Installing big pump to deal with large boat leaks

[MapisM]

[ QUOTE ]
centrifugal type pumps online that could be fitted to shaft drives

[/ QUOTE ]Yup, that's also a possibility, but definitely NOT a smart one.
Doing the same job with a pump connected straight to the engine via pto has huge advantages over that solution (still with the same billion liters per second capacity):
1) can be used regardless of whether you want/can spin the props;
2) can be used also as an independent firehose;
3) no bulky thingies attached in the worst possible place - shafts.

 

[jfm]

GSkip, pheran is right. Using the engine raw water pumps and Y valves (or cutting the hoses) is an old wives tale mistakenly repeated too often by skippers. These pumps might be driven by 800hp D12s in my case or much more than that on a pred92 but the size of those pumps is just tiny. There's no way they would overcome a 2 or 3 inch hole in a hull. Sure they'd make a contribution so worthwhile doing but it would be closer to 300 litres/hour than the 1000+ you need if you're in trouble. If you get a big prob you need, as you and others say, a method to bung up the hole. But you also need a bigger pump than the engine raw water pumps. you inevitably get back I think to a choice of one of these petrol jobs or a few of the electric ones, if you want to be serious about it

 

[oceandrive]

yep point taken, still think it's a very valid option though. I like the fire hydrant sugestion. as offers cover for the two worse synarions. and I have experience of these never used but look awsome.

I'm also eager to see of anybody comes back with a compresed air pump as I already have a compresor planned in which will be mounted high. for me now this could be a very valid safety solution. It's a good post you have started which makes us think, and having a plan when it goes wrong is the greatest comfort.

 

[MapisM]

Agreed, the Y valve might make some sense anyway, but not as bildge pumps, and regardless of engine power.
Otoh, I just made - out of curiosity - a quick calculation of the result you could get by a pump sized to take full advantage of the engine power. You could get either:
- a 130k cubic meters per hour flow with a differential head of 2 meters (that's 2 millions liters per minute...), or
- a 4.3k mc/hr flow with a differential head of 30m (still 71k l/min, not too bad as a firehose!)
All the above for each of your engines!
Not sure you'd have enough room for such pumps in the whole boat, though... /forums/images/graemlins/grin.gif

 

[jfm]

And if I got a pair of pumps that could absorb 800hp mapis the boat would do 33 knots. Newton's frist law! Firms like KaMeWa already make such pumps . My crew girl would find it hard to hold the end of the pipe too!

 

[MapisM]

Well of course you'd drive either the pump OR the shaft, not both together.
But I must admit that I didn't consider the hose handling troubles for your crew girl.... /forums/images/graemlins/blush.gif

 

[jfm]

Compressed air is unlikely to work. Those compressors rely on the fact the user only calls for air 50% of the time (ie if it is a hand tool, it's often off) and during the in between times the compressor is recharging the reservoir tank. For an emergency pump out you need continous power supply, and the compressor wont be powerful enough (ie 3-4hp) to drive the sort of pumps you'd need to keep the pred afloat. You need one of the 5hp petrol engine jobs or a couple of the electric jobs, minimum, and forget the compressor. All imho. At least you have massiv engine room to put all this in. I'll likely have to get the electrics (and the Y valves) becuase the petrol pumps are too hard for me to store

I'm glad people can see the logic in a big pump. It is of course a bit like a liferaft purchase. you hope never to use it but if that day when you need it comes around you'll kick yourself for not havng spent the £300 to buy it

 

[jfm]

[ QUOTE ]
Well of course you'd drive either the pump OR the shaft, not both together.

[/ QUOTE ]

No, the pump itself would drive the boat. If you have 2x 800hp water pump and you point the hose pipes over the transom and squirt the water, the boat will move forwards at 33 knots, approx. Action=reaction, Newton's first law. This is all a KaMeWa does - it squirts a jet of water out of the transom into the air

 

[MapisM]

Fine, but I was sticking to the original "emergency bildge pump" scenario.
It'd be hard to fit a Y valve to a waterjet impeller, though it's quite some food for thought!

