normally means a high entrainment speed and thus a high EHL film thickness, and so less wear. By moving the surfaces in opposite direction, contra-rotation, can produce a high sliding speed with a low entrainment speed. If two test materials are rubbed together at different speeds in opposite directions it is possible to obtain high sliding, and thus plenty of wear, in boundary lubrication conditions. The current tests have involved a ball on disk mini traction machine, as shown in Figure 1. The problem then becomes measuring the wear, which is distributed along a wear track on
Sealing Technology June 2006
FEATURE
both surfaces, in a metal-to-metal combination. The current work, which is studying metal-tometal lubricated contacts, has developed a technique using atomic emission spectroscopy with inductively coupled plasma (ICP-AES). This permits very accurate assessment of the wear particles in the oil. The results so far have demonstrated good repeatability and have been compared with alternative measurement methods. More details of the test method and results obtained can be found in Reference 1. The method of wear measurement discussed in this work is very specific to the sliding pair combination being tested. However, the basic test method provides an interesting approach as seal testing presents the same problem. It is usually very difficult to accelerate material testing without creating unrealistic loads. Increasing the speed increases the lubrication often to the benefit of the mating pair and not the test period. This paper may provide the source of ideas for some new approaches to this ever-present problem.
Reference 1. J. Fan and H. Spikes: New test for mild lubricated wear in rolling-sliding contacts. STLE
Figure 1. Diagrammatic view of the ball on disk tester used for the contra-rotating tests.
Annual Meeting, Las Vegas, Nevada, USA, May 2005.
Contact: Professor Hugh Spikes, Head of Tribology Section, Department of Mechanical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK.
Tel: +44 20 7594 7063, Email: [email protected], Web: www.imperial.ac.uk/me This article is based on a presentation made by Professor Spikes to the British Fluid Power Association (BFPA) Technical Committee TC 16: Fluids on 26 January 2006.
Patents Piston seal
Seal with leakage vent Applicant: Waters Investments Ltd, USA This invention discusses methods of providing a defined path to vent fluid in the event of seal failure. It is concerned with preserving the integrity of surfaces with closely controlled tolerances to prevent damage in the event of a leak. This patent is concerned
particularly with high pressure gas chromatography up to 1400 bar, but the designs shown appear to be similar to those which are standard practice on other high pressure fittings. Patent number: WO 2006/023653 Inventors: J. Angelosanto, J.A. Luongo and F.A. Rubino Publication date: 2 March 2006
Applicant/Inventor: G. Liepold (USA) This patent relates to piston seals that may be used for the transfer of sterile fluids. A plastic piston has circumferential channels that contain a ribbed plastic wiper that
seals against the cylinder bore. A number of geometries are shown. There is additionally a design that is cantilevered from the piston skirt. Patent number: WO 2006/015324 Publication date: 9 February 2006
Valve gasket with retainer Applicant: Waters Investments Ltd, USA This patent is concerned with the seals for valve components on equipment such as high pressure liquid chromatography instruments. Once a gasket has aged and creep has occurred it is susceptible to being displaced when the pressure fluctuates. Analytical instruments, in particular,
Sealing Technology June 2006
are sensitive to the rebound and pressure ripple effect, and pressure can be from 350 bar up to 1400 bar. One of the valve components will have a receiving groove to retain the gasket in position during pressure fluctuations. Patent number: WO 2006/02400 Inventors: J.A. Janiuk et al. Publication date: 2 March 2006
Examples of the piston and seal arrangement for a sterile fluid transfer device, from WO 2006/015324.
13