How to use Teryair air motors for mixer applications
Do’s and Dont’s
May 2021
Why air motors for mixer applications?
Pneumatic motors are very suitable for use as stirrers for the following reasons.
- Air Motors are explosion proof and safe for running in all kinds of explosive atmospheres. (ATEX certification is a must, all Teryair air motors are ATEX certified.
- Air Motors are cool running – expanding air cools the motor naturally.
- Air Motors are capable of being stalled with no damage to equipment and with no energy consumption when stalled.
- Air Motors are compact and have higher power to weight ratio when compared to electric motors.
- Air Motors are easy to manipulate speed and torque with a simple throttle valve, no expensive VFD drives are needed.
- Air Motors are instantly reversible if needed.
Before you incorporate an air motor into your Mixer please make sure you follow these simple concepts.
Concept No 1. Air motor rotor Isolation
DO NOT connect the mixer shaft directly to the motor rotor. See fig. No 1
This is incorrect and will lead to the shaft bending and axial loads coming directly onto the motor spindle bearing.
The result is premature failure of rotor bearing and possible air motor rotor bending and fast wearing of internal components.
The correct way is shown here in Fig No.2
This is correct because any shaft bending loads is properly absorbed by an intermediate bearing of proper size. Axial loads are also absorbed by this bearing. This bearing is chosen correctly depending on the shaft length and horse power and speed of the arrangement. Basically one can use a heavy duty bearing in this area that will absorb the bending loads and axial loads. Further replacement of such bearing is an economical and a simple job, compared to the air motor repair.
Please isolate the air motor rotor !!
Concept No 2. Torque, Horsepower and Speed.
If speed of an air motor is reduced by reducing air input by a throttle valve, PLEASE BE AWARE that there will be a proportionate drop in horse power and torque, in some cases the motor is starved for air and simply cannot turn the impeller. It’s like trying to start a car in the 4th gear, there is simply not enough torque and it will stall.
Make sure that you have enough air supply coming to the motor
All teryair motors are available with industry standard flange mounting to fit standard third party gear boxes. For any assistance with gear box selection please contact teryair.
Many users confuse cfm with pressure. Note that you must deliver enough cfm (flow rate of air in cubic feet per minute) as mentioned otherwise motor will not develop power.
A rule of thumb is that each 1 HP compressor electric motor size generates about 3-4 CFM of compressed air flow at about 90 PSI
Concept No 3. Impeller selection
General rule of thumb is to go with the smallest diameter of impeller that does the job. Larger impellers require exponentially higher horse power and higher air supply.
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Fluid viscosity is a factor and the more viscous a fluid the more horse power is needed to effectively mix it. Use a higher horse power motor for higher viscosity fluids (Teryair makes upto 9.5 HP air motors)