Introduction
Ukrainian industry is facing an acute need to improve energy efficiency and reduce product cost. Many production lines still use outdated pneumatic control systems, developed back in the last century. Pneumatics have significant operating costs, associated with constant air leaks, low efficiency coefficient of compressor stations and limited positioning accuracy.
Switching to modern electromechanical drives allows not only to reduce energy consumption, but also to meet strict requirements of European energy efficiency directives (in particular, EU regulations on eco-design). The chief engineer of UNITEC-D GmbH in Augsburg receives daily requests from Ukrainian plants regarding modernization of shut-off valve units and linear movements. Old equipment often continues to operate formally, but compressed air generation consumes a huge share of the company's overall energy consumption.
Evaluation of obsolete systems
Before making a decision on major overhaul or complete replacement of pneumatic drives, it is necessary to conduct an audit of the current condition of the equipment. The table below lists the key criteria for assessing outdated pneumatic systems according to the requirements ISO 1101 and EN ISO 4414.
| Evaluation Criterion | Typical condition of a pneumatic system | Critical threshold for replacement |
|---|---|---|
| Compressed air coils | 15–30% of the total generation volume | Over 20% pressure loss in the network |
| Positioning Accuracy | ±1.0 – ±5.0 mm (depending on load) | Positioning requirement better than ±0.5 mm |
| Energy Efficiency COP | 10–15% (from electrical energy to mechanical work) | Low efficiency below 15% in the range of 6–8 bar |
| Maintenance costs | Regular replacement of seals, dryers, filters | Failure rate over 4 times per year per node |
Modern Alternatives
The main obstacle to modernization is the psychological barrier: "the system is working, why change it?". However, the economic calculation of total cost of ownership (TCO) demonstrates the advantage of electric mechanical drives. As a standard modern component for replacing heavy pneumatic cylinders and positioners, we consider the module REXROTH 3701202000, which provides high accuracy and minimal energy consumption.
| Technical parameter | Standard pneumatic cylinder (Ø80 mm) | Electric drive (based on REXROTH 3701202000) |
|---|---|---|
| Energy source | Pneumatic network (6 bar, compressor station) | Electrical network 400V AC / 24V DC |
| Positioning Accuracy | Limited by end switches (without intermediate points) | Up to ±0.05 mm using an encoder |
| Energy consumption | High (compressor continuous operation on leaks) | Only during movement (Energy-on-demand) |
| Working temperature | -10°C ... +60°C (sensitivity to moisture in the pipeline) | -20°C ... +80°C (IP65/IP67 protection class) |
| Mean Time Between Failures (MTBF) | ~15 000 hours | Over 50,000 hours (according to ISO 13849-1) |
Calculation of Return on Investment (ROI)
Let us consider a real economic case for an average Ukrainian machine building plant, which operates 20 linear pneumatic drives on one stamping line. The calculation is based on the following input data:
- Cost of electricity for industry: 6.5 грн/кВт·год (with VAT).
- Working time: 3 shifts of 8 hours, 250 days per year (6000 hours/year).
- Air consumption per one pneumatic cylinder with diameter 80 mm at stroke 300 mm: approximately 15 liters per cycle.
- Number of cycles per hour: 300.
Annual energy consumption of the compressor to ensure operation of these 20 cylinders (taking into account losses in the network 25% and compressor efficiency) is approximately 110 000 kW·h per year. In monetary equivalent, this equals 715 000 грн per year for only one section.
When switching to electric-mechanical drives (in particular components of REXROTH class 3701202000), energy consumption is reduced by 70%, since the drive consumes energy only during the direct movement of the working organ. Annual electricity costs drop to 214 500 UAH. Savings amount to 500 500 UAH per year.
Additional consideration is given to the reduction in maintenance costs (avoiding the purchase of repair kits, lubricants for pipelines and elimination of hose connection leaks) — this saves approximately 120 000 грн per year. The total annual saving amounts to 620 500 грн. Capital investments for replacing 20 drives together with control systems and installation robots amount to approximately 1 240 000 грн. The simple payback period (Payback Period) is exactly 2 years.
Step-by-step implementation plan
In order to minimize production line downtime during modernization, UNITEC-D engineers recommend a clear phased plan:
- Audit and inventory: Fixation of all parameters of existing pneumatic circuits, determination of mounting points and dimensional limitations.
- Design of transitions: Development of adapters and transition plates for installation of electric drives without changing the equipment base structure.
- Pre-programming: Setting up the controllers and motor drivers on the UNITEC-D test stand before sending to the customer's facility.
- Installation during planned stoppage: Replacement of equipment during scheduled technical maintenance (for example, on weekends). The installation time for one unit does not exceed 4 hours.
- Startup procedures: Sensor testing, end position calibration and safety check according to DSTU EN ISO 12100.
- Ефективність (ККД): Зросла з 12% до 82%.
- Cycle time: Reduced from 1.2 s to 0.85 s thanks to rigid servo motor speed profile control.
- Рівень браку: Знизився з 2.4% до 0.1% завдяки відсутності ривків та точному позиціюванню продукції.
- MTBF (Mean Time Between Failures): Increased from 8 000 hours to over 45 000 hours.
- ISO 1101: Geometrical product specifications (GPS) - Geometrical tolerancing.
- EN ISO 4414: Pneumatic fluid power - General rules and safety requirements for systems and their components.
- ISO 13849-1: Safety of machinery - Safety-related parts of control systems.
- DSSTU EN ISO 12100: Machine Safety. General Principles of Design. Risk Assessment and Risk Reduction.
- Ecodesign Directive 2009/125/EC concerning industrial electric motors and compressed air systems.
Technical Problems and Ways of Their Resolution
Modernization of pneumatic systems to electric ones is accompanied by certain challenges that need to be addressed during the design phase:
Main error of engineers — simply copying the force of a pneumatic cylinder onto an electromechanical screw without considering the dynamic characteristics of acceleration and braking. We always calculate peak loads according to the standard ISO/TR 14121-2.
The problem of free space deficiency in control cabinets is solved by using compact servo amplifiers with DIN-rail mounting. The problem of dust and moisture protection in metallurgical or food industry workshops is addressed by selecting drives with protection class not lower than IP65, certified according to CE and UkrSEPRO.
Case Study
On one of the food industry enterprises in Ukraine, the sorting and packaging line was modernized, where 12 pneumatic distributors and cylinders were used. The main problem was the uneven speed of movement due to pressure drop in the main line during parallel connection of other consumers.
Results after modernization:
Startup and validation
After completion of the installation works, mandatory tests are carried out to check compliance with the technical specifications. The operation of emergency stops, correct signal transmission to PLC and the temperature regime of the electric motors under load are checked. All documents are formed according to the requirements of DSTU for handover into operation in Ukraine.
Conclusion
Replacing outdated pneumatic drives with modern electromechanical equivalents is a critically important step for Ukrainian manufacturing facilities aiming to reduce energy consumption and improve product quality. UNITEC-D GmbH supplies both proven components (including modern equivalents REXROTH 3701202000) and ready engineering packages for the modernization of industrial equipment. Please browse our catalog: UNITEC-D E-Catalog.
