Re: Push-Pull Dust Collection
Push pull systems can also be applied for dust control to provide greater contaminant control via the jet flow than is possible with a hood alone, allowing a much greater "reach" from the collection hood. This has been applied in foundries in the shakeout step to control airborne silica from the mold sand. ■
Re: Push-Pull Dust Collection
Darren is certainly right. While predominantly used for tank / open vessel applications, the push-pull system is finding new uses everyday.
The "push" system is very effective in transporting the contaminated airstream in a controlled manner over a much greater distance than that contaminated air can be "pulled" by an exhaust hood.
As outlined in the ventilation handbook, care must be taken to ensure that operator exposure is not increased (if applicable) by incorrect design, application and operation of a push - pull system. ■
Re: Push-Pull Dust Collection
The push-pull system has been used in certain dust and dust-fume applications, but there is a risk of generating extra dust and increasing dust loading in the exhaust/collection system (due to entrainment of high velocity jet). Hence, it has only had limited application.
peterwypych@uow.edu.au ■
Pull-Push Dust Collection
Pull-Push is an excellent application for dust collection. One important design tip will insure its success - provide for 10% more Pull volume than Push volume. That is easily done even with single blower systems.
Dennis Hauch ■
Push Pull
Excellent point Dennis. ■
Re: Push-Pull Dust Collection
The points made by posters are all good and relevant. I have discovered that the exhaust quantities used in the subject "test rig" are 30 to 40% more than would be used with conventional techniques, also that there is a "drop-out box" in the exhaust ducting at the back of the chute. Evidently testers found that there is a heavier dust load than normal (as warned by Peter Wypich). I question whether this technique gives any better control than the normal one. It is certainly more complicated, more expensive to build and maintain.
Michael Reid. ■
Re: Push-Pull Dust Collection
I would just like to know on following points:
1) How does it compare on cost / price basis.
2) Comparison of space required for installation.
3) Technical gain i.e. comparison of quantity of dust present in surrounding place.
Regards,
Ishwar G Mulani.
Author of Book : Engineering Science and Application Design for Belt Conveyor.
Email : parimul@pn2.vsnl.net.in
Tel.: 0091 (0)20 5882916 ■
Pus Pull Dust Collection
From where I sit, I think that PP dust collection is for cases where there is an open area that needs dust control eg open topped tanks.
For belt conveyors etc., the key is inflow velocity at all openings whihc is greater than the velicty of any generted dust particles. Closing up all opening as much as possible helps as long as the extraction volume is higher than the induced volume, thermal expansion etc etc...or u will have a jet stream of dust coming out.
Thanks
James Morrish ■
Re: Push-Pull Dust Collection
I have found out that the designer's intention is to blow adhering dust off a product of uniform size (briquettes). The owner claims very good dust control as shown by videos, but I claim you will get that anyway using 40% more airflow than standard methods. It will require lots of testing and measurement to find out which method is more effective.
Michael Reid. ■
Re: Push-Pull Dust Collection
As the specialist designer of the equipment in question I have been following this thread with much interest and intrigue.
Should anyone wish to understand our approach to systems design I invite you to visit our website at
www.tandt.com.au
Unfortunately I am not able to discus the particular system system being reviewed by this thread as the IP involved with its design is a matter of confidence between ourselves and our client.
However I do commend the discussion content as being certainly well founded... and, yes Dennis, you are quite correct, the 10 percent factor is included in all our designs where adequate and relevant.
Whilst certain assumptions have been made in regard to the purpose and characteristics of the system in question the design principles employed are based on accepted and well proven practice that covers more than just the simple push pull system design methodology as defined in that quite venerable manual produced by the ACGIH as recommended practice.
In response questions raised by IGM
1) costs reflect the function
2) the system has been fitted within an existing conventional transfer
3) the technical gain is in accord with desired outcomes
In response to comments by MJR, the system is as you state "a test rig", so it follows that reserve capacity is a desirable feature (that may not be fully utilised).
Best wishes for the new year to you all
rogert@tandt.com.au ■
Push-pull Dust Collection
I recently came across a test rig using the so-called push-pull arrangement in a conveyor transfer chute. The material is iron ore at 4,000 tones/h.
A blower is used to blow air from the front of the chute to a collection hood at the back.
I am aware of the use of this technique for fume collection, e.g., on plating tanks. Has anyone heard of its application to dust collection?
Regards,
Michael Reid. ■