Aerated Suction Problems

[stanier]

Has anyone experience of aerated suction conditions and how one removes the air so that it does not affect pump capacity. The installation is a sea water intake where the suction line is approximately 50m long. At low tide where choppy conditions exist air entrainment affects the pump capacity. This is not described as air coming out of solution but a quantity of air entrained by wave action.

Because the suction conditions will be negative at close to the pump a conventinal air release valve is not seen as the solution. Some have suggest the need for vacuum pump to eliminate the air. I have thought of bleeding the discharge through an ejector and using this to pull a vacuum on the suction at the impeller eye.

Your ideas, particularly those put into practice successfully, would be most welcome.

 

[Lovison]

Saw your thread on pump-zone earlier and commented on a few items.

1. Can you attach a sketch of the suction inlet design showing the high and low tide levels.

2. What type of entry nozzle to you have on the end of the pipe?

3. Does the entry have a grating over it?

4. Do you have organic growth that grows on the grating and if so how often is it cleaned.

5. Has the original design been modified since being engineered?

Just need a few more details.

Wayne Wayne E. Lovison
service-parts@naglepumps.com

 

[stanier]

Wayne,

I'm sorry I cant give you a sketch as I am pursueing this for a colleague on the other side of Australia.

I am advised that the suction pipe is laid on the seabed to a vertical 90 elbow to which is fitted an inlet basket strainer. The strainer is oversized . It is designed to prevent seaweed entering the suction.

Divers have been down and confirmed the suction isnt blocked. They observed a high level of air bubbles at the inlet.

Its a new installation. One of a number. Only this site suffers the problem.

What I am really after is a device that some how gets the air out and closes when the air is exhausted. Preferably something that has been used before.

cheers
geoff

 

[Teuchter]

What you are looking for is an interceptor or air separating chamber on the pump suction to remove air on a continuous basis while the pump is running. Such devices are commonly used in marine pumps for what is known as snoring duties where suction lines become uncovered due to the motion of the ship. The device is basically a Tee in the suction line bolted to the pump suction branch. A float valve in the tee controls the air flow that is drawn out of the tee by a liquid ring vacuum pump mounted on the top of the tee. Equally you could use an ejector to provide the vacuum, as you suggested, although you may have trouble restarting the pump if you lost flow completely.
I believe companies who supply vacuum systems or marine pump manufacturers may be able to help you.
teuchter

 

[Teuchter]

What you are looking for is an interceptor or air separating chamber on the pump suction to remove air on a continuous basis while the pump is running. Such devices are commonly used in marine pumps for what is known as snoring duties where suction lines become uncovered due to the motion of the ship. The device is basically a Tee in the suction line bolted to the pump suction branch. A float valve in the tee controls the air flow that is drawn out of the tee by a liquid ring vacuum pump mounted on the top of the tee. Equally you could use an ejector to provide the vacuum, as you suggested, although you may have trouble restarting the pump if you lost flow completely.
I believe companies who supply vacuum systems or marine pump manufacturers may be able to help you.
teuchter

 

[quark]

Stanier,

Somehow your idea of ejecting air out of suction line reminds me of proverbial egg and hen. (And I can assume from it some portion of PMM I. Pardon my ignorance if I am not well versed in these two things)

Vacuum pumps is a better option and widely used. I think you can try out a priming pot.