Question: What is a Type 21 mechanical seal?
A Type 21 mechanical seal is a specific type of single mechanical seal that is commonly used in centrifugal pumps. It consists of a rotating seal face that is attached to the pump shaft and a stationary seal face that is mounted on the pump housing. The two faces are pressed together by a spring and create a seal that prevents the fluid from escaping.
The stationary seal face in a Type 21 mechanical seal is typically made of carbon or ceramic materials, while the rotating seal face is usually made of a harder material such as tungsten carbide or silicon carbide. Type 21 mechanical seals also have an elastomer secondary sealing element, commonly made of Viton, EPDM, or another similar material.
Type 21 mechanical seals are designed with an O-ring to provide axial drive to the rotating seal face, which helps to maintain a positive seal. They are commonly used in a wide range of applications, including water and wastewater treatment, chemical processing, and food and beverage processing.
One of the advantages of Type 21 mechanical seals is that they are relatively easy to install and maintain. They can be used in a variety of pump designs and are typically less expensive than other types of mechanical seals. However, they may not be suitable for all types of fluids or operating conditions, and in some cases, other types of mechanical seals such as double mechanical seals or cartridge mechanical seals may be required.