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Steel cord belt joint procedure Belt width- 1400mm , Top rubber 8 mm, Bottom rubber 4 mm , Cord dia 3.6mm . Number of cords 112 ,Belt joint width 600 mm.

First of all make a flat platform having wooden ply in the center. Mark the splice length on both theends. Splicing angle to be kept as 0.3W (W- Belt width). Mark the belt center line on belt, Belt jointlength kept 600 mm (for 1400 mm belt width).

600 mm

W(1400mm)

0.3WThe belt jointing work to be carried out in dust free & moisture free environment

First cut the edge rubber of belt and after that remove top & bottom rubber. Rubber to be peeled off by cuttingwith the help of belt knife & pull the rubber with the help of frog clamp & chain block. Belt joint edge should bechamfer cut at the angle 30 0, knife edge should not be kept vertical.

After removing top & bottom rubber cords will get exposed. Cords to be separated by cutting the rubber from between the adjacent cords & cords separated.

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After exposing cords, each cord to be buffed, to remove excess rubber around the cord. The aim is to roughencord surface for increased adhesion and bonding. Care must be taken that cord wires should not be exposed andalso cord wires should not be damaged.

After buffing the cords, Belt joint edge also to be buffed. This end should have the angle of about 45 to 60 0.

After cord preparation, both the ends to be kept in jointing position & all cords to be aligned by keeping 600 mmgap between the joint ends. Belt center line to be marked on both the ends. Sharp cut to be marked on centerlineto make the mark permanent. After aligning the both the ends nails to be inserted on both the ends so that joint

position not get disturbed. Preheat the cords on heating plate upto 135 0 C then cool cords upto 75 0 C. After thisapply rubber cement compound on all the cords. Whole cord area should be covered. Allow the cords to dry untilit is no longer sticky.

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Cut the end of each cord by 100mm. Starting from the center cords to be aligned. Between each cords fillermaterial (4mm x 4mm rubber strip) to be provided. Filler strip to be fixed by stretching. At both sides of jointthere will be free space , where no cords are available. In this space filler rubber to be provided.

After laying all the cords, cement compound layer to be provided on whole area of joint.

Apply tie gum layer (1 mm thick) on the cords. Again one layer of cement compound to be provided on tie gumlayer. Compound layer of Nylon & Top rubber to be pasted on tie gum layer.Apply nylon net on joint area to protect the vulcanized rubber Put flat bars in both side of joint (to avoid thecompounds squeezing out when temperature and pressure is given ), then clamp both the flat bars with the help of

belt edge clamp. Put top heating plate on the joint ensure whole joint area to be covered by heating plates. Insertthe tightening bolts in between the heating plate channels. Bolts to be tightened equally in cross direction toensure equal pressure on joint area. Now we give hydraulic pressure to compress the belt in joint area, againclamping bolts to be tightened. After initial tightening following table to be followed during heating.

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HEATING TEMPERATURE

When the temperature of heating plates exceeds 100 0C, the hydraulic pressure should be raised to 380bar. Furtherincrease in temperature leads to a hydraulic pressure upto 400 bar. Vulcanizing temperature is maintained

between 140 to 145 0C by switching ON & OFF.

CURING TIME

The curing time depends upon the thickness of the belt.

Curing time(Min.) = Basic Time (15 min) + Belt thickness (mm.) x 1 Min.

Curing temperature = 140 + 50C

When heating period is over, the splice should be kept under the same full pressure, until the heating plates havecooled down to 60 0C.

Heating Temperature 0C Hydraulic Pressure (bar)

50 80

60 90

70 100

80 110

90 120

100 140