Which type of Beckett design will you choose?

[blueheaven]

Hi guys,

Just want to know what type of Beckett skimmer designs you prefer?

The Tangential design is connecting the injector to the reactor chamber with a pipe at a tangent(angle) to the tube. This causes the swirling effect in the reaction chamber.

Direct injection is you connect the Beckett to a box and use a baffle to separate the foam and the water and direct the bubbles into the reaction chamber.

So each design has its pros and cons, which one do you prefer and state the reason why

[Achilles Tang]

It so easy to achieve a swirling design for longer contact time, just turn the nozzle at an angle and the foam jet will swirl like a whirlpool. Seeing instant dirty foam collecting on top of the whirlpool really turns me on! Hahaha!

[blueheaven]

It so easy to achieve a swirling design for longer contact time, just turn the nozzle at an angle and the foam jet will swirl like a whirlpool. Seeing instant dirty foam collecting on top of the whirlpool really turns me on! Hahaha!

But the debate goes on to say whether the swirling will cause the bubbles to fuse together to form big bubbles.

I am surprised that no one prefers the direct type

[Achilles Tang]

From my personal experience & opinion, it won't happen to a very large extent. The surface tension of saltwater bubbles is rather strong and even with a tall reaction chamber, the surface integrity of each bubble remains strong enough to only break at the water surface.

Fusing of small bubbles into big bubbles only happens when the bubbles collect on a 'ceiling' or ledge, staying still and then merging together if they stay in contact long enough (like a few seconds) and then collect enough mass to rise as one large bubble and then you get a small 'burp'... which is seeing one big bubble rising amidst the tiny bubbles. Happens very rarely.

The design of any skimmer will determine if occasional 'burping' does occur, but should be easily rectified unless its a design flaw.

[blueheaven]

No one uses the Direct injection method at all?

[cmswong]

The direct injection only advantage is shorter in height.

As what I can see from my DIY SKIMMER upgraded from spray

to spray eductor with direct injection.

[RockyBoy]

I saw this from Skimmer design

Quoted there :

According to Escobal: "...the volume of air in a skimmer can never be greater than about 13% of the volume of the skimmer or the bubbles will merge. Experimental measurements are in agreement..." (Escobal, p. 96). So if you hear any manufacturers out there claiming that their product will inject more than 13% air into the skimmer body, then I would highly suspect that they're not going to be able to acheive the proper bubble size inside their skimmer.

[blueheaven]

According to this article in the Reefkeeping issue, the benefits of the Tangential design is that it increases the contact time in the chamber by swirling and allows for a lower performance pump to be used. So does it mean that a Tangential deisgn skimmer with a powerful pump will increase its effeciency even more?

http://www.reefkeeping.com/issues/2002-03/fm/

And also mentioned about the Direct Injection method, the benefits is that it allows for a shorter reaction chamber. The downside is that it requires a stronger pump as the bubble inconsistancies causes burping.

Since we are doing tests on skimmers, why not we try out these two designs and see which one effectively removes junk from the tank.

[blueheaven]

From my opinion, swirling or not swirling does not make significant improvement to the effeciency of the skimmer.

If you view the two different types of Becketts that people DIY in RC, the skimmate produced is much less the same standard (based on visual perception).

I was initially going for Tangential Injection but the increased length of the reaction tube is really an important factor to condsider in terms of cost and space availability.

Any other testimonials from those who DIY their own skimmers?

[blueheaven]

Just saw AT's thread on his new skimmer

Actually looking at direct but now more intersted in swirling :lol:

[Tanzy]

I like direct injection. Simple neat effective.

On tall chambers the increased contact time of tangential injection is lost as the water runs of of energy so it turns into a turbulent mess anyway.

Rheology of fluids seems to suggest that random tubulence produce better mixing than laminar swirling.

[Achilles Tang]

To me, direct injection means the foam still gets blown in one direction and still gets to go up, albeit in a turbulent fashion.

So why not just angle the foam at an angle and you get a nice swirling where the prolonged contact time means better performance?

[Tanzy]

Directing the foam means the foam goes through more pipes and I don't think swirling gives good mixing.

[blueheaven]

Yeah i asked my lecturer and he said that most likely the swirling takes place at the sides and gradually weans off towards the middle.

I think AT is talking about the direct injection and not directing the foam.

But from my point of view, I also think that more pipes will actually be detrimental to the skimmer's effeciency

[Tanzy]

I usually refer to water after the air injector as foam. I like the beckett as close to the mixing chamber and the column as possible.

The downside is that when the skimmer is switched off, the beckett chamber gets flooded.

[blueheaven]

Actually why not we do a drain like those in the skimmer cup to drain off excess water. Anyway, its so easy to make....

[Tanzy]

That is the prefered design. A valve in the chamber to drain water when necessary but the flooded chamber usually clears itself when the skimmer starts again.

[blueheaven]

Well I hope those who voted for Tangential can share their views