Using surface air to blow the ballast tank

[cstranc]

Let me see if I

Let me see if I understand.

When I first looked I thought the siphon was to prevent air from leaking out of the tank. I'm not so sure any more.

The air intake on the left of the picture is a straight tube. So if you blow air into the tank while it is submerged the air would just exit via that tube.

But if the air intake on the left had a dip/siphon that went below the tank level then you could blow the tank at depth, and snort on the surface.

I don't think you need the siphon on the way to the motor as long as the inlet is at the bottom of the tank.

Does that sound right?

[JWLaRue]

I fail to see what

I fail to see what the function/advantage of the syphon is,
can you please explain ?

Well, the principle advantage is that there is no change in the weight of the sub (and therefore the trim) due to using Propel. As long a there is a sufficient battery charge, you can keep running the boat...no need to refill the Propel tank after 6 or so blows.

Since it's not a closed system like the OTW dive modules, the sail (or 'periscope') needs to be above the water surface in order to get any air, but depending on how the boat is trimmed that may or may not be an issue.

-Jeff

[cstranc]

I see what you mean

I see what you mean about the fail safe working fine when you are submerged. If the pump is pumping water out of the tank it will create space for the air that the emergency supply is providing.

But do you need a dip in the air intake tube to prevent that air from escaping while submerged?

[scott t]

Looks to me what the

Looks to me what the siphon does is prevent having to close off the
vent tube. When vent (snorkel) and siphon are above the water level no water enters the tank until the pump pushes it over the siphon. After the
siphon goes below water level the water can continue to enter through
a leaky pump.
Is this correct?

-Scott

[kazzer]

My Low Pressure Compressors have

My Low Pressure Compressors have 3 independent bellows in them, and the water will not pass through until the pump is rotated. Therefore one does not need to worry about back-flows etc.

Also, gear pumps are going to be very bulky, compared to our pumps.

We have found no need for any anything other than connecting the intake pipe to the pump and the exhaust pipe to be poked into the ballast tank. It really is that simple.

We are looking in the future to building our Sub-driver ballast tank bulkheads with the blower already installed. Pump will be in the dry compartment.


The SNORT system works, it is very simple and doesn't need over engineering!

[mylo]

'Doesn't need over engineering' ...

The

'Doesn't need over engineering' ...

The simplicity is what I love about it, it's going to be a tough sale for Chris though.

Mylo

[cstranc]

Ohh no. I am totally

Ohh no. I am totally sold.

I think its great and will be using this for the Sierra. Ordered the pump already...

[fbradasc]

Looks to me what the

Looks to me what the siphon does is prevent having to close off the vent tube.

Yes, this is the point, with the siphon you can use a leaky pump as well, without the need of valves at all.

When vent (snorkel) and siphon are above the water level no water enters the tank until the pump pushes it over the siphon.

As soon the pump pushes water over the siphon, the water falling in the ballast tank make a little vacuum in the siphon hose reducing a little bit the load on the pump.

After the siphon goes below water level the water can continue to enter through
a leaky pump.
Is this correct?

-Scott

Implementing the siphon is as simple as folding a long hose connected from the pump to the ballast tank

[redboat219]

Hi,
Norbert Bruggen discussed somewhat similar

Hi,
Norbert Bruggen discussed somewhat similar system in his book. He called it an Aspirated, Pumped Ballast tank. Here the ballast tank is a rigid fixed container fitted with an open vent pipe at the top. At the bottom is a valve: when the valve is opened water flows in from the outside. But instead of using an air compressor when you want the boat to surface he used a gear or centrigual pump to force the water out of the tank through a discharge pipe. As with the snort this system won't work if the vent is under water.

[cstranc]

But this system can work

But this system can work underwater.

If the air is blown into the tank when the pump is running, the pump starts the water flowing down the vent into the tank preventing the air from escaping.

[redboat219]

But this system can work

But this system can work underwater.

If the air is blown into the tank when the pump is running, the pump starts the water flowing down the vent into the tank preventing the air from escaping.

