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18
Note: If the impeller and magnet capsule spin freely, these parts may continue to be used. If the impeller
does not spin freely, this indicates the bearing is contacting the rear casing. The pump must not be operated
until the worn or damaged parts have been replaced.
n
Wear Checking Steps
1. After thorough decontamination of the pump, remove liquid end assembly from motor bracket.
2. Remove front casing from the liquid end.
3. Insert magnet capsule with impeller into rear casing.
4. Measure clearance between backside of impeller shroud and face of rear casing, dimension "A" shown
below.
Dimension A
Model MDH-(F)
MDH-(F)400/401/422/423/425-D & E
Wear limit of Impeller thrust
New
Replace
Inches (mm)
.102 (2.60)
.039 (1.0)
5. Physically confirm that clearances are adequate by spinning impeller by hand in rear casing.
• Tips are not worn out beyond wear limit:
The impeller and magnet capsule rotate smoothly in the rear casing and there is clearance at the A
and B sections.
• Tips are worn out beyond wear limit:
The impeller and magnet capsule do not rotate smoothly. Contact between the rear casing and
impeller at location A, or contact between the rear casing and the magnet capsule bearing at location
B, as shown in the figure above, does not allow for the continuous smooth rotation of the impeller
and the magnet capsule assembly. The tips of the impeller thrust and/or the spindle are excessively
worn. In this case, replace the impeller and rear casing.
If no recess or dimple has been created on the spindle face due to wear by the tip of the conical thrust,
the rear casing need not be replaced.
