The wearing parts of multistage pumps usually include shafts, shaft seals, shaft sleeves, bearings, impellers, etc. After the pump has been in operation for a period of time it is necessary to regularly check all wear parts and, if necessary, rework or replace them. Negligence of work may lead to errors in operation.
1. Multistage pump impeller
Check the wear and corrosion of the water pump impeller, and replace with new parts if necessary.
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2. Wear ring and clearance
Determine the clearance. If the maximum clearance reaches or exceeds the allowable amount, the wear rings and related impellers between the middle sections should be replaced with new ones. The allowable clearance between the impeller and the wear ring is specified 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 gap is the diametrical gap
index:
1) Indicates cast iron or soft carburized steel
2) Indicates stainless steel
3. Balance
It is recommended that the impeller of the water pump must be checked for dynamic balance on the dynamic balancing machine alone, and the unbalance amount should refer to ISO1940, Q = < 2.5. Rotor dynamic balancing is performed according to the contract.
4. Concentricity of multi-stage pump shaft
Support the water pump shaft on the support surface (V-type iron/roller) to check the coaxiality of the shaft (maximum allowable radial jump 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 cold and hot conditions. If the operating temperature of the multistage pump exceeds 100 °C, 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 balance 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
