Service instructions

Bonding of Rubber V-ropes

Procedure

Bonding procedure valid for:• On-site bonding of a V-rope over a welded

joint.• Repairing bonded V-rope.• If bonding a V-rope to a new belt on-site, please

contact SPS technical support.

The ends of the undamaged V-rope should be cut square (i.e. 90˚ to the belt edge). 1

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Tools and materials• Heating plate• V-grooved clamping bar• Thermometer• Screw clamps• Drilling machine• Expandable rubber roll, Ø50 mm • Grinding belt, 36 or 50 grits• Etched rubber V-rope• Redux tape or TESA tape (formerly Technicol) • Super glue• Chisel• Stapler (when using Redux tape)• Iron (when using TESA tape)• Solvent, which does not leave a film• Rags

For repairs onlyRemove the loose parts of the V-rope together with any contamination from the area of the belt where the bonding is to take place.

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Clean the area of the belt to be bonded using clean rags and solvent. It is essential that the belt surface is completely clean and dry.

Grind the area in a longitudinal direction to the belt. Roughen the area with a grind-ing belt, 36 or 50 grits, fitted on a 50 mm diameter expandable rubber roll. A drilling machine is recommended for this purpose.

Cut a piece of new V-rope 1% longer than the required length. The ends must be cut square to precisely match the ends of the existing V-rope on the belt.

The flat surface of the V-rope (i.e. the surface to be bonded) must be etched with sulphuric acid. To test the effectiveness of the etching, bend the V-rope and check for surface cracks in the rubber. If no cracks are visible, do not use the V-rope.Note: this test is valid for nitrile and natural rubber.

Clean the V-rope and the area to be bonded using clean rags and solvent.

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Cut a piece of Redux tape or TESA tape to the same length as the new section of V-rope.

The following procedures should be used to apply the bonding tape: • For Redux tape, remove the protective plas-

tic film and attach the tape to the V-rope using staples at intervals of approx. 100 mm. Alternatively, apply the Redux tape using a bead of Redux 120.

• TESA tape should be attached to the V-rope using heat (a normal domestic iron is recommended). After ironing, remove the plastic interleafing which protects the TESA tape on the topside.

Place the heating plate under the belt.

Place the V-grooved clamping bar on top of the V-rope and press down gently.

Clamp the assembly together with screw clamps.

Cure the Redux tape at 175°C (350°F) for approximately 15–20 minutes until the colour is light brown. (A straw yellow colour means too short a curing time; orange-red means too long).

TESA tape is cured at 150°C (300°F) for approximately 15 minutes until the colour darkens to a reddish-brown.

When the curing process is complete, care-fully remove the V-grooved clamping bar.

Place a couple of drops of super glue on each end of the new section of V-rope. Place the new V-rope on the belt and hold the ends together until they are securely bonded.

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When the V-rope has cooled down, check the bond by carefully twisting it with pliers.

For repairs only A belt installed on a meat cutting line should be heated to 150°C (300°F) for 15 minutes before curing the V-rope in order to remove any fat from the material.

Trouble shooting

Any of the following conditions can result in poor-bonding results:

• Insufficient cleaning and degreasing of the belt and V-rope.

• Insufficient roughening of the belt at the bond-ing area.

• Dirty or greasy fingermarks on the belt or on the rubber after they have been degreased.

• Use of old (brittle) Redux tape or TESA tape.• Bonding with the interleafing plastic still

attached to the bonding tape. • Failure to etch the V-rope – the rubber surface

must contain fine cracks.• The V-rope not having been properly clamped.• Curing at the wrong temperature.• Moving the belt while the V-rope is still warm.