Charles,

The best splice for a particular belt is that recommended by the belt manufacturer. If you use a finger splice on a belt that the manufacturer states that a step splice is requied, you have assumed responsibility for the splice strength and have unfairly exposed the belt manufacturer to complaints that their belt does not meet your expectations.

For fabric carcass belts, finger splices are commonly used for single ply belts. Overlap or scab splices are alternatives. Althogh combination finger/step splices are used for some two ply belts, most two ply belts are spliced with the step method. Three ply (and above) are normally splice using the step method.

If you are splicing, finger or step methods, the critical factors include splice length, proper preparation, no damage to the fabric, cleanliness, use of proper splice materials, and proper cure time/pressure/temperature.

If you are using a splice service company to do your splice work, it pays to use a company with a good reputation. It is false economy to pay an inferior company two or more times to do a splice when a good company will get it right the first time. If you are doing your own splicing, it pays to have your technicians properly trained.

Again, follow the belt manufacturer's recommendations - they have done the tests!

Best of luck in your splicing.

Regards, ■

Hello Charles,

I agree with Mr. Dave Miller’s reply.

We have to follow the instructions of the belt manufacturers for the type of joint recommended by them alongwith their recommendation for vulcanising materials, because they know the best about their belt and they will be recommending such things after necessary testing and field data.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyors.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

We too use high tension belts and do 90% of our splices hot vulcanized.

Contact your belting supplier and ask them to give you a copy of their splicing procedure manual. All reputable manufacturers do not have a problem in doing this. This is the best resourse for me.

Ensure that the splicing company that you are dealing with is certified by the belt manufacturer in case you ever need warranty. They will not warranty their splices unless the installer has been certified by them.

Most manufacturers issue a certificate or an ID card for each technician that takes the course.

Good luck.

Gary Blenkhorn ■

Dear Charles,

Finger splices are recommended when a high strength fabric and low number of plies are used.

Step splice strength efficiency drops as the number of plies is reduced. Finger splices do not have a drop in efficiency with fabric construction.

Finger splices are more difficult to build and require increased accuracy in preparation. As others have stated, you need a qualified finger splice specialist.

There is another way to gain significant splice strength (>30%), using a conventional step pattern. I have promoted the concept to Goodyear and Bridgestone. The procedure has been successfully tested on a splice dynamic test machine. We are waitiing on their further interest. There may be a small difference in cost of splice material to apply our method. There is no difference to the splice contractor.

Dupont wrote a white paper on their finite element analysis for kevlar fabric finger splice techniques over 12 years ago. I believe there is a Bulk Solids paper from an Australia university study on the subject. I'll let you do the leg work.

Lawrence Nordell

Conveyor Dynamics, Inc.

www.conveyor-dynamics.com ■

Additions to the above:

Finger splices need special preparation to enhance the fabric cut ends to bond to the rubber. Poorly treated fabric ends cause premature failure. There is concern that this condition is a cause of finger/fabric reliability.

There is an movement to sell higher Safety Factor fabric belt with a SF> 10:1 up to 13:1 to accomodate the damage produced at the transfer from impact, cut and gouge. Kind of makes the splice strength design issue mote.

The use of a better chute design, that eliminates such damage, is slow to catch on. Belt manufacturers want to sell $$$ belt so they don't promote the use of better chutes and improved splice strength that yield lower strength belting and associated costs.

Lawrence Nordell

www.conveyor-dynamics.com ■

Scandura have recently done some studies on their splicing procedures for finger vs scab and step finger. The results can be found at the link below.

http://www.scandura.net/assets/splic...HW%20Belts.pdf

Gary Blenkhorn ■

One thing I often see done wrong when using a step splice, is the lap is done in a direction that cleaning and sealing systems have a tendency to peel the splice open rather that skimming across the splice. This will reduce the life of the splice, and may cause damage to belt cleaners and skirt seals. ■

Hello again Charles,

There have been good replies to your initial query.

As Lawrence Nordell has pointed out, finger splices require special care. As Gary Blenkhorn has indicated, Scandura has conducted a study on various splice results for their single and two ply straight warp belts. As I and Ishwar Mulani have indicated, you should follow the recommendation of the belt manufacturers. And as Larry G. has pointed out a poorly done splice can create problems.

