Boiled In Oil.
There is plenty of relevant information in a previous thread started by Mr Ganesh a few months back. Manufacturers eventually got involved and the technology was explained rather well.
In your case there is also a negligence element. 180mm of misalignment was found only after the failure which doesn't say much for the housekeeping.
That sort of scenario suggests that perhaps the temperature sensor might not have been working either. Otherwise you might have had some indication of previous overloading due to the belt rubbing the sideplates.
Mindfull of the previous thread. Is there any way of indicating if a backstop is working or are we obliged to trust in good maintenance? There is a word for "How can you be sure the light has gone out after you close the fridge door?" but I forget it. ■
Holdback Force Monitoring & Load Sharing - Single & Dual Drives
First reporting of holdback force monitoring.
Conveyor Dynamics, Inc. (CDI) developed some years ago a holdback load sharing device based on our 7100 kW incline conveyor design at Palabora in 1988. Palabora was designed to load share and from field measurements, it did the job. More recently, we have supplied a commercial version for Australia and Brazil. This holdback can be fitted with a tell-tail indicator ( non-electronic) that gives the value of the force on the holdback arm. Thus, an operator can see the value and record the trends or have an electronic sensor (LVDT) type report each stop the value and note the trend if the holdback begins to fail.
The main focus was to provide load sharing on multiple driven pulleys. However, it can also report the force on a single drive pulley with one or more motors. ■
Coupling Damage
Thanks to all who read and respond.
There are certain points what I have been trying to analyse.
1) Off track of the belt conveyor and rubbing on the corner can create some load on the motor but will it be that much to damage coupling. What about the protection of the motor. The motor should trip in case of overloading. It didnot trip. So it means the motor protection did not work.
2) If the temperature of the fluid went high , it should have been sensed by the temperature measurment unit but there was no alarm related to high temperature. SO it means the temperature sensing unit did not work.
3)The high fluid temperature should have been released from the fusible plug.But it did not. So it means the fusible plug did not work.
all these observation indicates towards some other reasons.... like the alignment issue , or as the hold back mechanism failed..It resulted the belt to run in reverse direction in very high speed which resulted the belt to move out of track and also over speed damaged the coupling... ■
Re: Reasons For Fluid Coupling Damage ?
FYI:
https://forum.bulk-online.com/showth...plings-Blasted
Regards,
Lyle ■
Damage Control
Dear Mr. Panthripu,
https://forum.bulk-online.com/showth...plings-Blasted
This is in General --> General Aspects, last post @ 2011-10-27 by Frank Holden.
Then:
#1 If the coupling exploded, you still have the holdback: What does the competent person say about the primary reason for holdback failure and the point in time when it occured?
#2: If not one of three temperature-based control devices reacted, probability is quite high that this could not be the root cause. I assume, that motor trip control is by PTC ?! However, some chance is, that you have a protocol of motor current --> do you have a readout, and what does it say?
#3: If there was 180 mm misalignment, pls. allow me the question: Didn't the belt already wander off the pulley or over the edge of some idlers?
BTW, straight names ... ; however, did you contact the mentioned supplier?
Regards
R. ■
Re: Reasons For Fluid Coupling Damage ?
Originally Posted by panthripu
Primary observation after incident were
The fusible plug of the coupling did not operated .
there is a temperarature sensing unit which senses the temperature of the fluid of the couplind continuously. this unit also did not give any signal for high temperarure.
Both above finding indicates that the coupling did not damage because of the temperature.
It was observed after incident that the backstop of the the conveyor was not working/failed.
The belt conveyor was found drifed/swayed at tail end pully almost 150-180mm.We dont know if this sway is result of reverse movement of the belt with load or during normal running it was swayed.
Your expert comments please...
What could be reasons for failure.
If the conveyor is rubbig the pully guard cover at tail end can it overload the conveyor in such a extent that it will damag the coupling.
Dear Mr.panthripu,
Could you please upload the general arrangement drawing of this conveyor? Do you have alarm history ( sequence of start, stop, tripping with reasons etc., ).
Conveyor would have gone out of track when it was running in reverse due to gravity of the material on the belt. Motor would be out of line. We cannot blame the Belt Track switches. Do you have brakes as additional protections ?
