Speak with one of our experienced engineers

Contact us

Pressure during hot vulcanising

Pressure during hot vulcanising

The traditional way to apply hot vulcanised rubber lagging onto a pulley is to use uncured calendar sheets. These sheets are made up of multiple layer plies to achieve the final lagging thickness that are then wrapped in a fabric blanket and cured in an autoclave.
As conveyors have increased in capacity, the amount of power being transmitted though the rubber lagging has also increased. As a result, we are now seeing failures of rubber lagging due to delamination of drive pulleys and high-tension bend pulleys.
This type of failure can be eliminated using a different method of applying hot vulcanised rubber lagging.
right

The Elastotec Hot Vulcanised Rubber Lagging system offers

Elastotec hot vulcanising lagging system has a no delamination no debonding with a 3 year warranty.

Traditional method

Traditional hot vulcanised rubber lagging using uncured calendar

When you use an uncured calendar rubber sheet made up of multiple plies there’s an inherent risk of those plies delaminating because there’s always a weak point even after curing.

This method requires enough pressure for the different layers to vulcanise together onto one layer. When steam heated autoclaves get to the vulcanising temperature, around 140°C, pressure in the autoclave is 400KPa. This pressure is not enough to force the different layers into moulding together.

Sheets

Elastotec Hot Vulcanised Rubber Lagging

Elastotec hot vulcanised strips are moulded in a press at 20,000KPa to shape it. This high pressure eliminates the risk of any delamination within the rubber.

Moulded strips with the diamond pattern are vulcanised to the pulley through a 1.2mm uncured rubber layer added to the back and sides of the moulded strip.

ELASTOTEC HOT VULCANISED SYSTEM WITH NO RISK OF DELAMINATION OF LAYERS.

right

Traditional method

Sheet calendard rubber is applied using wide wet blanket fabric that in the autoclave will shrink and will apply some pressure.

There are several reasons some rubber liners prefer to use blanket fabric. These reasons include:

  • Easy to apply on large pulleys that are difficult to rotate
  • Quick to apply
  • Smooth finish after curing to minimise the chance of machining being required.
 

These sheets are used as they apply some pressure to the lagging but not enough to deform the surface and end up with a non-straight lagging finish that would then need to be machined to be rectified. Blanket fabric provide an even finishing but do not apply enough pressure to always ensure a good bond between of the rubber layers and a good bond to the steel.

blanket_fabric
Wide wet blanket fabric

Elastotec Hot Vulcanised Rubber Lagging

image011

To ensure no debonding from the pulley, Elastotec lagging is only applied through approved applicators using 75mm wide nylon curing tape wrapped around the pulley overlapped 50% and two passes. Test pieces are also wrapped around the pulley and then tested.

Overnight soaked nylon curing tape applied to pulley with pressure, 50% overlap and 2 passes
nylon_curing_tape_mark

Nylon curing tape marks on moulded strips showing the pressure applied

Elastotec hot vulcanising system does not require machining after vulcanisation to obtain good TIR.

image016

Metal test piece wrapped to pulley and cured in autoclave. Result after  autoclaving with metal piece embedded in lagging piece showing the pressure applied.

Traditional method

Not enough pressure between the layers of uncured rubber introduces delamination risk.

Elastotec Hot Vulcanised Rubber Lagging

adhesion_test
Adhesion test piece with 100% rubber tear and >20N/mm adhesion force.

Elastotec Hot Vulcanised Rubber Lagging application using moulded strips is a simple application process with no machining or hand grooving required, that eliminates the risk of delamination.

 Save as PDF

Let’s talk

If you work in the mining industry, involved in conveyor maintenance, pulley manufacturing, conveyor design and conveyor maintenance, then, we would like to work with you to bring engineered pulley lagging solutions to the industry.