Remember that the splice strength is basically based on the shear strength of the tie gum used (approximately 0.030 inch thick rubber) - that is, the only thing holding the belt together is a very thin rubber strip. Scab splices offer the greatest surface area, but suffer from increased stiffness in the splice area. Finger splices are normally used with singler ply or occassionally with two ply (stepped finger splice) belts. Step splicing generally is preferred for multi-ply belts. Steel cord belts are essentially spliced using a finger style splice method (they are essentially a single ply type of construction).

The only aspect of finger splicing that concerns me is that the splice is a hybrid that bonds both warp and weft cords. Because of this, the strength potential is somewhat comprimised. However, the alternatives of using a scab or overlap splice is not attractive due to the stiffness issue.

It would help if you would indicate which belts you are considering.

Hopefully, I have not confused the issue.

Regards, ■

Hello Charles,

Just some remarks about the lastest information on vulcanizing technique.

Our company is a manufacturer of throwing belts, high power transmission belts, cable pulling belts and special belts with EP or PP fabric, steel cord or kevlar cord. We use all differents methods of vulcanizing (finger splices, V-step splice, overlong splice etc.) but most of our belts are spliceless winded and hot vulcanized in order to meet the requirements (sometime more than 100 ft per second).

All differents techniques need a long experience and a lot of know how about the little secrets for doing it perfectly. Like Lawrence Nordell told, finger splices are difficult to build and require increased accuracy in preparation. No problem if you do it in a factory in very confortable and clean conditions. Of course it will be very different if you want to do on site. In Germany the company TIP TOP SAAR sometime installes finger splices in underground black coal mines for the main belts. They have developed a transportable high precision cutting machine especially for that. It takes more than 24 hours to do a good splice. If you want more information maybe you can contact the CEO M. Kirchner (eMail: office@tip-top-saar.de).

Like you know black coal mines usually use mechanical fasteners because it is very quick and easy to installe but it is not a solution for long life time. If you want to shorten the down time and to increase your productivity maybe the Super-Screw is the right solution for you. This fastener is made with the same structure as the fabric belt itself : a multiply carcass and rubber as cover material and additionaly metal inserts under the cover. The fastener will be installed with self taping screws on the carcass of the belt. Everybody can installe this fastener within 1 or 2 hours. Like a hot splice it it dust proof, elastic, scraper compatible and provide a long life time for the splice (see on our web site www.mlt-usa.com). I'm sure that's the best practible developement in this field.

As example the swiss vulcanizing company AIR-GOMM usually makes very short kevlar fabric finger splice (technique of Dupont) for tunnel belts. Instead of loosing 12 hours AIR-GOMM utilizes today the Super-Screw fasteners even for a 4 miles belt of type ST1700. In this case they add some glue during installation. If you want more information maybe you can contact the CEO M. Erkan (eMail: info@air-gomm.ch). He can give you some information about his expereince with finger splices and Super-Screw fasteners in swiss tunnels.

Edgar Jakob

MLT GmbH

www.mlt-deutschland.com ■

Originally Posted by Gary Blenkhorn

We too use high tension belts and do 90% of our splices hot vulcanized.

Contact your belting supplier and ask them to give you a copy of their splicing procedure manual. All reputable manufacturers do not have a problem in doing this. This is the best resourse for me.

Ensure that the splicing company that you are dealing with is certified by the belt manufacturer in case you ever need warranty. They will not warranty their splices unless the installer has been certified by them.

Most manufacturers issue a certificate or an ID card for each technician that takes the course.

Good luck.

Gary Blenkhorn

We have found that we have helped countless mining, quarrying and crushing companies steer away from hot and cold vulcanising.

Why have to spend thousands of dollars on splicing crews, travel time and accomodation, when in a matter of 2 hours anyone can fit up a super screw join for a fraction of the price and no downtime.

They are available in Abrasive resistant, Heat resistant to 200 degC , FRAS and also anti magnetic for metal detectors.

Welcome to the real world of conveying.

David Cotton

Director

WA Belting Solutions

www.wabelting.com.au ■