Dear Mohan,

Assuming that the header air flow does not contain any dust, a gas velocity of 25 m/sec to 30 m/sec can be used to calculate the header duct cross sectional area.

A calculation check should be made to verify the pressure drop.

Success ■

Originally Posted by Mohan

hi,

What will be the minimum header size for a central vacuum system using 100HP blower.

it has 3500m3/hr and 5000mmH2O.

please give me some approximate calculation or size

-------------------------------------------------------------------------------------------------------------------------------------------------------------------

Mohan,

SO if your blower generates a pressure gradient of approximately 58.333337 cubic foot

per minute flow in suction service.

At what regulated Hg gauge indication?

What do you mean by your statement that the blower has 5000 millimeters of H2O ?????.

What you are using equals 197 inches of water column, why are you using this figure?????????????????????????????

A "pressure gradient" created for a specific vacuum has a

maximum millimeter measurement of -760Hg mercury or

29.92 Hg inches mercury at the best vacuum attainable.

Are you mistaking the positive pressure gradient value for the pressure gradient created for the negative in suction service? ■

Leon,

3500 m3/hr equals 58.3333 m3/min (not 58.3333 cfm)

Here a vacuum (pressure difference over the blower) is meant of 5000 mmWC, which equals 5mWC or a vacuum of 0.5 bar.

This is 19.7 inches of water column

Have a nice day ■

Originally Posted by Teus Tuinenburg

Leon,

3500 m3/hr equals 58.3333 m3/min (not 58.3333 cfm)

Here a vacuum (pressure difference over the blower) is meant of 5000 mmWC, which equals 5mWC or a vacuum of 0.5 bar.

This is 19.7 inches of water column

Have a nice day

Hello Teus,

Please accept my apologies for my mathematical error.

I have eliminated caffeine in my daily coffee :^). ■

Originally Posted by Teus Tuinenburg

Dear Mohan,

Assuming that the header air flow does not contain any dust, a gas velocity of 25 m/sec to 30 m/sec can be used to calculate the header duct cross sectional area.

A calculation check should be made to verify the pressure drop.

Success

Dear Teus,

25-30 m/s seems too high, isn't it?

if it is used for vacuum cleaning, it will have dust. In this case maybe better to consider 18-22 m/s air velocity. ■

Dear Masoomeh,

If the duct is carrying dust, then the air velocity has to be designed in

combination with the type of dust (in specific the suspension velocity)

and the occurring air velocity along the wall and the local absolute pressure.

These parameters can be designed, using the appropriate duct diameter.

Actually, a dust vacuum system should be considered as a pneumatic conveying system

with a very low SLR.

Success ■