O-ring failure can be damaging, expensive, and even deadly if someone gets injured by malfunctioning equipment. Fortunately, o-ring failure causes are well-known and can be prevented. In this blog, we’ll cover how to troubleshoot and prevent five of the most common causes of o-ring failure.
General Causes of O-Ring Failure
Causes of o-ring failure fall into a few general categories. Contributing factors can include:
- Material selection mistakes
- Size mismatch
- Design flaws
- Installation errors
- Temperature excess
- Pressure deformation
- Friction damage
- Chemical degradation
- Lubrication neglect
These underlying causes commonly manifest in some typical patterns. Here are five of the most common causes of o-ring failure and how to spot and fix them:
1. Compression Set
A compression set occurs when an o-ring subjected to prolonged pressure remains in a flattened position that permanently deforms its shape. This can reduce seal integrity.
Causes:
- Incorrect selection of elastomer material with poor compression set or heat resistance properties.
- Poor design.
- Incomplete hardening during curing.
- Overly tight sealing.
- Excessive temperature.
- Swelling from chemical reaction to fluid.
Solutions:
- Select a material with low-set properties, resistance to heat from operation and friction, and compatibility with system fluid.
- Check o-ring physical properties during installation.
- Use the correct squeeze for the seal.
2. Extrusion (Nibbling)
Extrusion occurs in high-pressure systems when pieces get torn away from the low-pressure side as if they had been “nibbled” away. This can disrupt seals in applications such as hydraulic cylinder piston rods.
Causes:
- Excessive pressure.
- Surplus clearance.
- Oversized o-rings.
- Soft o-ring material.
- Sharp gland edges.
- Chemical degradation from fluid.
Solutions:
- Select materials with proper pressure tolerance, hardness, and chemical compatibility.
- Size o-rings correctly.
- Adjust gland clearances and edges by machining.
- Protect o-rings with backup o-rings.
3. Heat Hardening and Oxidation
Heat and oxidation can cause o-rings to exhibit cracks and pits. This often accompanies compression set flattening. It can reduce sealing and cause leakage and failure.
Causes:
- Excessively high or low temperatures or high stress.
- Plasticizer evaporation.
- Reactions with ozone or ultraviolet light (UV light).
Solutions:
- Use temperature-resistant materials.
- Operate systems at lower temperatures and pressure.
- Minimize exposure to oxygen and UV light.
- Use materials with antioxidants, anti-ozonates, and UV stabilizers.
4. Abrasion
Abrasion occurs when repetitive contact between o-ring surfaces and surrounding housing leaves scrapes, lines, and breaks, leaving an o-ring that looks dull, worn, or flat on one side. This can compromise seals and cause o-ring failure.
Causes:
- Poor lubrication.
- Excessive temperatures.
- Rough finish on dynamic seals.
- Fluid contamination of glands.
Solutions:
- Use o-rings with abrasion resistance, temperature resistance, and internal lubrication.
- Polish dynamic seal glands.
5. Spiral Failure
Spiral failure occurs when hydraulic cylinders with long strokes get caught on cylinder walls or other system components. This leads them to slide and roll instead of rotating correctly on a plane, leaving a series of spiral cuts at 45-degree angles. Spiral failure can cause o-rings to leak or break.
Causes:
- Out-of-round cylinder bores or other components.
- Uneven gland surface finishes.
- Excessive clearance with side loads.
- Slow stroke speeds.
- O-ring pinching or rolling during installation.
- Soft o-ring materials.
- Deficient lubrication.
Solutions:
- Inspect out-of-round components.
- Adjust surface finish interfaces of cylinder bores and piston rods.
- Adjust stroke speed.
- Install o-rings properly.
- Select harder o-ring materials.
- Use alternative o-ring designs and back-up o-rings.
- Improve lubrication or use internally lubricated o-rings.
Other Causes of O-Ring Failure
These are only some of the potential causes of o-ring failure. Other causes can include:
- Chemical degradation
- Contamination
- Explosive decompression
- Extraction
- Installation damage
- Outgassing
- Overcompression
- Plasma degradation
- Thermal degradation
Download our seal failure reference guide for more information on how to avoid o-ring failure.
Prevent O-Ring Failure with the Right Rubber Supplier
Devastating o-ring failure consequences can be avoided when you know what to look for and how to prevent it. Proper material, sizing, and design selection are foundations for o-ring longevity. Correct usage and maintenance will extend the life of your o-rings. Following these general guidelines will help prevent the most common causes of o-ring failure.
Choosing the right rubber supplier makes implementing an effective o-ring failure prevention strategy easier. Manufacturer’s Rubber & Supply helps you find the right o-ring for your needs by providing the largest selection of rubber products in the Northeast. Our catalog includes metal o-rings, natural o-rings, fluoro silicone o-rings, and many other materials in all sizes. We provide sizing charts and quotes to help you select the correct o-rings for your needs. Our Parker O-Lube barium-based, and Super O-Lube silicone-based petroleum grease extends the lifespan of your o-rings. Contact our team for more information about o-ring applications, sizes, and orders.
