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May 18, 2022 View:

Stainless steel lobe pump and centrifugal pump comparison analysis

Self-priming centrifugal pump shaft power is increased with the flow rate, when the flow rate Q=0, the corresponding shaft power is not equal to zero, but a certain value (about 60% of normal operation). This power is mainly consumed in the mechanical loss. At this time the pump is full of water, if the long time operation, will lead to the pump temperature rising, pump shell, bearing will be hot, serious may make the pump body thermal deformation, we call bored head, at this time the head is a large value, when the outlet valve gradually open, the flow will gradually increase, self-priming centrifugal pump shaft power also slowly increase.
A. Flow head characteristic curve
The relationship between the performance parameters of the pump and the mutual change and the mutual restriction: first of all, the pump's frontal top speed is the prerequisite.
B. Flow power curve
C. Flow efficiency curve
It has a curve like a hilltop shape, when the flow of centrifugal pump is zero, the efficiency is also equal to zero, as the flow increases, the efficiency also increases gradually, but the efficiency decreases after increasing to a certain value, the efficiency has a high value, near the rate point, the efficiency is higher, this area is called the rate area.
The performance curve of self-priming centrifugal pump has three main curves: flow head curve, flow power curve, and flow efficiency curve.
It is the basic performance curve of self-priming centrifugal pump. The centrifugal pump with specific speed less than 80 has the characteristics of rising and falling (both convex in the middle and downward curved on both sides), called the hump performance curve. The centrifugal pump with specific speed between 80150 has a flat performance curve. The centrifugal pump with a specific speed above 150 has a steeply descending performance curve. Generally speaking, when the flow rate is small, the head is high, and as the flow rate increases the head gradually decreases.
The performance parameters of self-priming centrifugal pumps such as flow rate Q head H shaft power N speed n efficiency have a certain relationship with each other. The relationship between them is represented by a curve, and this curve is called the performance curve of the pump.
The basic structure of a self-priming centrifugal pump is composed of six parts: impeller, pump body, pump shaft, bearing, sealing ring, and stuffing box.
The lobe pump is compared with the centrifugal pump, which has been widely used because of its simple structure and low cost. It is compared with the lobe pump mainly has the following differences:
(1) The lobe pump is a volumetric pump, the delivery flow can be more controlled also can be easily made into a variable pump. The output flow of centrifugal pump is not controllable, and decreases with the increase of resistance; the lobe pump has strong self-priming ability, while the centrifugal pump must be filled with liquid before operation.
(2) The lobe pump has a very low speed, generally between 200rmp and 600rmp, and the material being conveyed is output smoothly without its composition being damaged. The speed of the centrifugal pump is very high, and the material to be conveyed is subject to strong impact and centrifugal force, so the centrifugal pump often produces the phenomenon of inconsistent material composition when conveying the mixture, so that the quality of the finished product is reduced. And the universal transfer pump is the choice to solve this problem, so it is especially suitable for conveying mixed materials and even materials containing solid particles.
(3) lobe pumps can be used to convey very high viscosity substances, so they are also called colloidal pumps. And centrifugal pumps do not have this characteristic.
(4) lobe pumps can be easily made into varieties with higher output pressure, such as 150kgf/cm2, which is suitable for long distance or high resistance quantitative conveying.
(5) The lobe pump is more complicated and precise to make, and the cost is high, which is the big difference between it and the centrifugal pump.