September 16, 2025
Washers are essential for maintaining the integrity and performance of bolted joints. While it is technically possible to create a functional joint between two flanges using only bolts and nuts, omitting washers can lead to premature wear, leaks, and costly maintenance issues. By distributing load evenly, preventing surface damage, and reducing friction, washers extend the service life of flanges, gaskets, and pipelines while ensuring consistent sealing performance. In any system requiring reliable pressure containment, vibration resistance, or corrosion protection, washers are a necessary component on bolts, not an option.
What is a Washer?
A washer is a thin, flat disc or ring placed between the head of a bolt or nut and the surface being fastened to improve the performance and longevity of the bolted connection. It distributes the clamping force evenly, protects surfaces from damage, reduces friction and wear, and can enhance sealing to prevent leaks in pressurized systems.
Washers serve several key functions:
- Load distribution: They spread the clamping force of the fastener evenly across the flange surface.
- Surface protection: They prevent localized damage to softer materials and gasket faces.
- Friction reduction: They reduce wear and galling between mating surfaces.
- Seal enhancement: Specialized sealing washers prevent fluid leakage in pressurized systems.
Washers are made from materials such as stainless steel, carbon steel, brass, PTFE, nylon, rubber, or composites, with material selection depending on operating conditions. For instance, high-temperature systems may use stainless steel or G-10 glass epoxy, while applications requiring electrical isolation use non-conductive materials. In flange assemblies, understanding the purpose of washers is essential to achieving a reliable, leak-free seal.
Why Are Washers Necessary?
Washers distribute the load, which helps to prevent damage to the joint’s bearing surface. This makes them useful for a wide variety of applications, including flange joining and gasket installation. Washers provide extra stress resistance, which not only prevents damage but also serves to counteract movement and give additional protection against corrosion.
Types of Washers and Their Uses
When considering types of washers, the right choice depends on both the mechanical requirements and environmental conditions of the system. For flange and gasket installations, two main categories are most relevant: metal washers and insulating washers.
1. Metal Washers (Structural Washers)
Metal washers are typically made from carbon steel, stainless steel, or zinc-plated steel. Their primary function is to provide strength, distribute load, and prevent surface damage. These washers are used in high-pressure or high-stress applications where mechanical integrity is critical.
- Flat Washers: The most common type, used to distribute load and prevent surface wear.
- Spring or Lock Washers: Designed to resist loosening from vibration or thermal cycling.
- Fender Washers: Have a larger outer diameter for greater surface protection.
2. Insulating Washers (Isolation Washers)
In many flange assemblies, especially those involving cathodic protection systems or dissimilar metals, electrical isolation is critical. Insulating washers prevent the passage of electrical current through the bolted joint, protecting against galvanic corrosion and stray current damage. These washers are typically made from epoxy resin, PTFE, nylon, G-10 glass epoxy, or rubber. When used with insulating sleeves and gaskets, they form part of a complete flange isolation kit, which is essential in pipelines carrying corrosive or conductive fluids.
Selecting the Right Washer
The correct washer type depends on application-specific factors such as:
- Operating pressure and temperature
- Chemical exposure and fluid type
- Electrical conductivity requirements
- Mechanical load and vibration levels
Choosing the appropriate washer ensures reliable gasket performance, prevents joint failure, and maintains long-term system safety.
Why Are Washers Important in Gasket Sealing?
In gasketed flange systems, maintaining uniform compression across the gasket surface is essential to achieving a leak-tight seal. This is where washers provide their most important contribution.
Washers serve as a mechanical interface between the fastener and the flange, ensuring that the applied bolt load is evenly distributed across the gasket area. This consistent load prevents uneven compression, which can cause premature gasket failure, leaks, or blowouts.
Let’s explore why washers are important in gasket sealing and how they enhance system performance:
1. Preventing Leaks
Sealing washers and isolation washers often feature compressible materials that deform slightly during installation. This creates a tight, leak-proof barrier between the bolt and the flange, minimizing the risk of fluid or gas escape under pressure.
2. Protecting Gasket and Flange Surfaces
Washers prevent direct contact between the bolt or nut and the flange surface, protecting both from scratches, galling, or localized wear. This not only preserves surface integrity but also reduces the need for flange resurfacing or replacement during maintenance.
3. Ensuring Uniform Pressure Distribution
A well-designed washer ensures even bolt load distribution, which in turn ensures uniform gasket compression. This balanced load improves sealing performance and extends gasket life, especially in systems subject to thermal or pressure cycling.
4. Vibration and Shock Absorption
Washers act as dampers, absorbing mechanical vibrations and thermal shocks that might otherwise loosen bolts or damage gaskets. This feature is particularly valuable in rotating machinery and pipelines exposed to high dynamic loads.
5. Contamination Prevention
In certain applications, washers help block contaminants such as dust, moisture, or corrosive media from entering the joint area, preserving both the gasket and fastener condition.
6. Electrical Insulation
In isolation flange kits, non-conductive washers made from materials such as PTFE, rubber, or G-10 glass epoxy prevent stray electrical currents from passing through the bolted joint. This is crucial for systems operating in corrosive environments or those requiring cathodic protection.
Washers are included in all Durlon isolation kits. Our washers are available in a range of materials, including PTFE, G-10 glass epoxy, and SAE zinc, each chosen for its performance under challenging industrial conditions. Browse our online store for more information on our washers, gaskets and other sealing solutions.