Compression Stops and Collars for Gaskets

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Compression Stops and Collars for Gaskets

We stock a range of compression stops and collars for EMI and environmental gaskets. Limit stops and collars can be fitted to EMI and environmental gaskets prevent over-compression or the distortion of mating surfaces.

With surface mounted EMI and environmental gaskets, the aim should be to limit the compression of the gasket to between 10% and 20%. 10% being the minimum with a solid silicone style of gasket. This means some form of compression stop or limit is essential with surface mounted gaskets to prevent over compression.

Compression stops can be built into many styles of gasket, or made as an integral part of the flange. Their height should equal that of the maximum compressed height of the gasket. Compression stops fitted into gaskets can be in the form of collars or washers so that fixing bolts can pass through them or as solid studs located either side of a fixing bolt.

The thickness of the gasket for a known application can be calculated as follows e.g. Consider a gasket which can be compressed between 10% and 25% to be used on flanges which are not perfectly flat, i.e. the flanges without gaskets touch at some points and leave gaps in others. Since the gasket will compress between 10% and 25% we will require 25% compression at the
high points and 10% at the low points (the “gaps”). The greatest gap is therefore 15% of the gasket thickness. If that gap is 0.45mm, then a gasket of 3.0mm thickness is required

This is fine in theory provided that the flanges do not “bow” when placed under load. To overcome flange distortion, fixings may need to be added, the number of which will be determined by the flange stiffness/rigidity.

We recommend Electromagnetic Testing Services Ltd to test EMI shielding products in your application.

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