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Lama Sinto
Member

Join Date: Jun 2010
Posts: 7

Fan Modulation

06/28/2010 12:56 PM

i have a gas suction system from electrolysis pot cell through a ramifying pipeline to a treatment station. a centrifugal fan is situated downstream.

when pots are stopped, parts of the pipeline are isolated fron the network and the total quantity of gases getting into the fan reduces. there is also a decrease in the flow rate and system load. all along the fan turns at the same speed

i wish to have the same flow rate at the chimney( situated after the fan) independent of the number of pots functionning. i have chosed to use an inlet vane damper.

i have doubts if this will be able to keep my flow rate constant or it will just match the static pressure of the fan to the corresponding system load.
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Tornado
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Technical Fields - Technical Writing - New Member Engineering Fields - Piping Design Engineering - New Member

Join Date: May 2009
Location: Richland, WA, USA
Posts: 21017
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#1

Re: Fan Modulation

06/28/2010 2:40 PM

It seems the fan inlet damper inlet damper would only add to the flow restriction from the closed pot valve(s). Could you add a dummy source of outside air and open it up whenever a pot valve is closed? Or would the change in gas composition then cause some further problem?

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Anonymous Poster
#3
In reply to #1

Re: Fan Modulation

06/29/2010 7:20 AM

Actually the inlet damper will bring about system effect. we shall correct this by changing the treansmission pulley.

opening system to external air will increase flow rate fo sure but will dilute the gases and result in a decrease in the concentration, another parameter of interest in the process.

there is a compromise to make but my interest is to increase flow rate. what technique do i use for this
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Tornado
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Technical Fields - Technical Writing - New Member Engineering Fields - Piping Design Engineering - New Member

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Location: Richland, WA, USA
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#4
In reply to #3

Re: Fan Modulation

06/29/2010 11:45 AM

If no outside gas is allowed, maybe you could 1) Open some valves wider on the remaining pots to maintain the same pressure in the line feeding the fan, or 2) Speed up the fan to maintain the flow. To do the latter, think in terms of running the fan at 75% speed when all pots are connected, full speed when a pot is shut off. (That's just an illustration; your actual proportions may differ.)

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MOURADIG
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Join Date: Nov 2007
Location: Beirut
Posts: 33
Good Answers: 2
#2

Re: Fan Modulation

06/29/2010 2:00 AM

Get a VFD to drive your fan motor. Get a Flow meter with analog output of the measured media. And a DDC or a PLC with PID loop capabilities, and you figure out the rest. Contact me if need be.

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