The differences have to do with seal squeeze, seal stretch, and occupancy of the gland. The inch group is intended for general use. The series includes the O-ring dimensions Part 1 , the optimum gland dimensions for the O-ring depending upon scientific application Part 2 , the quality requirements of the O-ring Part 3 , the materials used for O-rings for general-purpose applications Part 5 ; and the back-up rings used to protect the O-ring in high-pressure service Part 4. The last four digits indicate the inside diameter rounded to one-tenth millimeter. The first digit of the Size Code indicates the cross section group A-E , while the last four digits indicate the O-Ring inside diameter rounded to one-tenth millimeter.
Additionally several custom dimensions are also kept in stock. Zielinski, President, PolyMod Technologies, Inc. One standard addresses multiple lip packing sets, and one standard addresses standard test methods to assess the performance of hydraulic seals. Six more standards address the gland or housing dimensions for bearings and other seals. It lists the basic material properties required for O-ring materials for many general-purpose applications. Each size is designated with a dash number and can be described using two values: the inside diameter and diameter of the cross-section. The hardware and gland dimensions are based upon requirements that are universally accepted for optimum sealing conditions.
The metric group is intended for aerospace use. With all this information available in international standards, designers worldwide can now incorporate the most effective and optimum sealing solution for their hardware and be assured the sizes, dimensions, and the quality requirements of the O-ring Part 3 , the back-up rings used to protect the O-ring in high-pressure service Part 4 , and the materials used for O-rings in general-purpose applications Part 5. If one purchased an O-ring from Sweden, it might not work in equipment designed in France or even in similar equipment designed in Sweden. Because of this, it became obvious that O-ring and hardware size standards were needed. The improved packing ring is the modern O-ring. Optionally, this designation may be followed by a letter indicating the quality level N - normal quality; S - special quality. Class S addresses the quality requirements for optimum performance industrial applications and aerospace applications.
O ring gaskets are closed ring gaskets with a round cross section and are produced of Elastomers and plastics. In the 1970s, as companies became more international, it became obvious that an international O-ring standard was required. Upon enquiry specific sizes can also be produced after agreement. Finally, greater than 90% of the O-ring sizes used in the world are now specified in one standard. Each size is designated by a letter A - E indicating the cross-section. This included some new sizes for aerospace metric O-rings.
There are charts included in the document that provide the acceptable squeeze range for different cross-section O-rings in different applications. Each application, each fluid, and each environmental exposure requires unique polymer materials compounded into formulations to provide optimum performance and resistance to chemical attack. Class B O-rings have slightly wider tolerances and are suitable for general-purpose applications. Chilson, Specialty Products Manager, PolyMod Technologies, Inc. Seal stretch was overlooked by Christensen and earlier users of O-rings, but has been found to be a significant factor in seal life and performance for dynamic applications. The metric group describes 360 O-rings.
In contrast to the inch system, the nominal and physical dimensions of metric O-rings match precisely. The space that is being filled must be about 10% to 15% smaller than the cross-section of the O-ring in order for O-ring to seal properly. Finally, what would an O-ring standard be without addressing the composition of the O-ring? This created the problem that there were no universal standards for O-ring sizes or housings glands. Because the standard is so comprehensive, it has readily been accepted by all industries, including aerospace where it has been written into specialty O-ring standards. This was followed by another revision in 2002 with only a few changes, most of which were corrections on sizes. This did give sizes for O-rings, but no hardware dimensions to use with these seal sizes. This need was satisfied nationally by creating standards for O-rings used in equipment manufactured in that specific country.
That is, a 1 mm O-ring will have a cross-section of 1 mm. The sealing effect is reached by the elastic deformation of his cross section. We offer O-rings in inches and well as metric measurements. These requirements differ for piston and rod applications, as well as for face seal applications. . Class N is the standard of acceptance for general-purpose O-rings.
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