After the end of the lapping process, we begin with the valve assembly. In this video, you can find a better view of what a Double Wedge Double Disc valve, with parallel seats, is. It is a really smart and reliable design, but not too many manufacturers have the expertise to supply it.
This valve is commonly used for the isolation of boiler water main feed lines. It is also very useful for cryogenic applications, when the effect of the differential thermal contraction may require an extra thrust to close the valve properly (zero leakage).
If you want to learn a little bit more about the most reliable shut-off valve, visit https://babcockvalves.com/special-valves/#double or download our Gate Valves brochure from https://babcockvalves.com/downloads/ and go through pages 10 to 13.