VFD is one of many methods of soft-starting any conveyor - trough or pipe. The physics are the same. In some respects, the pipe is more forgiving in horizontal and vertical curves. Too high a acceleration force can cause a trough belt to leave the idler support system, and even leave the idler trough geometry.

With pipe conveyors, the worst event is a head discharge collapse of the pipe shape and high rotation of the pipe seam that may lead to spillage or lead to a highly misaligned seam at the pipe conveyor discharge point. This, in turn, can cause the pipe to become offset from its centerline, that it will not properly discharge its load, it may fold in half and capture the remaining material on its return with unacceptable consequences.

VFD, DC drives, Wound Rotor Drives, Magnet Clutches, Scoop Control Fluid Couplings, Delay Fill Couplings, Dodge (BALDOR) CST, and Air Clutch soft-start mechanisms are a few of the many types of regulated torque and speed P&ID controls that are used to program a known torque level to achieve a predictable starting-acceleration velocity vs. time ramp.

Why do you specifically ask about pipe conveyors? They are no different than trough belts. Their behavior may vary somewhat from a trough conveyor. Each has its limits on momentary vs. steady-state tensions. ■

Why do some prefer a VFD and when?

This is a complex questions with many answers:

1. Power savings

2. Predictable physics in the hands of a knowledgable engineer

3. Flexibility of starting ramp - preset Hz vs. time, torque vs. time, speed vs. time; tension vs. time

4. Easy to repair with proper tools and training

5. No oil, seals, bearings, filters, pumps, flow sensors, thermal sensors, .....

6. Electronics age and become obsolete can be a problem

7. Need an electronics technician to trouble shoot, beyond reading a computer or PLC diagnostic output

8. Client prefer to use or not use based on past experience, based on site personnel, ......

9. One power module can be used to start multiple conveyors in a sequence - very cost effective

10. Mean-Time-To-Repair can be faster than any other method of bringing a spare on-line to replace a malfunctioning VFD power module - can apply a universal spare

11. Less costly systems can be implemented when the conveyor is not complex and does not need a strain-dwell regulator, 4th quadrant braking, ......

Others can add more - there are many points of view on when a VFD is the best choice or too complex a machine. Ask Mr. Spriggs. ■

Dear Shakee

It is not mandatory to provide VFD for all Pipe conveyors.

Main advantages of VFD on pipe conveyors are

1.0 Pipe conveyor needs Lot of training during Commissioning one can train the belt by adjusting Training rollers by running the conveyor at lower speed . This is not possible in absence of variable speed drive .

2.0 In case of multiple drives in conveyor speed and load sharing can be done smoothly

3.0 Soft stating

4.0 Can run the conveyor at different speeds based on load requirement

A R SINGH ■

Hello,

Earlier respondents have already given enough information.

Pipe conveyor is also a type of belt conveyor. So, considerations applicable to belt conveyor for type of drive, to achieve performance together with economy, will also apply to pipe conveyor, in general.

The pipe conveyor can be of short length to very long length. Accordingly its drive can have electric soft start or simple fluid coupling or delay fill fluid coupling or scoop type fluid coupling or VVFD drive.

The pipe conveyor cannot be so short like belt conveyor because of its inherent constructional features. Also, belt has to do complex and intricate activity of flat to trough to pipe, etc., and therefore I have not mentioned DOL (direct on line) starting, which would have large variation in tensions.

Ishwar G. Mulani

Author of Book : Engineering Science And Application Design For Belt Conveyors (new print November, 2012)

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: conveyor.ishwar.mulani@gmail.com

Website: www.conveyor.ishwarmulani.com ■

Hello Sirs:

Pipe conveyor belt need a stable conveyor system from steel bracket to conveyor idlers, especially for conveyor idlers which need thicker steel pipe (4.5mm at least) and bigger idler diameter (127mm at least) becasue of long distance delivery.

Jienasi roller has some experience for supplying such kind of conveyor idler, please find more information by logging on http://www.jienasi.com

With best regards for all

Steven ■