 

[oceandrive]

No think the compressor point is very valid. what could be worse than watching the pump go on and off when your going down /forums/images/graemlins/shocked.gif

I like the fire hydrent with a draw from either the outside or the engine room. I will sort this whilst at the boat show.

 

[burgundyben]

[ QUOTE ]
Using the engine raw water pumps and Y valves (or cutting the hoses) is an old wives tale mistakenly repeated too often by skippers. These pumps might be driven by 800hp D12s in my case or much more than that on a pred92 but the size of those pumps is just tiny.

[/ QUOTE ]

Indeed, and I think a false impression is given by the speed at which exhaust water exits, looks a lot more than it really is (bit like blood inside the mouth...)

But its pumping capacity none the less that comes almost for free and in a situation such as the hypothetical one we are considering they might just make the last bit of difference.

Edit - thought of a couple more things, first, if I had the space on board and was not as neurotic about keeping the old girl light I'd have a huge petrol pump on board, or maybe two. Second, the RNLI carry petrol pumps....there's a clue.

 

[npf1]

The centrefugal pump is the Ericoson Safety pump. See here http://www.pumpitout.nf.ca/

 

[michael_w]

What about an Ericsson Safety Pump? It's a centrifugal pump which fits round the shaft. By all accounts, it pumps a phenomenal amount of water. When not pumping it acts as an extractor fan.

I haven't got the shaft length to fit one to my boat.

 

[jfm]

Agree all that Ben. In other words, don't rely on the Y vlaves but as they are "free" pumping power which at least make a contribution you might as well fit them.

 

[jfm]

I think we're at croseed purposes Mapis/ . You wrote "the result you could get by a pump sized to take full advantage of the engine power". All I mean is, if you had such a pump and you pointed the hose over the transom, the boat would move forward 33kts. No extra jet drive impeller needed. The impeller is already inside the pumps you were postulating! This is how a jet works. They are just pumps and they squirt water out of a pipe at the back of the boat. An 800hp bilge pump is the same thing basically as an 800hp jet

 

[wakeup]

Could you put an electonic valve opener/change on the Y valve and have that activated to swtich back to the sea cock via a float switch thus ensuring you don't run the engine dry once bilge has been emptied?

 

[jfm]

You could, but those motor units for seacocks are pretty expensive, like £450 a pop. I use them on the black tank seacock, to make for easier black tank pump out underway, and they are nicely made with a small motor, worm drive gearbox so the seacock is operated slowly with high torque, and limit switches at the ends of the travel so you can have LEDs on the dash telling you they have opened or closed, etc, and also a casing design so you can remove them with no tools to operate the cock manually. Hence the £450 price for the 2 inch variety

I think twud be unneseccary. You can just remeber to operate the UY valve when dried out. You might well find you run for the travel lift with the leak still leaking and the Y valves set to bilge all the way. Also the engine exhaust alarms will tell you if you run the engines dry (if the sensors survive the flooding )

 

[MapisM]

[ QUOTE ]
and you pointed the hose over the transom

[/ QUOTE ]Darn, that's what I didn't think of... /forums/images/graemlins/grin.gif

 

[MedDreamer]

[ QUOTE ]
Best solution IMHO is petrol driven portable pump as already proposed

[/ QUOTE ]

Would need to reguarly change the petrol though. Hopefully you would never use it but it would presumably be on constant standby therefore you wouldn't want to find that when you needed it the old petrol in the tank had "gone orf" and the bloomin thing won't start.

 

[MapisM]

[ QUOTE ]
When not pumping it acts as an extractor fan.

[/ QUOTE ]I wasn't aware of it, though it's logical when you think about it.
That's a good point in favour of these pumps.
Even more so in slow revving boats, where on one hand the engines breathing is hardly enough for a proper engine room ventilation, and on the other hand it's less of a problem fitting them on shafts.
...I might even give it a thought myself...