What is the m.y of reinforced flexible graphite gasket pads?

I would like to ask what mm.y refers to; if it is the corrosion rate, then it should be mm/y or mm/a

Sorry, it was a typo; it should be the m and y values for gasket performance.

This post was last edited by Pinocchio on 2017-12-20 at 13:24. The shims likely refer to the m and y values. See https://bbs.hcbbs.com/thread-1670146-1-1.html. Below are the materials found online; they seem to be sample documents from some gasket manufacturer. The m value is the same as that in Table 10 of the compilation instructions for HG20592～20635-1997, while the y value takes on a relatively high value. https://bbs.hcbbs.com/forum.php?mod=image&aid=1306145&size=300x300&key=60927e8855aed1ac&nocache=yes&type=fixnone Different metal frame tooth shapes and different thicknesses for flexible graphite gaskets result in different m and y values; it is possible to consult the gasket manufacturer for this information. https://bbs.hcbbs.com/forum.php?mod=image&aid=1306139&size=300x300&key=26aa0c79b51e680a&nocache=yes&type=fixnone

Regarding the gasket coefficient for flexible graphite composite gaskets, this is actually a source of concern for many designers. It is understood that the values used are those specified in standard HG/T 20613-1997; however, for some reason, this table was removed from the 2009 version of the standard. Attached: According to this table, m and y should be 2 and 22.8 respectively. However, regarding the value of m\y, many people believe that it is necessary to consult the gasket manufacturer for a recommended value; I think this is unscientific and impractical. Who decides on the gasket manufacturer before even starting design and before production begins? If it’s a long-term partner of the manufacturing unit, it’s possible; but if it’s the design unit, who knows which gasket manufacturer’s gaskets will be used, right? Furthermore, the calculation according to the Watthaus-Flange method takes into account only the flange strength design, without considering the sealing design. Moreover, there is a significant difference between the designed bolt load and the actual bolt load; therefore, I think it’s acceptable to use the data from the old standards when no my parameter is provided, as long as a larger margin is left for the bolts……

Large gasket manufacturers can provide the m and y values for gaskets; of course, these are only for reference. The following are AIG’s data. https://bbs.hcbbs.com/forum.php?mod=image&aid=1306205&size=300x300&key=25b8d6cc2e2e5ad9&nocache=yes&type=fixnone

Thank you all for your generous help. Since in many cases this value actually falls within a certain range, and we usually only use the exact value in our calculations, is it necessary to specify the m and y values separately when purchasing gaskets?

When purchasing gaskets, there is no need to specify the m and y values separately. The m and y values are set values, used solely for the theoretical calculation of gasket load in strength calculations. There is no way to check whether the m and y values of a gasket are qualified, so m and y values cannot be used as acceptance criteria for purchasing gaskets. For gaskets not listed in GB150, it is sufficient to indicate in the strength calculation document the source of the m and y values; there is no standard for judging right or wrong. The actual gasket load has little relation to the m and y values; the criteria are no leakage and no overloading of the bolts.

The m and y values of flexible graphite gaskets: Currently, national and international codes for flange connections still use the y and m coefficients when determining bolt loads. However, the available data are limited to traditional gasket designs and materials; therefore, we determined the y and m values for this type of gasket using the method recommended by ASME F586. According to the definition in ASTM F586, the y-value is the gasket stress at which the specified leakage rate is achieved under a constant internal pressure of 0.014 M Pa; in this paper, the allowable leakage rate in general industry is taken as 1×10-3 ml/sec. For the “index” value, the standard y-value can be obtained from the test data listed in Table 2: y = 2 × 15 = 30 MPa. As for the m and y values of flexible graphite gaskets, according to the same standard definition, the ratio of the gasket stress to the internal pressure of the medium at a medium pressure of 2 MPa is the m value; this value can also be determined from Table 2 for this test: m = 35 / 2 = 17.5. It should be noted that the m value measured in this test refers to a sealing gas (N2), with an “index” leakage rate of 10^-3 ml/sec. This value is on a different order of magnitude compared to those in typical standards, which use liquids and specify allowable leakage rates; it is approximately 3 to 5 times higher.