There is no advantage to having it on one pulley vs another. We put them on the pulley closest to the PLC inputs for the shortest wire run. In our case it is typically on the snub closest to the drive or on the first bend of the gravity take-up.

On short conveyors with only 2 pulleys it is of course on the tail pulley. ■

Sounds sensible, particularly on long machines. ■

Originally Posted by sganesh

Dear Experts,

What are the advantages of a speed sensor, particularly if the conveyor has gravity take up?



Regards,

Well, it lets you know the conveyor is actually going. ■

Originally Posted by sganesh

Dear Experts,

What are the advantages of a speed sensor, particularly if the conveyor has gravity take up?

Regards,

A speed sensor can be used to monitor slippage in the system or can also be used as a zero speed switch.

We don't use a speed sensors per say. We have a proxy switch pick up a rotating target on a non drive pulley that is sensed for 50% of the rotation. This signal is an input to the PLC so that the PLC knows what "normal' is as far as revolution per minute based on counting pulses per minute. Pulse on + pulse off = 1 revolution. We then set a threshold limit that shuts down the conveyor when that threshold is breached. We also use this method as a zero speed shutdown. ■

Surely that is a speed sensor, it senses the speed using a digital principle ■

Originally Posted by designer

href="showthread.php?p=69865#post69865" rel="nofollow">

Surely that is a speed sensor, it senses the speed using a digital principle

Yes you are correct designer. But it would not be marketed as a "speed sensor".

There are speed sensors that are marketed just for that purpose only.

As in the Seimens Sitrans WS100 pictured here.

href="https://forum.bulk-online.com/attachment.php?attachmentid=26145&d=1299788737" id="attachment26145" rel="Lightbox69866" target="blank">■

G'day,

I would put it on any non-drive pulley as it will tell you if the belt is not running. If it is fitted to the drive pulley, then it will only trigger if the drive coupling has failed.

The drive pulley will also fail to indicate a slipping belt. ■

Originally Posted by Gary Blenkhorn

Yes you are correct designer. But it would not be marketed as a "speed sensor".

There are speed sensors that are marketed just for that purpose only.

As in the Seimens Sitrans WS100 pictured here.

Looks suspiciously like a "Whirligig" to me

http://www.go4b.co.uk/uk/documents/whirligigUK.pdf ■

Reading the comments so far, the speed sensor being referred to appears to be a belt slip detector. Most of the conveyors I have had anything to work on, have been one on the driven pulley/s in the form of a speed encoder or proximity & multi tag target ring set to set the belt speed and acceleration and de-accellaration rate of change during starting, running & stopping. The encoder or proximity sensor has a further corresponding sensor/s to detect speed differentials away from the main drive pulley/s, and is usually situated at the tail pulley. There are other places where other sensors can be located so the digital (or analog) data can be logged to achieve a stability throughout the entire length of the conveyor. This is the reason that most PLC programs run with a minimum of 11 rungs in the PLC program and on particularly long belt systems, 13 or 14 rungs may be required.

Hope this helps. ■

Originally Posted by sganesh

Thank you all.

Request to go through the first post on this thread. To detect the slippage in the system, what should be the best pulley ? Of course we cannot fix it in drive and take up pulley. Among the remaining other pulleys, I thought tail bend pulley is the best option.

Regards,

To detect slip, the best pulley is the tail pulley. Of course, if you are using a shaft mounted speed sensor, you will have to make sure that the tail pulley has a live shaft. ■

We always put them in the tail pulley. But there is no difference choosing other pulley, but, as a standard, we always try tu use the same place. ■

Originally Posted by Gary Blenkhorn

A speed sensor can be used to monitor slippage in the system or can also be used as a zero speed switch.

We don't use a speed sensors per say. We have a proxy switch pick up a rotating target on a non drive pulley that is sensed for 50% of the rotation. This signal is an input to the PLC so that the PLC knows what "normal' is as far as revolution per minute based on counting pulses per minute. Pulse on + pulse off = 1 revolution. We then set a threshold limit that shuts down the conveyor when that threshold is breached. We also use this method as a zero speed shutdown.

Normally A proxy switch, which picks up signal from the rotating target on the non drive pulley is ussed as ZSS,which switch of the motor if it does not attain the rated speed in predetermined time(this time depends on the mass to be accelarated,5to 8 secs),while starting.The switch also switch off the motor when the speed drops due to any reason like chute jamming,belt snapping,or belt slip on the drive pulley on account of poor lagging, rain etc.For all these purpose the ideal position of ZSS is on the snub pulley immediately after the drive pulley.In case of more than one drive pulley the ZSS should be fitted on all drive snubs.

Rgds,

NarayananNalinakshan ■

You need a full angle of wrap of at least 180 degrees to ensure the speed sensor records accurately therefore if it is not the take up it needs to be the tail pulley. If it is the tail pulley you need to make sure that there is sufficient take up tension at all times that the sensor does not detect slip for reasons of lack of take up tension

Cheers

Colin Benjamin

Gulf Conveyor Systems Pty Ltd

Conveyorsystemstechnology.com ■