There are a lot of factors that influence the life of a splice. Having said that, chemical bond and hot vulcanize spilces are stronger splices (CEMA - Belt Conveyors for Bulk Materials- fifth edition).

As I see it, the following are areas you should review:

1. Belt Manufacturer - I have worked on many diferrent brands of belt, and there characteristics all vary. Some are recommended for chemical or hot splicing only, because of the carcass. Others have poor adhesion levels because the carcass is not treated and mechanical splices are the preferred choice.

2. Operating conditions - If this is a high heat application you must follow the manufacturers recommendations and I recommend using only there hot splice kits.

3. Used Belt - Resplicing existing belt, in my experience, gives you lower adhesion levels. The factors that contribute are: moisture, uneven belt wear (vulcanizer cannot give you even pressure throughout the spice area), and belt fatigue.

4. Action Plan - When a chemical or hot spliced belt fails and emegency service is required it can be best to install a mechanical splice. The reason I say this is that the environmental conditions may not be satisfactory, at this time, to do a chemical or hot bond. Also the pressure to get the system up and running usually means short-cuts are taken and the splice results are not the optimum adhesions. Install a mechanical splice and then schedule a time for a resplice at a later date.

5. Scheduled Service - The time factor also applies to this. If a short window is allowed to perform a resplice the splice is subpar. If you get your service quoted by a number of different companies you want to educate yourself to know what it takes to give you the best final product. Lower initial cost may cost you more in the longterm if the price is too low to do a proper job. ■

I ran out of room in my first reply.

I will shotly point out other factors: proper step size in the splice, proper splicing procdures, proper splice area, proper spicing gums and a proven cold bond cement, carcass fatigue, cover thickness, etc.

If you would like to give me more details on exactly where the splice failed,what type of spice, what type of belt, and system details I will give you my opinion. ■

John,

The three splice methods (mechanical, cold cure, and vulcanized) are all acceptable means of splicing fabric carcass belts. Vulcanized splices should be used for steel cord and aramid fabric belt splices.

As far as a comparison is concerned, vulcanized splices and cold cure splices give comparable splice strength ratings, while mechanical splices give ratings at, or slightly higher than, the belt's ratings. Mechanical splices tend to have a shorter life span and require more maintenance than cold cure or vulcanized splices.

Mechanical splices can generally be done quickly by facility maintenance personnel. Cold cure and vulcanized splices, to be done properly, generally are done by technicians trained for the work -- do to the sensitivity of the belt for proper stripping and splice lay-up.

The short term cost (including down time costs) comparison for the three splicing choices are cold cure most expensive, vulcanized medium, and mechanical least expensive. The long term cost comparison has mechanical splices as the most expensive because of multiple down times, cold cure as medium expensive, and vulcanized as least expensive.

Because vulcanized splices provide the highest strength ratings and also are the most cost effective over the life of the belt, these splices are normally the splice of choice. Mechanical splices should be used in emergency situations, where speed to get the belt back up and running is the paramount consideration, or in situations where cold cure or vulcanized splices are not practical.

Cold cure splices should be used where the capital cost of the vulcanization equipment is prohibitive to the user.

Literature sources on the subject include the CEMA book mentioned, belt manufacturer literature, Mr. Mulani's book, the RMA guide on conveyor belts, et al.

Regards, ■

WOW!! Good Thread responses:

Might I add questions to separate the variables of damage due to splice, belt, product damage, bad loading station design, enviromental influences, et al. and the generals. I believe the above have a good start on it and will continue.

A better response might be forth comming if we know:

1. Type of belt material PVC, SBR, Cloroprene .....

2. Product

3. Environment temperature range,

4. Muck build up, pulley configuration and their isssues

5. Lump sizes

6. Width, speed, loading config., tonnage, .....

7. Age in service

8. Dynamics (start/stop) and splice stress

9. Tensile members - steel, polyester, nylon, ......

This can get pretty lengthy to do it all.

Lawrence Nordell

Conveyor Dynamics, Inc. ■

Hi John,

Pathfinder Supreme is an excellent belt for your application. It has good carcass strength characteristics and the rubber is designed for your bulk material.

Since you have experienced a problem, or problems, with the splice and are tasked to do an analysis, you should consider the following:

[1] Examine the failed splice to determine the nature of failure ? fabric failure, tie gum cohesive failure, or tie gum adhesion failure. Confirm that the splice tie gum was adequately cured and is not porous. Confirm that that the rubber and fabric in the splice are not heat damaged (i.e. overcured). Confirm that the fabric is not damaged. Look for signs of contamination between the tie gum and fabric. Take photographs for your records.

