Maxi Melt offers wear monitoring service, if necessary at the customer premises. Based on the wear found we evaluate with you whether a regeneration is feasible.
CYLINDER: REPAIR THROUGH A LARGER INNER DIAMETER
A worn cylinder, bimetallic or nitrided, can be repaired by honing the inner diameter to a larger diameter. In case of nitrided cilinders a new nitriding treatment shall be made with a depth of 0,4 ÷ 0,5 mm to ensure the necessary hardness. A honing operation must follow so that all dimensions are within the new oversized tolerances. In case of a bimetallic cylinder only the boring neeeds to be honed. No renitriding and honing is necessary. Of course the outer diameter of the screw, valve and eventually end cap innerdiameter must be adjusted to the new (larger) dimension of the cylinder. This is a cheap but effective solution but has one disadvantage: the repaired cylinder and screw become non standard equipment and dedicate spare components shall be stored.
CYLINDER: REPAIR THROUGH INSIDE BUSHING
In special cases a cylinder can be repaired by reline the worn area with a liner which shall be longer as the screw stroke (5D) so the valve operate at the original nominal diameter. The liner can be made of nitrided steel, hardened steel but also of bimetallic alloy.
SCREW: FLIGHT TOP WELDING
For screws with diameters larger than 60 mm it may be interesting, depending on the type of wear, to restore them by welding new material on the top of worn flights. This procedure can be applied only if there is no wear on the screw core or front-back flight radius, but only on 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. Important to mention is that a repaired screw will not last as long a new one. For further information about the welding alloys, please refer to the table of the original screws.