What Are the Parts of Mechanical Seal

Confusion about mechanical seal parts can lead to costly downtime, premature failures, and even safety hazards. Don’t let a lack of knowledge hold your operations back.

In this blog post, we’ll break down the key parts of a mechanical seal, from the primary sealing faces to secondary seals, springs, and more. By the end, you’ll have a solid understanding of how these components work together to keep your equipment running smoothly.

Primary Sealing Faces

The primary sealing faces are the heart of a mechanical seal. They consist of two flat, annular surfaces – one rotating and one stationary – that are pressed together by springs to create a seal.

Rotating Seal Face

The rotating seal face is attached to the shaft and rotates with it. It is typically made from a hard material like silicon carbide, tungsten carbide, or carbon graphite. The rotating face must withstand the friction and wear of constant rubbing against the stationary face.

Stationary Seal Face

The stationary seal face is mounted in the seal gland and remains static. It is usually made of a softer material compared to the rotating face, such as carbon graphite, glass/graphite filled PTFE, or nickel-bound tungsten carbide. The stationary face is pressed against the rotating face by the spring force.

Secondary Seals

Secondary seals prevent leakage between the stationary parts of the seal and the pump housing. They are usually O-rings, wedge-shaped rings, or V-rings made from elastomeric materials like FKM, EPDM, or PTFE. The secondary seals also accommodate any shaft misalignment or axial movement.

Springs

Springs provide the mechanical force to keep the sealing faces in contact. They are usually made from corrosion resistant materials like Hastelloy or Elgiloy, and are available in different designs like coil springs, wave springs, or bellows. The spring force must balance with the hydraulic closing force to maintain proper sealing.

Gland Plate

The gland plate is the stationary part that holds the seal assembly in the pump housing. It is usually made from stainless steel or other corrosion resistant alloys. The gland has ports for flushing or cooling the seal faces and for collecting any leakage.

Shaft Sleeve

The shaft sleeve covers and protects the pump shaft in the sealing area. It provides a smooth running surface and prevents damage to the shaft. Shaft sleeves are typically made from hardened stainless steel and are either press-fit or bonded to the shaft.

Drive Mechanism

The drive mechanism transmits rotational force from the shaft to the rotating seal parts. It can be lugs, pins, set screws, or keys. The drive must accommodate any shaft thermal expansion or axial movement.

Retainer

The spring retainer holds the springs in place and transfers the spring force to the sealing faces. It is normally made of the same material as the gland plate to avoid galvanic corrosion.

Wear Rings

Some mechanical seals have wear rings that absorb any friction between the rotating shaft and the stationary seal gland. Wear rings save the more expensive metal parts from damage. They are made from softer materials like filled PTFE and are easy to replace.