Balanced and Non-balanced Seals of Mechanical Seal Ring

The balance of the mechanical seal ring has a great influence on the sealing pressure of the contact surface. This sealing pressure depends on the effective cross-section of the seal itself and the pressure in the packing box. The section on the opposite side of the rotating face of the non-equilibrium mechanical seal ring is fully exposed to the pressure range of the packing box. This situation will make high pressure  between the sealing surface, which will make the working temperature increase, speed up the rate of wear. Under high temperature working conditions or liquid having greater corrosion and friction, it will greatly reduce the service life of mechanical seals.

Balancing mechanical seal ring can reduce the sealing pressure and extend the service life of the seal. The main shaft and shaft sleeve with steps are generally adopted to reduce the effective section of the rotary surface, so as to achieve the above purpose. However, do not adjust the net sealing pressure to close to zero level, because this may cause the the unstable working condition between the sealing surface, and may blow the seal due to sudden changes.

The answer to these sealing problems may be an unbalanced seal, which may be better for some services. For example, in some applications, there may be more emphasis on the safety of liquid leakage than on the life of the seal. In this case, the selection of the seal may also be understood as the choice of a higher seal pressure. Similarly, in the case of a cooler liquid seal, the increase in operating temperature may be negligible.

Regardless of the consideration, it is generally recommended to use a balanced mechanical seal ring when the packing box pressure exceeds 50psi.