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Text version of the page
| MetafleX Lolode Spiral wound gaskets | ||||||||||||||
| Some methods of calculation of the bolt load required to compress conventional spiral wound gaskets, result in figures which appear to over-stress the standard bolting of many ASME B16.5 class 150 and some 300 flanges. Spiral wound gaskets have been used successfully on these flange classes for many years. However, a lot more attention has recently been paid to the amount of compression that is actually achieved when standard bolting is employed. The replacement of asbestos with expanded graphite (SPG) filler, has improved this situation by producing equivalent sealing performance under lower compressive forces, as well as allowing greater compression for a given bolt load. It must be acknowledged that on certain flanges, the amount of available bolting may be insufficient to achieve the degree of compression normally recommended by gasket manufacturers, without exceeding the recommended bolt stress levels given in the flange design codes. However, in practise, gaskets have been found to be capable of effecting a good degree of sealing performance, especially at the system pressures associated with class 150 and 300 flanges, even though the gasket may not be fully compressed to the guide ring. | ||||||||||||||
| Typical load-com pression com parison | ||||||||||||||
| The Lolode gasket has been developed to satisfy those requirements for maximum sealing element compression, using the bolt stress figure of 25,000 p.s.i. given for certain material grades shown in the ASME code. The expanded graphite (SPG) filled Lolode, has the basic design and properties of a standard MetafleX® spiral wound gasket, but it has been carefully engineered to enable compression down to the guide ring under the limited load provided by ASME B16.5 or BS 1560 class 150 or 300 flanges. Lolode gaskets are available to ASME B16.20 and BS 3381 dimensions to suit class 150 and 300 flanges from V2" to 24" nominal bore. | ||||||||||||||
| (Note that the large diameter flanges to ASME B16.47 Series A and B do not suffer the same poor ratio of gasket area to bolt area as the smaller flanges such as 3" and 8" class 150, and hence Lolode gaskets are not required for these flanges). The graph above shows a comparison of the amount of compression obtained at a given gasket stress for the Lolode version compared to a standard Metaflex® SPG filled spiral wound gasket. It can be seen that the Lolode compresses down to the nominal guide ring thickness of 3.3mm at a significantly lower level of stress than the standard gasket. | ||||||||||||||
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