MSR Windburner

A sample unused valve assembly (from Lindal) is shown above upside down, and the cross-section is shown to the right. It is effectively the same thing you find on a pressure pack can of paint or fly spray - some of which are (or used to be) pressurised by butane or propane! The basic valve shell A is crimped onto the canister body. The outer black butyl rubber ring B (shown brown here) does the sealing there. The stainless steel spring E just visible inside the central blue polyamide cylinder F pushes a small (often red) polyacetal valve plug D against an inner black neoprene rubber valve seat C (shown pink here) under the metal top. This spring-loaded valve is why the canister is called 'resealable'. Part F is the blue bit in the previous photo. The disk D is pushed down by a pin located inside the threaded part of the stove body when the stove is screwed onto the valve, and this lets the gas out. The position of the pin is shown as a solid blue line. In some cases (eg Coleman Powermax) the blue pin is actually a tube and the gas goes up inside it. In most cases there is a hole in the stove body for the gas near the blue pin. Given the millions and millions of spray cans around the world, this valve would seem pretty reliable in sealing (even if the flow does sometimes get blocked up).