Double-Stack Self-Locking Washer (Compliant with DIN 25201)

Double-Stack Self-Locking Washer Compliant with DIN 25201 — Product Introduction

The double-stack self-locking washer that complies with the DIN 25201 standard is a highly efficient and reliable anti-loosening fastener for bolts, consisting of a pair of specially matched wedge-shaped washers. Based on the wedge-locking principle, it fundamentally prevents bolts from rotating loose under severe vibration and dynamic loads by increasing the axial rigidity and mechanical locking of the bolted joint. The washers are normally installed in pairs: the opposing faces feature radial fine teeth that embed into the connected parts, while the mating faces have high-inclination wedge teeth that interlock for locking. No additional chemical adhesive is required, it can be reused, and it is suitable for harsh working conditions that demand extremely high connection reliability.

I. Product Features

• Wedge-locking principle: The inner sides of the washer pair have inclined cams with an angle greater than the thread lead angle; once engaged they form a mechanical lock. When vibration tries to rotate the bolt loose, the lifting force generated between the washers increases the bolt’s axial tension, thereby preventing any further loosening.
• Double-sided biting design: The outer side of the washers features a radial serrated face that, when installed, firmly embeds into the underside of the bolt head or nut and into the surface of the connected part, preventing the washer body from turning with the bolt and ensuring that the locking action is produced solely by the inner wedge teeth.
• High-strength material with wide temperature range: Usually precision-manufactured from high-quality carbon steel or alloy steel through heat treatment; some can meet high corrosion-resistance requirements via coatings such as Dacromet or zinc-nickel, with an operating temperature range up to -40°C to above 300°C — far exceeding that of chemical thread-locking adhesives.
• Easy installation and inspectable: Supplied in pairs and installed without special tools — simply ensure the wedge teeth face each other and the radial teeth face outward. After tightening, the firm engagement of the washers can be verified visually, making the quality status directly observable.

II. Product Advantages

• Excellent anti-vibration and anti-loosening performance: Effectively resists severe vibration, impact, and alternating loads, especially suitable for dynamically loaded applications. Its locking reliability is several times that of traditional methods such as spring washers, and it is not prone to failure from lateral vibration.
• Does not damage the surface of connected parts: Biting through radial fine teeth rather than sharp-tooth embedding protects the joined surfaces, and because its locking action is smooth, it avoids the problem of excessive torque damaging threads during disassembly and assembly.
• Maintains stable preload: Over long-term use it compensates for preload relaxation caused by gasket creep, thermal expansion and contraction, etc., keeping the joint tight and greatly reducing the risk of leakage or loosening.
• Economical and reusable: Can be repeatedly disassembled and reassembled; its anti-loosening performance does not degrade due to heat or exposure to oil, and its total life-cycle cost is lower than that of adhesive-coated bolts or one-time anti-loosening parts.

III. Application Scope

• Rail transit: Bogies, rail fasteners, coupler devices, pantographs, and other critical fastening points inside railcars that are subject to strong vibration.
• Automotive and construction machinery: Commercial vehicle chassis; vibrating screens, crushers, and excavator buckets of mining and construction machinery at high-impact connections.
• Wind power and energy equipment: Wind turbine towers, gearboxes inside nacelles, generator sets and foundation anchoring, as well as connections in power transmission and transformation facilities.
• Marine and offshore engineering: Marine diesel engines, deck machinery, hatch covers, and various heavily vibrating pipe flanges and structural parts.
• Industrial pumps, valves, and compressors: Cylinder heads, bases, and pipe-joint locking of reciprocating compressors, plunger pumps, and other vibrating equipment.