Trelleborg Sealing Solutions Gives Background to New Global O-Ring Standard: ISO 3601-2:2008

Market Wire, September, 2008

Trelleborg Sealing Solutions, a worldwide leading supplier of high-quality sealing and bearing systems, shares its knowledge on ISO 3601, the standard covering O-Rings that has been revised to meet American and European, as well as Asian needs. ISO 3601 consolidates the long established AS 568B inch standard with the existing metric ISO 3601 and importantly, as it retains its original designation, means modification of documentation may not be required.

Until the harmonization between the AS and ISO standards, it was not possible to specify housing dimensions and retaining rings. Now two parts have been added to the standard that define these, while still in revision is a section on elastomer materials.

Class A corresponds to the American standard AS 568B in its current format. Class B allows production of O-Rings in technically acceptable and economical metric sizes related to inch sizes, which can then fit into metric grooves. Also, in Class B, the five standard cross sections are replaced with a table of tolerances using a formula.

"Changes to the existing standard were needed to reflect what was happening in the market place," says Bernd Murthum, O-Ring Product Manager for Trelleborg Sealing Solutions, who was the convener on the ISO working group responsible for this latest revision of the ISO 3601 O-Ring standard. "Discussions to harmonize the two standards have been ongoing for a number of years." The revised standard not only successfully embraces both the AS and ISO standard tolerance in a single standard, but also extends cross sections covered. "ISO 3601 and AS 568B only describe five standard cross sections. In reality, in the market place there are many more. Common practice was to use the principles of the ISO over a broader range of cross sections. This is now recognized in the revised standard."

Trelleborg Sealing Solutions has a high level of expertise in specification of O-Rings and other sealing elements within a wide range of industrial, aerospace and automotive applications. Design engineers can contact one of over 40 marketing companies worldwide for further information on this O-Ring standard or selecting the optimum sealing element for their specific application.

The five parts of the now valid O-Ring standard ISO 3601-2:2008 are as
follows:

ISO 3601-1:2008
Revised - Inside diameters, cross sections, tolerances and designation
codes
   -- Dimensions are expressed in both metric and inch measurements
   -- Class A is identical with AS 568B
   -- Class B is similar to the tolerances of the previous ISO 3601-1:2002
   -- Includes an equation to calculate the tolerance for the O-Ring inside
      diameter
   -- Range for O-Ring cross section diameter tolerances from 0.8 mm to
      8.4 mm

ISO 3601-2:2008
New - Housing dimensions for general applications
   -- Covers technology for measuring surface roughness of O-Ring housings
   -- Design recommendations for O-Ring squeeze, elongation and compression
      as well as maximum groove fill
   -- Equation for calculation of O-Ring cross section reduction caused by
      the elongation of the O-Ring inner diameter

ISO 3601-3:2005
Partially revised - Quality acceptance criteria for O-Ring surfaces

ISO 3601-4:2008
New - Retaining ring specifications
   -- Covers spiral Back-up Rings, solid type (cut/ uncut), concave type
      (cut/ uncut)
   -- Gives tolerances for outer and inner diameters for rod and piston
      applications
   -- Design recommendations but no size list for preferred housing
      dimensions

ISO 3601-5:2002
Currently in revision - Suitability of elastomeric materials for industrial
applications
   -- Will replace general information on material groups with detailed
      information of more practical use to design engineers
   -- Will comprise a selection table with important material groups
      related to the compatibility to fluids and operating temperatures

Background to Trelleborg Sealing Solutions and Trelleborg Group

Trelleborg Sealing Solutions is one of the world's leading developers, manufacturers and suppliers of precision seals. It supports its aerospace, industrial and automotive customers through 30 production facilities and more than 40 marketing companies globally. Within its portfolio are some of the longest established sealing brands, including Busak Shamban, Chase Walton, Dowty, Forsheda, Palmer Chenard, Shamban, Skega and Stefa along with a large number of proprietary products and materials such as Turcon®, Zurcon®, Orkot®, Isolast®, Stepseal® and Wills Rings®.

Trelleborg is a global industrial group whose leading positions are based on advanced polymer technology and in-depth applications know-how. Trelleborg develops high-performance solutions that seal, damp and protect in demanding industrial environments. The Trelleborg Group had annual sales 2007 of approximately SEK 31 billion, with about 25,000 employees in 40 countries. The Group comprises four business areas: Trelleborg Engineered Systems, Trelleborg Automotive, Trelleborg Sealing Solutions and Trelleborg Wheel Systems. The Trelleborg share has been listed on the Stockholm Stock Exchange since 1964 and is listed on the OMX Nordic List.