) and they have a really good write-up on the valves on their web page.
These valves are fundementally Trunion Ball valves with a pig-closure on the side. You shut the valve, blow down the body, open the closure, shove in the pig, close the closure, open the valve and the pig is launched. On the receiver end there is a perforated plate across the opening (I have tried to measure the dP across the plate and it is smaller than my instruments could diferentiate).
I've installed a half dozen pairs of these valves and really like them.
