If you mean the distance from the flap that the material disengages from the stored mass to commence accelerating in free fall, this varies across the opening according to the profile of the stressed arch that develops over the orifice and hence is very dependent on the flap size. This mobilised failing arch takes the form of a catenary, but for practical purposes can be considered as a parablolic dome over a square opening or a tunnel arch over a slot, the inclination of the ends depending on whether the hopper develops mass flow or not. With a mass flow hopper, the end slopes of the arch are inclined at the combined angle of the wall inclination and wall friction, whereas for a funnel flow hopper the arch end slopes are inclined at the angle of internal friction of the bulk material. The form of a parabola is y = K.X squared, where X = half the width of the opening and dy/dx = the end inclination of wall slope plus wall frictional angle for a mass flow hopper and the internal angle of friction for a funnel flow installation. This allows the height of the parabola to be calculated and a mean value derived for the average free fall distance within the hopper prior to exiting the flap opening. To this must be added any common external distance of fall. ■

Hello Shri Gaurav Srivastav,

Flap gate size will depend upon chute layout. Needless to say that engineer will make layout for least size of flap gate while ensuring material flow without choke-up. Material flow velocity will create force on flap gate, which is to be accounted for the material applicable velocity at flap gate (in a manner similar to turbine blade, not 100% identical).

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyors.

Author of Book : Belt Feeder Design and Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Pune, India.

Tel.: 0091 (0)20 25871916

Email: parimul@pn2.vsnl.net.in ■

Originally Posted by I G Mulani

Hello Shri Gaurav Srivastav,

Flap gate size will depend upon chute layout. Needless to say that engineer will make layout for least size of flap gate while ensuring material flow without choke-up. Material flow velocity will create force on flap gate, which is to be accounted for the material applicable velocity at flap gate (in a manner similar to turbine blade, not 100% identical).

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyors.

Author of Book : Belt Feeder Design and Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Pune, India.

Tel.: 0091 (0)20 25871916

Email: parimul@pn2.vsnl.net.in

Flap gate or divertor gate (mobile chute enclosed in box)- What will be the criteria for selection? Are there any specific advantages of using one instead of the other?

Regards,

Sid ■

A flap gate normally seals off one outlet port, whereas a diverter gate switches the flow between one route and another. There are many kinds of diverter gates, from a simple changeover flap in open chutes to a swinging bucket type that encloses the flow within a bifurcated chute. Selection of the more sophisticated types tends to be decided by the degree of containment required of the flow stream ■

Originally Posted by Lyn Bates

A flap gate normally seals off one outlet port, whereas a diverter gate switches the flow between one route and another. There are many kinds of diverter gates, from a simple changeover flap in open chutes to a swinging bucket type that encloses the flow within a bifurcated chute. Selection of the more sophisticated types tends to be decided by the degree of containment required of the flow stream

Another good question related to this thread is the determination of the necessary force to move the gate against the material flow.

I am not very sure about the used criteria for it, because it is dificult to establish the impact forces, because the interation time between particles and plate is unknown.

I would ask you guys about experimental data or precedures for such tests.

Regards ■

Originally Posted by calijorn

Another good question related to this thread is the determination of the necessary force to move the gate against the material flow.

I am not very sure about the used criteria for it, because it is dificult to establish the impact forces, because the interation time between particles and plate is unknown.

I would ask you guys about experimental data or precedures for such tests.

Regards

Typically a lever is used to move gates manually or a pneumatic cylinder is used to move them in many cases. ■