A worn element costs money. A new one costs money too. The question is which one costs less over the next twelve months.
Repair looks attractive on the invoice. A weld and a grind cost a fraction of a new part. The problem comes later, when the repaired part fails in the middle of a campaign and takes a barrel with it.
Welding puts heat into steel. The flight tip grows, then it shrinks as it cools. The whole element can bend a little, and a little is enough to change the clearance along the shaft.
A welded flight tip also loses its hardness in the heat-affected zone. The soft band sits right where the filler hits hardest, and it wears in a crescent shape within weeks.
You can hard-face a flight and get useful life from it. You need the right filler metal, a controlled preheat and a slow cool. Most workshops skip the preheat, and the result looks fine on the bench and fails in service.
Repair works on large elements with plenty of root thickness left. It works when wear stays local, for example on one face of a kneading disc.
It works on shafts, where you can build up a worn journal and grind it back to size. It rarely works on a spline, because the tooth profile carries the torque and a hand-finished spline never matches the original.
Scrap the element when the root has worn past the limit in your drawing. Scrap it when cracks run from the flight into the root. Scrap it when the bore has worn oval.
A repaired element needs a new fit check, a new balance check and a new clearance measurement. Add those hours to the invoice and the saving shrinks fast.
Ask one more question. Can you run the repaired part in a position where a failure costs little? Put it in the feed zone, not in the metering section. Put it on a line that runs a clean polymer, not on the glass-filled job.
Downtime costs more than parts on almost every line. If a repaired element runs half the life of a new one and fails without warning, the saving disappears in a single unplanned stop.
Count the hours, not the invoice. A new element that runs two campaigns and comes out with predictable wear beats a repair that runs one campaign and surprises you.
Check the bore as well before you spend money on a repair. A bore that has worn oval will not sit true on the shaft, and no amount of weld on the flight fixes that. Repair the outside of a part that has a good bore, or leave it alone.
Some plants keep a repaired element as a bridge. It fills a position while a new part travels, and it never runs a full campaign. That use makes sense on a line with long lead times and a tight schedule.
Label it clearly. A bridge part that ends up in the metering section becomes the failure you tried to avoid.
We supply new elements and we also quote repairs when the part justifies it. Send a photo of the worn area and the measurement at the thinnest point. We will tell you which route makes sense, and we will say so when the answer is scrap.
