Hydraulic seals are an integral component of most hydraulic systems. Usually made of a soft, flexible elastomer that provides exceptional water and air sealing capabilities, hydraulic seals are ring-shaped and primarily designed to eliminate or limit the leakage of fluid moving within a hydraulic or pneumatic system. Hydraulic seals also play important roles in excluding contaminants from and appropriately pressurizing the overall hydraulic system. Read More…
At Gasket & Seal Fabricators, Inc., we take pride in our extensive expertise in the design and manufacturing of high-quality gaskets and seals, particularly specializing in hydraulic seals. Our commitment to excellence drives us to deliver reliable solutions that meet the diverse needs of our clients across various industries. Our product range includes an array of hydraulic seals designed to...
Southern Rubber Company, Inc. was chartered in 1925 as the Carolina’s pioneer rubber company. The primary focus in the early years was oil jobber supplies, automobile tires, hoses and belts. As more industries located in the South, Southern Rubber Company, Inc. began to diversify, and replaced their automobile products with industrial rubber products including hose, gaskets and seals.
Kent Rubber Supply has been a trusted supplier of hydraulic seals since 1946. Focusing in exceeding customer service, we leverage the best equipment and the most knowledge staff to ensure we meet our customers unique needs. With our trusted experts, we determine the best rubber, foam, sponge or PVC material for your specific need. We continue serving customers both offshore and domestic.
Our list of inventory has grown since our founding over 20 years ago. We started small, but now offer an extensive product list of hydraulic seals, o rings, and other rubber products.
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Production
Hydraulic seals are typically crafted from elastomers and polymers—both natural and synthetic—known for their weak molecular attraction and exceptional elasticity. The primary materials used for hydraulic seals include rubber and plastics like PTFE (Teflon) and polyurethane. Other elastomers employed in seal production are butadiene, nitrile, butyl, and silicone. Most seals made from these elastomeric materials are produced through extrusion, while Teflon seals are uniquely sintered from powder form in an oven.
Seals can also be crafted from non-elastic materials like felt and leather. Certain hydraulic seals, such as bonded seals, utilize metallic components including brass, bronze, aluminum, carbon steel, and stainless steel. These metals may be plated or galvanized to enhance their resistance to oxidation and increase their durability. In bonded seals, a chemical bond forms between the rubber material and the metal, ensuring a strong adhesion.
Hydraulic Seal – Allied Metrics Seals & Fasteners, Inc.
Major Types and Operations
Hydraulic seals are commonly used in hydraulic cylinders, which are mechanical actuators that transform hydraulic pressure—from oil, water, or other pressurized fluids—into unidirectional force. These cylinders are essential for agriculture and forestry vehicles, construction equipment, and various other machinery.
They are typically positioned on the cylinder head, rod shaft, or within the piston. In these critical locations, they effectively prevent fluid from leaking between the rod and head, escaping to the outside of the cylinder, or flowing across the piston.
Hydraulic seals are divided into two main groupings: static and dynamic.
Static seals are commonly positioned in grooves and confined spaces, functioning as gaskets. Here, a gasket refers to a mechanical seal that fills the gaps between stationary mating surfaces, secured by the pressure from tightened bolts. While the number and specific locations of static seals vary depending on the cylinder structure, their primary role is to close the gaps between immobile surfaces. Static seals can be categorized into axial and radial types. Axial static seals are compressed between their top and bottom surfaces to create a secure seal, whereas radial static seals achieve the same effect by being compressed between their inner and outer surfaces.
Dynamic seals, also known as shaft seals, effectively close gaps between two surfaces that experience relative motion. They accommodate various types of motion, including reciprocation, oscillation, and rotation.
Reciprocating dynamic seals are positioned within glands that accommodate relative movement, traveling along an axis between inner and outer surfaces. These seals are commonly employed to power linear actuators, hydraulic cylinders, and pistons in internal combustion engines.
Oscillating seals work with shafts that turn through a limited range of motion around their axis. Due to the frequent rotation of these shafts, oscillating seals are typically crafted from durable materials and feature self-lubricating properties.
Rotary seals are installed where rotational motion occurs between a hydraulic device’s housing and shaft.
Main Types of Hydraulic Seals
The function of a hydraulic seal can vary slightly based on its position relative to the hydraulic cylinder. The most prevalent types are piston seals and rod seals. Both of these seals feature a flexible lip that makes contact with the housing or shaft, enhancing the seal’s effectiveness during linear motion. Collectively referred to as lip seals, piston and rod seals play a crucial role in ensuring the smooth operation of rotating equipment and machinery.
Piston seals play a crucial role in preventing fluid leakage or flow across the piston. Most piston seals are single-acting, focusing pressure on one side of the piston. This pressure build-up allows the piston to move smoothly within the cylinder and enables the cylinder to operate with maximum mechanical efficiency. As a result, dynamic piston seals are vital for the effective functioning of hydraulic systems. Double-acting piston seals, on the other hand, apply pressure to both sides of the piston, driving the attached ram. In contrast, static piston seals address the gap between the piston and the piston rod, rather than between the piston and the cylinder bore.
