What Is a Labyrinth Seal and How Does It Work

Leakage of fluids and gasses in rotating machinery can lead to catastrophic failure and downtime. Labyrinth seals effectively control this leakage in turbomachinery by creating a tortuous path to limit fluid flow. These non-contacting seals consist of a rotating element with teeth and a stationary element with cavities that work together to significantly reduce leakage.

This blog post provides a comprehensive overview of labyrinth seals, explaining their function, key components, and the different types available.

What Is a Labyrinth Seal

A labyrinth seal is a type of non-contacting mechanical seal used to control leakage and reduce wear in rotating equipment such as turbines, compressors, and pumps. It consists of a series of intricately designed grooves or channels that create a tortuous path for the fluid or gas, effectively restricting flow without direct contact between the rotating and stationary components.

How Labyrinth Seals Work

The primary sealing mechanism in a labyrinth seal relies on the creation of a series of pressure drops as the fluid navigates through the complex maze-like passages. As the fluid enters the labyrinth seal, it encounters a series of alternating teeth or fins on the rotor and stator surfaces. These teeth are precisely machined to maintain a small clearance between the rotating and stationary components. As the fluid flows through the narrow passages, it experiences sudden expansions and contractions, leading to turbulence and fluid shear.

The repeated changes in flow direction and the accompanying turbulence cause the fluid to lose velocity and pressure at each labyrinth stage. This pressure drop creates a sealing effect, minimizing the amount of fluid that can leak through the seal. The more intricate the labyrinth path and the higher the number of sealing stages, the greater the sealing efficiency.

Components of a Labyrinth Seal

Rotating Element (Rotor)

The rotor is the dynamic component of the seal, typically attached to or integrated with the rotating shaft. It features a series of projections or teeth that extend radially outward, forming one side of the labyrinth path.

Stationary Element (Stator)

The stator is the non-rotating part of the seal, usually mounted within the equipment housing. It incorporates corresponding grooves or channels that match the rotor’s profile, creating the intricate labyrinth path.

Types of Labyrinth Seals

Straight-Through Labyrinth Seals

In this design, the teeth or fins on the rotor and stator are aligned in a straight path, perpendicular to the axis of rotation. As the fluid passes through each constriction created by the teeth, it experiences a pressure drop and velocity increase, reducing leakage. Straight-through designs are simpler to manufacture and are suitable for applications with lower pressure differentials.

Stepped Labyrinth Seals

Stepped labyrinth seals feature teeth or fins that are offset from one another, creating a more tortuous path for the fluid to navigate. The fluid must change direction multiple times as it passes through the seal, further reducing its pressure and velocity. This design provides better sealing performance compared to straight-through seals and is preferred for applications with higher pressure differentials or more stringent leakage requirements.

Material of Labyrinth Seals

1. Torlon PAI (Polyamide-imide): Torlon PAI is a high-performance thermoplastic with excellent mechanical strength, stiffness, and thermal stability. It offers good resistance to wear, creep, and chemical attack, making it suitable for labyrinth seals in demanding environments. Torlon PAI labyrinth seals can operate at temperatures up to 275°C (527°F) and are commonly used in aerospace, oil and gas, and chemical processing industries.
2. PEEK (Polyetheretherketone): PEEK is a semi-crystalline thermoplastic known for its exceptional mechanical properties, chemical resistance, and thermal stability. Labyrinth seals made from PEEK can withstand temperatures up to 250°C (482°F) and provide excellent wear resistance. PEEK seals are often used in high-temperature, high-pressure, and chemically aggressive environments, such as those found in the oil and gas, chemical, and aerospace industries.
3. Vespel PI (Polyimide): Vespel PI is a high-performance polyimide material that offers outstanding thermal stability, chemical resistance, and dimensional stability. Labyrinth seals made from Vespel PI can operate at temperatures up to 300°C (572°F) and provide excellent wear resistance and low friction. These seals are commonly used in aerospace, semiconductor, and high-temperature industrial applications.
4. Fluorosint (Enhanced PTFE): Fluorosint is an enhanced polytetrafluoroethylene (PTFE) material that combines the low-friction and chemical resistance properties of PTFE with improved mechanical strength and wear resistance. Labyrinth seals made from Fluorosint can operate at temperatures up to 260°C (500°F) and provide excellent sealing performance in chemically aggressive environments. These seals are often used in chemical processing, food and beverage, and pharmaceutical industries.