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SPLICING & VULCANISATION
 
SPLICING OF STEEL CORD BELT
PREPARATION
 
The portable splicing press must be assembled up to the bottom platen on a firm foundation at a suitable height and a table placed on either side of it to provide a level working surface. The working tables should be as wide as to the press platen which in turn would be about 200mm wider than the belt width. The length of the tables should be 3 metres long. The belt ends should be overlapped across the press platen after having a center line marked on them about 12 metres long on each ends.
 
The following tables should be followed for the types of splice to be chosen for a particular belt.
 
The total splice length = L-1 + 0.4W,
L-1 = From Table No. 8
W = Belt Width
 
Table No. 8
BELT TYPE SPLICE TYPE L-1 (mm)  
ST-1000 & below 1 700 -
ST-1250 1 900 -
ST-1400 1 1000 -
ST-1600 1 1000 -
ST-1800 1 1100 -
ST-2000 2 1200 400
ST-2250 2 1350 450
ST-2500 2 1500 500
ST-3150 2 1900 650
ST-3500 2 2100 700
ST-4000 2 2400 800
ST-4500 2 2700 900
ST-5000 2 3000 1000
ST-5400 2 3300 1100
       
SPLICING AND REPAIR MATERIALS
1 Top Cover layer
2 Bottom Cover layer
3 Bonder Rubber 2mm thick cut pieces to suit the cord diameter.
4 Bonder Rubber gum sheet of 0.4mm thick
5 Splicing solution (available in the market)
6 Solvent oil.
 
VULCANISATION
The belt would be spliced according to the table using either Type - 1 or Type - 2 method. The belt ends would therefore be marked out as per to the type - 1 or 2 and the overlap of the belt ends should be arranged so that a length of approximately 200mm remains outside the splice are on each end. The angle of the joint should be same as that of the portable press which is normally 20 deg. The lines are drawn on the belt surface to mark the end of the joint and diagonal cuts are made at an angle of 15 deg. Down to the cords to define the ends of the splice area. The covers can then be stripped off removing the back cover first. When the back cover has been removed the cords should be separated by cutting vertically down each side of the each cord to a depth approx. to the diameter.

The belt end is then turned over and the top cover is removed by pulling off again in strips but no further cutting is required. The chamfered ends of the belt should now be well roughened with a wire brush and then cleaned along with the exposed cords with a solvent rag before having a coat of solution. Turn the solution ends back, lay a piece of silk cloth over the bottom press platen and then place on it the back cover, cut to length with skived knife ends. Bonder layer up wards (the bonder layer contains a water soluble red dye for identification purpose.) The back cover is given two coats of solution and the cords and the belt ends another coat. Line up the center lines, attach the belt end to the back cover by matching the chamfers and roll pattern applying strips of bonder rubber of suitable thickness between the adjacent cords. Carefully check the alignment of the cords through to ensure they are straight in joint. When all the cords are laid fill in at the ends of the cords and also at the edges of the joint with unvulcanised rubber so as to ensure the splice area is level. Apply one coat of solution overall and lay the top cover sheet over the joint area. Roll well down the entire joint area and release the trapped air by pricker roll. The edges are then trimmed and another ply of silk fabric applied over the joint. Suitable side iron are placed along the joint, the top platen of the press is placed in position and the top beams are bolted with the bottom beams. Clamp the irons with sash clamp. Heat up the press to the vulcanization temperature of 1400C and adjust the pressure to 10-12kg/sq. cm. on the belt surface. Maintain the temperature for the specified time (40-50 min) according to the belt thickness. Switch off the heating after specified time and cool the belt to 700C before removing the press.
 
COMMISSIONING
When the belt has been made endless, then check that all the drums and the idlers are placed to their places and are perfectly aligned. The belt should then by run for 10 sec. interval and check that the belt is not touching any part of the structure or approaching nearest to 20mm of the obstruction and if found satisfactory, then run for 20, 30, 40, 50, 60 sec and so on and finally five a full run of the conveyor. If any fault is found, rectify it and then run the belt again till satisfaction. The load should be applied and any further corrective action is required that should be taken immediately.