Pressurized water pump ballast systems

[spitfiremk3]

Hi... Could someone who owns a OTW or simliar type boat with the pressurized water pump ballast system share some info with me on:
How well the system works? What PSI does the pump or pumps need to run at? Has anyone ever built one of these systems on spare parts? What did they use for a pump(s)? And any other general info on this system to educate the masses. Any info will be GREATLY APPRECIATED!!!
THANX
Scott

[crazy ivan]

Scott,
I built one using

Scott,
I built one using an automotive windshield washer pump and it works fine. Running off a 6 cell MiMH battery pack it develops around 7 psi. This means it will fill the tank (made from PVC pipe) less than half full. A higher pressure pump would fill it more, allowing for a much smaller tank. I don't know what pressure the commercial kits use, but I believe it is much higher. My pump works through a one way check valve to fill, and an electric valve lets the water out. In theory, it will work down to around 14 ft. depth. A higher pressure system, of course, would work deeper. With the valve closing off the tank, the system can be operated in a proportional manner without the water pressure from the depth further compressing the air inside as you go deeper, so your trim is not affected as you dive. Since the tank is only partly full, the water inside can slosh around and severely impact the balance of the boat, so it is very important to put baffles in the tank to prevent this. A shorter tank would be less affected by this than a longer one. Overall, it is a very simple, but reliable system.

[Guest]

I've had a play with

I've had a play with one of the OTW modules.

The pump is a Sureflow item, which uses little rubber diaphragms, so is a positive displacement design. A different motor (speed 500 or 600 type) is fitted I think from the sureflow design.

You can purchase Sureflow style pumps on ebay. They're cloned items so much cheaper than genuine Sureflow units.

These pumps are quite efficent and have a high flow rate.

The tank is vented into the dry compartments, a little electronic board is used to control the pump, and probes mounted inside the tank detect the water level- full and empty. Because the tank is vented, the air is not heavily compressed, and the tank is easily filled to about 80% capacity.

The disadvantage with the venting, is that you have a lot of moist air kicking about in the module, where you have all your electronics.

If the water is cold the moist compressed air will condense on the cylinder walls, and you end up with a bit of a fog inside your module.

In practice, this doesn't seem to cause any big problems, but you should be aware of it.

[Wheelerdealer]

Should point out that in

Should point out that in the OTW system, the ballast tank is vented to the main WTC and water probes limit the amount of ballast you can take on board. I believe you need a pump that pumps bothways as the increases pressure with the WTC may not be enough to empty the tank from depth (especially if you have a large WTC).
The Sheerline system is the one with the sealed pressurised ballast tank.

[spitfiremk3]

another question???

So a 35psi pump like in the pic with adjustable high limit pressure switch should work AOK? Do you need a reversing switch on the pump also to assist the empting of the tank? Or just a seleniod valve and the internal tank pressure does the rest. My boat is a SSY 1/32 type 9 and will be running on 2 12v batteries.
THANX
Scott

[adriaticsea]

Hi Spitfiremk3,

the pump in the

Hi Spitfiremk3,

the pump in the pictures looks interesting...just to build up equipment references, may I ask you the brand and model type of that pump?
Thanks in advance!
BEST REGARDS MAURO

[Guest]

Re: another question???

So a 35psi pump like in the pic with adjustable high limit pressure switch should work AOK? Do you need a reversing switch on the pump also to assist the empting of the tank? Or just a seleniod valve and the internal tank pressure does the rest.
Scott

Yep, that'll work.

You can use a servo to pinch the hose up with a wheel mounted on the servo horn.

If you want to use tank pressure to vent the tank, you may want to run two hoses- one from the pump and one from the valve. I'm not sure if these pumps are self sealing, however if not, fit a one way valve inline with the pump, so the water can only go in one direction.

Here's a link to cheap clones of sureflo designs-

http://cgi.ebay.co.uk/Marine-Fresh-Wate ... dZViewItem

Andy

[spitfiremk3]

More Questions

Some more questions concerning the presurized pump system??? With a ballast tank of a net volume of 102 fluid ounces( I will need about 64oz's of water in the tank as a starting point to submerge the boat)... And a ShurFlow 40PSI pump... Does anyone have a rough idea of how much space I will need for the 40PSI of compressed air that is above the water in the ballast tank? Or will I have to go it the hard way... Trail and error...
THANX
Scott

[spitfiremk3]

My boat I am building is a SSY 1/32 typeIX

I boat I am building for thee above pressurized pump system is a type IX SSY boat in 1/32 scale... BIG BOAT...
THANX
Scott

[Guest]

Re: More Questions

Some more questions concerning the presurized pump system??? With a ballast tank of a net volume of 102 fluid ounces( I will need about 64oz's of water in the tank as a starting point to submerge the boat)... And a ShurFlow 40PSI pump... Does anyone have a rough idea of how much space I will need for the 40PSI of compressed air that is above the water in the ballast tank? Or will I have to go it the hard way... Trail and error...
THANX
Scott

i thin kthe formula is this
Filled pressure in tank = ((orignal volume[102] / original vol [102] - water in tank vol [64] ) x 14.504 [correct to absolute pressure]) - 14.504 [absolute pressure]

In your case the pressure in the tank would be 24.4PSIG.
@ 40PSI you will have 74.8 floz of water in your tank

[spitfiremk3]

Pressure tank size

My tank now is 102 OZ's (fluid oz's.). I have not glued the ends on yet so I can cut down the tank in size. I am trying to get info so I don't have to experiment and build 6 different tanks. To get 64 fluid ounces of water in the tank at 40 PSI, how big does the tank have to be (with the compressed air)? I am also putting baffles in the tank.
THANX
Scott

[Guest]

87fl oz, assuming im correct,

87fl oz, assuming im correct, i would tend to use the bigger tank providing there is space and run lower pressure, that way if your orignal calculation was off you can increase the pressure to get more displacement

[spitfiremk3]

THANK YOU!!! ALBION

THANX ALBION!!! GREATLY appreciated!!! I will try that. I will keep the tank a few ounces bigger, just in case. Your info keeps me from building a whole bunch of different size tanks just to experiment with.
THANX to those in HONG KONG!!!
Scott Tingley
New Milford, PA., USA

[spitfiremk3]

To Alboin

Hi Albion... That's Singapore... Excuse me... Thank You for the info.
THANX
Scott

[Guest]

I wouldn't be running 40

I wouldn't be running 40 PSI in a plastic tank!!

The maximum you should be aiming for is 20 PSI, and probably closer to 15 PSI.

High pressures should only be used with a properly constructed metal tank IMO.

Also bear in mind that the higher you go pressure wise, the less efficient your pump will be.

Andy