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Pneumatic & Hydraulic Seals

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    Pneumatic & Hydraulic Seals are crafted to protect systems that leverage reciprocating motion. Your seal prevents leakage, keeping your machinery safe from damage, so a poor choice might not only be expensive, but dangerous, too. Hydraulic seals can tolerate high-pressure environments, often relying on composite, multi-part components with integral rings. In contrast, pneumatic seals are designed for less pressurised environments, but they’re often equally demanding, particularly in systems that use higher operating speeds. Both hydraulic and pneumatic seals must tolerate axial motion, sealing in both directions if reciprocating motion is required. Bi-directional seals are most effective for this purpose, but the cut, design, and fabrication of your wear rings are equally important.

    The specifications of your seal must include just the right operating materials and dimensions. When it comes to hydraulic seals, Cotter Marketing stocks only the finest brands, assuring you of a sturdy, well-designed product. If you’re replacing seals on hydraulic cylinder systems or need a quality pneumatic seal, we’ll find just the right set of specifications for your unique application. Browse our range to find the most revolutionary products in the business.

    Pneumatic & Hydraulic Seals

    21K Wiper Seal

    ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Machined, Positive-Rake Profile, Abrasion-Resistant Wiper

    Hydraulic seals and pneumatic seals

    22K Rod & Piston Seal

    Single-Acting U-Cup for Hydraulic Cylinders/Presses

    10K Super Monoseal U-Cup

    Single-Acting U-Cup for Optimal Radial Seal Loading

    5K Wiper Seal

    ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Molded, Positive-Rake Profile, Abrasion-Resistant Wiper

    Hydraulic Seals and Pneumatic Seal Partnership Benefits

    Having the right supplier delivers all the benefits of a perfectly chosen and well crafted seal, matched to your requirements by an experienced group of specialists. Seals are key to the health of your hydraulic and pneumatic cylinders. A well-chosen O-Ring also plays a core role in ensuring flawless sealing. Your supplier is a partner who can benefit you by:

    • Keeping your system and its components safe from irreparable damage.
    • Sourcing the finest brands in the industry.
    • Giving you access to a wide range of sealing solutions that hold up in demanding environments.
    • Offering seal materials robust enough to protect your system from external contamination.
    • Keeping your hydraulic cylinder in motion using the right choice of static or dynamic seals.
    • Creating a physical barrier between housing and casing for pressures of over 1500 p.s.i.
    • Helping you to source O-Rings appropriate for use with several different mineral oils, water-based chemicals, air, and water.
    • Ensuring that your seals prevent leaks when exposed to pressure and radial or axial movement.
    • Helping to ensure that you meet ISO standards.
    • Assessing your component design details to identify the right seal for your purpose.

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    Guide to High Pressure Hydraulic Pump Seals, O-Rings, and Pneumatic Seals

    Your choice of hydraulic seal can be divided into four broad configurations, including rod, piston, symmetric, and axial. Some suit reciprocating movement systems, while others improve contaminant resistance and spike loads. Categories include:

    • Piston Seals: Radial seals that are fitted into the shaft, connecting with the housing bore with a sealing lip.
    • Rod or radial seals: Here, the seal is integrated into the housing bore using a sealing lip to sustain contact with the shaft.
    • Symmetric seals: These work well as both piston and rod seals
    • U-cups.
    • Axial Seals, which seal housing or components by sealing axially.
    • Hydraulic cylinder seals, which seal openings between components inside hydraulic cylinders.
    • O-Ring hydraulic seals, which act as toric joints between two or more parts.
    • Flange packings.
    • Hydraulic motor shaft seals, which seal motors and pumps against dirt particle exposure.

    Hydraulic seals leak from wear, so materials are as important as other design elements. They’re often made from polyurethane, rubber, and other forms of plastic. Industrial and natural rubber are robust and resistant to cracking. They can wear down, however, so polyurethane and PTFE suit some harsh environments better. Most seals resist abrasion and extreme temperatures, but every material has its own response to environmental factors.

    Silicone, for example, has poor tensile strength, but it resists extreme temperatures and is food safe. EPR is resistant against weak alkalies and acids, while neoprene functions better when exposed to ozone, ammonia, and freon. If you need high abrasion-resistance in environments that are exposed to extreme cold or heat, polyurethane may suit you best.

    Some Popular, High-Quality Seals Include:


    21K Wiper Seal

    This positive-rake wiper is able to clear away foreign matter and prevent contamination. It has a robust profile that protects against abrasive materials that would otherwise contaminate your components. The 21K performs well as a pneumatic seal and a hydraulic seal. Its wiper flange has a bump that offers static sealing.


