New Splice Assembly Technique for Wire Reinforced Belting

Splices are usually the weakest link in a conveyor belt system. The problem is amplified as the system demand is pushed to the limit. In comparison to 10 years ago, today's systems are longer, wider, faster and the systems are being operated near or at maximum load condition.

At the same time, well known established societies and committees, as well as leading engineering firms, are drafting more comprehensive design guidelines, pushing conveyor belt manufacturers to increase their knowledge of dynamic splice performance and increase the confidence level of the splice design; so that a lower safety factor can be used.

Belt safety factors are determined based on the dynamic splice efficiency of the belt and have been discussed in detail in literature 1'2 and also defined in international standards3. As end-users are becoming better educated in this respect, minimum splice efficiency levels are not uncommon at the present. Therefore, we should expect to see more effective system designs, in terms of system performance/functionality and cost in the future.

Controllable variables in cord reinforced belting design such as; step length, transition zones, butt gaps, pulley diameter, dynamic adhesion, cord separation and cord design will remain critical during the design phase. Other less controllable variables, like workmanship, cord alignment, proper cord separation (in the splice), material contamination and dimensional variability in the splicing material, will surface and become pivotal in achieving the new guidelines and to ensure that the required level of performance of the new splices will be met.

The present paper will review Goodyear's new splice assembly technique for wire reinforced conveyor belts. The new technique will address the critical splice assembly operation and in the process optimize the splice in terms of geometry, cord alignment, workmanship, assembly time (length dependent) and splice crew size.

The technique is based on using "grooved rubber matrix" that can be produced in bulk and delivered to the job site in a specially designed container.

The typical field vulcanization requires many hours and involves the precise execution of several critical operations. It usually starts by erecting a shelter as protection from the elements followed by the set-up of the bottom half of the field vulcanizer. See Figure 1.

The mating ends are overlapped with sufficient belt, properly measured and secured in place. One of the belt ends is folded over back onto itself. The cover and cord stripping operation follows. Note: 1) The overlap distance must be greater than the total splice length (splice length + bias) to insure end alignment and also that the required splicing length will be achieved during vulcanization. 2) Depending on the stripping technique a small section of belt, 3" to 6" long by full width, is left undisturbed at the tip end of the mating ends. This facilitates the cord handling during and after the cementing operation. See Figures 2 and 3.

Once the covers and cords are stripped, the identification of either the center cords (odd number of cords in the belts) or the center line of the mating ends (even number of cords) is completed and, depending on the stripping technique, the cords are gently buffed or de-flashed. Also, the surface of the receiving skives in the cured belt ends are buffed as well to improve adhesion. See Figures 4 and 5.

Release paper and thermocouples are applied and secured to the bottom platen. A template with the splice geometry is marked on the paper so that the splice length, bias, transition zones, step lengths, etc. are clearly visible at the side edges during the assembly of the splice.

The mating ends are positioned at the corresponding locations on the release paper template, squared, center lined and firmly secured. See Figure 6.

Exposed cords from both ends are solvent washed and wrapped in clean protective plastic film and folded out of the working area. Cement is then applied in a generous amount and allowed to dry. This operation is done twice. The drying time depends on the relative humidity. Note: 1) The tacky nature of the cement acts as a magnet for dust, paper, plastic and other type of foreign materials. 2) Any foreign material must be removed before assembly. 3) The cords have a tendency to stick to themselves if they are not properly separated and sorted. See Figure 7.

The prepared pulley cover composite is measured and skives made. Mating surfaces (cured to green) are cemented and allowed to dry. Next, the pulley cover section is inserted in place. See Figure 8.

The next operation is the splice assembly. This is the most critical, time consuming, tedious and labor-intensive phase of the splicing process. Starting at the center of the splice one of the following methods is observed: a) Splices with an even number of cords: An uncured rectangular rubber piece (noodle) by the full splice length is placed at the centerline of the splice. Then, the first two cords are cut to length and laid. See Figure 9. The rest of the cords are cut and manually positioned in accordance with the splice pattern design, b) Splices with odd numbers of cords, the centerline cord in place at the centerline of the splice and supported by two noodles. The rest of the cords are cut and manually laid according to the splice pattern design. See Figure 10.


Figure 9. Splice With Even Number of Cords	Figure 10. Splice With Odd Number of Cords

Notes: All efforts are made to keep the noodles centered, straight and laid in position without stretching them. The same is true for the placement of the cords.

Splice crews are required to frequently check cord alignment and cord separation and project a finished width. Occasionally, the splice has to be de-assembled and reassembled to meet the finished width of the belt.

The cord alignment in the splice depends on the following factors: a) Amount of time given to the process, b) Attention to details, c) The correct handling of the rubber inserts (noodles), d) Two consecutive splices made by the same crew on the same system are not necessarily identical, e) Belt constructions with large diameter cord of 10.5 mm and above, present an additional challenge in terms of splice assembly. If a single noodle is used the volume of rubber provided by the noodle has to fill large voids around the cords. Rubber from the insulation gum will flow to fill these voids causing cords to randomly shift position within the splice. This situation has the potential of creating undesirable stress concentration spots in the splice. To mitigate this condition, four additional smaller rubber noodles are recommended in conjunction with the main noodle. This five-piece noodle assembly requires extra time to complete. See Figure 11.

