Liner plates worn — when to replace them
Symptom
Countersunk bolt heads start to show, the floor is uneven, the paddle gap cannot be set, or there are holes through a liner.
Likely causes
- Normal wear, fastest at the centre of the floor between and under the two shafts.
- Quartz-rich, angular aggregate, or stones above the mixer's rated size.
- Paddle gap too large, leaving a layer that wears unevenly.
- Slurry behind a liner through a loose bolt or joint, so the plate does not sit flat and cracks.
Most likely and cheapest to check first.
Checks
- Clean the liners and measure the remaining thickness with an ultrasonic gauge, or at plate joints with a caliper.
- Record every plate on a liner map every 3 months.
- Calculate the wear rate in mm per 10,000 m³ to know when to order the next set.
- Look at the back of removed liners for hardened concrete.
Fix
- Replace when the remaining thickness reaches about one third of the new thickness, or when bolt heads are exposed.
- Replace in sets by zone, not one plate at a time, so the floor stays even.
- Fit new bolts, clean fully behind each plate, reset the paddle gap, and retighten after one day.
Stop the equipment if
There are holes through a liner and concrete reaches the tank shell.
Parts you may need
The liners protect the shell
Liners are cast or rolled plates bolted inside the tank. Typical materials are Ni-Hard cast iron (about 530 HB) and high-chromium cast iron (600–650 HB). New thickness is usually 12 to 25 mm depending on mixer size and position. Write the new thickness in the plant log on the day you fit them. Without it you cannot calculate the wear rate.
CAUTIONNi-Hard and high-chromium liners are hard but brittle. Do not hammer them.
COST OF NEGLECTA liner left until it has holes lets concrete grind into the tank shell. Repairing a shell means cutting, welding and re-boring bolt holes: days of downtime instead of one shift.
⚠ Every check inside a machine starts with full lockout. Safety disclaimer