Introduction: Challenges in hydraulic drives and the importance of functional safety
Hydraulic drives are used in industrial installations for transmitting energy and controlling mechanical processes. However, due to high pressure, high temperature and high level of responsibility, hydraulic drives have a high risk of causing accidents. Functional safety is critical for ensuring safe operation of systems, according to standards DSTU, EN and ISO.
Fundamental Principles: Physics and Mechanics of Hydraulic Drives
Hydraulic drives operate according to the laws of hydraulics and fluid mechanics. The main principles are Pascal's law and Archimedes' law, which determine pressure distribution and fluid displacement. The safety of hydraulic drives is ensured through pressure control and compliance with execution standards.
Safety valve equipment complies with standards EN 13442, ISO 1219-1, IEC 60947-2 and DSTU 2828:2022. These standards establish requirements for functional safety, including selection of performance levels (Performance Levels, PL) and requirements for conformity.
Technical specifications and standards: classification and requirements
Functional safety of hydraulic drives is defined through performance levels (PL) and safety integrity levels (SIL). Performance levels are defined from PL a to PL e, according to EN ISO 13849-1. Each level corresponds to the appropriate level of reliability and compliance.
Standards used include:
- EN 13442: Safety Valve Equipment Requirements.
- ISO 1219-1: Standards for hydraulic systems.
- IEC 60947-2: Requirements for switches and distribution devices.
- DSTU 2828:2022: Functional Safety Requirements in Ukraine.
- ISO 281: Pressure Measurement Requirements.
Selection and calculation: criteria and formulas
The selection of safe valve equipment depends on the nominal pressure, system capacity, and requirements for functional safety. The calculation of the valve size is performed by the formula:
Q = A * vQ — volumetric flow rate, A — cross-sectional area, v — flow velocity.
Table 1 provides recommendations for selecting valves depending on performance levels:
| Performance Level (PL) | Pressure (bar) | Temperature (°C) | Material | Mean Time Between Failures (MTBF, hours) |
|---|---|---|---|---|
| PL a | 100–300 | −20 to +100 | Steel | 10000 |
| PL b | 300–500 | −20 to +120 | Stainless steel | 5000 |
| PL c | 500–800 | −20 to +150 | Titanium | 2000 |
| PL d | 800–1200 | −20 to +200 | Nickel | 1000 |
| PL e | 1200–1500 | −20 to +250 | Titanium + Nickel | 500 |
Correct Installation and Commissioning: Practical Recommendations
Installation of safe valve equipment must be carried out taking into account temperature, pressure and environment. Valves must be fixed using special flanges and connections. It is necessary to perform tightness tests before use.
Setup Steps:
- Compliance check.
- Connection to the system.
- System startup in test mode.
- Pressure and temperature control.
- Data recording for further analysis.
Modal Failures and Cause Analysis: Problem Definition
Most common causes of hydraulic drive failures include valve failure, pressure drop and overheating. Visual signs of failure include fluid leakage, change in flow and temperature deviation. Cause analysis is performed using the Failure Mode and Effects Analysis (FMEA) method.
Table 2 lists the most common failures:
| Modal Disconnection | Causes | Visual indicators | Method of analysis |
|---|---|---|---|
| Valve failure | Wear, incorrect installation | Fluid leakage, pressure drop | FMEA |
| Overheating | Incorrect ventilation, high pressure | Temperature change, evaporation | Thermal analysis |
| Pressure Reduction | Purchase of incorrect components | Reduction of productivity | Hydraulic Analysis |
| Fan failure | Overheating, high pressure | Temperature Change | Electrical Analysis |
| Return to initial position | Incorrect settings | Incorrect operation | Mechanical analysis |
Predictive Maintenance and Condition Monitoring: Methods and Techniques
Predictive maintenance of hydraulic systems is performed using monitoring of pressure, temperature and electrical parameters. Methods include the use of pressure sensors, thermocouples and electrical measuring instruments. Data analysis and prediction systems are also used.
Monitoring systems must comply with standards EN 61508 and ISO 13374.. They ensure compliance with functional safety requirements.
Comparative table: safe valve equipment options
Table 3 provides a comparison of three variants of safe valve equipment:
| Option | Level of execution | Pressure (bar) | Temperature (°C) | Material | MTBF (year) | Price (USD) |
|---|---|---|---|---|---|---|
| Option A | PL c | 500–800 | −20 to +150 | Titanium | 2000 | 500 |
| Variant B | PL d | 800–1200 | −20 to +200 | Nickel | 1000 | 800 |
| Variant C | PL e | 1200–1500 | −20 to +250 | Titanium + Nickel | 500 | 1200 |
Conclusion: Select the correct components for safe operation
Functional safety of hydraulic drives is critical for ensuring reliability and safety in industrial systems. Selection of correct components, compliant with standards, will ensure long-term operation and reduce the risk of accidents.
UNITEC-D GmbH — reliable supplier of components for hydraulic systems and safe valve equipment. Our products meet the requirements of DSTU, EN and ISO. Choose the right components for your system — visit our catalog at https://www.unitecd.com/e-catalog/.
List of references
- EN 13442:2019 — Requirements for safe valve equipment.
- ISO 1219-1:2019 — Standards for hydraulic systems.
- IEC 60947-2:2019 — Requirements for switches and distribution devices.
- DSTU 2828:2022 — Functional Safety Requirements in Ukraine.
- ISO 281:2017 — Pressure Measurement Requirements.
