The fan type
The fan shall be a double inlet centrifugal fan with a steel forward impeller, driven by a direct connection, coupling or belt. The fan structure shall allow the impeller to be easily drawn out so that the impeller can be maintained or cleaned.

Quality standard 
When each fan leaves the factory, it shall be accompanied by the certificate of qualification and the factory inspection report, and the production enterprise shall have the ISO9001 quality system certification.

The fan impeller
The impeller shall be steel forward centrifugal impeller, all welded.The impeller shall be statically and dynamically balanced to reach the G2.5 level of ISO1940 .When the impeller is at the highest allowable speed, it should be able to maintain a stable airflow and low noise.The impeller characteristics should effectively avoid the performance degradation caused by the sliding of the working point.When the working temperature is lower than 200℃, the impeller material adopts Q235A and Q195B.When the working temperature ranges from 200℃ to 450℃, the impeller material should adopt 304 stainless steel to ensure the strength of the impeller and avoid creep deformation during high-speed operation at high temperature.

The fan casing
The fan housing shall be made of steel and shall be thick and strong enough to support the maximum operating weight of the fan.Fan housing shall be continuously welded.The fan housing must be equipped with an access door to remove foreign matter entering the fan.

Air inlet
The fan inlet should be designed strictly according to the aerodynamic characteristics, with smooth and linear surface, and good rectification effect, which can effectively reduce turbulence, improve the efficiency of the fan and reduce noise.

Surface treatment
The surface of the fan shall be polished and cleaned first to remove convex foreign bodies, welding slag, burrs, sharp edges, iron scraps and oil, and then electrostatic spraying epoxy resin or high temperature resistant coating (used in high temperature environment), there shall be no bump, sag, crack, wrinkle, peeling phenomenon.

Transmission structure (only applicable to belt type and shaft type)
The fan shaft should be through fine car conditioning treatment, the hardness reached HB250 ~ 280, the maximum load should be greater than the maximum fan speed of 35%, the shaft should be added to the shaft shield.When the working temperature is below 250℃, the fan shaft material should be 45# steel.When working temperature is 251℃~450℃, the material of fan shaft should adopt 304 stainless steel.The support structure shall adopt integral cylindrical bearing box, and the bearing life for internal use of the bearing box shall be greater than L10:80,000 hours;The bearing shall be lubricated with lithium grease, and the amount of refueling shall be added according to the direction of oil level mirror on the bearing box.When the operating temperature is higher than 80℃, the bearing should be lubricated with high temperature grease.The pulley shall be made of cast iron and shall be sized at least 130% of the driving power.Belt pulley, belt should be equipped with protective cover.The coupling should adopt the elastic coupling, the safety coefficient of power transmission and torque should meet the design requirements of the fan, and the coupling should be equipped with a protective cover.

The motor
The motor shall be closely matched with the load of the fan, with protection grade IP54 and insulation grade F.Motor bearings shall be ball bearings and lubricated.The motor and drive mechanism should be placed outside the airflow to avoid accumulation of grease or dust in the airflow.

Explosion-proof structure (explosion-proof type only)
The fan shall conform to GB 26410-2011 standard explosion-proof structure, the air inlet is inlaid with copper ring or aluminum ring, the motor shall adopt explosion-proof motor, the whole machine shall pass the national explosion-proof certification, and the manufacturer shall have the explosion-proof electrical production license.

Nameplate
Permanent stainless steel nameplate should have clearly identifiable fan number, model number and product serial number (i.e., unique identification for each fan) to ensure easy access to the history of accessories for customers.