What are the wearing parts of multi-stage pumps and how to inspect and maintain them?
Jul 03, 2025
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The wearing parts of multistage pumps usually include shafts, shaft seals, sleeves, bearings, impellers, etc. After the pump has been running for a period of time, all worn parts need to be checked regularly and reworked or replaced if necessary. Negligence in work may lead to operational errors.
1. Multistage pump impeller
Check the wear and corrosion of the pump impeller and replace it with a new one if necessary.
2. Wear rings and clearances
Determine the clearances. If the maximum clearance reaches or exceeds the permissible value, the wear rings between the intermediate sections and the associated impeller should be replaced. The permissible clearances between the impeller and the wear ring are shown in the table below.
| Specs | DS40 ,DS50 | DS80 | DS100 ,DS150 | DS200 | index |
| Minimum clearance (mm) (new parts) |
0 .3 | 0 .35 | 0 . 4 | 0 . 45 | 1 |
| 0 .45 | 0 .5 | 0.55 | 0.6 | 2 | |
| 0.6 maximum clearance (mm) (old parts) |
0 .6 | 0.7 | 0.8 | 0.9 | 1 |
| 0.9 | 1.0 | 1.1 | 1.2 | 2 |
The clearance is the diameter clearance
Index:
1: indicates cast iron or soft carburized steel
2: indicates stainless steel
3. Balance
It is recommended that the pump impeller be dynamically balanced on a dynamic balancing machine. The unbalanced amount should refer to ISO1940, Q=<2.5. The rotor dynamic balancing should be carried out according to the contract.
4. Concentricity of multi-stage pump shaft
Support the pump shaft on the support surface (V-shaped iron/roller) and check the coaxiality of the shaft (maximum allowable radial runout 0.025mm) as follows:
| Working speed | ≤3000 rpm | > 3000 rpm |
| Maximum allowable radial runout | 0 . 025 | 0 . 02 |
If the radial runout exceeds the allowable runout value, the shaft can be straightened in a cold or hot state. If the operating temperature of the multistage pump exceeds 100℃, the shaft of the multistage pump is not allowed to be straightened.
5. Stuffing box
Check the abrasion of the shaft sleeve. If the diameter of the abrasion does not exceed 1mm under the standard size (not suitable for the shaft sleeve whose surface has been specially polished), if necessary, it can be re-processed and equipped with a packing ring according to the new size.
6. Bearing
Clean the bearing of the multistage pump with clean oil, and replace it with a new bearing if it is damaged.
7. Balance drums and drum kits
Check the exact dimensions of the balance drum diameter of the multistage pump and the diameter of the balance sleeve; the maximum allowable clearance (mm) is as follows:
| DS40 ,0550 | DS80 ,DS100 | 05150 ,05200 | index |
| 0 . 3 | 0 . 4 | 0 . 6 | 1 |
| 0 . 4 | 0 . 5 | 0 . 7 | 2 |
The gap is a diametrical gap.
index:
1: Indicates cast iron or soft carburized steel
2: Indicates stainless steel