Reduce costs

Lower your operating costs and reduce CO₂ emissions – find out why more and more companies are replacing pneumatic drives with electric linear motors.

Replacing pneumatics with industrial linear motors

LinMot as a pneumatic replacement: Electric linear actuators are displacing conventional pneumatic cylinders in an increasing number of applications. Reasons for this include the poor efficiency, high commissioning, conversion, service, and maintenance costs, as well as the limited controllability of pneumatic systems. A recent total cost of ownership comparison demonstrates that, given current component and electricity prices, electric linear actuators pay for themselves within a few months, even in simple point-to-point movements with two end positions, and help to significantly reduce the CO02 footprint. They also offer greater flexibility in the design of production processes and production monitoring systems.

Pneumatics: 2/3 of the operating costs are spent on energy.

Pneumatic drives are characterized by low acquisition costs, robustness against external influences (e.g., temperature fluctuations and dust), and high overload resistance. Furthermore, they are easy to handle and require no holding current when installed vertically. Compressed air is also used in many workshop and industrial environments for transport and cleaning tasks, meaning that compressor systems are necessary anyway. It's no wonder, then, that pneumatics have found widespread application and are found in many factory halls.

Compressed air is one of the most expensive energy sources because compressors can only convert a small portion of the energy used into usable power – the significantly larger portion is released as waste heat. State-of-the-art technology can achieve an efficiency of around 30%. Further improvements are hardly possible due to the almost reached physical limits. In addition to the already high losses from the motor, compressor, start-up, and run-down phases, as well as losses from compressed air treatment, losses from leaks in the distribution systems are also a factor in practice. As a result, in reality (without optimizations), after further conversion losses in the actuator, only about 5% of the energy used is available as usable power (Figure, Slide 19). Efficiency can be increased through optimal design of the piping system and actuators, consistent leak detection, and heat recovery. The German Federal Ministry for the Environment estimates the energy-saving potential at 20 to 40%, while other experts anticipate significantly higher savings.

Even if all these potential savings can be utilized, compressed air systems with a maximum achievable overall efficiency of 10% still use the energy extremely inefficiently. This is also reflected in the total cost of ownership (TCO) of a compressor: While approximately 10% of the total costs are for the purchase and another 10% for maintenance, energy costs typically account for 70 to 80% of the total costs over the compressor's lifetime!

It is therefore not surprising that more and more companies are trying to eliminate the use of compressed air from their operations or reduce it to an absolute minimum in times of rising energy prices and increased environmental awareness (keyword CO2 emissions).

For pneumatic drives, almost without exception alternatives are now available that do not require compressed air.

For linear motion applications, the highly efficient and universally applicable tubular electric linear motors offer a suitable replacement in many cases. LinMot offers these in a wide variety of designs and performance classes.

 

Cost comparison of pneumatic cylinders and linear motors using a concrete practical example

Although electric drives are initially more expensive to purchase than simple pneumatic cylinders, an analysis of the total costs over a life cycle shows that LinMot's industrial linear motors, in particular, pay for themselves within a few months or even weeks, even in simple point-to-point movements with only two positions to be approached. This is clearly demonstrated by the following example of a horizontal point-to-point movement with a 400 mm stroke and 15 kg moving mass, which is executed at 30 cycles per minute and a 50% duty cycle (= cycle time of 2.000 ms).

 

Energy costs with a linear motor solution

The required positioning time of 500 ms for this task is achieved with an acceleration of 10 m/s² and a travel speed of 1 m/s. The acceleration time, during which the linear motor effectively performs work, is then 100 ms. This means that the effective power consumption occurs only during one-fifth of the positioning time. During standstill and when traveling at a constant speed, the motor consumes no power except for friction compensation. The kinetic energy generated during braking is converted into electrical energy within the motor (generator effect) and stored in the DC link capacitors of the servo controller, where it can be used for the next cycle. This application can be implemented, for example, with a LinMot linear motor of frame size P01-48x240F in combination with a LinMot servo controller type E1100-XC/B1100-XC with a continuous power consumption of less than 100 W.

Assuming an annual operating time of 8.000 hours (three-shift operation) and an electricity price of EUR 0,12/kWh (price for large industrial consumers including taxes according to EUROSTAT), the annual energy costs amount to EUR 96. A pneumatic solution, on the other hand, would be significantly more expensive.

Energy costs when using a pneumatic cylinder

If a load mass of 15 kg is to be moved pneumatically at a (maximum) speed of 1 m/s as required in the application example, the evaluation of the corresponding characteristic curves for the design of pneumatic cylinders from a renowned manufacturer shows that a pneumatic cylinder with a 50 mm piston diameter must be used.

