The 250DK240A water pump is a single suction horizontal split type two-stage centrifugal pump. The pump uses two symmetrically arranged single suction impellers to balance axial forces, while residual axial forces are borne by two angular contact bearings. Therefore, the correct installation of angular contact bearings is particularly important.
According to the design and installation instructions, the front end (motor end) of the 250DK240A water pump adopts two paired angular contact bearings (36318 type), and the rear end adopts two radial ball bearings (6318 type), as shown in Figure 1.
The two angular contact bearings at the front end are used to withstand residual axial forces, so they cannot be installed as floating bearings (as the floating end does not have the ability to withstand axial loads). Therefore, a tight transition fit is selected between the bearing seat and the outer ring of the front end bearing. The two radial bearings at the rear end can only withstand radial loads. Due to the large span between the front and rear bearings, in order to avoid the shaft from getting stuck due to the expansion force of the shaft line, the bearings at the rear end should be movable. Therefore, a relatively loose transition fit is selected between the bearing seat and the outer ring of the bearings at the rear end. This can precisely meet the stress requirements of the bearing.
However, the 250DK240A water pump from a water source was not assembled according to the design drawings during actual installation. Instead, two angular contact bearings were divided into front and rear bearing seats, as shown in Figure 2.
In this way, the angular contact bearing (36318 type) installed at the rear end cannot withstand axial loads, while the front end only has one angular contact bearing, so it can only withstand unidirectional axial loads.
Although the 250DK240A water pump adopts a symmetrical arrangement of impellers to balance axial forces, it is impossible to achieve complete balance. The residual axial force is not constant and the direction is not constant. It is actually a swinging load (the load direction and value are uncertain). If the actual load direction is opposite to the load direction that the bearing can bear, it will inevitably cause bearing damage. The bearing of the 250DK240A water pump is damaged because of this.
2024 July 3rd Week VAFEM Product Recommendation:
Agricultural machinery requires better seals for contaminated conditions, provisions for misalignment, and economical mountings for shafts and housings. VAFEM offers bearings for disc harrows, planters, mowers, rakes, all types of balers, tillage, seeding and forage harvester equipment, combines, cotton pickers/stripers, and other agricultural equipment like silo unloaders and grain elevators.
We also offer a complete line of insert ball bearings, shaft mounted with either tapered adapters or locking collar or set screws. Our proven seal designs include low torque shields to heavy-duty triple lip seals. Disc harrow bearings are also available with either round, square, or hexagonal bores. All bearings are available with or without re-lubrication holes.
https://www.vafem.com/products/Agricultural-Bearings/775.html
2024-07-22