Re: Belt Joint Failure Carrying Damp Material
Hello Stinkler:
There are many possible reasons why a resplice might fail over a new belt splice. Can you describe the nature of the failure?
Prime possibilities include:
1) carcass contamination
2) improper splice materials
3) poor splice technique
Regards, ■
Re: Belt Joint Failure Carrying Damp Material
The rough age of the belt at first failure was 16 months
The joint was reconstructed
The joint failed after 4 weeks and was reconstructed
The joint failed again within 6 months
The belt was then changed.
Both joints showed signs of tearing between plys.
Seperate contractors jointed the belt. Using international standard techniques and the correct splice kits
The first joint had been left open overnight before being joined and cured.
This may have had an impact on the life of this joint, but more generaly would a damp belt ply ( at the time of jointing ) reduce the in-service life of a joint. I am assuming that trapped moisture in a joint would reduce its strength.
Additionally is nylon cored belt susceptible to chemical ( there is an amount of Lime in the feed material ) or damp attack. If so is there a more appropriate material for this belt ? ■
Re: Belt Joint Failure Carrying Damp Material
Dear Stinkler,
Can you clarify whether the repaired joint is using unvulcanized fresh belt section or trying to repair failed rubber section.
The HRFR designation refers to a hot belt or fire resistant belt?
How much free belt is left in the takeup prior to repair, after repair, and how much is required for conveyor operation?
If you are using any of the old rubber or prior vulcanized rubber, the old rubber, having one cure already is not the best procedure.
If the repaired section is using new or fresh 16 month old belt, then it would seem there are some vital conditions not spoken of:
1. If this is a hot belt compound, then there is some missing info you need to convey
2. Is this the second belt to be installed in this location - you say the new belt with a fresh joint lasts 16 months and then after two failures it was replaced?
3. First failure is in 4 weeks and 2nd failure is in 26 weeks - why do you think there is such a difference - seems you are doing something not related to belt construction with a four times increase in life with an ageing belt? I would look to your technique as well as possible other conditions. Maybe you can do better with better spliceing techniques.
4. Is belt overstressed due to operating conditions not described such as: belt tracking,
a) belt starting control is poor,
b) idler transition - errors at head or tail overstress edges,
c) material build-up and belt cleaner don't do their job,
d) snub pulley too close to drive if in use,
e) belt tracking errors from loading or splice construction
f) long list of unknowns .......
Good Luck,
Lawrence Nordell
www.conveyor-dynamics.com ■
Re: Belt Joint Failure Carrying Damp Material
The 16 month initial splice failure seems short. When they reconstructed the splice, did they try to use the old steps or did they expose fresh fabric? (If the former, that is the likely culprit.)
I consider it poor practice to leave exposed joint steps overnight -- dirt, moisture, or other contaminents can adversely affect the splice. With some fabric coatings, oxidation can be a problem.
Trapped moisture is a splice will reduce the splice life.
You mentioned that there was tearing between plies. Does this mean that the fabric is tearing, or just the tie gum. If the fabric is tearing, especially at a step line, it is likely that the fabric was knicked, cut, buffed, or scored during the splice operation. If this happens, the splice strength and life will be lowered.
Although Nylon/Nylon carcasses can wick moisture and whatever chemicals are carried in with the water, limestone should not be a problem (I say this without checking chemical resistance tables). I presume that the belt being used was chosen for a reason. As such, recommending alternate carcass constructions without knowing your system would not help you -- check with your belting representatives or consult with a consulting engineering firm with expertise in the field.
Have your belt manufacturer analyze the failed splices.
Finally, the problem may not be with the belt or the splicing. Your system may be asking too much of the belt. Typical system problems include high-tension break points; undersized pulleys; poor impact load zones; inadequate cleaners; improper transition zones; et cetera.
Hope this helps. ■
Re: Belt Joint Failure Carrying Damp Material
Thanks for your assistance.
The final outcome was the belt we were using was under rated for the application.
We were using 1000/4
The actual tension we have calculated in the belt is around 110Kn/m
We are uprating the belt to 1250/4 ■
Splice Joint Failure
stinkler
You mentioned that you were using "international standard techniques and the correct splice kits"
I would highly recommend that you get the hot vulcanizing splice procedure from your belt manufacturer and follow those excactly.
It might even be wise to have a rep (with expert knowledge in splicing) from the belt manufacturer present during the splicing stage to oversee the splicing contractor. This could easily be negotiated when purchasing the belt. Most good belt companies will offer this as a service.
It is also wise to have the splicing contractor certified by the belt manufacturer. Your belt supplier can give you a list of these contractors.
Good Luck
Gary Blenkhorn ■
Gary Blenkhorn
President - Bulk Handlng Technology Inc.
Email: garyblenkhorn@gmail.com
Linkedin Profile: http://www.linkedin.com/in/gary-blenkhorn-6286954b
Offering Conveyor Design Services, Conveyor Transfer Design Services and SolidWorks Design Services for equipment layouts.
Joint Failure
in my experience over three decade in this line,it is very difficult to
pin point the reason for the joint failure
how ever the following points have to be studied
1 selection of correct specified belts for your application
2 running the beltwithout spurt loads
3 maintaining the level of conveorswithout undue modulation
4 giving correct tension rating of belt while in run
5 the quality of splicing material supplied by the supplier should be checked
6 sampling of piece belt joint should be made using the supplied splicing materials and to be tested in lab for seperation, pull out strength etc
7workmenship while splicing the joint should be 100%
foolproof
8 maintaining correct specific pressure in the belt joint area
9 maintaining correct temperatureto avoid under heating and over heating
10 maintaining correct curing time
11 correct cleaning agent to clean the belt wrt solvent
12 correct no of steps of splice should be decided to attain the most required joint strength
13 everyone knows that weakest point in the running belt is joint area
17 keep both the conveyor ie top and bottom idlers in tact
like this lot of points have to be studied
after the joint failure a failure analysis should be made
and come to a nearer solution for the failure
a docmentation is a must for joit failures to minimise future joint failures
as long as we use belt we will come across joint failures and we should equip ourselves to attain 0% failure which is a long way
but we at our works because of our expertise we minimise joint failures
still i can write .it is non conclusing subject
by for noe
n.kathiravan ■
Belt joint failure carrying damp material
Is there any reason why a Nylon carcas N17 HRFR belt joint should fail prematurely in operation.
The material conveyed is Belnded mix feed into a sinter plant. This consists of Iron ore , burnt lime , sinter return fines etc. The material is damp and is warm ( 20 - 30 C )
The conveyor is inclined at around 25 degrees , is around 250m long and has a GTU.
A brand new belt with a fresh joint lasts well, but a rejoint in an old belt only lasts around 4 months.
My current strategy is to renew the belt once the need to rejoint arises, this is obviously costly.
Do I need to change the belt material ? ■