Hydraulic Seal Buying Guide

Hydraulic Seal Buying Guide

Graham ScuttFeb 5, '19

Are you wondering “which hydraulic seal is right for my needs?” This comprehensive guide gives you information on a wide range of seals, helping you always choose the right one for your project.

Hydraulic seals come in a variety of shapes and sizes, but more importantly are specially developed to accommodate different cylinder speeds, temperatures, applications and materials.

Made to be placed in a groove or within a combination of rings to form a seal that prevents leakage in a hydraulic application, they are a critical component to keep machinery safe, secure and free from damage.

Hydraulic Seal Materials

In order to maximise longevity and functionality in specific applications, hydraulic seals are made from a wide range of materials, each with their own specific properties. Based on criteria such as operating temperature, chemical interactions, pressure and fluid types, manufacturers select the materials that can handle each environment best.

The most common materials for hydraulic seals are Polytetrafluoroethylene (PTFE), rubber and polyurethane.

Static vs. Dynamic Hydraulic Seals

There are two styles of hydraulic seals that can be used in certain applications. Selecting the right type of seal for the style of application is vital to ensuring that your hydraulic application runs smoothly and is free from leakages.

Static hydraulic seals are essentially gaskets for hydraulic systems. They seals sit directly within a groove and create a seal in a confined space, not moving at all.

Dynamic hydraulic Seals are placed within a hydraulic operating system that is in motion. These seals are used to create a sealing system in a wide range of hydraulic components, including the shaft, pistons and bore of hydraulic cylinders.

Different Styles and Uses of Hydraulic Seals

Piston Seals

Piston seals are dynamic hydraulic seals that are used to prevent the passing of any fluid past the piston, as the system pressure forces the piston down the cylinder in a hydraulic system.

Single-acting piston seals only have to block the pressure from one side of piston, retaining the pressure which powers the piston to move along the cylinder.

Double-acting pistons require pressure from both sides to force the piston along the bore, meaning that in order to properly seal them you must use a double-acting seal that can seal the dynamic pressure from both sides.

Types of Piston Seals:

PCA Piston Seals: Made for one-piece pistons, these double acting seals are intended to be wear-resistant in light and medium duty applications.

PCQ Piston Seals: Made from a blend of polyurethane and NBR, the elastic material and small housing needed to fit the seal made it easy to implement.

PCR Piston Seals: A double-acting seal, the mechanical strength and thermal stability make them perfect for one piece pistons.

PEE Piston Seals: Using polyester anti-extrusion and POM bearing rings, these double-acting NBR seals are ideal for sealing one piece pistons.

View our piston seals here

Rod Seals

Rod seals are vital to maintaining an efficient hydraulic system, as they are responsible for both preventing fluid leakage from within a hydraulic cylinder and protecting it against dirt and other exterior contaminates.

Static seals that installed directly into the housing or glands of a system, rod seals are designed to provide dynamic sealing pressure while the piston rod is in dynamic motion.

Types of Rod Seals:

RFD Rod Seals: Also known as Single Acting Split Housing, these are heavy duty seals that also include an anti-extrusion ring for added protection. Made from rubberized fabric, the seal is simply added to the housing of a sealing area where it reduces friction and wear, keeping applications sealed and secure from harmful fluid leakages.

RTA Rod Seals: These Single Acting seals are used in hydraulic cylinders that have small groove dimensions. Fitted into the small housing, the RTA seals are combined with an NBR O-ring and PTFE inner to maximize sealing resistance against even the highest pressure.

RUB Rod Seals: Made for sealing piston rods, these Single Acting seals include an additional O-ring profile that lubricates and resists abrasions. RUB seals made from Polyurethane are most effective, including a 300 BAR resistance which is suitable for high-pressure systems.

View our rod seals here

Wiper Seals

Also known as scraper seals, they are often used together with other sealing components to let a ram rod pass through the inner bore of a seal, while preventing leakage.

Wiper seals are extremely important in ensuring that outside contaminants are kept out of hydraulic operating systems. By keeping everything from dirt to moisture outside of the system, scraper seals prevent any damage to rods, cylinder walls, seals and other important elements of the system.

When the wiper seals are not secured or fail, it can cause component failure in a fluid power system that leaves other pieces of the operation open to serious damage.

Most wiper seals are made from polyurethane and include a secondary lip that is used to catch any oil that has seeped past the main seal. The lip can also scrape any contaminants from the rod surface, giving them the title of “double-edged wiper seals”.

Types of Wiper Seals:

WRB Wiper Seals: These Medium Duty scraper seals have a special lip that help prevent moisture and dirt from accumulating on the rod. Made from an NBR compound, the seals are inserted directly into a grooved housing to provide a full seal in the system.

WRC Wiper Seals: Also including a lip, WRC seals do not extend past the cylinder cover. They are used in Medium Duty applications and can be installed into a simple groove design. Visit our range of WRC wiper seals here.

WCA Wiper Seals: Featuring a corrosion-resistant metal ring that encompasses the NBR seal, these Heavy Duty seals follow the side movement of the rod to keep it free from heavily deposited dirt.

WDA Wiper Seals: These double-function seals use the lip to prevent contaminants from building up, yet also have an additional element that prevents scoring on a seal. Used in Heavy Duty systems, WDA scraper seals can extend the service life of the seal by keeping them free from dirt, moisture and damage.

Wear Rings

Used in both piston and rod applications, wear rings keep pistons centered to allow for even pressure distribution on the sealing system.

Installed on the pressure side of the rod seal or on the opposite side of the piston to the rod, wear rings provide the opportunity for full extension and increased leveraging for both bearing surfaces.

Wear rings are often used in heavy duty hydraulic systems that operate under extreme pressure and temperatures. They can also be used in pneumatic applications that require low-friction, as their self-lubricating properties will increase the lifespan of the application.

Wear rings can be manufactured from a variety of materials including glass-filled PTFE, bronze-filled PTFE and glass-filled Nylon.

Types of Wear Rings:

Straight Cut Wear Rings: Also known as Butt Cut wear rings, they are the most suitable and easiest wear rings in most applications, as they are easily added to any system with rotary movement.

Angle Cut Wear Rings: Best suited for reciprocating movement systems, angle cut rings are designed to limit bearing stress at the gap and protect both rods and piston components.

Step Cut Wear Rings: Able to offer improved resistance to contaminants and spike loads, step cut rings both improve the bearing stress at the gap while also offering the highest level of performance in piston and rod applications.

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Get Expert Advice on Hydraulic Seals

Adding the proper hydraulic seal to your application can make all the difference between a safe, secure and long-lasting system or a failed seal that can cause irreparable damage to your components.

Contact us if you need advice.