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Author Topic: Centrifugal pump  (Read 4586 times)

redboat219

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Centrifugal pump
« on: January 25, 2011, 09:25:45 AM »

I'm interested in building a water pump/sealed tank ballast system.
The problem is I can't find a source of those gear type windshield washer pump here (Philippines).  The ones I see here are of the centrifugal type.
Some modelers advise against using them as they won't work against the increasing back pressure as the tank fills (although I see this as sort of a fail safe in case the pump gets stuck in the on position, there would be little risk of rupturing the ballast tank)

 Can I get away with using a centrifugal pump and a bigger tank?

thank you
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sheerline

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Re: Centrifugal pump
« Reply #1 on: January 25, 2011, 09:41:07 AM »

Redboat.
A centrifugal windscreen wash pump will deliver 20psi at 12 Volts.
Chris
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redboat219

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Re: Centrifugal pump
« Reply #2 on: January 27, 2011, 03:51:37 AM »

Redboat.
A centrifugal windscreen wash pump will deliver 20psi at 12 Volts.
Chris

So does this mean I can use one?
How high does the pressure get inside the ballast tank usually get anyway?
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Umi_Ryuzuki

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Re: Centrifugal pump
« Reply #3 on: January 27, 2011, 05:11:41 AM »

You shouldn't get any pressure in a  ballast tank.
The air should be venting as the tank fills with water.
Once the boat is at neutral bouancy, the dive planes can submerge or surface the boat.
Wne the dive planes have brought the snorkel up above the water's surface, the pump can
remove the water from the ballast tank, and the snorkel will allow air back into the tank.

 ok2
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redboat219

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Re: Centrifugal pump
« Reply #4 on: January 27, 2011, 05:35:25 AM »

Centrifugal pumps don't work in reverse.
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derekwarner

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Re: Centrifugal pump
« Reply #5 on: January 27, 2011, 05:50:49 AM »

redboat219 .....K-Mart  stores in Australia ...in the auto section sell 12 volt universal replacement windscreen washer pumps....they are a gear pump which is suitable for bi directional pumping

Failing that....most Model stockists should have a similar version but much more expensive  >>:-(......Derek
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Derek Warner

Honorary Secretary [Retired]
Illawarra Live Steamers Co-op
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www.ils.org.au

redboat219

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Re: Centrifugal pump
« Reply #6 on: January 27, 2011, 06:13:09 AM »

redboat219 .....K-Mart  stores in Australia ...in the auto section sell 12 volt universal replacement windscreen washer pumps....they are a gear pump which is suitable for bi directional pumping

Failing that....most Model stockists should have a similar version but much more expensive  >>:-(......Derek

Unfortunately I'm in the Philippines.... {:-{
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Umi_Ryuzuki

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Re: Centrifugal pump
« Reply #7 on: January 27, 2011, 07:03:52 AM »

Perhaps the windscreen pump out of a Volvo automobile.
I hear that those are gear pumps.  :-)
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sheerline

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Re: Centrifugal pump
« Reply #8 on: January 27, 2011, 05:37:43 PM »

Hi Redboat.
You didn't say whether you were using a vented tank or a sealed ballast tank. I use the sealed ballast tank in all my boats and a centrifugal pump is used in conjuction. The pump will force water in under pressure (20psi), the air in the unvented tank is compressed by the incomming water and when the air reaches the 20psi figure, the pump will cease to deliver any more water even though it is still rotating.
This does not impose any  additional load on the pump and won't damage it, in fact the pump speed will actually increase because it is no longer doing any useful work.
Stopping the pump will result in the water being discharged back down the tank feed line because the trapped air in the tank is pushing it back out and through through the pump inlet, so reversing the pump is pointless as it does not need this function to empty the tank.

A servo operated valve can be placed in the feed line from the pump to the tank along with a microswitch to turn the pump on and off. The valve and switch combination is arranged so the pump can be stopped, allowing the tank to retain it's pressurised ballast water, thus holding the sub down. Surfacing is achieved by opening the valve and allowing the tank to drain as previously described.
The sealed ballast tank requires to be built in a robust fashion and should be well engineered as it has to withstand 20psi max press.

Hope this is of some use to you.
Chris

 

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Albion

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Re: Centrifugal pump
« Reply #9 on: January 28, 2011, 09:56:30 AM »

This does not impose any  additional load on the pump and won't damage it, in fact the pump speed will actually increase because it is no longer doing any useful work.
Actually it is doing damage, left long enough it will damage the seal.

running a cent pump in reverse, it will still pump water forwards, just not as well
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submate

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Re: Centrifugal pump
« Reply #10 on: January 28, 2011, 10:42:40 AM »

Hi

AFC como drills do a good bi directional pump  11 (GBP) I am sure they will be willing to post on to you

Regards
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sheerline

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Re: Centrifugal pump
« Reply #11 on: January 28, 2011, 01:08:43 PM »

Albion. You will only damage the seal if you run them dry, the seal is lubricated and kept cool by the water. These pumps are rated as intermittent use, the motors are not rated for continuous running, therefore thay are perfect for use in subs. 
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redboat219

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Re: Centrifugal pump
« Reply #12 on: January 28, 2011, 03:51:32 PM »

Sheerline I plan to use a sealed ballast tank. :-)
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sheerline

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Re: Centrifugal pump
« Reply #13 on: January 28, 2011, 08:39:52 PM »

It'll work just fine redboat, just build your tank well and remember the max pressure when designing it. Don't rely on sealant to hold it together, back it up with some longditudinal stays so the end caps cannot possibly blow off. The system you are building will be simple, effective and above all, reliable.
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Albion

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Re: Centrifugal pump
« Reply #14 on: January 29, 2011, 01:48:21 AM »

These pumps are rated as intermittent use, the motors are not rated for continuous running, therefore thay are perfect for use in subs. 
Your earlier statement seemed to imply that it was ok to leave them running as they arent doing any work, if intermittant then i agree its fine. but left running the pump will suffer.
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kazzer

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Re: Centrifugal pump
« Reply #15 on: February 04, 2011, 04:14:46 AM »

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redboat219

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Re: Centrifugal pump
« Reply #16 on: February 04, 2011, 05:18:16 AM »



Is this what you are looking for?



Yes Kazzer, that's the one. But since it's not available locally, I'll try using the centrifugal type.
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