Labyrinth seal

                                                 Labyrinth seal

A labyrinth seal consists of several labyrinth strips in an insert. This seal operates without physical contact. The seal inserts are located in the stationary part of the compressor. They are split horizontally and easily interchangeable. Occasionally the labyrinth strips are also fitted to the rotor .  

 labyrinth seal 

The labyrinth seal breaks down the pressure difference by means of a series of throttling points, formed between the labyrinth strips and the mating surfaces. The leakage becomes less, the smaller the clearance between the labyrinth strip and the mating surface. The area of turbulence between the strips effectively assists the throttling process. The number of strips depends upon the pressure gradient.  

 a three-chamber labyrinth seal is shown. Its task is to prevent either atmospheric air entering the compressor or process gas leaking at the shaft. Use is made of a buffer gas, which should not, however, mix with the gas being compressed.  

👆 labyrinth seal

The buffer gas is supplied to chamber 1 at a controlled overpressure. Part of its flows outwards and prevents air entering, and the other part passes into space 2 which is connected to a leak- off line and has a lower pressure.

 Chamber 3 serves to equalize the pressures as the suction pressure is present at one end of the compressor and the higher discharge pressure exists at the other end. Accordingly, the chambers 3 at both ends are interconnected and, since both ends operate at the same conditions, can be monitored and controlled in common.

labyrinth seal 

 The pressure is set so that, on the one hand it is higher than in chamber 2, whereby a part of the stream flows towards it and mixes with part of the seal gas, and, on the other hand, it is lower than the seal gas pressure in chamber 1. This grading guarantees that, in the event of a disturbance in the discharge pipe, neutral seal gas can pass into the compressor via chamber 2, but process gas can never escape outwards. In normal conditions, the pressure gradient across chamber 2 prevents the ingress of seal gas into the process gas 4.  

The multi-chamber labyrinth system is variable. Thus, a seal only using seal gas without chamber 2 and a small flow of seal gas into the compressor is just as possible as a seal without seal gas, where a mixture of atmospheric air and the process gas is evacuated from chamber 2.