Introduction
Ukrainian industrial enterprises constantly face the necessity of reducing energy carrier costs and improving the accuracy of technological processes. Traditional pneumatic control systems have proven their durability over decades in harsh conditions of metallurgy, machinery manufacturing and food industry. However, from the perspective of current energy efficiency requirements according to EU directives and standards series ISO 50001, pneumatics demonstrate low overall efficiency — often at the level of 10-20% due to pressure losses in the network, leaks at connections and inefficiency of energy conversion by compressors.
The main reason for the modernization is the physical and moral wear of the equipment, as well as the non-compliance with current accuracy tolerances. An additional driver is the regulations regarding the reduction of CO2 emissions and the industrial safety standards (EN ISO 13849-1). Modern electric drives in combination with advanced modular controllers, such as Allen Bradley 1756-OB16D for high-density discrete outputs, provide microprocessor-controlled positioning with accuracy down to a micrometer and significantly reduce the consumption of electrical energy.
Evaluation of obsolete systems
Before making a decision on dismantling the existing pneumatic equipment, the chief engineer must conduct a condition audit. Outdated pneumatic cylinders and distributors often become a source of unexpected downtime due to wear of seals, formation of condensate and freezing of mufflers at high operating speeds.
For an objective assessment of the feasibility of modernization, the following criteria system is used:
| Evaluation Criterion | Typical condition of obsolete pneumatics | Target indicator of the electric drive |
|---|---|---|
| Positioning Accuracy | ±0.5 – ±2.0 mm (depending on stops) | ±0.01 – ±0.05 mm (servo drive) |
| Energy consumption | High (compressor station continuous operation) | Low (consumption only during movement/holding) |
| Noise Level | 85 – 95 dB (exhaust air through mufflers) | less than 65 dB |
| Mean Time Between Failures (MTBF) | 8 000 – 12 000 hours | 30 000 – 50 000 hours |
Comparison of Technologies: Pneumatics versus Electric Drives
The objection "but the old system is still working" is the most common barrier from production managers who focus only on initial capital expenditures (CapEx). However, analysis of total cost of ownership (TCO) demonstrates the advantage of electric systems in the medium-term perspective.
| Technical characteristics | Pneumatic drive (double-acting) | Electric servo drive with PWM |
|---|---|---|
| Nominal Efficiency of the System | 10% – 15% | 75% – 85% |
| Intermediate Position Control | Complex (requires additional sensors and proportional valves) | Smooth, fully programmable throughout the entire stroke |
| Sensitivity to the environment quality | High (requires dried, clean air with lubricant at ISO 8573-1) | Low (depending on the protection class of the housing, usually IP65/IP67) |
| Maintenance costs (per year) | Frequent seal replacement, elimination of air leaks | Periodic lubrication of the screw pair |
Calculation of Return on Investment (ROI)
For the economic justification of the project, we will perform a calculation for a typical production line with 20 pneumatic cylinders Ø50 mm, operating in three shifts (6000 hours per year) at a pressure of 6 bar.
- Витрати повітря одного циліндра: при ході 200 мм і 15 циклах за хвилину споживання становить приблизно 45 нормальних літрів на хвилину (Нл/хв).
- Total consumption of the group: 900 NL/min or approximately 5.4 m³/min.
- Power consumption of the compressor: approximately 0.12 kWh of electrical energy is required to produce 1 m³ of compressed air at a pressure of 6 bar.
- Річні витрати електроенергії на пневматику: 5.4 м³/хв × 60 хв × 6000 годин × 0.12 кВт·год/м³ = 233 280 кВт·год. При середній ціні електроенергії для промисловості в Україні 6.0 грн/кВт·год це становить 1 399 680 грн на рік.
Switching to electric-mechanical drives reduces energy consumption by 65% due to the absence of losses from leakage and operation of the drive exclusively under load. The annual electricity saving amounts to approximately 909 792 UAH. Additionally, we consider the reduction in maintenance costs of compressor equipment and line downtime by 40 000 UAH per year.
General investments for replacing 20 drives, including Allen Bradley 1756-OB16D controllers for control and power drives, amount to approximately 1,200,000 UAH. Calculated payback period (Payback Period) is 1.25 years.
Implementation Plan
In order to minimize the downtime of the production process, the modernization is carried out in stages:
- Planning and audit stage: UNITEC-D engineers carry out a full inventory of existing forces, speeds and mounting dimensions. Compatibility of signals with existing PLCs is determined.
- Previous purchase and assembly: order and inspection of components, including interface modules and protective fittings.
- Previous mounting of supports: installation of mechanical transitions during planned technical maintenance (for example, on weekends).
- Commissioning and Setup: connection of power cables, integration into a control system based on ControlLogix controllers, setup of drive parameters.
- Startup procedures: no-load test runs, emergency stop checks, and handover to operation.
Technical Problems and Ways of Their Solution
During the replacement of pneumatic with electric, engineers encounter constructive and electrical limitations:
- Limited space on the equipment: electric-mechanical drives with gearboxes and servo motors often have larger dimensions in length compared to compact pneumatic cylinders. Solution: application of compact rodless linear modules or integrated motors with feedback.
- Impulse Loads: Pneumatics absorb shocks due to the compressibility of air. Electric drives are rigid kinematic systems. Solution: installation of spring dampers or programming of soft start and stop in the controller.
- Управління сигналяцією: дискретні сигнали керування вимагають надійних комутаційних модулів з гальванічною розв'язкою. Використання міцних плат виходів, таких як Allen Bradley 1756-OB16D, гарантує безперебійну передачу команд на керуючі реле та драйвери привідної техніки відповідно до норм EN 61131-2.
Case Study
On one of the enterprises producing building materials in the Dnipro region, a modernization of the ingredient dosing unit was carried out. The old pneumatic system provided a dosing error of ±1.5%, leading to overconsumption of expensive additives by 2.3% per month. Constant leaks in the pipelines reduced the pressure during peak load hours.
Modernization Results:
- Accuracy of dosing is increased to ±0.05%.
- Annual material saving amounted to 1 850 000 грн.
- Energy consumption of the dosing drive has decreased by 70%.
- MTBF of the node increased from 6 000 to 45 000 hours.
Startup and validation
After completion of the installation, tests are carried out according to DSTU EN 60204-1 (Machine safety. Machine electrical equipment). Acceptance criteria include:
- Insulation resistance test of power circuits (not less than 20 MΩ at 500 V DC).
- Testing of the emergency stop (Safety Stop).
- Measurement of the actual response time of the drive under full load.
- Verification of compliance of operating parameters with the design documentation.
Summary
Modernization of outdated pneumatic drives by switching to electromechanical systems is a strategic step for Ukrainian manufacturers, aimed at reducing energy consumption, eliminating unexpected downtimes, and achieving maximum process accuracy. Experts from UNITEC-D GmbH provide full support for modernization projects: from enterprise audit and supply of control components to selection of reliable modules, such as Allen Bradley 1756-OB16D. Get acquainted with the nomenclature of advanced components for automation in our UNITEC-D E-Catalog.
Normative references
- DSSTU EN ISO 13849-1:2016 Safety of machinery. Detailed design of safety-related control systems.
- DSSTU EN 60204-1:2015 Safety of machinery. Electrical equipment of machines and mechanisms.
- ISO 50001:2018 Energy Management Systems. Requirements and guidance for use.
- Ecodesign Directive 2009/125/EC concerning the efficiency of industrial drives and compressor equipment.
