Source: Nanyang Pump (Qingdao) Co., Ltd
1. Concept of screw centrifugal pump
A key part of the spiral centrifugal pump is its unique spiral centrifugal impeller, which has both a spiral section and a centrifugal section. It combines the advantages of both the high efficiency of the traditional centrifugal pump and the non clogging of the spiral pump, so it is called the spiral centrifugal pump.
2. Origin of screw centrifugal pump
The spiral centrifugal pump originated in Switzerland and aims to help Peruvian fishing plants transport live fish from fishing boats. With the non clogging and soft transmission characteristics of the spiral centrifugal impeller, the pump can transport live fish from the fish net to the ship and then to the processing plant from the ship in good condition. With the increasing development and improvement of products, the application field of spiral centrifugal pump is gradually expanding.
3. Application field of screw centrifugal pump
It is widely used in municipal sewage, sludge, petrochemical industry, pulp wastewater, food treatment and other fields.
4. Characteristics of spiral centrifugal pump
Compared with ordinary impurity pump and vortex pump, the structure of spiral centrifugal pump determines that it has the following characteristics:
A. Good non clogging performance: the large channel formed by the blade, combined with the inlet guidance and screw propulsion, can transport the liquid containing large particles and fibrous substances, especially the long fibrous objects can pass smoothly. The concentration of solids transported is higher than that of other types of non clogging pumps, and the drift diameter can be much higher than that of traditional centrifugal impellers with similar outer diameters. B. Soft transmission, good non-destructive performance: solid and liquid two-phase fluid gradually advances under the balanced spiral force, and the flow direction does not change suddenly, so the flow is balanced. It is especially suitable for transporting activated sludge in the process of sludge treatment, and can maintain the characteristics of activated sludge. C. High efficiency, wide efficiency zone D, and flat power curve. E. Characteristic curve with steep drop: when the head changes, the flow changes little, which can ensure continuous and stable operation. F. The suction performance of the pump is good: the pump blade extends forward to the suction inlet, so the gas containing medium can be pumped. When a small amount of gas is inhaled, the performance, vibration and noise of the pump are basically unchanged. When the gas content exceeds 40%, the pump can still operate despite intermittent vibration. G. High solid content.
5. Application of Screw Centrifugal Pump in Sewage Treatment
In our extensive investigation, the prominent problem reflected by the sewage plant pump is that it is often blocked. One reason is that a lot of construction waste was not cleaned up in time before the pump room was used for water supply. Many loose small stones, small steel bars, and scaffold pipe clamps were still left at the bottom of the inlet pump room after the construction was completed. Another reason is that the sewage itself contains various kinds of garbage. Although there is a grid to intercept, the coarse grid spacing is generally 20-30mm. Sundries, especially fiber materials, will still get bigger and bigger in the water pump like snowballs until the impeller is blocked and the equipment stops running.
For traditional centrifugal pumps, when the water flows into the volute, it is thrown out by centrifugal action. Due to the sudden change in the direction of the 90 degree angle, it is bound to produce an obvious collision. This sudden change in the direction is easy to make solids stay in the volute or on the impeller due to inertia, thus causing blockage, and greatly reducing the pumping capacity of traditional centrifugal pumps.
But in fact, when passing through a large number of fiber objects (such as hair, women's stockings, sanitary napkins, etc.), these fibers are caught by the impeller after entering the pump body, and wound on the impeller until the pump stops. At the same time, the traditional centrifugal pump is powerless in conveying fiber solids. The diameter of spherical particles passing through solids declared by traditional non clogging pumps is only for regular solid particles, and cannot reflect the ability to transport fiber objects.
The advantage of the screw centrifugal pump is that the impeller has a twisted spiral blade, which extends axially from the suction inlet, and the radius of the blade gradually increases, forming a very open spiral flow channel. The shell is composed of suction port, lining and volute. The impeller at the suction port generates spiral propulsion, and the impeller at the volute generates centrifugal action. After the solid particles enter the impeller, they enter the pump body with the paraboloid formed by rotating along the spiral blade under the balanced spiral force. The sharp angle at the blade inlet guides the debris to the axis attachment, and then uses the spiral action to propel it along the axis, although it also rotates 90 degrees, However, the trajectory of particles passing through the spiral centrifugal pump is gradual, so the liquid flow passes through the pump in a smooth open channel under the condition of low stress and low mixed flow. And this unique design also allows liquid with large solid content to pass through without blocking.
For the very soft and easily entangled hair and other small fibers, the impeller inlet liner is designed with a unique protrusion, which can effectively leave these fibers, so that the impeller is located behind the protective ring. This not only prevents the impeller tip from snagging the fibers, but also prevents the damage to the impeller tip caused by the filament wound impeller, and solves the fiber blockage problem of the traditional non clogging pump.
