Adjustment of Line Pressure Drop

Posted in: , on 12. Sep. 2012 - 09:45

I am facing problem at one of our project where crushed bottom ash being pneumatically conveyed to silo. The compressure have been ordered already. The two end points remaining same threr is a change in pipe rack layout for which two additional bends are required to be included in the route. Vendor is now claiming that this will induce additional loss for which conveying rate will reduce. Kindly advice how the pressure drop can be kept same.


D De

Re: Adjustment Of Line Pressure Drop

Posted on 12. Sep. 2012 - 09:54

Dear D De,

Of course, the additional 2 bends create extra velocity losses and therefore create extra pressure drop at the same capacity or a capacity loss at constant pressure.

Having been a project manager myself, I know that design modifications during a project are usual.

In your case, the vendor should be able to predict the change in capacity (or pressure).

If the vendor cannot indicate the influence of extra bends at a given location, the question raises immediately, how did the vendor designed the installation in the first place?

Unfortunately, you added 2 bends, giving the vendor the opportunity to wave his guarantee.

Actually, he should change his guarantee for the new situation. ( Also when you removed 2 bends)

Kindly advice how the pressure drop can be kept same.

I assume that you want to keep the pressure drop the same and maintaining the capacity.

That is not possible.

One of the 2 has to change.

If the original design has some spare pressure, then there is no problem. Maintain the feeding rate and the pressure will rise accordingly.

To predict the influence of the 2 extra bends at this moment is to execute the design calculations and the calculations for the modified installation and compare the results.

Without having the installation- and material data it is not possible to say more specifically.

Optimizing an installation with simple measures is sometimes possible (VFD to regulate airflow, increase pipe diameter, small booster, etc)

I realize that my reply does not help you much.

In case you need more to the point information, you have to supply the installation data.

Have a nice day



Pressure Drop And Loss Of Conevying Capacity

Posted on 12. Sep. 2012 - 09:48

Dear Debashisde,

You will not lose conveying capacity if the present pressure drop is less than the maximum discharge pressure rating of the conveying system blower. With 2 more bends, pressure drop will increase but the new pressure drop may still be below the blower pressure rating. If the blower is already running at its maximum pressure, in that case, it will be necessary to make some changes in the pipeline to reduce the pressure drop. For this change, your options are to shorten the pipe line if a new route is possible, or to increase the pipe diameter.

Best regards,

Amrit Agarwal

Pneumatic Conveying Consulting


Re: Adjustment Of Line Pressure Drop

Posted on 13. Sep. 2012 - 07:07

Dilute phase?

Try to vent part of the air before the rotory valve by installing a branch, a hand valve that is adjustable.


1. start the blower

2. slowly speed up the rotory valve and monitor the pressure. The pressure will keep raising.

3. when the pressure raises to the old point, stop raising the speed of the rotory valve. slowly open the vent valve and monitor the pressure.

4. as pressure drops down speed up the rotary valve.

5. keep monitoring the pressure to make sure blocking or slugs are not formed. when this happens the pressure will raise quickly. you need to stop the rotary valve immediatly.

6. then you get the bigest capacity of the same pressure drop.

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