Next, the butt gaps and transition zones are filled with the corresponding compound. The prepared top cover composite is measured and skived. The appropriate rubber cement is applied to alt mating surfaces (green to cured) and allowed to dry. After the top cover has been applied, the splice is trimmed to width. See Figure 13. Note: Figure12 shows a fully assembled two-stage splice without the rubber filling of the transition zones and butt gaps.


Figure 12. Splice Without Rubber Filling	Figure 13. Splice After Rubber Filling

Fill steel of the correct thickness is placed and secured on the field vulcanizer along with release paper and thermocouple. See Figure 14. Power source and hydraulic source are connected and the splice is ready for vulcanizing. See figure 15. The total splicing time will vary.

The press preparation, centering/securing of the mating ends cord stripping, cord patterns establishment, cord sorting, release paper thermocouples application and pulley cover insertion remain unchanged. The major departure from the norm in Goodyear's new assembly technique starts with the elimination of the cementing operation and its associated time and affinity to attract foreign materials.

The second major difference is the replacement of the rubber noodles by an uncured Goodyear rubber mat with predetermined number of grooves of specific radius, pitch and width. The rubber mat will lead to the formation of panels that can be longitudinally stitched as required.

The first step with the new procedure is the positioning and centering within the splicing area of the middle panel on the pulley cover (plus transition tie gum). Next, starting at the center of the splice, cords are solvent washed and cut to length in accordance with the splice design and placed in the corresponding groove. See Figure 16.

Additional panels are then stitched to the center panel, cords washed, cut to length and assembled in the corresponding groove as per the splice design. This operation is continued until the splice is properly assembled. See Figure 17. Note: Figure 18 illustrates the various splice components.

Next, the butt gaps transition zones and outside cords are filled with the corresponding compound. Top panels are applied followed by the application of the top cover. Afterward, the splice is trimmed to the correct width.

Preforms are rubber matrixes; hot formed with limited amount of heat history added to the material, and using precision made tooling, ensuring product uniformity. The product is formed with a pre-established number of grooves to form panels using a patented Goodyear process. Once made, the product is transferred to special support media, wrapped and allowed to cool under constant conditions to produce a dimensionally stable product. Afterward, the material is transferred to specially designed shipping containers* where it can be delivered in bulk to the splice site in the required amount. See Figure 19.

Ensure proper cord separation and alignment in the splice since the material is machine made and is dimensionally stable.
Minimum cord shifting due to rubber flow.
Improve splice dynamic performance.
Reduces splice assembly time up to forty percent through the elimination of noodles and cement.
Improve workmanship and promote splice uniformity.
Better cord rubber encapsulation.
Minimize contamination due to cement use.
The technique is environmentally friendly.
No major deviation from the current splicing procedure.
Material can be delivered in bulk to the job site in a specially designed delivery container*.

Prototype loops with splices for the ST1250 and ST4500 belt constructions were built using the new technique with a control splice for each construction. Subsequently, the samples were dynamically tested based on DIN 22110/34 at the Goodyear Marysville Conveyor Belt Technical Center. After the completion of the test the splices were stripped and analyzed for internal damage. The test outcome was rigorously reviewed and the data analyzed.

ST1250
Testing load condition: 6.67% to 53.5% of the rated load of the belt strength
Type of splice: Single Stage.
Control splice run 18,797 cycles.
Splice with new technique completed 25,034 cycles. An increase of thirty percent in performance.


Figure 23	Figure 24

The control splice shows broken cords in the transition zone while the splice with the new technique does not. See Figures 23 and 24.

ST4500
Testing load condition: 6.67% to 60% of the rated load of the belt strength
Type of splice: Three Stage.
Control splice was removed after 14,595 cycles.
Splice with new technique achieved 19,390 cycles. An increase of thirty percent in performance


Figure 26	Figure 27

The elongation of the splice with the new Goodyear technique is smaller than the control. See Figure 25.

The control loop exhibits two broken cords in the splice at 14,600 cycles and numerous frayed cords in the splice. See Figure 26.

The loop with the new technique shows one broken cord in the splice and numerous frayed cords in the splice. Three broken cords were found in the transition zone, indicating that the splice is no longer the weakest link in the system. Note: Transition zone is the blending distance between the belt and the actual splice and there are two per splice. See Figures 27.

ST7000: Canada. Five Stage Splice. 13.4 mm cord. (Splice design was tested at the University of Hannover and achieved 13,996 load cycles at 50 percent of load). The Splice assembly time was reduced from 16.5 hours to 3 hours. Note: A five-piece noodle assembly (Main noodle plus four-corner noodle. See Figure 11) was replaced with the preform. [Approximately twenty five percent of the splice time]


Picture 1

Picture 2	Picture 3


Picture 4	Picture 5

ST3500: Utah U.S.A. Two Stage Splice. 8.00 mm. cord. The splice assembly time was reduced from 3 hours to 1 hour. [Approximately ten percent of the splice total time].


Picture 6	Picture 7

Picture 8	Picture 9

The author wishes to express his sincere appreciation to his fellow team members and leadership team for their contribution and support in the realization of this paper.

The author has twenty yeas in the Engineering Product Division of the Goodyear Tire & Rubber Company. He is currently a Project Engineer with fourteen years of experience in the areas of conveyor manufacturing, process improvement, quality and research and development at the Marysville Ohio plant. He holds Bachelor and Masters degrees in Engineering from the University of Nebraska.

Pedro E. Rengifo.
13601 Industrial Parkway
Marysville Ohio. 43040 USA
Tel: +1-937-644-8924. Fax: Tel: +1-937-644-8937
E-mail pedro.rengifo@goodyear.com