Introduction to rubber processing and safety issues - HSE

Rubber feed nip
One of the simplest methods of preventing finger access to the nip is to use a fixed nip bar that extends
the length of the rolls, positioned no more than 6 mm from the surface of the roll to prevent a trapping
point.
When rubber is fed manually into the nip access can also be prevented using the feed table as a distance
guard, with integrated mesh guards at either end. Dimensions should meet the requirements of BS EN
ISO 13857:2008 Safety of machinery. Safety distances to prevent hazard zones being reached by upper
and lower limbs.
There is also a risk of the operator getting entangled with materials and dragged over the table towards
the nip. To control this risk position a horizontal interlocking trip bar just below and slightly to the front edge of
the feed table so that the operator cannot approach the nip between the rolls without hitting the trip bar. This
should then operate two limit switches, one at each end of the bar and bring the rolls to rest in not more than
an eighth of a revolution.
If closer approach is needed for feeding then an interlocked ‘manager guard’ should be used, with dimensions
meeting the requirements of BS EN ISO 13857:2008. This consists of sturdy parallel bars that prevent finger
access to the nip. A push-stick designed to fit between the bars helps feed the rubber to the nips.
Fabric feed nip
When combining, fixed nip guards are often not practical because of the varying thicknesses of material being
calendered and the need for lower roll adjustment. A ‘limited movement’ guard can therefore be used which
consists of an interlocking guard of closely spaced bars or hoops/loops. The guard pivots around a horizontal axis
and if a hand is drawn between the guard and a roll, the guard operates a position sensor, which stops the
rolls. After the hand is removed the guard returns to its rest position but this does not cause restarting.
Take-off and wind-up devices
Running nips at various take-off and wind-up rollers, including the coated cloth wind-up mandrel, can create trapping
and entanglement hazards. When assessing the risk it is important to take into account:
the machine speed;
whether the roller or mandrel is powered or not;
the sheet tension;
the strength and tackiness of the material;
the need for approach.
Most rubber sheet and rubberised fabric will be very strong when under tension, and capable of inflicting
serious injury.
Use automatic tensioning equipment, as it should not be necessary for operators to feel or manually adjust
the tension of the cloth whilst it is in motion. Use devices such as slipping clutches to regulate tension, and
'banana' or bowed rollers to reduce creasing, as they will also reduce the need for approach.
Where there is a significant risk of injury, prevent access to the running nip by interlocking guards, pressure
sensitive mats or photoelectric safety systems.
For start up, fix the cloth liners to the mandrel whilst it is still stationary.