As far as I know, unless otherwise the technicians / inspection engineers are very shrewd, there are lot of chances that they can fail to predict the possible failure of hold backs in near future. Many times they happen as surprise.
I have update this link with additional information :
https://forum.bulk-online.com/showth...plings-Blasted
Thanks & Regards, ■
Fluid Coupling Damage
Dear Panthirup,
I had some experience of similar nature.
1.If the belt mis-alaignment for 180 mm, was there,the rubbing of the belt with structures,might have damaged the belt as well.
If there was edge damage for a substantial length,the misalignment reason could be attributed.
2.Has some one tried to start the belt which was rolling back due to failure of backstop.
3.When there is failure of back stop, the belt roll back speed is enormous which makes the counter weight to hit limits,has this happened.
4.All protection system ( motor overload,Fusible plug,backstop,temperature gauge etc) cannot fail at a time.
5.Motor overload takes some time to trip,because it is adjusted not to trip during starting (Starting current 600% to700%).
6.A thorough investigation is required.Whatever may be the findings, please post it in this forum for reference.
7.I remember, similar case discussion in this forum earlier.
Rgds,
Narayanan Nalinakshan.
Originally Posted by sganeshCould you please upload the general arrangement drawing of this conveyor? Do you have alarm history ( sequence of start, stop, tripping with reasons etc., ).
Conveyor would have gone out of track when it was running in reverse due to gravity of the material on the belt. Motor would be out of line. We cannot blame the Belt Track switches. Do you have brakes as additional protections ?
As far as I know, unless otherwise the technicians / inspection engineers are very shrewd, there are lot of chances that they can fail to predict the possible failure of hold backs in near future. Many times they happen as surprise.
I have update this link with additional information :
https://forum.bulk-online.com/showth...plings-Blasted
Thanks & Regards,
■
Fluid Coupling Failure
Hi
Thanks again to all the participants
Unfortunately we dont have any kind of historical trends for motor current but yes the logs of the events are available. Just before failure the conveyor was stopped and there as no command for start up again.Within 20 seconds of stoppage of the conveyor , the coupling damaged.
The belt was found misaligned at the tail pully only ,which i personally believe because of reverse movement of the conveyor. The main reason of this assumption is that the belt was not found damaged or the there were no severe rubbing marks of the tail pully cover. If it had been running with such misalignement for longer time , the belt would have been damaged as mentioned in above replies.
Motor is controlled with siemens simocode which are no doubt,one of best motor controllers.
I agree with that when the belt runs freely in reverse direction due to gravity, the speed of the coupling will be tremendously high above critical speed which damages the coupling before the oil temperature rises above the fusible temperature of the coupling or tripping temperature of the coupling.
One more thing which i believe that during reverse direction due to gravity ,if start command is given ,it should trip the motor.There is no doubt that the current will be much more ,almost 5 to six time full load current and in such condition the motor should trip with in 10 seconds as per our settings.
Still to avoid such conditions we are modifying the logic . So that if there is no command for motor and the speed sensor is still giving signal,It will assume the reverse movement of conveyor due to backstop failure. It will lock the start operation of the motor electrically. That means the conveyor can not be started and will generate an alarm.
The other thing we are planning is to fix the thruster brake arrangment.
But one thing is still answerless that what kind of check are there for ensuring healthiness of backstop. ■
Reasons for Fluid Coupling Damage ?
We recently had a failure in the fluid coupling (Flender make) of a inclined belt conveyor ,. The conveyor was running with load and stopped and after few seconds the coupling exploded.
Primary observation after incident were
The fusible plug of the coupling did not operated .
there is a temperarature sensing unit which senses the temperature of the fluid of the couplind continuously. this unit also did not give any signal for high temperarure.
Both above finding indicates that the coupling did not damage because of the temperature.
It was observed after incident that the backstop of the the conveyor was not working/failed.
The belt conveyor was found drifed/swayed at tail end pully almost 150-180mm.We dont know if this sway is result of reverse movement of the belt with load or during normal running it was swayed.
Your expert comments please...
What could be reasons for failure.
If the conveyor is rubbig the pully guard cover at tail end can it overload the conveyor in such a extent that it will damag the coupling. ■