Dear Mr. R G Iyer,

The word best is a subjective issue. The best could be different for different people depending upon the importance or gradation attached to following issues :

1) Initial price

2) Operational price

3) Replacement price

4) Availability of services and spares in emergency situations

5) Attitude, capability and preferences of maintenance staff

6) Technical performance when being new

7) Technical performance after 2 to 3 years

So, please make your decision based on above consideration and marks allotted to each of the aforesaid issues by your organization.

The subject is something like a car buying friend asks which car is the best then what reply can be given? The answer / recommendation will depend upon the buyer's priorities.

The type of tippler and tipping cycle is not mentioned in your query. This greatly affects the technical requirement of the particular drive. Furthermore the tippler drive is also affected by the design of marshalling equipment (specific to tippler operation) because the time taken away by the wagon change is to be deduced from the total time cycle. Hence, type of drive for wagon tippler cannot be decided or replied in isolation. It is to be analysed as a complete system i.e. wagon in-haul, tipping operation, and wagon out-haul etc.

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.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

Most if not all car dumpers are electric motor/multiple belt sheave belt driven through a gear box.

Its the simplest way is the belt driven gearbox transmitting power through a shaft to a spur gear drive mounted on the perimeter of the dumper frame. very simple, very dumb, no fuss no muss, easy to repair

The simpler you make it the simpler it is to repair and maintain-do not forget that part.

Are you building your own dumper? If so it would be simpler to have a dumper manufacturer give you a quote for a complete unit.

Do not bother with a variable frequency drive or a hydraulic drive unit as it is not, repeat not needed. Do not make it harder to maintain by doing this.

A three phase motor that is wired and operated properly with a reversing switch is very easy to work with and maintain.

480 volt three phase power is all you need delivering that power through a gear box.

be sure to use an explosion proof motor and wiring connections for same.

The operating cycle is slow for a dumper anyway and you are depending on gravity to dump your coal into the flood loading bin under the dumper. ■

OK-so if I am correct in my thinking of what you said, you will have a railroad car spotter to move the cars to and beyond the tippler.

You do not need a VFD electric motor for this-a standard 3phase motor is all you need as I stated before- if you can not obtain this go to the hydraulic set up.

1. make sure the hydraulic power pack has case drains in the pump driving the system and the hydraulic motor or motors doing the work if they are gear or piston motors if so equipped.

2. Vane pumps and motors are the fastest for warming up to operating temperature.

3. specify Vickers components if possible for the

power unit and motors. You will not need a big hydraulic motor or motors to run the system.

4. inlet and return filters filtration should be at 10 micron with "Schroeder" brand filter housings and filters.

The intank suction filter should be avoided at all costs, replacing it with an external canister drop in oversized filter before the pump.

Do not restrict the inlet flow of the suction side of the pump under any circumstance as it will destroy the pump from heat damage and cavitation-air bubbles.

Do not restrict the inlet or outlet sides of the pumps or motors as it will also affect operating performance and it will cause overheating.

Use steel hydraulic lines wherever possible as they are the strongest and have the longest life.

They also allow the system to shed heat quickly due to the steel pipe.

if you use BSP thread pipe fittings make sure you have a good stock of BSP and only BPS O-rings for these fittings. (British Standard Pipe thread and orings-blue dot o-rings-Aeroquip brand.

If two motorsa are used to drive rotary dumper:

be sure to plumb the motors in a series paralell

hydraulic cicuit and use 2 single section flow dividers for each motor to regulate oil flow on both sides-it prevents the dumper from accelerating under load and allows for a smooth return cycle.

If you like I would gladly look at the sytem if you send schematics and pictures of the components

for no charge-providing the photo quality is good and complete for the entire set up. Just remember that once you buy it your stuck with it. ■

Dear Mr. Iyer,

Best is a relative term. In my opinion hydraulic drive ( High torque with low speed Hogglaunds make) will give you better performance.

Regards.

A.Banerjee ■