You could look at some of the newer chevron graphite packing materials, i think garlock make one, we have tried them on this type of application with success, but be aware they are very sensitive to installation and loading
Hope this helps
May be a bit late
77/312 is still under consideration as far as i can understand, it requires the manufacturers to undertake approval and type testing to emissions standards, it is similar to the new ISO standards, as far as the big players are concerned, Exxon/BP both are going with a version...
A bit late on this Thread
BP have a program to measure and calculate the relationship between helium and Methane, as all new gate and globe valves are tested with Helium for safety reasons, the max emission is 50 PPM methane that equates to 100 PPM helium this is a bit contravercial however it...
We must remember that the issue of leak tightness is driven by two standards
1. Laboratory - Specs we all use M and Y factors etc,API etc
2. Field experience, having just finished a flange
monitoring program, flange leakage is uncommon
especially if you measure against EPA standards ie...