Why do some centrifugal pumps have O-rings attached to the static rings of their mechanical seals?

The static rings of the mechanical seals of chemical centrifugal pumps are sometimes equipped with O-rings and sometimes not. 

What are the advantages of having O-rings? 

ATACH Pump Factory analyzes as follows: 

The O-ring configuration of the static ring in the centrifugal pump mechanical seal is mainly to establish a reliable static seal between the static ring and the gland, in order to prevent the medium from leaking at this connection point. 

The O-ring deforms under pre-compression to fill the sealing gap, thereby generating the initial sealing force. 

Its elastic properties can adapt to the contact surface. 

Its elastic properties can adapt to the minor defects of the contact surface, ensuring the reliability of the seal; 

its elastic properties can adapt to the minor defects of the contact surface, ensuring the reliability of the seal; 

when the medium pressure changes, the deformation of the O-ring will adjust to maintain the sealing effect. 

The deformation will automatically adjust to maintain a stable sealing effect. 

The application of O-rings on the stationary ring can effectively solve the leakage problem. 

The stationary ring, as a fixed component of the mechanical seal, is connected to the gland ring and the gland. 

This connection is a static sealing point. 

This sealing point is susceptible to installation errors, the installation of the O-ring in the groove or the surface roughness. 

After compression in the O-ring groove, a rebound force is generated, and the elastic compensation capacity of the O-ring can make up for these deficiencies and the rebound force, closely adhering to the sealing surface, blocking the medium along the shaft sleeve or the gland, and preventing leakage. 

Choosing an O-ring as an auxiliary sealing element has significant leakage reduction capabilities; this design is simple and effective, and is suitable for various pressure and temperature conditions. 

Its advantages include a simple structure, low cost, easy installation, and a wide range of applicable pressure ranges. 

The failure of the O-ring may be caused by various factors, such as a static seal groove with a compressive strength of over 100 MPa. 

It can adapt to various media and working conditions. 

Dimensional deviations, installation scratches, or material mismatches can occur. 

Therefore, during design and use, the installation compression amount must be strictly controlled (typically 18%-22%), and a material compatible with the medium must be selected to ensure long-term sealing performance.