Unlike a linear motor, energy (compressed air) must be supplied throughout the entire movement.

Furthermore, the kinetic energy is absorbed by dampers during braking and cannot be stored for the next movement. According to the data sheet, the selected cylinder consumes 0,02529 dm³ of air at 6 bar per millimeter of travel during a double stroke. With a stroke of 400 mm, this results in a consumption of 10,37 dm³ per cycle. At 30 cycles per minute, the pneumatic cylinder requires a total of 150.000 Nm³ of compressed air per year in continuous operation (8,000 hours/year). Taking into account pressure, reduction, and leakage losses on the order of 25%, the compressor must compress and feed approximately 190.000 Nm³ of air into the pipe network. A standard compressor (750 kW motor power, 7,500 Nm³/h air output) can compress 1 Nm³ of air to 6 bar using 0,130 kWh of electrical energy, including losses from start-up, run-down, and compressed air preparation (totaling approximately 25%). This results in annual energy costs of around €3.000 (€0,12/kWh * 0,130 kWh/m³ * 190.000 m³), ​​more than 30 times higher than its electric counterpart. At higher cycle rates, the ratio would shift even further against the pneumatic cylinder.

 

Full cost accounting

In a full cost calculation, investment and maintenance costs must be added to the pure energy costs. Studies have shown that these together account for approximately 20% of the total operating costs. In the example examined here, this means that around €750 must be allocated annually for these costs, bringing the total operating costs to €3.750. Manufacturers of pneumatic solutions estimate the total costs (after energy efficiency measures!) at €0,025 per standard cubic meter of compressed air. For our example, this results in total annual operating costs of €3.750 for the 150.000 Nm³ of compressed air required by one cylinder, thus supporting the calculation example above.

In contrast, a linear drive, including all components necessary for operation (cables, inverters, etc.), costs more than a pneumatic drive (including valves, hoses, etc.).

However, due to the significantly lower energy costs, the electric drive pays for itself in less than half a year, after which there are noticeable savings!

In our example, the energy costs exceed the investment costs for the pneumatic cylinder after just three weeks.

When investment and energy costs are analyzed in the application example, the use of an industrial linear motor results in savings after just 12 or 24 months. Savings of €2.300 or €5.900. compared to the use of a pneumatic cylinder.

This shows that while air is free, compressed air certainly is not!

Due to rising electricity prices, the annual operating costs per bottle in this application example were in 2010 at 3,840 EUR (@12 EUR/kWh), but have increased until the Year 2022 at 7,400 EUR (@0,26 EUR/kWh) almost doubled.

CO2 emissions

Switching to an electric linear actuator can drastically reduce CO2 emissions. The additional 24.000 kWh required by the pneumatic cylinder in the example calculation corresponds to an annual emission of 12,000 kg of CO2, based on the German energy mix of 500g CO2/kWh.

The CO02 balance also clearly speaks in favor of switching to electric direct drives.

A 3 kg pneumatic cylinder produces 12,000 kg of CO2!

Greater future security through innovation and flexibility

The electric version offers advantages beyond lower energy consumption, including greater flexibility in designing production processes and monitoring systems. Electric linear actuators can execute motion sequences in a controlled manner, with significantly greater dynamics and higher repeatability. Since the motion profile can be freely programmed, even complex motion sequences can be implemented quickly and easily and adapted to new requirements as needed – even during operation. Linear actuators are considerably quieter and more durable. They are insensitive to load fluctuations and can start and stop smoothly. Furthermore, the evaluation of data generated by the inverter allows for the monitoring of various process parameters without additional sensors, which can also be used for remote system diagnostics. Finally, fewer individual components are required, which are also significantly easier to maintain and replace compared to pneumatic systems, resulting in lower installation, maintenance, and logistics costs.

Conclusion

When more than two positions are required, when synchronization with a vertical shaft is necessary, or when the dynamics or service life of a pneumatic cylinder is insufficient, designers have long relied on LinMot's linear direct drives. Due to the high operating costs of pneumatics, the use of LinMot pays off. industrial linear motors Increasingly, however, this also applies to simple point-to-point movements with only two end positions. This is especially true when the movements are performed regularly in cyclical operation and pneumatic cylinders have to be generously dimensioned due to the speed and load conditions. In this case, the electric linear actuator pays for itself within a few weeks.

Lower costs.
Less CO₂.

Compressed air costs money – more than most people realize. We help you sustainably reduce your energy consumption and switch to a technology that pays for itself in just a few weeks.

Discover your potential now

Lower costs. Less CO₂.

Compressed air costs money – more than most people realize. We help you sustainably reduce your energy consumption and switch to a technology that pays for itself in just a few weeks.

Discover your potential now

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