    Chesterton 22K Rod and Piston Seal

    Like the 21K, this hydraulic seal provides static sealing. It keeps the seal stable and prevents rolling, so it’s ideal for rod and piston sealing in hydraulic applications. It has a U-cup design that can prevent all leakage across the full operating range. It’s easy to install, relying on lip geometry to prevent rolling and keep the hydraulic seal stable.


    Super Monoseal U-Cup Hydraulic Seals

    The U-cup design of the Chesterton 10K Super Monoseal takes care of radial sealing loads in high-friction environments. Rod and piston designs are offered, both of which can act as pneumatic seals and hydraulic seals. They’re highly resistant to pressure, relying on a positive-rake lip to keep contaminants from your components. This product can be manufactured in any size.


    5K Wiper Seal

    Chesterton’s 5K Wiper Seal acts as a positive-rake wiper to not only clear away foreign particles, but dislodge them, too. It’s generally used to protect retracting rods and rams and has a flared profile that protects against loose particle abrasion. Wipers can multitask as hydraulic seals and pneumatic seals.

    Chesterton is world-famous for its wide range of pneumatic and hydraulic seals, many of which are made from advanced fabrications. The brand comes with few size limitations, so they can be optimised for a huge range of applications. Chesterton has the expertise to combine just the right materials and applications for any press or cylinder across industrial markets. It relies on special geometries to address excessive clearances and offers solid U-cup pneumatic seals perfect for dated, worn equipment that has lost its original shape. If you need ease of installation, the brand also produces flexible split design hydraulic seals. Its anti-extrusion rings can be custom made in rectangular, continuous, split, and contoured designs, so no matter your needs, Cotter Marketing LTD can fulfil them.


    Frequently Asked Questions

    Why do hydraulic seals fail prematurely?

    Hydraulic seals are often exposed to heat, so they tend to become hard, which exposes them to cracks and a loss of elasticity. Excessive exposure to ozone or sunlight can cause crumbling. Extrusion occurs when rings wear down, creating gaps in mated surfaces due to excessive pressure. When the seal’s surface becomes uneven, it loses its capacity to heal. Exposure to sharp foreign matter can cause grooving and fractures. Burning and back-pressure can also cause fractures in pneumatic seals. Swelling happens when hydraulic seals absorb too much fluid. Lubrication is an important way to prevent wear, which can smooth down the face of the seal. Pneumatic seals wear down too rapidly under high temperatures and contaminant exposure.

    What is a good lifespan for hydraulic seals?

    Most manufacturers expect their hydraulic and pneumatic seals to last at least two to three years, but those with Standard API 682 specifications may last longer. Some hydraulic seals can last over eight years.

    How much leakage is acceptable in pneumatic seals?

    Even the slightest leak can be dangerous. Hydraulic fluid that’s exposed to thousands of pounds of pressure can penetrate skin and bone. Leakage in pneumatic seals can keep your system from working at all. Pneumatic systems rely on compressed air and speed to function. If water penetrates the system, it can be rendered useless.

    How can you detect a hydraulic seal leak

    In hydraulic cylinders, the rod may creep or drift as a result of leakage. Fluid will bypass the piston seal and your cylinder may lose the ability to hold its usual load. Air leaks can cause rattling or prevent your system from working entirely.

    Which lubricants should you use on hydraulic seals?

    The market is well-populated by proprietary lubricants, each with their own components and properties. Every material has its own ideal lubricant. Rubber pneumatic seals work well with a silicone lubricant or grease. High-viscosity silicone oil works well with most seal materials. It doesn’t swell or soften rubber the way hydrocarbons do, but it can’t be used on silicone pneumatic seals. Mineral oil and water glycol are anti-rust and excellent kinematic viscosity, so they can prevent friction and premature wear. Water-glycol is an eco-friendly alternative that comes at a low price, but it corrodes steel.

    What causes lapped seal faces to open?

    Open seal faces are usually caused by clogging in movable components. Pneumatic seals must move freely if they’re to maintain their shape. If the film on sliding components changes state, it can result in a lapped face. Vaporised or crystallised films can be highly destructive.


    Cotter Marketing is large enough to present a huge range of hydraulic and pneumatic seals, but small enough to provide personal service. We’ve been in business since 1973, so we bring a wide berth of knowledge to the table. Never satisfied with stasis, we constantly improve our services. As the only Irish distributors of several globally-recognised brands, we deliver only the finest hydraulic and pneumatic seals to diverse industries, from power generation and mining to food processing and pharmaceutical manufacturers. Whether you are looking for a variety of pumps or anything from gaskets and joint seals to industrial lubricants and mechanical seals, Cotter Marketing can provide what you need at a competitive price point.

    Simply get in touch with our team and we can help you source the industrial products and equipment you need to get the job done.