Product category:
Bearings and guideways - rotary and linear
News Release from: Igus UK | Subject: Plain Bearings for Underwater Applications
Edited by the Manufacturingtalk Editorial
Team on 27 October 2004
Plain bearings for underwater
applications
According to extensive tests performed by a pump manufacturer there was no serious alternative to the large-scale use of graphite bearings at that time.
According to extensive tests performed by a pump manufacturer approx 2 years ago, there was no serious alternative to the large-scale use of graphite bearings at that time
This article was originally published on Manufacturingtalk on 21 Jul 2008 at 8.00am (UK)
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In a direct comparison in terms of wear, all plastic plain bearings achieved poorer results.
Even when the advantages of polymer bearings were taken into account, replacing graphite bearings was not an option.
igus, a leading manufacturer of maintenance-free plain bearings made from heavy-duty polymers, have now introduced a completely new, redesigned bearing that is clearly superior to the wear resistance of graphite bearings.
Further reading
Energy chains investigated for vibration
RWTH Aachen recently carried out a study, 'Vibration investigations on energy chains', which showed that igus' E6' energy chain exhibited minimum vibration and maximum smooth running.
Why oil or grease bearings - go plastics
Igus reported that a recent study found half of machinery lubricants seep into soil and water or evaporates, whereas tribo-optimised plastics bearings need no oil or grease.
Plain bearings do not need oil or grease
The iglidur plain bearings from igus are tribologically optimised so that they run without any oil or grease, therefore no contaminants escape into the environment.
Its test results were good enough for igus to launch an extensive development programme with an ambitious aim: find a material that is clearly superior to graphite bearings in terms of resistance to wear under water.
Determining a suitable location was the first step.
But several preparations had to be carried out in advance: a test bench had to be developed that could be used to test several bearings under water, while simultaneously subjecting the bearings to different loads.
For the duration of the test, which could amount to several months, it was necessary to ensure a constant flow of water around the bearings at all times.
The bearings had to be accessible and easy to replace.
It also had to be easy to check and top up the water level.
All known materials with a good chance of success were then tested.
The results were then used to draw initial conclusions about the structure of the planned, water resistant bearings.
The development of new materials then began: various basic polymers were combined with suitable fillers.
Initially, all new materials had to compete against one another in a long-term endurance test, run over a period of 100 hours, to establish their wear resistance.
igus discovered a material that reduced the degree of wear found with graphite bearings by a factor of 10.
It was also proven to be extremely abrasion resistant.
The tests had an interesting side effect: in the course of developing this underwater bearing, 2 types of material performed equally well.
The material iglidur UW is characterised not only by excellent wear resistance, but also the fact it is very inexpensive.
A cost advantage of more than 50% versus graphite bearings can be achieved for applications in which bearings are required in large quantities.
However, the second material can also be an interesting option for some applications: with this material, the thermal stability is significantly higher, which means that it is appropriate for use on automotive applications, close to an engine.
This material continues to be tested at igus.
iglidur UW plain bearings are manufactured as ready-to-install bushes, in almost any size, and comply with pump manufacturer requirements.
However, the test trials will not be over for a long time.
Now that the endurance tests have been successfully completed, the next step involves researching special features.
How do plain bearings behave in saltwater and waste water? Dr Ralf Selzer, Materials Developing Engineer at igus GmbH: "Trial tests in conjunction with a customer are just as much a part of the test programme as standard tests.
What the new material can actually achieve can only be proved in practical applications.
This includes tests in saltwater and in contaminated environments.
Our customers support us by providing their concrete data, which we can then reproduce in our laboratory." Table 205-1 "Properties" property graphite bearing polymer bearing wall thicknesses note minimum wall thicknesses freely designable handling of the bearings, assembly sensitive very robust costs high low resistance to chemicals good thermal stability very good limited Graphical representation 205-2 Average wear [µm/km] Graphite POM, mod PEEK, mod PPS, mod PPS PBT PEEK Graphical representation 205-3 /4 Average wear [µm/km] Compound Graphite Table 205-5: Material properties material properties of iglidur UW general properties thickness colour black maximum absorption of water at 23C and 50% rel. Request a free brochure from Igus UK ...
humidity: weight per cent maximum absorption of water: Shore hardness D: thermal properties upper long-term application temperature upper short-term application temperature upper short-term application temperature lower application temperature electrical properties volume resistance surface resistance.
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