A locking gasket is a functional gasket that prevents threaded connections from loosening due to vibration, impact, or dynamic load by increasing friction, elastic deformation, or mechanical interlocking. Widely used in mechanical, construction, automotive, aerospace and other fields, is to ensure the long-term stability of fasteners key components. Their core functions, types, operating principles and typical applications are detailed below:
I. Core Functions: Anti-Loosening, cushioning, compensation.
Anti-Loosening
Resist loosening caused by vibration, impact or alternating load in threaded connections to prevent nuts or bolts from falling off. Bolt connections in car engines, for example, can be subjected to prolonged high-frequency vibration, and lock washers can greatly reduce the risk of loosening.
Vibration Cushioning
Absorbs vibration energy is absorbed by elastic deformation, the impact of load on the joint is reduced, and the surface of the joint is protected from damage. For example, in the flange connection of a wind turbine tower flange connections, the locking gasket cushions the vibration caused by wind loads.
Gap compensation
Fill gaps in joints due to material fatigue, temperature fluctuations, or prolonged use to prevent fasteners from loosening due to gap expansion. For example, in a steel bridge connection, lock washer compensates for gaps caused by thermal expansion and contraction. ii. Main Typess and Working Principles
1.Friction-Enhanced Type
Spring Washers
Structure: Spiral rings with incisions create an elastic structure.
Mechanical principle: During tightening, the gasket is compressed to create elasticity, increasing friction between the nut and the connecting member, thus preventing loosening.
Features: Low cost, simple installation, but limited anti-loosening effect of high strength bolts, which may lead to force degradation.
Purpose: Low vibration environment such as low voltage pipe and electrical equipment.
Internal and External Tooth Lock Washers
Structure: The surface of washing machine is characterized by misaligned teeth, the tooth tips which is bent alternately.
Mechanical principle: The tooth tips is joined with the nut surface and connecting components to enhance the anti-loosening effect through mechanical clamping.
Features: Loose resistance better than spring gasket, but may damage mating surfaces.
Application: Suitable for Moderate vibration environments such as construction machinery and agricultural equipment.
2. Elastic Compensation Type
Elastic Lock Washers
Structure: Wave or disc design, high elasticity. Principle: absorbs vibration energy through elastic deformation and compensates the gap caused by material fatigue or deformation.
Features: Fatigue resistance, long life, but relatively high cost.
Application scope: applications requiring high reliability, such as rail transit, aerospace, etc..
Double-stacked self-locking washing machine
Structure: composed of two serrated washers. During installation, the larger tooth surfaces are in contact with each other, and the smaller tooth surfaces are in contact with the nut and the connecting components, respectively.
How it works: During vibration, the larger tooth surfaces moves upward, locking the bolt with a slope angle difference (α > bolt thread angle β) to prevent loosening.
Features: Loose resistance is more than 4 times that of conventional solutions and is suitable for extreme temperatures (-50°C to +300°C).
Purpose: Suitable for high frequency vibration, such as engine and transmission systems.
3. Mechanical interlock
Wedge self-locking gasket
Structure: Like the NL30 series, the Nord-Lock NL30 series consists of two wedges, one at top and one at the bottom. Principle: When tightening the bolt, the wedge slope engages with each other, and the tension of the bolt is transformed into frictional resistance through elastic deformation to maintain a stable preload.
Features: No additional locking device, anti-loosening effect lasting.
Application: Used for dynamic load scenarios of wind turbine tower flanges and mining machinery.
III. Typical Application Scenarios
High Vibration Environments
Aerospace: Threaded connections between aircraft engines and landing gear can be subject to prolonged and severe vibration. Double-stack self-locking gaskets or wedge self-locking gaskets can significantly improve connection durability.
Automotive: Bolted connections for power components such as transmission and suspension systems are made using internal and external tooth lock gaskets or elastic lock gaskets to prevent loosening.
Dynamic Load Scenarios
Rail transit: Threaded connections of bogies, wheels and other areas must be able to withstand alternating loads and temperature fluctuations. The locking gasket maintains the preset clamping force by dynamically compensating.
Wind Turbine Equipment: Tower flange connections of tower plate must be able to withstand vibration and bending stress caused by wind loads. Wedge self-locking gasket ensures connection stability. Corrosive Media Environments
Marine Engineering: Threaded connections between ships and offshore platforms need to be protected from spray corrosion. Stainless steel lock washers can extend the service life of equipment.
Chemical Equipment: Threaded connections on pipes, valves and other parts shall be chemically resistant to corrosion. Coated lock washers provide additional protection.
IV. INTRODUCTION Selection Recommendations
Selection based on Vibration Frequency
For high frequency vibration environment such as aerospace, double stack self-locking gaskets or wedge self-locking gaskets are preferred. Its mechanical interlocking structure has high reliability.
For low frequency vibration environments (such as construction machinery), internal and external tooth lock gaskets or spring gaskets can be used to balance cost and performance.
Select by Load Type
For dynamic loads,such as alternating stresses, choose gaskets with elastic compensation capabilities, such as the NORD-LOCK series.
For static loads,such as fixed brackets, a combination of common spring gaskets or flat gaskets can be used to reduce costs.
Selection based on environmental conditions
Verify the thermal expansion coefficient of the gasket material for high or low temperatures to avoid preload loss due to temperature variations. Stainless steel or galvanized gaskets should be used in corrosive environments to prevent rust from affecting loose-proof properties.