Internal edge-to-edge splice distance should be at minimum 2000 x the steel cord diameter for steel cord construction. A breakdown of the criteria is derived from:

a) allowable step length within the splice > 100 x the steel cord diameter

b) not telegraph the strain action within a splice to an adjacent splice, that exacerbates the peak strain within the splice pattern so that only one splice is being bent over a pulley at one time, with the adjacent splices. Thus, 2 x total splice length is the second allowance and then added to c) following

c) timing between pulleys should be greater than 5 seconds between splices to allow the rubber's strain to fully decay, in addition to the above criteria.

Thus, a 10mm steel cord diameter, of a ST-5000 N/mm strength rating, would have a conservative step length of 100 x .010m = 1.0 m, have 2 to 4 splice steps depending on the ability of the splice designer for a maximum length of 4 m. Assuming a 5 m/s belt speed the internal distance between splices would be 25m. Bending stress influence across adjacent pulleys will stretch the minimum recommended distance between splices to 33m (110 ft).

Assuming a 3m/s belt speed and 4mm steel cord diameter, of a ST-1200 N/mm rating, would have 0.4m of the single step x 2 ends plus decay time distance of 15m equals a minimum distance of 15.8m (52 ft.).

These are CDI minimum criteria for steel cord belts. The distance must also consider the splice table setup and need for end alignments that are outside the adjacent splice distance. ■

I neglected to note the allowance for inaccurate installations.

Probably less than 50% of the splice vulcanizing contractors know how a splice works in the details. If they do not know, and no one tells them, then they are prone to make errors. Some are big. You often see the dog leg shape from misaligned sections emanating from the splice. When the belt centerline shifts, it is usually a splice construction error. Chopped cables, irregular gaps between cables, inaccurate alignment of belt ends, et al. are unfortunately common practice. DIN 22101 even made an allowance for these types of poor workmanship. I did not make note of this in the first response. I assumed the installation is first class.

Construction errors can also come from the factory.

So, how do you make allowances for shoddy work? Regardless of the rhetoric, it should be given a value, if you are uncertain of the contractors skill set. I propose a first guess is to double the minimum previously suggested to negate uncertainty.

Fabric belts are not our specialty. Let some one else offer insight. ■

If you want to make a hot splice or a cold splice you need a minimum distance between the splices because you have to make the steps or the finger (if it's a finger splice). Futher you have to respect is a critical distance of 1-2 m to be sure that it will work correctly.

The alternative is the use a mechanical belt fastener like on the attached pictures. With the MS fasteners or the Super-Screw fasteners the critical distance will be 1 m but it's possible to take less.

Attachments

bridge with ms45 fasteners (JPG)

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