din valve vs k

[jamiei]

I'll show a little ignorance or forgetfulness rather, whichever you choose to call it... what is the difference between static and dynamic? I remember the terms from rock climbing/rapelling, but I get them confused...

 

[joens]

I assume you are refering to O-rings .A static o-ring is one where neither part is moving as in a port plug. a dynamic o-ring is one where one of the parts moves against the o-ring as in the piston
joens

 

[The Chairman]

the O-Rings on the tank/valve interface and the Yoke/Din seat are static. The fitting that lets your reg twist uses a dynamic O-Ring.

 

[pescador775]

Jamee, so called 'dynamic' and 'static' O rings share enough traits in common that these words could be missleading. Probably, either should not be used without clarification. O rings operate in two ways. There is a type which seals by compression and the type that seals by friction. Both of these may be static or dynamic at different times such as insertion and squeezing which occurs during installation of a valve or tensioning a valve stem ring which is static in compression and also dynamic as the valve stem turns. There are two types of tank necks, for HP and LP. The LP tank uses a large neck opening and the valve O ring seals against a shoulder machined inside the neck. The compression of the valve against the shoulder crushes the O ring vertically. The whole O ring is flattened. Thus, it is important that the valve be properly torqued. The HP tank uses a smaller neck opening and the valve O ring merely slides into the opening and seals against the wall by friction which also involves a bit of compression on the O ring outer perimeter. Torque is somewhat less important. One can see that at this point, both O rings are 'static', they do not move. However, there are other types of systems, like piston regulators, wherein the ring seals by friction but also moves with the piston. This is not like the above tank examples in that the O ring is truly dynamic. If it doesn't move it is not doing its job.

Just think of how the O ring works and you can describe and name the process. Basically, they work by compression or friction and the same O ring can be used for either application or both depending on the system.