Is it appropriate to install it after winding graphite tape around the high-pressure octagonal gasket?
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For the flange sealing surfaces of equipment and pipelines such as the thermal high-pressure separator in the hydrocracking unit (with a pressure of 13.73 MPa, a temperature of 260 Rankine, and containing hydrogen sulfide), the cold high-pressure separator, the inlet buffer tank of the recycle hydrogen compressor, and the desulfurization tower, high-pressure octagonal gaskets are specified for use. Is it appropriate for the installation party to wrap graphite tape around these high-pressure octagonal gaskets during installation? What criteria can be used for installation? This post was last edited by Heart of the Ocean on 2009-3-4 20:34.]
Absolutely not. The sealing methods differ greatly: they do not leak at low temperatures, but leaks occur at high temperatures and cannot be eliminated; an octagonal gasket along with a liquid sealant can be used
It is possible in theory, and it is also used in practice. Graphite has excellent self-lubricating and ductile properties; after compression, it ensures good contact at the sealed joints. It also helps to preserve the integrity of the sealing surface, while compensating for any minor damage to steel-to-steel seals. We have also tried using pads after wrapping with PTFE tape, and there were no abnormalities in the performance. In the design of our Topsox synthesis tower’s head double-cone gasket, a sealing surface combined with graphite strips (self-adhesive due to adhesive backing) was used. The tower came online in 1995; during maintenance in 2003, it was found that the gasket and sealing surface were in excellent condition. Only the gasket and sealing surface were polished using metallographic sandpaper, and after replacing the graphite strips, the original gasket continued to be used. To this day, there have been no issues whatsoever – and this is in a high-pressure, flammable, and explosive environment with an operating pressure of 14.3 MPA. In other words, this method is feasible. But be careful to wrap the auxiliary sealing material evenly, and the graphite strip should not be too thick ； Tighten the bolts evenly. Thermal tightening or cold tightening must be performed again when putting it into use in cold and hot conditions.
Taking advantage of graphite’s self-lubricating and ductile properties, graphite strips are wound around high-pressure octagonal gaskets before installation; this is useful in practical situations such as when there are defects in the flanges of the equipment itself, or minor defects on the sealing surfaces of large-diameter pipe flanges. In some contexts, the Chinese describe themselves as bold yet cautious, with a strong emphasis on respecting science.
I personally think it’s not appropriate; I recommend using an elliptical pad, as its sealing effect is better than that of an octagonal pad!