Ultrasonic cleanig technology help? 1

[MrAnxious]

Hi all, I'm looking for some help on a topic where nobody seems able to be able to help me so far!

I am looking to apply ultrasonic cleaning in a big tank of hot acid about 15 feet by 6 feet by 6 feet deep with a liquid depth of around 4 1/2 feet.

I am being told by suppliers that I must hang the ultrasonic transducers into the liquid over the side of the tank or place them in the bottom of the tank.

I actually want to bond them to the outside of the tank bottom so that they (and the cables!) are out of harms way of the hot acid and in effect, the tank bottom becomes the ultrasound transducer and to my mind will give a good spread of ultrasound over the entire length/width of the tank into the acid.

Suppliers tell me that external mounting will not work but are unable to tell me why. I am told I need about 70kw of installed ultrasound transducers in the tank. This means about 35 x 2kw transducers hanging over the side of or lying on the bottom of the tank! I really want the transducers externally on the bottom of the tank! Anyone able to help here please? Thanks!!!

 

[GregLocock]

A properly designed system will do what you want, and with careful design could even achieve the desired pressure levels using less power than the immersed transducers. Unfortunately I don't know anyone with ultrasonic experience to help you further, but what you are asking is not inherently ridiculous. It may however be remarkably expensive, although probably cheaper than boiling transducers in hot acid would be.



Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[IRstuff]

Your tank probably has thick walls. You should try whacking the sides of the tank with your fist. Now imagine the transducers attempting to do that, and still transmit energy into the bath. Do you really think you can get those walls to move at ultrasonic frequencies?

As for the power, that's consistent with typical equipment, 2kW/90gal. Your tank, as described, holds 3000 gal, so about 67 kW.

http://upcorp.thomasnet.com/viewite...andard-39-90-gallon-cleaning-tanks?&forward=1

TTFN

FAQ731-376

 

[GregLocock]

IRstuff- you'd be above the coincident frequency for the wall, I think a cunning design using the modal behaviour of the wall would be the way to go. What do USN subs have over their hull mounted sonars? I'd guess glassfibre.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[IRstuff]

Sub sonars are outside of the hull, either flank-mounted or trailing. Of course, active sonar usage is pretty rare, it's almost all passive.

As for the walls, I think they're overly constrained. It's not enough to just make the frequency, but also the waveshape. A large, nearly flat, transducer is not going to produce enough in the way of cavitation points to do a good job of scrubbing.

TTFN

FAQ731-376

 

[GregLocock]

OK.

Howabout some sort of waveguide and a porthole in the side of the tank?

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[IRstuff]

Possibly, but see the picture here:

http://www.ransohoff.com/images/systems/immersibleslgr.jpg

That tank uses 4 transducers per wall, total of 8. Since each transducer puts out, presumably, a somewhat spherical wavefront, there is lots of interference, hence lots of cavitation bubbles.

One could possibly imagine having 8 cutouts, flush with the original walls, leaving only one side exposed, but the sealing will be critical, and prone to failure. Moreover, the outboard side still needs to be rigidly constrained, so that the energy is all directed inward. Ultimately, such a configuration is not much better than having the transducers mounted inside the tank, and is much more complicated.

These puppies are non-trivial in size, so it's not like some itty-bitty thing dangling in the solution. The tank in the picture is about 1/4 the size of the OP's, so roughly 18 kW over 8 transducers, about 2.25 kW each.

TTFN

FAQ731-376

 

[MrAnxious]

Hi, many thanks for those thoughts!

My logic is this- See those rectangular transducers in the link to Ransohoff? Well, inside those stainless steel boxes there are a bunch of individual transducers bonded to a (1/8" thick?) stainless steel plate then the assembly is welded up into a box.

Now then, if I made my tank wall 1/8" thick and bonded the transducers directly to the outside of the tank (just like the ones inside the Ransohoff box) why wouldn't it be just as effective?

One potential supplier (Blacksone Ney) has suggested a power input of 20kw with a variable frequency generator pack which seems a lot lower than the rule of thumb used by most suppliers above indicates. It is extremely difficult to validate any of this stuff, it seems a bit like black magic!

All thoughts appreciated! Thank you.

 

[JoeySoap]

This seems to be what the OP requires?

http://www.bransoncleaning.com/ultrasonic_transducer_bonding.asp

 

[spongebob007]

MrAnxious,
Who in the industry have you been in contact with? I know for a fact that you can bond transducers to the bottom of the tank. If you could, please provide me your email and I will help you out. I am an expert in the field of ultrasonics. I no longer work in the industry but I still do some consulting. I can put you in touch with the right people.

 

[spongebob007]

You are right, it is a bit like black magic.

 

[MrAnxious]

Spongebob, Blackstone Ney and Branson Ultrasonics have given me input on this. BN say external mounting transducers will be fine and ~20kw power output is all that's required. BU say that will not work and propose internal tank transducers @ ~70kw. Something really doesn't add up.

I am on the verge of abandoning this idea and fitting the tanks with air sparge pipes instead as a compromise solution. BU's budget cost to fit out the tanks is ~$320,000 per tank. I'm wanting to build 10 to 12 of these, and that's a lot of money for black magic!

 

[IRstuff]

Your two vendors are not using the same volumes. BN's own webpage:

http://www.blackstone-ney.com/04.TP_fundamentals_18.php

shows 20W/gal as the asymptotic power consumption. Your liquid volume, as described in your OP, is 3030 gal. At 20 W/gal, that comes out to 61 kW of power.

TTFN

FAQ731-376

 

[miningman]

Cant provide direct advice on ultrasonics but if you are starting to consider alternatives, try contacting one of the suppliers to the material handling ends of the mining business. When we get material hung up in underground ore bins we use explosives to knock them down but the guys on surface tend to get nervous. They affix heavy vibrators to steel ore bins to provide enough energy to knock down the material... essentially providing vibration to the structure. Depending on how much and what type of scale you are attempting to remove , this might work and would certainly be cheaper than the $$$ figures you quote.