Disadvantages of replacing the scoop type fluid coupling with a delayed filling chamber type fluid coupling are:-

1) Will not be able to get smooth start for the conveyor.

2) The starting tension on the belt will be more. As per IS 11592 standard, T1s (starting tight side tension)= x Te+T2. (acceleration coefficient) =1.2 for scoop type fluid coupling drive and can be upto 1.5 for delayed fill chamber fluid coupling drive. Hence the starting tension for a particulare effective tension will be more for a DFC drive. Hence the life of belt will be affected

3) More load on pulley frame and foundation because of the higher starting tension value. The beams may have to be strengthened

Advantages of replacing the scoop type fluid coupling with a delayed filling chamber type fluid coupling are:

1) Lesser maintenance issues. The failure of scoop actuator (esp in case of rotary actuators) is a frequent problem faced under indian operating conditions

2) Lesser loading of the beam supporting drive base frame

3) Easier and faster re-alignment of drive during maintenance. ■

Originally Posted by dnrajput

requirement for 2000 tph coal conv./iron ore conv. for steel and power plant.

one of our sister concern intenting to replace scoop type fluid coupling inplace of delayed filling chamber fluid coupling (DFC) where ever HT motor is involve.

please advise the advantage and disadvantage of replacement of scoop type fluid coupling inplace of delayed filling chamber fluid coupling (DFC)

In terms of feedback: what did your sister concern decide? ■

Hello,

It seems your question is why to have a scoop type fluid coupling for conveyors / equipment which have HT motors. The reply is as below.

The practice or specific requirement to provide scoop type fluid coupling (instead of traction type fluid coupling) for conveyors equipped with HT motors, has following reasons and background:

1) The HT motor cannot have start and restart in quick succession. Such successive starts are mostly 3 in one hour, with specific time interval in between. The electrical engineers are well aware about this and they will have a necessary information. Refer ISO / IS specifications / catalogue of reputed manufacturers of motors, for exact information.

2) Thus if conveyor equipped with HT motor trips (stops) for any reason, one has to wait and idle out the time till one can restart. This means a series of associated conveyors and equipments will not be able to convey material during this idle time and will result in losses. The inclusion of scoop type fluid coupling prevents such situation. The trip / stop command to ‘HT motor conveyor’ will act into scoop coupling control panel. It will empty the oil from working circuit of the scoop type fluid coupling and thereby no mechanical connection between motor and rest of the conveyor. Thus conveyor stops but motor continues to run. Likewise when need be, the oil comes back in the scoop coupling working circuit and conveyor comes in running mode. Thus scoop coupling prevents frequent start-stop of HT motor.

The requirement of ‘Scoop type fluid coupling for HT motor of conveyor or other equipment’ has mostly originated from plant operational and maintenance requirement. The waiting for conveyor to be operationally ready and thereby wasting time, is irritating during plant operation and also during commissioning.

Scoop coupling needs for design consideration such as A) Very smooth / gradual start in a specific manner B) Motor run-up time independent of load run-up time C) Acceleration of high inertial load D) To have economical equipment in certain situation etc., are separate issues. Such design considerations are not concerned with LT or HT motors.

Ishwar G. Mulani

Author of Book: ‘Engineering Science And Application Design For Belt Conveyors’. Conveyor design basis ISO (thereby book is helpful to design conveyors as per national standards of most of the countries across world). New print Nov., 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 ■

To add on to what Mulani Sir has written, normally the activation of safety switches on conveyor (pull cord and belt sway switches) are interlocked with scoop positioning of scoop coupling. When these switches are activated, the scoop tube goes into the working circuit preventing the runner from rotating. Hence motor need not be tripped. Frequent tripping of HT motors can hence be avoided.

Further practically at site, we have got great advantage of speed control while training the belt. Normally while centring the belt we take trial run at low speed initially for 20-30 minutes ■

Dear all,

This thread is very old. Little surprise to note that VVVF drives are not mentioned in the replies, though it was not mentioned in the question.

Regards, ■