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 Usage and type of 4-68 type centrifugal fan：
 4-68 type centrifugal fan Usage and type：
Used for general ventilation of factory and indoor situation.
Dual used to inlet air and outlet air.
Transmitted gas should be air or un-self burn, unharmful, unerosive gas.
No stick materials in the gas, dust and grain contain should less than 15mg/m3.
Air temperature less than 80℃.
Corrosion-control fiberglass fan could be made.
4-68 type centrifugal fan could be divided into two types: LG and RD.
Viewing from the one motor side, if the impellers rotate clockwise, it is called right hand ventilator .if the impellers rotate anti-clockwise, it is called left hand ventilator. The outlet place is shown by the outlet angle of the shell.
9-19、9-26系列№4～6.3高压通离心风机安装及外形表
4-68 type centrifugal fan Structure features：
№.2.8-5 is composed by impeller, shell ,air inlet and direct connection motor.
Besides the above apparatus, 6.3-20 also have power transmission part.
1)1) Impellers are made by twelve backward curved airfoil vanes, curved forehead plate and broad back plate, which all adopting steel. After the adjustment of dynamic balance, the fans are pneumatic performance, high efficiency and stable running.
2)2) Shells could be made into two types. The shells of No 2.8~12.5 are continuously welded, and couldn’t be dismantled. Shells of №.16、№.20 are three opened types. They can be divided into three parts from the horizontal middle and the vertical direction. They are connected by bolts.
3)3) Air inlet made in whole was set in one side of the fan , the section parallel with the shaft is curve, which could let the air in freely with less loss.
4)4) Transmission part : made up by main shaft, bearing case and shaft connection equipment
Disposal methods when flow volume is inadequate：
During using, the flow volume is often inadequate. It is mainly caused by the resistance fluctuation in the pipe net or working un-dynamic area. If the volume decreased gradually in a long time or abruptly in a short time, it is mainly caused by the plug of pipe net.
 If the inadequate flow volume happened in the first used of the fan, it mainly caused by the follow reasons:
1)1) The real resistance in the pipe net is much different from the counted one. From the general pipe net feature formula: P=KQ2, if the K is smaller than the counted K, the volume will be less.
2)2) Neglect the influence by the total pressure deviation △P. if the deviation is positive one, the volume will be larger; if the deviation is negative one, the volume will be less.
The larger or smaller volume could be deal with the follow methods:
1)1) using flow saving equipment
2)2) changing the speed of fan
3)3) using higher or lower pressure fan
4)4) changing pipe net resistance parameter
note: the flow saving equipment is generally used. But when the real volume is much larger than the needed one, this method is uneconomic as its much more power asked.
If it is applicable, the methods two and three are generally used.
If the volume remains smaller when all the flow saving equipments were opened, we should adopt method four to supply the volume. Method two and three could also be used, except the direct driven motor and shaft connected fans. Only the fans with transmission device could change the speed by means of varying the wheel diameter. But the max speed of the fan could nor beyond the max one showed in the performance chart, and the power of it should recounted.
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Performance and choice of 4-68 type centrifugal fans：
The performance here measured in standard condition, the performance in technology documents or in the ordering requirement all refer to the standard one.if the fan will used in substandard conditions, you should transform the parameters into the standard ones.
refer to follow the formulas：
Q1/Q2=nl/n2；
P/P2=(nl/n2)2(P1/P2)(pal/Pa2)[(273+t2)/(273+t1)]；
N1/N2=(nl/n2)3(P1/P2)[(273+t2)/(273+t1)]；
n1=n2
式中：Q-流量(m3/h)；
N-功率(kw)；
P-密度(kg/m3)；
t-温度(℃)；
P-全压(Pa)；
η-效率(％)
n-转速(r/min)；
Pa-大气压力(h)
Note: footnote‘2’ refers to the known performance and parameters, ‘1’ refers to the wanted performance parameters. Atmosphere Pa=101325Pa, temperature t=20℃, the atom condition in the relative humidity φ=50％, air density η=1.2kg/m3, gravitation acceleration g=9.8m/s2 in standard condition.。
4-68型离心通风机性能与选用件表
4-68离心通风机性能与选用件表（1）
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