Pass Engineers

Centrifugal fans type PA
PASS Centrifugal fan type PA essentially comprises a casing, pedestal, impeller and shaft with bearings, when necessary. The casing is manufactured from steel sheet with a circular inlet and a rectangular outlet. The larger sizes of casings are split to provide easy access for the impeller. The Pedestal is manufactured from steel sheet and supports the casing and bearing assembly for smaller sizes, whereas for larger sizes the pedestal supports only the bearing assembly.

The Impellers are both statically and dynamically balanced and manufactured for clockwise and anti-clockwise rotation for various pressure ranges and applications. A basic feature lies in the design of the impeller, the blades of which are in aerodynamic form. The standard Centrifugal Fans are made of M.S. construction.

PASS Centrifugal fan type PA essentially comprises a casing, pedestal, impeller and shaft with bearings, when necessary. The casing is manufactured from steel sheet with a circular inlet and a rectangular outlet. The larger sizes of casings are split to provide easy access for the impeller. The Pedestal is manufactured from steel sheet and supports the casing and bearing assembly for smaller sizes, whereas for larger sizes the pedestal supports only the bearing assembly.

The Impellers are both statically and dynamically balanced and manufactured for clockwise and anti-clockwise rotation for various pressure ranges and applications. A basic feature lies in the design of the impeller, the blades of which are in aerodynamic form. The standard Centrifugal Fans are made of M.S. construction.

The fans have the following distinctive features:

• Robustness


• Stable performance over a wide pressure-flow range


• High efficiency-upto 88%


• Grease valves for lubrication for the larger sizes

The PA fans are available in the following main variants:
PAL for pressure development upto 300 mm wg (3000 Pa)
PAM for pressure development upto 600 mm wg (6000 Pa)
PAH for pressure development upto 1100 mm wg (11000 Pa)

A correctly selected type of impeller gives increased life and optimum performance for different degrees of particulate content in the air.

PA. B
Impeller type B with backward curved blades is for handling air and other clean gases. This type of wheel gives a high total efficiency upto 88% depending on size.

PA.P
Impeller type P with flat backward sloping blades is for handling both clean gases and gases containing a limited amount of dust.

PA.T
Impeller type T with straight, radial blades is for dust-laden gases and for conveying systems. This wheel is open and is, therefore, also suitable for fibrous dust.

Select the direction (form), which best suits the dust layout.
PASS Centrifugal Fans of PA Series are available in seven discharge directions. While ordering, please mention the required discharge direction (form).

Driving Arrangements
PASS Centrifugal Fans are manufactured as per the following Arrangements.

arr-D arr-V aft-F

Arrangement - D
The impeller is mounted directly on the motor shaft. This arrangement is preferable when the fan speed corresponds to an asynchronous motor speed and is available generally for fan size 20 to 60.

Arrangement - V
The impeller is mounted on a shaft supported by two ball or roller bearings (bearing assembly) mounted on the pedestal. The arrangement is used when the motor speed does not permit direct drive or for possible change in the speed of impeller.

Arrangement - F
This is a combination of arrangement D and V. This arrangement is applicable for large fans where it is not possible to mount the impeller on the motor shaft. The impeller is mounted on a shaft supported by two ball or roller bearings. The bearing assembly together with the desired motor is coupled by a suitable coupling mounted on a common pedestal.

Fan Data
This basic fan capacity data are air quantity and pressure. There is often considerable confusion in connection with pressure specifications. The definition of fan pressure is as follows:

• Fan total pressure: The algebraic difference between the total pressure at the fan outlet and the total pressure at the fan inlet


• Fan velocity pressure: The velocity pressure corresponds to the average velocity at the fan outlet


• Fan static pressure: The algebraic difference between the fan total pressure and fan velocity pressure. The pressure developed by a certain fan is directly proportional to the density of the air/gas conveyed. Therefore the air or gas density must be known prior to selecting a fan

Note:
1.The maximum temperature allowable for this type of fan of standard construction is 350°C.
2. Arrangements can be made, wherever necessary, for providing heat - resistant painting of various grades, depending on the temperature of the air/gas to be handled.
3. The Cooling Disc of cast aluminium may be provided with Arrangement V & F fans only.
4. PA fans can be offered in other versions, e.g.

• In other materials (Stainless steel etc.)


• Lined with fibre glass


• Reinforced for increased wear resistance

5. Wherever required, these Fans can be supplied with spark-proof construction, the details of which can be made available on request.
6. While requesting for quotations, please state:

Intended use of the fan

Air/gas flow and pressure development required

Temperature and density of the medium at the inlet end of the PA fan

Arrangement and discharge directions required