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Fan stacks or fan ring is a boundary around the fan to separate air inlet and air delivery portion it is having three main components which are fan cylinder or fans cashing, air inlet or inlet bell, and fan diffuser or velocity recovery cone.

We can summarize the use of stacks is for maximizing fan efficiency, reducing sound levels near the fan system, preventing the reverse running of the fan due to external air interference, and minimizing discharge air recirculation.

The fan stack is an essential part of the cooling tower also in some of the special fan systems.
Stack individual component is also used separately or in combination for different application of fans.

FRP fan stacks are also a major component manufactured by Maya fan. Our fan stacks have been designed for the greatest surface finish on the working portion as well as having superior strength.

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Maya Fan stack enables high-velocity recovery efficiency, therefore overall system efficiency also improve which reduced auxiliary power cost. Fan stack is manufactured from 100% fibreglass reinforced polyester most of Maya fan stack are of double-finish design. An inner smooth surface of stack minimized friction losses which provide laminar airflow and minimum turbulence. outer surface provides high resistance against climatic conditions and good quality UV protection on both the surface prevent UV rays to hamper the stack life.

Fiber fan stack are highly reliable yet less in weight which significantly contributes to improving the overall life of cooling tower because unlike heavy concrete stack weight of FRP stack is just negligible.

Fan stack of an extended height promote the discharge of the saturated airstream at higher elevations, which minimizing the effects of recirculation and interference.

Cooling tower fan stacks

Fan Stack is a common term in cooling tower industries for the combination of three major components of airflow path, it includes an air inlet which is also known as fan bell or bell inlet, fan casing the portion in which fan operate this is also known as fan cylinder, fan shroud and fan ring, third part of the stack is a velocity recovery zone it is used to recover velocity pressure with the help of a conical divergent at fan exit this is also known as fan diffuser.

These stacks have vertical and horizontal ribs which make it very strong to sustain in high wind velocity condition. We are having the in-house capability to develop pattern and mould, therefore we can make any size of fan stacks and these are manufactured in easily assembled segments.

fan-stack frp-fan-ring

Fan Air Inlet/ Inlet bell / Fan Bell

In fan system the air behind fan come from large volume and have to pass through a small cross-section of fan casing for this fan develop negative pressure behind the fan which is equal in all direction and this negative pressure suck air from every direction which move toward the fan radially on minimum distance path therefore some of the air even move perpendicular to the axis of fan and due to inertia of air coming other than axial direction on the periphery of fan resultant air bend toward the centre of cashing and create Vena contracta on the periphery it is similar to picture 1 of river clearly visible vena contracta, But these phenomena remain much more severe in fans as the velocity of air in fan is much higher thus it impacts the fan performance significantly.

To reduce this phenomenon and to provide a smooth transition of air at fan inlet many different shapes are utilized to reduce the losses these are known as Fan air inlet, inlet bell or fan bell.

This inlet bell provides uniform flow at inlet, lower fan noise, turbulence, pressure drop and horsepower as well as increase airflow at same fan power.

Contact for inlet bell
  • Flange inlet

    Most of the time casing with flange and in some cases an extended piece is provided just to allow some extra distance for air equalization.

  • Conical inlet

    A conical shape is added which increase effective inlet area but the disadvantage of flange inlet still exist

  • Radial bell

    it is a maximum used inlet type and having very good advantage on system.

  • Elliptical bell

    it is mainly used in cooling tower and mining industries have a very good effect of flow guiding and equalization.


Maya Fan Inlet

We provide these fan inlet bell in different material and shape as per the requirement of individual case as in small fan we prefer to have aluminium rolled or formed bell, in heavy industrial application we recommend to go with inside finish FRP fan bell it is also recommended for the environment handling moist or chemical laded air, in the application where surface erosion is possible in such place steel inlet is supplied by Maya fan.


Fan casing

It is the portion which shrouded around the fan and cylindrical in shape, therefore, it is also known as fan cylinder of fan ring or fan shroud. This is the most important portion which partition +iv and –iv pressure plain, back or suction side is a –iv pressure plan of fan and front or delivery side is +iv pressure plain. The casing should be as accurate in shape as possible because in case of any irregularity it can cause vibration and may develop fatigue on the fan blade. Also it is very important to maintain least tip clearance which is a space between blade tip and cashing, as this is the place where two different pressure plane come in contact thus air tends to move back from +iv pressure to –iv pressure side, therefore, it is always preferable to maintain the minimum and uniform tip clearance in most of the cases it is considered to have less than 1% tip clearance.

Also, the problem of tip clearance become more critical with increasing pressure difference in the fan, with increasing tip clearance efficiency of a low-pressure fan can we spoiled up to 20 % and high-pressure fan will get stalled and air start circulation from this space.

The fan casing is integrated part of the fan, the casing is selected as per the fan application and its construction and material selected according to the application, environment in which fan work and the type of air fan has to handle. Fan casing can be made of aluminium alloy, milled steel, fibre reinforced plastic, wood, concrete or of special material as per requirement. only in case of retrofitting or in case of accidental damage separate cashing is required also we work in cashing modification i.e. providing or upgrading cashing for IGV (inlet guide vane)or OGV (outlet guide vane) following are the major cashing type offered by us -

  • Heavy duty robust integrated casing for mining fans
  • frp cashing for OEM of cooling tower and ACC
  • Fan shroud/ring in combination with inlet bell, delivery diffuser or both.

Fan Diffuser / Velocity Recovery Cone

In general significant amount of effort made by the fan is just wasted in exit air energy as fan draws air from the system and deliver it to the environment at atmospheric pressure (also be considered as zero pressure). So velocity recovery cone which is a conical cylinder of gradually increasing diameter is an ideal tool to minimize this exit air velocity and utilized the maximum amount of dynamic pressure recovery into the static pressure regain. The energy of air at any point of the system remain same therefore energy at fan and energy at exit is same only some loses in the path from fan plane to the exit plane happened so it can be derived as –


Customized Fan Stack

Every equipment manufacturer have its own design for cooling tower, air-cooled condenser, mine ventilation fans or in any other special fans therefore we at Maya fan manufacture fan stacks or its individual component (inlet bell, cashing, and fan diffuser) as per customer requirement we are having all necessary facility required to produce FRP or metallic fan stack.
We are having state of the art pattern and mould making a facility to develop customized tailor-made stack as per customer input drawing and specification. at Maya fan, we manufacture double finish fan stack for cooling tower and heat exchanger fans this double finish stack provide better efficiency compare to irregular rough surface single finish stack.
We also have fully equipped fabrication facility to manufacturer metallic stack, diffuser or casing. Also for small size high volume production bell, cashing and diffuser we are having automatic rolling and forming machine.

General Documents and tech sheet

  • Typical QAP
  • Proforma Of Drawing.
  • Test Certificate

Option for Selection

  • Stack Color.
  • Access Door.
  • Inspection Hole.
  • Customise stack as per your drawing.

Our Featured Partners

This is a list of few of our prestigious customer of fan stack and its components.