Referring to: http://www.cunicocorp.com/images/2250.gif I'm looking at some of the regulator/shut-off valves in use today, and as far as I can tell, every one of them kind of redirects the gas as they go through the plug in an awkward and flow-disturbing pattern. As with something as simple as even a bend in a pipe, there is head loss as the fluid moves around. How then does a fluid regulator stay efficient, especially when it goes toward higher mass flowrates where having a tiny cross sectional area for fluid flow might possibly make it locally supersonic. What other losses are associated with gas regulators? Are there any good resources I can pick up about regulator and shut-off valve operation? (by good resources I mean something that I can read through and finally design a shut off valve) One more question, how does the above regulator valve keep the fluid inside the regulator, given that the tolerance is never 100% accurate? (is there some grease to apply or something that keeps the fluid inside. Thanks in advance!