Question 1

What are Rotary Seals or Shaft Seals?

Accepted Answer

Rotary Seals also referred to as Shaft Seals, Oil Seals, or Lip Seals. Are designed to stop external contamination such as dirt, dust, water, and hazardous contaminants, from entering the moving parts, while retaining lubricant in the rotary applications.

The sealing effect is achieved by a garter spring which is normally used to ensure a constant force on the shaft. Rotary shaft seals are used between rotating and static machinery components.

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How Do Rotary Seals or Shaft Seals Work?

A rotary seal includes a sealing lip, a garter spring, and an external metal case. The sturdiness of the metal forms a rigidity and firm fix to the connecting components. The lip seal conducts the actual sealing function while the garter spring offers the required flexibility of movement. For vacuum applications rotary seals are designed differently and do not include a spring.

The basic design of the seal can be customised to suit specific requirements. These seals are extremely versatile and can be made of a variety of materials ranging from hard metals to plastic. The most common materials are steel, brass, silicone rubber, and EPDM.

Types Of Rotary Shaft Seals

There are different types of rotary shaft seals, each with its own specific design and materials. Some common types include:

Radial Lip Seals: These are the most common type of rotary seals. These seals are used in applications where the sealing surface is rotating relative to the housing. For low to high-speed applications, radial lip seals are designed in a wide variety of materials to best suit different fluids and temperature requirements.

V-Ring Seals: These are used for shafts that rotate in both directions. These seals are made of elastomer or rubber to prevent contamination from entering the shaft area and can handle high-speed applications.

Mechanical Seals: Mechanical seals are designed to seal against the rotating shaft using two flat surfaces. These seals can be made from a variety of materials including ceramic, carbon and metal and are typically used in high-pressure applications where a high degree of sealing is required.

Labyrinth Seals: Labyrinth seals are designed as a non-contact type of rotary seal which uses a series of grooves to create a curvy or tortuous path for the fluid or gas to flow through. These seals are effective at preventing contamination from entering the shaft area and are usually used in high-speed applications where there is a risk of fluid leakage.

Gland Packing Seals: They are typically used to seal a rotating shaft where the shaft passes through a stationary housing or casing, such as in a pump or a mixer. The packing material used in gland seals can be made of various materials such as graphite, PTFE, aramid fibre and carbon.

Choosing the Right Rotary Shaft Seal

For the proper functioning of applications, choosing the right rotary shaft seal is important. Several factors can affect the performance of rotary shaft seals, including:

Temperature: The performance and longevity of rotary shaft seal, can be affected by the operating temperature of the application, so choosing the right seal material is crucial.

Pressure: The pressure of the fluid being sealed can also affect the performance of rotary shaft seal, so it is essential that the seal chosen can withstand the pressure.

Speed: It is important to choose a seal that is designed for the appropriate speed range, so that the speed at which the shaft is rotating does not affect its performance.

Fluid type: Different fluids have different chemical properties that can affect the performance of the seal.

Benefits of Rotary Shaft Seals

Leakage Prevention: The primary function of a rotary shaft seal is to prevent leakage of fluids (such as oil, grease, or hydraulic fluid) from the housing or chamber where the shaft is rotating. By effectively sealing the gap between the rotating shaft and the stationary housing, these seals ensure that fluids stay contained within the system, reducing wastage and potential environmental hazards.

Contamination Protection: Rotary seals not only keep fluids in but also prevent external contaminants, such as dirt, dust, water, and other particles, from entering the system.

Friction Reduction: Using a well-designed rotary shaft seal can help minimise friction between the rotating shaft and the stationary housing and prevent wear on internal components, improving efficiency and reducing energy consumption.

Versatility and Reliability: Rotary seals come in various materials and designs suitable for different applications and operating conditions. They can be customised to manage a wide range of temperatures, pressures, speeds, and fluids.

Applications of Rotary Seals

Pumps: Rotary seals are used in pumps to prevent leakage of fluids such as water, oil, and chemicals.

Marine Applications: Used in applications such as propeller shafts, rudder shafts and thrusters to prevent leakage of seawater.

Food and Beverage Industry: Used in various food and beverage equipment to prevent contamination and ensure hygiene standards.

Pharmaceutical Industry: Used to prevent contamination and ensure product integrity.

If you require any further advice regarding Rotary Shaft Seals and their applications, our knowledgeable team at FPE Seals would be happy to help.

We stock, source, and supply a range of Rotary Seals. Can’t find what you’re looking for? We can also manufacture seals to your specification, in a full range of materials to meet your exact requirements.

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Question 2

How do Swivel Joints Work?

Accepted Answer

The Swivel Joint, also known as the Rotary Coupling, Rotary Union, Swivel Union, Rotorseal, and Rotary Joint, plays a key role in controlling hydraulic circuits on an excavator.

Excavators use many hydraulic moving parts, to help manoeuvre the mechanical arm, reposition the bucket, adjust the digging angle, and control the tracks or wheels.

This requires different hydraulic circuits,

Upper: Mechanical arm elements
Lower: Tracks or wheels

The swivel connects the two together through a central shaft, to avoid a mass of twisted, tangled, or torn parts. Holes bored into the shaft allows fluid to flow through the swivel to its targeted cylinder, and as the centre shaft moves independently without restricting fluid flow, both upper and lower elements can move in different directions.

Typical design of a Swivel Joint

All swivels are not the same and will vary based on the number of mechanical elements on the upper moving section. Swivel joints can require anything from 3 to 10 seals to function correctly.

FPE Seals offer a wide range of competitively priced, OEM quality replacement seal kits for the repair and maintenance of swivel joints on excavators. Find out more here or contact the team to discuss your requirements.

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What are hydraulic seals?

Why do we need seals?

Types of hydraulic seals

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What are Rotary Seals or Shaft Seals?

How do Swivel Joints Work?

What are hydraulic seals?

Why do we need seals?

Types of hydraulic seals

What to read next...

What are Rotary Seals or Shaft Seals?

How do Swivel Joints Work?

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