Rod seals are designed to stop external fluid leaks from cylinders. Typically single-acting, they are often complemented by a secondary rod seal for enhanced performance. Dynamic rod seals operate within the space between the piston rod and the cylinder head, while static rod seals close the gaps between the cylinder head and the cylinder bore. Beyond containing hydraulic fluid within the cylinder, rod seals also help regulate lubrication for the rod, the wiper seal, and the rod seal itself.
Hydraulic cylinders often feature various common types of seals. Rod wipers, sometimes called scrapers or wiper seals, prevent contaminants from entering the cylinder. These contaminants, such as dirt and moisture, can compromise the cylinder’s performance. As the wiper seals retract into the cylinder, they effectively remove these foreign particles.
Buffer seals improve rod seal performance by acting as a protective barrier against excessive internal fluid pressure. Additionally, they safeguard the rod seal from contaminants, like metal chips, that might infiltrate the cylinder.
Guide rings, often referred to as wear rings, fulfill a dual role: they center the piston and piston rod, guiding them through the cylinder and preventing metal-on-metal contact. These rings are installed at both the rod and piston positions within a hydraulic cylinder.
O-rings stand out in this list because their identification relies mainly on their shape rather than their function or location. True to their name, O-rings are donut-shaped and are available in a range of materials such as rubber, silicone, and fluorocarbon, as well as sizes from under an inch to several meters in diameter. When subjected to mechanical deformation from pressure, O-rings form highly effective sealing barriers. Their affordability and simplicity make them the most prevalent type of hydraulic seal available today.
There are also more specialized hydraulic seals.
Oil seals, known as metric oil seals internationally, are designed to withstand repeated exposure to hydraulic oil without breaking down or malfunctioning. Made from durable materials like polyacrylate, silicone, Teflon, and various fluoroelastomers, these oil seals effectively prevent leaks while retaining lubricants in rotary applications.
Metallic bonded seals are characterized by the way they are stuck to metal washers.
X rings, also known as quad or square rings, represent an advanced iteration of O-rings. With their four-lobed configuration, X rings deliver up to twice the sealing effectiveness of traditional O-rings while minimizing mechanical deformation. They are versatile enough to serve both static and dynamic sealing applications.
Applications
Hydraulic seals play a crucial role in maintaining the efficiency of hydraulic systems, making them essential across various industries. They are utilized in aerospace manufacturing, agriculture, automotive production, chemical processing, defense contracting, food processing, marine product manufacturing, medical and pharmaceutical development, nuclear power, pulp and paper industries, and waste disposal.
They are integral to a wide array of industries, each with its own unique set of applications. These seals play a crucial role in construction equipment, agricultural machinery, brake systems, clean rooms, conveyors, mixers, presses, valves, and testing equipment.
Certain hydraulic seals are designed for highly specialized applications. In the aerospace sector, custom seals like silicone sealant strips are essential for sealing hydraulic components in aircraft systems. In the electronics industry, seals such as EMI shielding gaskets are crucial for blocking unwanted electromagnetic interference in various devices.
Considerations
When choosing the right hydraulic seal solution, it’s crucial to consider more than just its ability to prevent fluid leakage. Hydraulic seals perform multiple essential functions and require proper maintenance to work effectively. Therefore, selecting a seal should involve evaluating the overall operating conditions of your hydraulic system. Aim to choose a seal that excels under these specific conditions, rather than focusing solely on its sealing capabilities.
An essential consideration is the space where the hydraulic seal will be used. This will influence the diameters of both the inner and outer seals, the housing bore, and the outer shaft dimensions. Additionally, it’s crucial for stakeholders to determine whether their application needs an axial or radial cross section and its corresponding diameter.
Additionally, those buying hydraulic seals should consider the vacuum rating, operating temperatures, chemical compatibility with the hydraulic fluid, maximum and minimum working speeds, and pressure ranges.
Consider a hypothetical scenario where we choose O-rings, taking various factors into account. One key characteristic to evaluate is the compression set, which indicates how well an elastomer returns to its original thickness after being compressed. This property is influenced by temperature changes, hydraulic pressure variations, and the specific fluid the O-ring interacts with. For example, very high operating temperatures might lead to significant swelling of the O-ring, necessitating a larger “housing” within the cylinder to accommodate this expansion.
It’s important to recognize that while all hydraulic seals play a crucial role, not all of them carry the same level of importance. Prioritizing which seals to use and how to apply them is essential. Maintaining internal pressure and preventing contamination are the top priorities for ensuring a hydraulic cylinder operates effectively, as contamination is the primary cause of hydraulic system failure. Therefore, the rod and wiper seals are especially vital because they help maintain internal pressure and keep contaminants out.
With the right considerations in mind, operators across all industries can anticipate dependable and efficient sealing solutions. It’s crucial to find an experienced and reliable hydraulic specialist or supplier to assist in the seal selection process. Top hydraulic suppliers provide services such as custom sealing materials, comprehensive documentation for various seals, and guidance on optimal operating conditions.
