What are the common fault points of double-end face corrugated pipe mechanical seals?

Recently, ATACH Centrifugal Pump Manufacturing Factory has come into contact with a customer. 

We believe this is a very good application example of double-end face mechanical seals, especially bellows double-end face mechanical seals. 

The introduction is as follows:

The light hydrocarbon transfer centrifugal pump of this British customer is an imported German pump. The pump model is HDAR-80/12, with a rotational speed of 2950r/min. 

The inlet pressure of the pump is 0.7mpa and the outlet pressure is 1.4mpa. 

The medium is liquid hydrocarbon and the seal is a double-end face bellows mechanical seal. 

Since the pump was put into use, the mechanical seal has frequently leaked. 

The main phenomena are: carbonization, twisting or cracking of the bellows, and discoloration of the metal surface of the friction pair, presenting as grass yellow and brown.

Cause analysis: The bellows broke due to poor lubrication of the medium, a large friction coefficient, and excessive torque on the bellows, which led to its breakage. 

The discoloration of the metal surface of the friction pair is due to insufficient input in the process, which leads to cavitation, dry or semi-dry friction of the mechanical seal, and seal failure.

Solution: To prevent the bellows from twisting and breaking, change the double-end face bellows seal to a multi-spring balanced seal. 

Reduce the gap of the sealing bottom sleeve, decrease the sealing pressure, and control the flushing volume of the seal. 

After the transformation, it has been sealed and operated continuously for two years. 

Practical experience has shown that liquid hydrocarbon pumps are suitable for small spring balanced mechanical seals but not for bellows seals.