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Thread: Boosters ? Do they boost anything ??

  1. #1
    jack_archer Guest

    Boosters ? Do they boost anything ??

    I have seen a number of "booster systems" being sold during the past 20 years. Some injection additional compressed air into the line and some have bypass configuration.

    The booster systems sold by Dynamic Air (&many others) inject additional air through booster valves.

    Can someone enlighten me...

    1. What exactly do these booster do ?
    2. Why use them ? What material characteristics warrant using them?
    3. Are we not increasing the gas velocity by adding more air to the line ?

    It appears to me that we are buying a lot of hardware without much understanding of the basics.

  2. Boosters

    There are many types of booster systems, and they do not all function the same. I will speak about the booster fittings offered by Dynamic Air.

    The Dynamic Air boosters perform 2 basic tasks: 1) eliminate plugging, and 2) control velocity. This actually leads to lower air consumption. I'll explain why.

    If a system without boosters is prone to plugging, the only remedy is to increase the air to material ratio (use more air). If the material to be conveyed has some variations in physical properties (moisture content, bulk density, particle size, etc), the air to material ratio must be increased to work for the worst-case scenario material properties. Since the booster fitting is an automatic plug breaker, there is no need to increase the air to material ratio to keep the system from plugging. Also, the Dynamic Air booster system, by design, is constantly plugging and un-plugging the conveying system. This is a good thing because it reduces the air consumption by increasing the resistance of air passing through the material.

    Finally, the booster allows the system to operate at a lower conveying velocity by introducing energy where the energy is needed...along the pipeline. Studies have proven that in most applications, a lower velocity system requires less energy to convey a given material. This is because the air velocities are lower (lower pressure drop due to air flow), less friction created in the bends, etc. The overall effect is lower air consumption.

    The extra benefit from is that if you have a fragile or abrasive material, there is less damage to the material and the pipeline!
    Dynamic Air Inc. (USA)

  3. #3
    Dennis Hauch - Freeport, TX, USA Guest

    Bypass vs. Boosters

    Jack,

    Your questions are right on the mark. The whole idea of boosters is an oxymoron. Boosters add gas to the conveying stream which is the last, I repeat, the last thing you want to do if you want to control velocity.

    The correct terminology here is bypass. The idea of a bypass is, when a blockage forms in the conveying line, to bypass some of the conveying gas to an area of lower pressure to effectively break up the plug so conveying can resume.

    There is a real need for bypass systems. Materials classified as Geldart Group B or Group C materials are candidates for bypass systems.

    Kind regards,

    Dennis Hauch

  4. Boosters

    Mr. Hauch,

    You use the term booster in general. Reality is that there are several different booster technologies. Since you lump the Dynamic Air booster technology in with all booster systems, I must state that you are clearly misinformed as to the technical aspects of the Dynamic Air booster technology.

    The Dynamic Air booster technology is also designed to automatically break a plug. However, unlike the bypass system you describe, the Dynamic Air booster technology directs the conveying gas to a point immediately upstream the plug to effectively break the plug. Also, you have made the naive assumption that just because there are booster fittings connected to the conveying line that the conveying velocity cannot be controlled. Nothing could be further from the truth.

    Furthermore, in the bypass system you describe, the conveying gas is directed to the area of low pressure. In a plugged situation, the pressure immediately upstream the plug is at or near the same pressure as the pressure vessel pressure (high pressure). The pressure immediately downstream the plug is at or near the pressure of the receiving bin (low pressure). So, if you want to break a plug, you need the conveying gas upstream the plug in order to break the plug. In the situation you describe, the bypassed conveying gas has bypassed the plug entirely.
    Dynamic Air Inc. (USA)

  5. #5
    Dennis Hauch - Freeport, TX, USA Guest

    Booster Rebuttal

    Jack Archer
    Dynamic Air

    I respectfully submit that the theories embraced by Dynamic Air regarding boosters ignore the laws of physics. I make two points:

    1) It is an irrefutable fact that gas injected by a booster into a conveying line will increase the conveying velocity. This can hardly be construed as velocity control and it is entirely in the wrong direction if a minimum / optimum conveying velocity must be maintained. The Dynamic Air response was Nothing could be further from the truth.

