4.0. SEALING ELEMENT DRAWING AND MEASUREMENT TECHNIQUES
Because the sealing elements are produced generally from elastomer with a moulding technique, measurement technique is different from that of mechanical engineering. For example, only the inner and outer diameters of a circular product are commonly measured in mechanical engineering.
This type of measurement is suitable for machining technology. However, it is not possible to take measurements with ordinary measurement tools (like callipers, micrometers) on seal products because of their elastic form.
Measurements which are illustrated in technical drawings below will afterwards enable easier product measurement. In this technical drawing, a diameter length has been provided. The dimensional tolerance is bigger compared to steel products.
Because of this reason, it would not be wrong to think that measurement mistakes will stay within tolerance. We can see that the all other dimensional measures of the sealing element are on the cross section.
Measurement would be made easily with a sample cross section from the sealing element and with the help of a measurement device like a profile projector or microscope.
In the table below, permissible tolerances for elastomer products (ISO 3302-1 1999 edition) can be seen. Here in this table, Class M2-F column is used which is used by world class sealing element manufacturers. It should be kept in mind that these tolerances demonstrate the maximum figures. Another important point is that and it is not always necessary to use ± deviation values as stated in that table. Seal designers always take into account working conditions of the seal and then decide on + or – tolerance staying within the permissible dimensions.
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TABLE-3-TOLERANCES FOR ELASTOMER |
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CLASS M1 |
CLASS M2 |
CLASS M3 |
CLASS M4 |
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NOMINAL DIMENSION |
F |
C |
F |
C |
F |
C |
F |
C |
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Permissible deviations of dimensions in mm |
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≤ 6,3 |
± 0,10 |
± 0,10 |
± 0,15 |
± 0,20 |
± 0,25 |
± 0,40 |
± 0,50 |
± 0,50 |
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6,3< |
≤10 |
± 0,10 |
± 0,15 |
± 0,20 |
± 0,20 |
± 0,30 |
± 0,50 |
± 0,70 |
± 0,70 |
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10 < |
≤16 |
± 0,15 |
± 0,20 |
± 0,20 |
± 0,25 |
± 0,40 |
± 0,60 |
± 0,80 |
± 0,80 |
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16< |
≤25 |
± 0,20 |
± 0,20 |
± 0,25 |
± 0,35 |
± 0,50 |
± 0,80 |
± 1,00 |
± 1,00 |
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25< |
≤40 |
± 0,20 |
± 0,25 |
± 0,35 |
± 0,40 |
± 0,60 |
± 1,00 |
± 1,30 |
± 1,30 |
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40< |
≤ 63 |
± 0,25 |
± 0,35 |
± 0,40 |
± 0,50 |
± 0,80 |
± 1,30 |
± 1,60 |
± 1,60 |
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63< |
≤100 |
± 0,35 |
± 0,40 |
± 0,50 |
± 0,70 |
± 1,00 |
± 1,60 |
± 2,00 |
± 2,00 |
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100< |
≤160 |
± 0,40 |
± 0,50 |
± 0,70 |
± 0,80 |
± 1,30 |
± 2,00 |
± 2,50 |
± 2,50 |
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Permissible deviations in (%) |
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160< |
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0,30 |
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0,50 |
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0,80 |
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1,50 |
1,50 |
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Extract from ISO 3302-1 (1999 EDITION) |
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TABLE 4-TOLERANCES FOR MACHINED PARTS IN PTFE OR OTHER THERMOPLASTICS |
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NOMINAL DIMENSION |
TOLERANCE ACCORDING TO DIN 7168 ‘’MEDIUM’’ |
RESTRICTED WORKS TOLERANCES |
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≤ 6 |
± 0,1 |
0,10 |
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6< ≤ 30 |
± 0,2 |
0,15 |
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30< ≤ 65 |
± 0,3 |
0,20 |
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65 < ≤ 120 |
± 0,3 |
0,30 |
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120 < ≤ 200 |
± 0,5 |
0,40 |
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Extract from DIN 7168 |
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