Effect of Slurry Pump Parts Wear on Pump Characteristic Curve
First, the influence of impeller inlet side wear on lift head.
All vulnerable parts can be divided into two categories: the first kind includes parts whose wear affects the pump characteristic curve, such as impeller, impeller inlet side seal (seal ring and adjusting ring, guard plate); second kinds of parts whose wear can not pump the characteristic curve, such as water pressure chamber, suction pipe, impeller side cover plate side guard plate. The first kind of parts does not affect the characteristic curve of the pump because of all surface wear. For example, even when the inner surface of the impeller cover is most worn out, the pump characteristic curve does not change.
In the initial stage of operation, under the action of hydraulic abrasive fluid flow, the local roughness of the runner surface is smoothed, and the head and efficiency of the pump are improved due to the hydraulic loss reduction surface in the pump. However, this improvement is only temporary, because the surface of the parts formed by the impeller entry seals is worn (running very fast), causing the overflow to increase, that is, the pump head will drop.
The following is how the pump's lift characteristic curve changes along with the blade inlet side wear.
The blade is gradually shortened, especially from the side of the back cover plate, and the relative velocity of flow around the blade increases with the change of the angle of attack. At this time, the theoretical lift related to power is not changed, and the pump head decreases, which indicates that the hydraulic loss of impeller inlet increases. According to the results of Jandman experiment, the additional hydraulic loss relation of impeller entry at the inlet of the blade is determined. The possible increment of hydraulic loss in the impeller is determined as follows: Q=300m3/h, n=600r/min, impeller inlet diameter D1=500mm, blade inlet width b1=300mm, and blade inlet side arrangement.
Due to wear, the blade length decreases by an average of 100mm. That is to say, when p=30 degrees, the radius R increases 50mm, that is, the circumferential velocity of the blade inlet side increases, so the relative velocity of the blade flow increases.
The circumferential velocity of impeller flow at the inlet of the impeller after wear.
Radial velocity of impeller flow at inlet of impeller
The relative velocity of the flow in the middle of the blade inlet is
Additional hydraulic loss caused by wear of inlet blades
If the pump head is 48m, the head of the blade is 48-3.6=44.4 (m) after the blade edge wear, and the head is reduced by about 7%.
After wearing at the inlet of the blade, the suction performance of the pump deteriorates. With the increase of wear volume, the average radius of the entrance edge of the blade increases, which results in the decrease of the axial velocity of the impeller inlet and the increase of the circumferential velocity U1, especially in the area where the wear is greatest.
Cavitation margin is a function of parameter (an) Tan (p:/2). When the circumferential velocity and radial velocity of liquid flow are relative to the initial point of flow beam flowing into the blade after wearing, the cavitation margin is still a function of this parameter. Slurry Pump Manufacturer