Simon,What you are describing is the hard ballast tank. It's used to set neutral buoyancy. It has to be able to take the pressure of the deep from outside and you HP air system pressure from within. You have the operation down exactly correct.
The open bottom tanks on a K-250, 350 are referred to as soft tanks. They are open bottom and do burp. They can be just about totally enclosed but you should leave a vent hole to the sea so you don't inadvertently leave some air in it and dive deep. They are not made to withstand neither the pressure of deep diving or your HP system pressure. These open bottom MBT tanks are used to raise the sub up out of the water so you can open the conning tower hatch and not flood the sub. They are either full of air or full of water.
On the hard tank, you do need a water inlet/outlet valve, an air vent valve and a HP air valve to blow the water out when you have to. I didn't put a pressure gauge on mine to monitor tank pressure, but I'll probably add one sometime.
Dan H.----- Original Message ----- From: "SIMON WALKDEN" <mrsym0r@gmail.com>
To: <personal_submersibles@psubs.org> Sent: Saturday, July 02, 2005 4:39 PM Subject: [PSUBS-MAILIST] ballast valve
Hi again, I've been thinking about how a simple valve could be used to vent a ballast, and i'm a bit stuck for ideas. The way I understand it is this: WHEN OPEN FOR FLOODING : a vent opens on the bottom side to allow water in, a vent opens on the top to allow escaping air out, and ballast air is not pumped in. WHEN IN NORMAL STATE (NOT FLOODING OR EMPTYING) : the top and bottom vents are closed, ballast air is not being pumped in. WHEN EMPTYING BALLAST : a vent opens on the bottom to allow escaping water out, the top vent remains closed, ballast air is pumped in to push the water out. So, you've got two vents that need to be opened and closed, and compressed air that will at times need to be released into the ballast tanks. In this example, I've not used the K-250/K-350 design of an open ballast tank, as I've read in several people's posts that they've been a bit unimpressed with their ballast tanks 'burping' when travelling on the surface. Has anybody had any thoughts about this in the past? -Simon ************************************************************************ ************************************************************************ ************************************************************************ The personal submersibles mailing list complies with the US Federal CAN-SPAM Act of 2003. Your email address appears in our database because either you, or someone you know, requested you receive messages from our organization. If you want to be removed from this mailing list simply click on the link below or send a blank email message to: removeme-personal_submersibles@psubs.org Removal of your email address from this mailing list occurs by an automated process and should be complete within five minutes of our server receiving your request. PSUBS.ORG PO Box 311 Weare, NH 03281 603-529-1100 ************************************************************************ ************************************************************************ ************************************************************************
************************************************************************ ************************************************************************ ************************************************************************ The personal submersibles mailing list complies with the US Federal CAN-SPAM Act of 2003. Your email address appears in our database because either you, or someone you know, requested you receive messages from our organization. If you want to be removed from this mailing list simply click on the link below or send a blank email message to: removeme-personal_submersibles@psubs.org Removal of your email address from this mailing list occurs by an automated process and should be complete within five minutes of our server receiving your request. PSUBS.ORG PO Box 311 Weare, NH 03281 603-529-1100 ************************************************************************ ************************************************************************ ************************************************************************