The popularity of air motors is on the rise as a result of their many advantages. However, not all pneumatic motors are made the same, so choosing the right one for your application can prove the difference between project success and failure. For the purposes of this blog post we will focus on vane-type air motors as they are more suitable for regular operating cycles, where speeds of no more than 10,000 rpm are required.
To provide an example of the differences between air motors currently available on the market, consider the following. Across modern industry, oil and oil mist are avoided wherever possible to ensure a clean work environment and comply with H&S regulations. With this thought in mind, you should select an air motor from a manufacturer that actively avoids using components which require lubrication. The P1V series from Parker, for example, is equipped with vanes for intermittent lubrication-free operation at power below 1000 watts, which is the most common application of air motors.
For those of you working on food-grade projects and other hygienic/high cleanliness applications, check that external components are made from stainless steel. In our P1V-S range, for example, the air motor and planetary reduction gear are built into a polished stainless steel housing. Moreover, the output shaft, which is also made of polished stainless steel, is sealed by a fluorocarbon (FKM) rubber seal. Note that this design means the motors can be deployed under water to a depth of around 8 metres. These drive solutions are particularly suitable for use in industrial agitators and mixers, as used in the paint, food and pharmaceutical industries.
Once the physical aspects have been decided, you can set about calculating the required power of the air motor. Many factors come into play here, including direction of rotation, air pressure working range, air class quality and, principally, expected torque and speed under load.
Basic power can be calculated using an established formula: P = M x n / 9550. Here, P is power output in kW, M is nominal torque in Nm, and n is nominal speed in rpm. As a tip, you should always select a motor which is slightly too fast and powerful, then regulate its speed by throttling the flow and torque by reducing the pressure to achieve the optimum working point. Also, ensure that the pressure supplied to the inlet port of the motor is correct, so it can work at maximum capacity. If the valve supplying a large motor is too small or the supply line is underspecified, you might find that the pressure at the inlet port is so low that the motor cannot function.
Further factors determining the selection of an air motor include the position in which it will be used. Also, will standard or spring-loaded vanes be required? Spring loaded vanes are selected to ensure they remain pressed against the cylinder when the motor stops, and when working at low speeds.
Will you require an integrated brake? If so, it’s worth noting that brake motors must only ever be supplied with unlubricated air, otherwise there is a risk of oil from the supply air getting into the brake unit, resulting in poor brake performance or no braking effect whatsoever.
Watch in this video Parker’s latest range of air motors and the benefits they can bring to your project.
Article contributed by Franck Roussilon, product manager, Actuators Europe, Parker Hannifin, Pneumatic Division Europe