On Sat, 19 Jan 2008 17:25:39 -0800 (PST), "
wrote:

... The major working parts are a knife and spring held
in place by a pin that is attached to a diaphragm that is held in
place by another spring. When it operates water pushes against the
diaphragm through two hollow pins on the knife side of the device
forcing the diaphragm into the low pressure chamber thus pulling the
retaining pin out and releasing the knife.
There is one mysterious feature. On the top of the pressure casing
there is a small resin colored plug. It is visible from the outside
of the case through a hole in the label. I presume this keeps the
device from exploding if you take it up into space or something. ...
I suppose it is worth looking to make
sure it is there periodically, particularly if the release has been in
an airplane.

-- Tom.


...er.... It takes about 6 psi EXCESS pressure like 13 ft depth of
water to actuate the sprung knife?

Clear on up to outer space, there is no excess pressure I know of.
Or am I misssing something?

Brian W