    2) The only effective way to accommodate an immovable, impermeable plug in the conveying line is to bypass conveying gas to break off the leading edge of the plug, in an area of lower pressure, to progressively reduce the length of the plug until conveying can again resume. The Dynamic Air approach would add booster gas at the trailing edge of the plug, which would only increase the strength of the plug.

    The Dynamic Air respondent does not name himself and closes his responses with Dynamic Air Inc. so I assume he speaks for the company.

    Dennis Hauch

  6. Dynamic Air booster technology

    Mr. Hauch has made some bad assumptions about the Dynamic Air booster technology. It is very clear he does not understand the Dynamic Air technology. I would ask, for the sake of the audience, that he refrains from comment on a system he is not an expert in!

    1) The first bad assumption is that an increasing velocity is detrimental to velocity control and obtaining the minimum / optimal conveying velocity. The Dynamic Air booster technology allows the system to convey at lower velocities because of the ability to convey without the worry of plugging. That allows the system to operate at the minimum air to material ratio and minimum velocity. For example, a system starting at 100 ft/min increasing to 500 ft/min (500% increase) is certainly better in terms of wear and degradation than a system starting at 2000 ft/min increasing to 3000 ft/min (50% increase).

    2) The second bad assumption is that the addition of conveying gas upstream a plug is a bad thing. A plug is at a specific location (point in space) in the convey line. The plug itself may be buried in a section of pipe filled with material, but the actual plug location is a fixed point. This being the case, introducing compressed air immediately upstream the plug is exactly what is required to break the plug.
    Dynamic Air Inc. (USA)

  7. #7
    Dennis Hauch - Freeport, TX, USA Guest

    Bypass / Booster Finis

    Jack,

    At this point I will conclude the dialog between myself and the Dynamic Air representative. My purpose was a spirited exchange between us that would provide answers to the questions that you posed in your original thread. I trust this has happened, but I must say that in the process I was disappointed in the professionalism exhibited by the respondent from Dynamic Air.

    Please dont hesitate should you have any questions.

    Regards,

    Dennis Hauch

  8. #8
    In my long career I have used Dynamic Air's booster systems to control the conveying velocity and thus reduce particle attrition. I have seen terminal velocities with these systems as low as a few meters/sec with solids to air ratios as high as 80 to 100. In my opinion, dense phase conveying lines with primary air, and injection of secondary air with "flow controlled line injectors, so called boosters" do have a place in pneumatic conveying.

    Regards

    Amrit Agarwal (Tim)

    Pneumatic Conveying Consultants
    polypcc@aol.com, or, pccsolt@enter.net

  9. #9
    bvsarma Guest

    Boosters

    It it nice that fundamental questions are being asked. The reason being that Pneumatic conveying is considered still as a state of art rather than science. I wonder if the doctor operating the patient or Missile scientist will consider their field as state of art not science!

    Sorry! What am I driving at is that now a days, basic research in understanding fundamental principles of Pneumatic Conveying is not done at all. I thing it all stopped from 80s. May be due to PLCs, which take care of any adverse situations.

    Why can not a Technical institute undertake this and let a PHD student give the solution, rather than discussing for next 20 years!

  10. From what I know, pneumatic conveying technology is today more science than art. A number of universities around the world now have PhD programs in pneumatic conveying. Since the early 80's dense phase conveying technology is much better understood and is being used effectively.
    The word "booster" is not understood by many people. These should instead be called secondary air injectors. Several technical papers by well known institutes have been published on them.

    Regards,

    Tim Agarwal
    Pneumatic Conveying Consultants

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