Introduction: The challenge for uninterrupted production
Hydraulic accumulators play a critical role in ensuring the stability and reliability of hydraulic systems in industrial installations. Their use makes it possible to reduce pressure losses, stabilize the flow of liquid and perform the functions of reinforcement, shock absorption and energy storage. However, choosing the right type of battery is a complex technical decision that affects system longevity, efficiency and cost-effectiveness.
Ukrainian industrial installations that use hydraulic systems are obliged to meet the requirements of international standards and domestic regulations. This creates the need to use certified components that meet the requirements of DSTU, EN, ISO and UkrSEPRO. This article examines the technical basis of hydraulic accumulators, their selection, preload and practical recommendations.
Fundamental principles
Physics and mechanics of hydraulic systems
Hydraulic accumulators use the laws of hydraulics to store energy in the form of compressed air or another gas phase. The general principle of operation consists in storing energy in gas, which is separated from the working fluid by a special element - a membrane, a piston or a cylinder.
During system operation, when the pressure drops, the accumulator restores the pressure, providing energy to the system. This ensures stability and reduces the requirements for additional energy sources. Battery performance depends on its design, materials, preload pressure, and hydraulic parameters.
Types of batteries
- Membrane: Uses an elastic membrane to separate gas and liquid. Membranes can be made of rubber, synthetic polymers or composite materials.
- Piston: Uses a metal piston to separate gas and liquid. The precision of execution and the tightness of the piston determine the durability.
- Air: Uses an air balloon or ferromagnetic element to store gas. Can be of different sizes and configurations.
Technical specifications and standards
Norms and classification systems
Hydraulic accumulators must meet the standards that ensure their use in industrial conditions. Basic standards:
- ISO 281: Establishes testing and compliance requirements for hydraulic accumulators.
- EN 12931: Establishes requirements for hydraulic accumulators in industrial use.
- DSTU 3119-2005: Establishes requirements for the production and use of hydraulic systems in Ukraine.
- UkrSEPRO: Establishes certification requirements for industrial components in Ukraine.
Classification and assessment
Hydraulic accumulators are classified according to the following criteria:
- Pressure: 10–400 bar
- Volume: 1–500 l
- Temperature: -20°C to +80°C
- Material: Stainless steel, aluminum, polymers
- Efficiency: 85-95%
- MTBF (Mean Time Without Failure): 5000-20000 hours
Selection criteria and calculation
Operational requirements
The choice of accumulator depends on the specifics of the system, pressures, temperatures and energy requirements. Main criteria:
- Working fluid pressure: 10–400 bar
- System volume: 1–500 l
- Temperature mode: -20°C to +80°C
- Battery efficiency: 85-95%
- Materials and certification: CE, UkrSEPRO
Calculation of preload
The preload is determined by the formula:
P_initial = P_operational × 0.7
where P_operational is the operating pressure of the system, P_initial is the preliminary load. This factor of 0.7 is set in ISO 281 to ensure battery stability.
Solution in the table
| Criterion | Membrane | Piston | Air |
|---|---|---|---|
| Material | Rubber, polymers | Stainless steel | Aluminum, polymers |
| pressure | 10–400 bar | 10–400 bar | 10–400 bar |
| Temperature | -20°C to +80°C | -20°C to +80°C | -20°C to +80°C |
| Efficiency | 85-90% | 88-92% | 85-95% |
| MTBF | 5000–10000 hours | 7000–15000 h | 6000–12000 h |
| Certification | CE, UkrSEPRO | CE, UkrSEPRO | CE, UkrSEPRO |
Practical recommendations for installation and debugging
Installation and adjustment of hydraulic accumulators must be performed taking into account the requirements of the standards and the specifics of the system:
- Installation: The accumulator must be installed on a horizontal plane, taking into account the pressure and location in the system.
- Preload: Perform preload according to the formula P_initial = P_operational × 0.7.
- Testing: Test for tightness and compliance with standards ISO 281.
- Monitoring: Use pressure and temperature sensors to monitor battery health.
Causes of defects and root cause analysis
Hydraulic accumulators can fail for various reasons. The most common defects:
- Fluid leakage: Due to fluid leakage through the piston or diaphragm. It is characterized by a change in pressure or an incorrect fluid level.
- Air leaks: Changes in system pressure can cause air leaks. It is characterized by a decrease in battery efficiency.
- Mechanical Damage: Improper installation or improper preload can cause diaphragm or piston damage.
- Temperature effects: Elevated temperature can cause fluid leakage or change in material properties.
Predictive maintenance and condition monitoring
Predictive maintenance of hydraulic accumulators is carried out using the following methods:
- Pressure Monitoring: Pressure sensors are used to detect changes in pressure that may indicate a leak or defect.
- Temperature Monitoring: Excessive temperature may indicate fluid leakage or material damage.
- Leakage test: Regular tests are performed according to the ISO 281. standard
- Efficiency Monitoring: Using energy analyzers to detect changes in battery efficiency.
Comparison table
| Criterion | Membrane | Piston | Air |
|---|---|---|---|
| Material | Rubber, polymers | Stainless steel | Aluminum, polymers |
| pressure | 10–400 bar | 10–400 bar | 10–400 bar |
| Temperature | -20°C to +80°C | -20°C to +80°C | -20°C to +80°C |
| Efficiency | 85-90% | 88-92% | 85-95% |
| MTBF | 5000–10000 hours | 7000–15000 h | 6000–12000 h |
| Certification | CE, UkrSEPRO | CE, UkrSEPRO | CE, UkrSEPRO |
Conclusion and suggestion
Choosing the right type of hydraulic accumulator is a critical step in the design and operation of hydraulic systems. Taking into account the requirements of standards, efficiency, materials and preload ensures the reliability and durability of the system.
United-D is a reliable supplier of components for hydraulic systems. Our batteries meet the requirements of ISO, EN, DSTU and UkrSEPRO. For complete information on batteries, their specifications and certification, visit our e-catalogue:
https://www.unitecd.com/e-catalog/
List of references
- ISO 281:2017 - Hydraulic accumulators - Requirements and test methods
- EN 12931:2018 - Hydraulic accumulators - Requirements for production and use
- DSTU 3119-2005 — Hydraulic systems — Requirements for production and use
- UkrSEPRO — Certification requirements for industrial components
- UNITEC-D — Technical specifications and certification of batteries
