Under the design conditions, fans with wind pressure of 15kpa ~ 0.2MPa or compression ratio of E = 1.15 ~ 3 are called blowers, and centrifugal blowers with two or more impellers in series are called multistage centrifugal blowers (the adjacent impellers must be connected by guide vanes).

       Multistage centrifugal blower is widely used in blast furnace, cupola, coal washing jig, mine flotation, sewage aeration, chemical gas making and other occasions where air needs to be transported, and other special gases can also be transported. This series of blowers are characterized by high efficiency, low noise, stable operation, no pulse, wide stable area, clean, dry and oil-free gas transmission, few vulnerable parts and simple installation, operation and maintenance.

       The multistage centrifugal blower is composed of three parts:

       1. Host part: blower host, motor (general type, outdoor type, explosion-proof type), joint common base of host and motor, direct coupling of host and motor.

       2. Accessories: elbow, muffler, filter, general purpose mesh filter, special purpose (microporous aeration, etc.) low, medium and high-grade filter.

       3. Supporting parts: the inlet butterfly valve of fan (manual type and motor-driven type), motor control starting cabinet, flexible joint D series multistage centrifugal blower are multistage, single suction and double support structures. Coupling drive is adopted. From the motor end, the blower rotates clockwise. There are two kinds of fans: high-speed and low-speed. The main shaft is designed with steel shaft, with non-contact zigzag seal, without wear and heat. The sealing performance is excellent. The bearing seat is separated from the shell. The casings are made of grey cast iron. The fan casing below D400 is divided radially and in series. The main shaft of the rotor is made of high-quality carbon steel, and the impeller is made of aluminum alloy. For blowers above d400-2, the fan casing is of integral series type, the main shaft is made of high-strength alloy steel, and the impeller is made of high-strength alloy steel. Labyrinth seals are installed at the inlet ring of each stage impeller, between stages and both ends of the casing to prevent gas leakage. After static and dynamic balance correction, the blower rotor runs smoothly. The multi-stage centrifugal blower adopts rolling bearing and sliding bearing. Generally, rolling bearing and lithium base grease are used for lubrication below D400. The large unit adopts sliding bearing and pressure oil supply for forced lubrication. The lubricating oil is 32 or 46 turbine oil. The lubricating system includes main shaft pump, motor oil pump, oil tank, oil cooler, oil filter and high-level oil tank. When the unit is shut down due to power failure, the high-level oil tank can continue to maintain lubrication for a certain period of time to ensure the safe shutdown of the unit.