Methods to Distinguish Between Internal and External Sealing of Bellow Seals

The most common method of sealing inside a bellow seal is to install the sealing element inside the packing box. However, this practice requires the wet end of the pump to be removed during sealing maintenance, and its main advantage is that the sealing environment is easy to control.

The outer seal of the bellow seal is installed by reversing the direction of the static seal face and the rotary unit on the spindle is located outside the gland of the stuffing box.

External sealing has the following five major advantages:

1. Easy installation;
2. Relatively low cost;
3. Continuous monitoring and cleaning;
4. Suitable for small packing boxes that cannot be sealed internally;
5. As its position is close to the bearing, it has little influence on the spindle deviation.

The main disadvantage is that the centrifugal force will be solid particles from under the seal to seal the contact surface. Therefore, this type of seal is primarily suitable for clean and non-abrasive liquids.

In recent years, separate seal has become another important additional characteristic in the outer seal of bellow seal. The separate seal is a complete assembly, installed between the packing box and the bearing sleeve. This design eliminates the need to remove the pump each time the seal needs to be replaced. This type of seal is being developed in conjunction with other design criteria. Since this design is easy to replace seals, it is important to resist the temptation to simply replace the seals without further investigation into the source of the failure.