Pneumatically actuated pressure controls have enabled speciality tyre
manufacturer, OTR to maintain the right curing conditions from batch to
batch, considerably enhancing its production quality.
OTR Tyres uses three autoclaves to cure a variety of tyres up to 1.4m rim
size, in a process that can take up to 24 hours. At the start of this
process, compressed air at 2barg is applied to prevent any separation of
the plies, while steam at 5.5barg is introduced to heat the autoclave to
140oC. At the end of the curing cycle, the tyres are cooled by water. In
a previous arrangement, the process involved a degree of manual control,
relying on an experienced operator to achieve the precise settings for
each batch. Clearly, this was not guaranteeing consistent conditions from
batch to batch.
The company decided to automate the process fully, and pneumatic control
valves supplied by Spirax Sarco were installed as part of this control
system, developed in-house by OTR as part of a refurbishment project on
one of the autoclaves. Pressure and temperature sensors within the
autoclave relay information via a SCADA system to a centralised control
computer, which regulates the air, steam and water valves.
The arrangement achieves optimum pressure and temperature conditions
throughout the duration of the process without any operator intervention.
In fact, the system has managed to maintain production conditions to
within +/-0.1barg and +/-1oC, thus ensuring cure repeatability, and this
success has prompted OTR to automate the remaining two autoclaves using
the same equipment.