Introduction
Hydraulic seals are critical components that ensure the tightness and efficiency of hydraulic systems. Their selection, calculation and installation affect the durability, efficiency and safety of production equipment. This article examines the technical background, standard requirements, selection and installation methods, and blowout preventers for hydraulic seals.
Fundamental principles
Hydraulic seals perform the function of keeping the fluid in the system, preventing it from leaking through the joints. They do this by creating microelastic contact between surfaces. An important factor is the choice of material that can withstand temperature, pressure and mechanical loads.
Rod seals are used to seal the rods of hydraulic cylinders, while piston seals provide a seal between the piston and the cylinder. Selectors (wipers) remove contamination from surfaces, which reduces the impact of dust, dust and other contaminants on the interior space.
Technical requirements and standards
Hydraulic seals must meet the requirements of the following standards:
- ISO 281: Dynamic durability of seals
- DIN 51825: Seals for hydraulic systems
- ISO 1042: Standards for hydraulic seals
- EN 837: Requirements for hydraulic seals for industrial use
- ISO 6892-1: Requirements for mechanical properties of materials
Here are examples of technical characteristics:
| Type of sealing | Maximum pressure (MPa) | Operating temperature (°C) | Material | Service life (hours) |
|---|---|---|---|---|
| Liquid sealing | 35 | -20 to 120 | Natural rubber (NBR) | 5000 |
| Piston seal | 40 | -30 to 150 | Ethylene propylene rubber (EPDM) | 7000 |
| Selector | 30 | -20 to 100 | Kapron (Nylon) | 6000 |
Selection criteria and calculation
The choice of seals should take into account the following criteria:
- Working fluid pressure
- The temperature of the working environment
- The material of the serviced surface
- Piston speed
- Frequency of use
The formula for calculating the liquid flow through the seal:
Q = A * v * Δp where:
- Q — fluid flow (l/min)
- A — compaction area (m²)
- v — movement speed (m/s)
- Δp — pressure difference (Pa)
Installation and debugging best practices
Installation of hydraulic seals must be performed in accordance with the following recommendations:
- Use appropriate cleaning products
- Install the seal taking into account the eccentricity
- Keep surfaces clean
- Use special marking devices
- Perform testing after installation
Knockout causes and root cause analysis
The most common reasons for knocking out hydraulic seals:
- Wrong choice of material
- Insufficient size or centering
- Increased pressure or speed
- Incorrect installation
- Contamination of the working fluid
Visual signs of knocking out:
- Fluid leak
- Material cracking
- Changing the shape of the seal
- Increased surface temperature
- Increased noise in the system
Knockout prediction and condition monitoring
The following methods are used to control the state of hydraulic seals:
- Pressure measurement
- Temperature sensors
- Acoustic control
- Fluid flow monitoring
- External visual control
The use of appropriate sensors allows detection of knockouts in the early stages.
Comparison table
| Type of sealing | Maximum pressure (MPa) | Operating temperature (°C) | Material | Service life (hours) |
|---|---|---|---|---|
| Liquid sealing | 35 | -20 to 120 | Natural rubber (NBR) | 5000 |
| Piston seal | 40 | -30 to 150 | Ethylene propylene rubber (EPDM) | 7000 |
| Selector | 30 | -20 to 100 | Kapron (Nylon) | 6000 |
| Liquid sealing (semi-elastic) | 45 | -20 to 150 | Synthetic rubber (FKM) | 8000 |
| Piston seal (semi-elastic) | 50 | -30 to 180 | Synthetic rubber (FKM) | 9000 |
Conclusion
Hydraulic seals are critical components of hydraulic systems. Their selection, installation and monitoring must be done according to standards to ensure the longevity and reliability of the systems. All components used in this article can be purchased from UNITEC-D GmbH. For details and to choose the right seal, visit our e-catalogue:
https://www.unitecd.com/e-catalog/
Sources
- ISO 281: Dynamic durability of seals
- DIN 51825: Seals for hydraulic systems
- ISO 1042: Standards for hydraulic seals
- EN 837: Requirements for hydraulic seals for industrial use
- ISO 6892-1: Requirements for mechanical properties of materials
