What is Mechanical Seal?
A mechanical seal is a device that is used to provide seals at the entry or exit point of a rotating shaft. It is a vital component in the centrifugal pump systems. This device preserves the pump systems’ integrity by keeping contaminants out and preventing fluid leaks. The mechanical seal is widely used on different seal designs to lubricate secondary seals, control seal environment, and detect leakage.
The mechanical seal consists of rotary seal face, stationary seal face, and integral stuffing box cover. Depending on the variable processes and pump types, there are different types of mechanical seal to choose from. Each seal type has its special characteristics and design that make them suitable for specific applications.
Different Types of Mechanical Seals
The balanced mechanical seals are specifically ideal to higher operating pressures, commonly above 200 PSIG. These seals are also perfect when handling higher volatility and low lubricity liquids.
This type of seal exhibit minimal product leakage due to the face film that has tighter control. The unbalanced mechanical seal is a perfect option for more complicated balance seal.
The pusher mechanical seal has one or more springs to keep the seal closing forces. It can provide higher pressure sealing and has a drawback to the primary seal face elastomer.
The non-pusher mechanical seals utilize an elastomer or metal bellow to sustain seal closing forces. This type of seal is perfect for high temperature and dirty applications.
The conventional mechanical seals are commonly inexpensive. They are frequently installed on extensive service equipment.
The cartridge mechanical seals integrate different seal elements into one assembly. They can reduce the potential error for assembly and time needs for seal replacement.
Mechanical Seal Design
A basic mechanical seal design is composed of 7 components, such as:
- Stationary Component
- Stationary Component Sealing Member
- Rotating Component
- Rotating Component Sealing Member
- Spring
- Gland Plate
- Clamp Ring
Sealing Points of Mechanical Seal
The mechanical seals have 4 primary sealing points, including:
- The seal between stationary and rotating faces, known as a primary seal.
- The seal between stuffing box face and stationary member, such as gasket.
- The seal between the shaft sleeve and rotating member, known as a secondary seal.
- The seal between the stuffing box and gland plate, usually, o-ring or gasket.
Why Use Mechanical Seal?
- No visible leak
- Can’t damage the sleeve or pump shaft
- Less maintenance as seals has inboard springs
- The mechanical seal has lightly loaded faces that consume minimum power
- Lessen bearing contamination in normal operation
- Less corrosion
- Can seal a vacuum
- Less clean-up of the area
- Up to 20 years life warranty
Features of Mechanical Seals
This seal is pre-assembled components of mechanical seals. It makes easier installation and prevents the possible error occur in the mechanical pump seal installation.
Seal pots are needed in the mechanical seals to provide a buffer fluid for dual cartridge seals. They can provide not just a lubricating buffer but they also provide cool or heat barrier fluid.