[2] If unsure about your own splice analysis, give the failed splice to the Goodyear, Marysville plant for analysis. They will be able to tell if the splice was done correctly.

[3] Find out the operating conditions of the conveyor at the time of splice failure.

[4] Gather normal operating conditions data on the conveyor.

[5]Obtain a history of past belt experiences on the conveyor.

Unfortunately, getting an accurate picture of how the belt and conveyor have been running is difficult, as many operators tend to ignore their systems until there is a major problem. Thus, from their viewpoint the system will have given no signs of a problem before the catastrophic event occurred. Even with this impediment, you can learn how the system was operating by examining the conveyor and belt.

Good luck! ■

A couple other areas I would look at are:

1. Pulley Diameter - with the 1/16 cover, you have to ensure the pulley diameters are correct. Top point on the splice may be opening up due the forces as you wrap the pulley.

2. Breaker - I would also recommend putting breaker material at the points. If you are hot vucanizing, breaker with a thin skim of rubber will flow niceley. This will keep that top point from wanting to open.

Let me know what happened to the splice

Good Luck! ■

Check out Goodyear's website as per link below for vulcanized splice troublesooting.

http://www.goodyearindustrialproduct...leshoot.html#P

Gary ■

One other item - you should add to your contractor audit is to request a copy of their splicing certification card or certificate of each technician that will work on your belts. Ensure that they are certified by the belting manufacturer.

Gary ■

A couple of other items when anylizing vulcanized splice failures (cold or hot)

1. Make ceratin splice lap direction is correct so belt cleaners and dust seals tend to slide over the splice rather than dig into the splice.

2. Mechanical splices should be recessed so belt claeners and sealing systems will not damage the splice ■

The responses are all very good. Of course, I do disagree about the costs including downtime. I represent Flexco, the mechanical conveyor belt fastener manufacturer.

We have 26 men who work directly for us, Flexco, around the US and Canada. Their job is to assist distributors and end users such as yourself with any problem relating to conveyor belt systems.

Where are you located? I can have one of our people contact you to look at your conveyor(s). These guys also know and work with the various belting reps. ■

I forget to mention that you can also take a look at our web site, www.flexco.com. ■

Hallo Mr. Jstrabav,

I think Dave Miller of ADM Consulting gave a good overview of the different methods of splicing with their main advantages and disavantages.

He forgot only one think: the Super-Screw fastener !

It is a new fastener made with a multi-ply synthetic and high elastic textile carcass, a hardened rubber as cover material and metal pieces under the cover. This fastener will be installed on bias by placing the belt carcass between the top cover and the bottom cover of the fastener after removing the cover of the belt, and by fixing them with specific self taping screws and a power screw driver.

Depending on the used textile it is possible to reach up to 100 % of the belt strength. Because it is elastic and mechanical fixed with a long reach back on the belt carcass the dynamic/fatigue strength remain high. Due to the rubber cover it is also wear resistant. In opposition to traditional fasteners it is dust proof and compatible with scrapers.

Some customers use it since 4 years and tell that they experienced a similar life time as with cold or hot splicing. Depending on the application, it is sometime better, sometime it is worse: but is is possible to make a durable splice within a view hours.

On the attached picture you can see the installation of a Super-Screw fastener on an old belt P2000 in a lignite open cast mine. The belt carrys up to 8000 tons/hour. It is 72"wide, the pulley distance is approx. 6000 ft. On the conveyor there are two scraper of Martin Engineering. After 3 hours 1/4 it was possible to restart the belt !

Really the Super-Screw is a different and new technology.

Today it is possible to speak about four different technologies:

- hot splicing

- cold splicing

- metal fasteners

- Super-Screw lacing

If you want further details about this new technologie, please look on http://www.mlt-usa.com or send me an email.

Regards

Edgar Jakob

Attachments

installation lignite mine (JPG)

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Continuation of the points raised:

Standard type mechanical fasteners have an inherent flaw that shortens their life with respect to chemical and thermally bonded splices. The belt structural integrity is dependent on the 3-dimensional elastic compatibility between the splice joint and the parent belt. Mechanical fasteners locally increase the elastic rigidity and thereby increase the localized strain in the belt's carcass.

Belts fail due to the flexual strain cycling. The high elastic incompatiblility between parent belt and mechanical fasteners produces a higher fatigue strain cycle and thus shorter splice life.

This is an area of continuing research.

Lawrence Nordell

Conveyor Dynamics, Inc. ■