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一、PURPOSE

Boiler Inducet-draft-fan are suitable for ventilation systems of industrial boilers with various coal materials as fuel and equipped with smoke and dust removal devices, which can be selected and used in all the occasions with appropriate air coming conditions and performance.Temperature of air delivered is generally not over 250°C.

二、STRUCTURAL FEATURE

Centrifugal fan generally consists of parts of air hlet, impeller; scroll case, outlet, gearing device, base and motor.

effect of pressure extension.
(1) inlet: inlet is made into an integer and set up at the side of scroll case of fan. Shaped conductor of axial cross section of inlet is streamli ne, the current can enter impeller equably so as to reduce flow loss and improve efficiency of impeller.
(2) Impeller: impeller is the most important part of centrifugal fan, its function is to invert mechanical energy into gaseous static pressure energy and kinetic energy. Impeller generally consists of front panel, blade, back panel and axial panel (wheel hub). Through balanceable emendation, operation will be smooth, and gas performance is good.
(3) Scroll case: scroll case is the passage of gas current, shaped conductor is usually log spiral with effect of current collection and guidance to outlet. Scroll case also has certain
(4) outlet: a passage for gas to flow out of fan. CXjtlet is drilled with bolt hole and can be connected with air pipe.
(5) Gearing device: consists of principal axis, bearhg housing, rolling bearing, pulley or clutch. One end of principal axis is connected with impeller, the other end is connected with piiley or clutch.
(6) Base: used to bear the weight of scroll case, beari ng device and motor, mantle and base are made into overall structure. It is not necessary for the user to make a nd in stall the base by himself, making installation easy.

三、VERSION

Centrifugal fan is divided into d extra I fan and laevogyra te fan according to rotary direction of impeller. It is called dextral fan and expressed with right if front view from one side of m oto r or gearing device finds impeller rotates clockwise, and called laevogyrate fan and expressed with left if front view from one side of motor or gearing device finds impeller rotates counterclockwise.

Location of outlet of centrifugal fan is expressed with the a ngle of outlet of mantle. The adjustment scope of location of outlet of centrifugal fan is generally 0 degree to 225 degrees and the space is 45 degrees. Information about angle of outlet will be provided upon goods ordering.

Common driving types of fan are as follows:

Driving Type A: centrifugal fan is not set up with gearing device,motor and impeller drive in connection.

Driving Type C: centrifugal fan is set up with gearing device, impeller and pulley are respectively located at both ends of gearing device, motor drives through pulley.

Driving Type D: centrifugal fan is set up with gearing device, impeller and clutch are respectively located at both ends of gearing device, motor drives through clutch.

(Remarks: Figuration of fan and its installation chart are shownon the table below.)

四、PERFORMANCE SELECTION

Parameters in blower performance table are worked out as follows:Ns4?Ne6.3: on the basis that smoke medium status, namely air temperature t=20(TC, atmospheric pressurePa = 101325Pa, air density p =0.745 kg/m3, Those above : Na8? Ns 12.5worked out on the basis that smoke medium status, namely air temperature t=140°C, atmospheric pressure Pa = 101325Pa, air density p = 0.85 kg/m3 In case that the application status is not coincident with specific status in the performance table or blower's rotating speed changes, it is necessary to convert performance of application status into that of specific status in the performance table, and then select blower according to converted performance.

五、INSTALLATION AND OPERATION

Centrifugal fan is set up with monolithic base and it is not necessary for the user to make and install base by himself, h installation, the user just needs to place the monolithic fai on the ground and fix it with anchor screw. The user may also select special absorber of this factory and place monolithic fan on level ground through absorber, and anchor screw is not necessary easy for installation and adjustment.

In fan’s operation, phenomena of over-sufficient or insufficient runoff often occur main ly because of inaccurate calculation of resistance of pipe network, or variable resistance of pipe network. In fan’s operation, the runoff gradually decreases in a long period of time, or suddenly decreases in a short period of time, mainly because of blockade of pipe network.

When the fan is newly installed, phenomena of over-sufficient or insufficient volume flow occur in formal operation mainly because of the following:

1. Difference between actual value and calculated value of pipe network resistance is too big. It is known from formula of regular pipe network characteristics of P=KQ2 that if the actual value of K, the coefficient of pipe network characteristics, is less than the calculated value, the volume flow will increase, rf the actual value of K is more than the calculated value, volume flow will decrease.

2. In selection of fan impact of , warp of total pressure value of fan itself is not considered. When the actual total pressure of fan is positive warp, volume flow will increase, and when the actual total pressure of fan is negative warp, volume flow will decrease.

Warp of volume flow of fan can be eliminated through the following methods:

(1) Adjusting volume flow with throttling gear, for example, with air damper or shutter.

(2) Changing speed adjustment volume flow of fan's impeller.

(3) Replacing with adjustment volume flow of fan with higher pressure or lower pressure.

(4) Changing adjustment volume flow of pipe network resistance. It is necessary to point out: throttling gear is generally adopted to adjust volume flow of fan. But when the actual volume flow is much more than the required volume flow, it will cause much waste of electric power and will be very uneconomical. If possible, reduction of fan speed or replacement of fan with lower pressure should be adopted. When throttling gear is in full operation, if volume flow is still too small, it means that the throttling gear is out of effect, and it is necessary to change pipe network to reduce resistance so as to increase volume flow. It is also possible to adopt methods of increasing speed of fan impeller or replacing with fan with higher pressure. However, the maximum speed of fan should not exceed the maximum speed in the performance table and it is necessary to calculate motor power.