Pump to use with underwater suction cups

[Danno1997]

Hi all, forgive my naivety when it comes to pumps but I would like some advice on pump selection for a couple of suction cups I want to use. The Cups will be used sub sea so the media they will be pumping will of course be seawater. I have two suction cups I intend to use both separately but utilising the same pump. The first cup measures Ø250mm and is required to lift 70kg which I have been told it is easily capable of. The second cup is smaller at Ø150mm and is only required to lift 30kg. Neither cup will achieve a perfect seal due to the nature of the media they are lifting so the pump will have to run constantly to maintain suction. My question is what kind of pump will be most suitable for the task in hand? Centrifugal? How will it cope with the reduced flow once the suction cup is effectively engaged on the target? Anybody recommend a manufacturer that might be able to help?

Thanks

 

[BigInch]

No... but I'm also not sure why you would need a pump to evacuate the suction cups. They work the same way under water as they do in air and I don't need a pump in air. I just press the suction cups on the glass. Maybe you could explain why your case is different? Is it because you think there will be continuous leakage around the sealing surface?

http://virtualpipeline.spaces.msn.com

 

[Danno1997]

The items we are lifting have a very uneven corroded surface which will be coated to one degree or another with hard and soft organic growth. The implications of dropping the items would be fairly serious from both an environmental and financial point of view and i for one would not trust a suction cup used in this environment to maintain vacuum. Using suction pumps for this purpose is fairy common place for applications such as docking ROV's and object retrieval and you can buy pumps designed for this purpose, however they tend to be fairly large multi-role units used for cleaning and dredging tasks as well as suction cup operations. We require a much more compact unit which i can power using a hydraulic motor possibly combined with a gearbox.

Thanks Dan

 

[BigInch]

Gotcha' I note you also say you "don't trust suction cups". I always find that when I get some hairs standing up about something, it seldom turns out to be a good idea in the end. Given your apparent doubts, or shall we say marginal enthusiasm about suction cups, the environmental and financial concerns and the rough marine growth, etc. are you sure they're the way to go? No need to answer. Its just one of the boxes on the "reality check" form.

http://virtualpipeline.spaces.msn.com

 

[Danno1997]

At first I was extremely skeptical, however I have since seen them in operation on a larger scale in very similar environments and they seem to work surprising well. We have explored many different avenues in order to come up with a viable solution to the safe handling of these items and despite their apparent shortcoming suction cups were deemed to be the 'pick of a bad bunch'. All said and done I have got hold of what should be some very suitable cups and designed what I hope is a well thought out manipulator all I need now is a suitable pump, hence I’m on this forum asking for help. Has anyone had experience of Cat pumps?
(not Caterpillar).

 

[rzrbk]

Off the top of my head, an eductor seems like it would work. It would not care of suction flow were reduced to zero, and be small enough it could probably be installed at or near the cup. A centrifugal pump, remotely mounted, would supply water for the motive force.

 

[EdStainless]

What depth are you going to be working at?
I like the eductor idea, the fewer moving parts the better.
I have used ones from Fox for pulling vacuum in very dirty systems. I have also used them for pumping and mixing chemicals all in one step.

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Rust never sleeps
Neither should your protection

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[Danno1997]

150 meters, yeah it sounds good but i still need a pump to make the eductor work

 

[Artisi]

To drive an eductor you now have a different set of circumstances. The eductor supplier / designer will be able to advise you on the required flow and head needed to operate the eductor to the parameters you set for operation of your suction caps. Once you this information it is a simple matter of selecting a pump to operate at the required flow and discharge pressure.
First up - get eductor selected / designed and then ask the forum again about what you need for the driving unit.

 

[EdStainless]

The eductor will have a flow and pressure drop for the fully open condition and a flow and PD for the blanked off condition. Then you find a centrif. that will handle both.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection

http://www.trent-tube.com/contact/Tech_Assist.cfm