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Hydraulic Cylinder Seals: The Different Types and their Application 

hydraulic seals next to a timing belt

Hydraulic cylinders play a vital role in multiple industries, including aviation, civil engineering, construction, and manufacturing. Hydraulic cylinder seals, which block fluid in these machines, are needed to keep the cylinders running properly but should be replaced periodically, as they can wear out due to continual use. If a cylinder registers a drop in hydraulic pressure, overheats, begins shaking more than normal, or starts making loud banging or clunking noises, it’s wise to check the seals for signs of damage. Leaking is yet another sign that a cylinder may be broken or damaged.

What are Hydraulic Seals Used for?

Hydraulic seals serve multiple purposes. Some cover the gap between two surfaces to prevent fluids from getting past a joint. Others prevent fluid from entering the piston head and stop fluid from leaking from the cylinder. Some types of hydraulic seals can also prevent contaminants from entering the machinery.

What to Consider When Choosing a Seal

There are many types of hydraulic seals to pick from. While some may be arguably better than others, in most cases choosing a hydraulic seal is a matter of identifying which type of seal would be best for a particular cylinder. Following are some points to consider to ensure the seal is a good match for the device in question.

Material Compatibility

Hydraulic seals can be made from various materials. A company that needs a new seal will want to make sure the material chosen is compatible with the cylinder in question. A seal that isn’t compatible with the cylinder or the workload may shrink or break, which could damage other parts of the cylinder.

Pressure Rating

The pressure rating on the seal will play a large role in determining how the hydraulic cylinder can be used. Medium-pressure seals have a PSI ranging from 150 to 500 and can be ideal for low-pressure use. High-pressure seals may have a PSI of up to 10,000. When choosing a seal, bear in mind that most seals can’t operate at their upper pressure and speed ratings at the same time.

Temperature Range

The temperature range varies depending on the seal chosen. Typical options include seals that can handle from -50°C to 120°C (-60°F to 250°F) and seals that can handle from -40°C to 200°C (-40°F to 400°F).

Size and Dimensions

Hydraulic cylinder seals come in various sizes, and it’s not hard to find ones to fit standard devices. However, it can be challenging to find the right seal for a custom device. If you aren’t sure about the right seal size or dimension for your device, you can measure it with a tape measure and calipers.

Chemical Resistance

Fluid compatibility is important when choosing a new seal. Some may be able to handle water but not mineral-based oils. Others may be incompatible with synthetic and/or fire-resistant fluids.

Keep temperature ranges in mind when determining chemical resistance, as a seal that may be compatible with a liquid at room temperature may not be able to handle that same liquid in extreme cold or heat.

Types of Hydraulic Seals Found in Auto Equipment and Lifts

Piston Seals

Piston seals come in multiple materials and different sizes. They are designed to prevent fluid and other media from bypassing the piston. Piston seal options include lip seals, compact-squeeze seals, and application-specific designed seals.

Rod Seals

Rod seals ensure pressurized fluid won’t leak out of a system. They are also available as uni-directional seals that only seal pressure from a single side. Rod seals are available as lip seals, PTFE cap seals, compared squeeze seals, and application-specific design seals.

Wiper Seals

Wiper seals can not only prevent fluid leakage but also stop contaminants from entering the shaft mechanism. There are snap-in and press-in wiper seals as well as seals designed to keep out certain pollutants. Options include dust and particle exclusion seals, dry rod operation seals, and low friction system seals.

Buffer Seals

Buffer seals are bi-directional. They seal most of the rod while allowing some fluids to pass through to the secondary rod seal. They also pump fluid from the secondary rod seal back into the system and protect the main rod from the effects of shock pressure loading.

U-Cup Seals

U-cup seals get their name from their U-shaped design. They typically have an outside static sealing lip and an inside dynamic sealing lip. There are also O-ring loaded U-cup seals (also known as loaded lip seals and PolyPaks) and these are ideal for users who need optimum sealing performance at low pressures.


O-ring seals are designed to stop the passage of gasses and liquids. They can be shaped like a donut or torus and are one of the most common seal options on the market. They can be purchased in just about any size and you can install them on your own or using a cylinder seal kit.

Vee Packing Seals

Vee packing seals are designed to prevent leaks. They have multiple lips and many have both a male and female adapter. These seals are ideal for use in medium to heavy-duty devices and can be used with either single or double-acting cylinders.

Wear Rings and Guide Rings

Wear rings and guide rings are used in cylinders to prevent certain parts of the cylinders from coming into contact with each other. They typically have a longer lifespan than seals.

What Materials Are Used in Hydraulic Seals?

Seals can be made from multiple materials. Common ones include polyurethane, rubber, engineered thermoplastics, nitrile, silicone, and Polytetrafluoroethylene (PTFE).

Finding A Reliable Parts Provider for Your Needs

Seals may be small, but they play an integral role in keeping a hydraulic cylinder operating as it should. Failure to notice and replace a damaged seal on time can not only cause equipment problems but also pose environmental hazards. That’s why companies throughout the United States turn to SVI to find the seals, seal kits, and other products they need. Our warehouse stocks over 40,000 products, offers ideal pricing programs, and has two ready-ship warehouses to ensure fast shipping to any destination. Get in touch with us to find out more about our products, special offers, shipping times, and more.

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