Barrel cooling and heating system for screw extruder

An extruder barrel section comprising:

• a first barrel pad,
• a second barrel pad,
• an extruder liner;
• the first and second barrel pad co-operating to define a recess configured to receive the extruder liner;
• the length of the first and second barrel pad less than the length of the extruder liner such that the extruder liner defines an end surface that projects beyond the first and second barrel pads on at least one side, the end surface configured to abut the end surface of another extruder liner;
• and
• a locking structure configured to lock the first barrel pad to the second barrel pad with the extruder liner therebetween;
• wherein the extruder barrel section (200) is configured for coupling with the other extruder barrel section by coupling the end surfaces (734) of the extruder liners (202);
• wherein the end surface of the extruder liner includes either a plurality of alignment pins or a plurality of slots;
• each alignment pin configured to be received by a corresponding slot defined on the end surface of the extruder liner abutting it, wherein the slot has a width substantially equal to that of the alignment pin and a length larger than the width of the alignment pin permitting relative thermal expansion between the pair of extruder liners.