Barrel: Repair Through A Larger Inner Diameter

When a barrel, both bimetallic or nitrided, is worn out can be repaired by boring a larger inner diameter. In case of nitrided barrels, a new nitriding treatment shall be made with a depth of 0.4 - 0.5 mm to ensure the necessary hardness.

A grinding operation must follow, so that all dimensions stay within manufacturing tolerances. In case of bimetallic barrels, only the boring is necessary without any other refinishing operation. Of course the outer diameter of the screw and eventually front end components must be modified to the new (larger) dimension of the barrel. This is a cheap solution but has one disadvantage: the repaired barrel and screw become non standard equipment and dedicate spare components shall be stored. In case of twin screw barrels repairing, please consider our technicalbulletin about extrusion.

Barrel: Repair Through Inside Bushing

In special cases a barrel can be repaired by fitting in the worn area an inside bushing.

The bushing can be made of nitrided steel, hardened steel but also of bimetallic alloy.

Screw: Flight Top Welding

For screws with diameters larger than about 60 mm, may be

convenient, depending on the type of wear, to restore them

by welding new material on the top of worn

out flights. This procedure can be applied only if wear did not

affect the screw core or rear and front radius, but only the top

and sides of the flights. There may be the need

to apply also an inox material, but this shall be evaluated from

case to case. Last thing to say is that a repaired screw will not

last as a new one.