I think it would depend on how fast your pump can move the water out. Too slow and it would just cause the gases to bubble out the vent tube.

[cstranc]

I think you are right.

I think you are right. If air enters the tank twice as fast as the pump removes water then half the air will go up the tube...

[cstranc]

I am getting ready to

I am getting ready to use the "snort" system for my Sierra. It has a big ballast tank, so the idea of using surface air sounds great.

I think depending on the type of pump you use you need slightly different setups. I'm not sure I have the right pump terminology but...

"closed pumps" do not allow water to flow through them when they are not running. This includes: gear, valve, and peristaltic pumps.

"open pumps" do allow water to flow through them when they are not running. This includes: centrifical pumps.

If you have a "closed" pump then your setup can look like.



The tube to the surface can go straight up. As long as the top of this tube is above the surface then pumping water out of the tank will suck air down the tube, and empty the tank.

Pumping water into the tank will force the air at the top of the tank out of the tube and fill the tank.

Leaving the pump off it will prevent water from flowing in, and since the top of the tube is above water it will remain at it's present fill level.

When you are submerged if you were to just open the Clippard valve and let propell into the tank, the propell would rise to the top of the tank and since there is no place for the water to exit the tank, the Propell would escape up the submerged air intake tube.

To prevent this you also run the pump to pull water out of the tank. This way the Propell can occupy the space that was taken by the water you are pumping out. As mentioned in an earlier post, if you push in more Propell than you are pumping out water then some of that propell will just escape up to the surface.

I suppose if you are running low on power and cannot drive the pump you might get an un-happy trail of bubbles on the surface from your ballast tank...


If you have an "open" pump then your setup could look like:



The water and air tubes both go up and down, effectively trapping the air in the ballast tank so it does not just escape.

If you used the same layout as the "closed" pump with an "open" pump and set your model on the surface... With the pump not running water would flow through the pump into the tank, and air would simply exit via the surface air line, until all the air was gone and you explored the depths. Ohh dear.

So the first thing we add is the water tube rising above the water surface line (A). IF there is air at the top of this trap then it will prevent water from flowing into the tank because the water would need to rise higher than the surface before it went down into the tank.

Next we add the downward trap (B) on the air tube. When you are submerged and blow propell into the tank this will prevent the propell from simply rising up to the surface through the air line. It will effectively trap the propell in the tank, forcing the water to be leave the tank through the water tube and pump.

Lets see. On the surface, with the pump off the trap A prevents water pouring into the tank so she stays on the surface.

Pumping water into the tank forces air out and we submerge.

When we are submerged and blow Propell in (even with the pump off) it will get trapped in the tank by the B u-trap. With the pump on it will still accumulate in the tank.

With the open snort if you stay out too long and your batteries run down then all you need is enough juice to trigger a clippard valve and you will see your model. I like this.

Sounds great. A little bit more fault tolerant.

But I think there is room for a problem.

The "open" style snort could possibly fall prey to a siphon effect. You want to sit a little lower in the water so you run the pump to push some water in the tank for a second. This gets the water flowing. Now when the water is flowing it will happily rise above A to flow into the tank and cause an air flow past the B u-trap. That's exactly what a siphon does: while flowing the water goes a little higher so it can end some place much lower... So you use the pump for a second, but the flow does not stop until the tank is full... That's not good.

I am sure there must be easy ways to prevent the siphon effect so you don't get a "self sustaining dive" when the motor turns off. It probably just requires putting in some flow restrictions and ensuring that you trap water at point (B) and air at point (A)...

Then again the "closed" style is certainly more compact.

[Guest]

Geared pumps do leak a

Geared pumps do leak a bit I'm afraid.

Andy

[skip asay]

For 10+ years, the Albacore

For 10+ years, the Albacore and Marlin kits, as well as a slew of others have used the SubTech ABP pump and TEE valve combination very successfully. The ABP pump is a high volume pump capable of moving a lot of water in either direction. It is an "open" type of pump so failsafe in the form of compressed air or Propel works just fine. The TEE valve keeps the water out of the ballast tank when on the surface. It's pure simplicity!

Skip Asay