Straying from the belt manufacturers splicing procedures may void warranty.

It is highly recommended to go with specifications and procedures supplied by the belt manufacturer. Why would you want to reinvent the wheel?

Here is a good read but they too mention following the manufacturers procedures. http://conveyorbeltguide.com/SteelCordBeltSplicing.html ■

Dear Sebastian,

Conveyor Dynamics, Inc. (CDI) have conducted hundreds of laboratory tests with multiple belt suppliers using simple coupon 3 wire and 5 wire assemblies, and hundreds of fatigue loops on various two pulley dynamics loading. I have published many articles on the critical parameters. Some were presented in BSH magazines. Except for special stress stiffening cases with special core gum rubber the general rules of thumb are:

1. Step Length ...................................... 100 (min.) x steel cord diameter 80% effective; 125 ( recommended) x steel cord diameter = 90% effective; >150 to reach 100% effective. Some belt suppliers offer splice steps @ 80 x steel cord diameter, which yields about 70% dynamic splice efficiency at 15,000 load cycles.

2. Splice Core Gum Gap (between cables in the splice) = g/d ( gap/diameter) = 0.35 for moderate to good fatigue strength depending on the supplier. No gap should be less than 0.25 without a large fatigue strength penalty for most mfgrs. CDI has published many articles on splice designs and parameters that show what can be achieved with prudent designs.

3. When ST-rating N/mm goes beyond ST-5000 N/mm, other design factors can have a strong influence. There is a hierarchy between suppliers and the achievable fatigue strength for a coupon, and separately for a fully configured splice with a minimum of 5 repeat step patterns. Some providers have substantially high fatigue resistance. Some steel cord constructions have superior elongation values (smaller is better).

4. There are superior splice patterns as well as dimensions, beyond the 2-step pattern. As commented on a separate thread, CDI has designed ST-5100 N/mm with a 2-step pattern, where some would go to a 3 and 4 step sequence.

5. CDI has successfully designed and tested ST-10,000 N/mm, with multiple loops, that achieved > 15,000 load cycles at 55% efficiency with a 5 step pattern.

6. Cables larger than 8 mm must take care to evacuate the trapped gas and not let gas bubbles go into solution, without suffering a major loss of strength. ■

Dear Sebastian,

You say you have doubts about the ST-5100 N/mm splice. What are your doubts?

CDI have not published the details. The method is our intellectual property. Many tests were conducted to characterize the endurance dimensionally and with specific material properties.

First we tested the core gum and steel cord capacities using small coupons to evalauate cord breaking capacity and then the endurance of the core gum at various gap dimensions for the nominated steel cord construction. Then 5 repeat pattern loops were constructed and placed on the Hannover test rig, so others would not complain that our 2-pulley test machine had special biases.

The belt was installed in Chile many years ago. We conducted fatigue analysis testing and achieved 60% endurance after 15,000 load cycles. Hannover says 10,000 load cycles are sufficient at 36% for SF=6..7:1. ■

Sebastian,

Here are two Bulk Solids Handling (BSH) publications and a SME paper I authored or co-authored on splice designs:

1. 1991(BSH), No. 4, pp. 863-868; "BELT CONVEYOR STEEL CORD SPLICE ANALYSIS Using Finite Element Methods" - Nordell, Qiu, Sethi

2. 1993 "STEEL CORD SPLICE DDESING & FABRICATION TECHNIQUES", Paper presented at AIME-SME Annual Convention, Reno, Nevada, USA, February, 1993

3. 1993 (BSH), No. 4, pp. 685-693; "STEEL CORD BELT & SPLICE CONSTRUCTION Modernizing Their Specification, Improving Their Ecomonics" -L. Nordell

Hope you find the reading worthwhile. ■