Jim sorry been gone for a while.
You are correct not very clear.
The volume of air that is removed is
only in the line between the pump and
the ball valve to the exterior. This small
volume seems to work well for a controlled amount of vacuum. I turn
the pump on and pump to 125 psi or so
shut the pump off and then open the
ball valve.
Dean
In a message dated 1/6/2011 9:22:53 A.M. Central Standard Time,
JimToddPsub@aol.com writes:
Hi Dean,
Copied below is the part I didn't understand. If you
pump [it] up to 150 psi, that seemed to imply a tank. What is holding
the 150 psi if not a tank? It could be a very small one integrated in
the pump housing.
The pump could only over-pressure the cabin at depth if it
were drawing air from some source other than the air within the cabin.
Drawing air in one end of the pump and out the other would not create any
additional pressure within the cabin.
In order to overpressure at depth (to lessen the pressure
differential at a given depth) you have to introduce more air (more molecules)
into the cabin or heat the same amount of air.
Best regards,
Jim
In a message dated 1/5/2011 10:56:04 A.M. Central Standard Time,
Recon1st@aol.com writes:
I pump it up to a
150 psi or so turn it off and then open
a ball valve to the exterior. The pump
will go up to 250 psi so I could actually
do a little overpressure condition at depth if needed.