Dry gas seals used in the centrifuge

Improvement of the mechanical seal
Centrifuge traditional mechanical seals, mechanical seals are the advantages of simple structure, mature technology, machining accuracy is not required; drawback is that life is short, power consumption, there must be a liquid medium to lubricate and cool the sealing surface, the production process parameter fluctuations great seal. Since the operation centrifuges, mechanical seal life has been very short, only five months longest, replace the mechanical seal needs 28h, seriously affecting production. And after the mechanical seal (referred mechanical seal) failure is leaking liquid hexane, hexane is flammable, explosive media, not only the existence of a significant security risk, but also caused serious pollution to the environment. Based on this, we decided to change it to dry gas seal, to enhance economic efficiency and eliminate security risks. Dry gas seal is the most advanced form of a non-contact seal, mainly by the rotating ring, stationary ring, ring, spring, spring seat and sleeve components.
After rotating ring sealing surface grinding and polishing process, and the processed fluid at the dynamic pressure grooves, Figure 2. Dry gas seals rotary ring is rotated, the dynamic pressure of the sealing gas is sucked into the tank, the throttling effect of the sealing weir, into the sealing surface of the gas is compressed under the action of the gas pressure, the sealing surface is open, the gas flow forming a thin gas film between the two sealing surfaces and a thickness of 3 ~ 5um,high security cable seals when the reaction force together with aerostatic air film and the formation of the spring force is equal to the thickness of the air film is very stable, thus ensuring the seal reliability.

We analyze the structure of the centrifuge, decided not to change the device structure, the use of double-end dry gas seal, the same size as the original seal size, and a similar structure, easy to install, see Figure 3. Taking into account the process medium plastic powder, using hexane for cleaning sealed chamber for cleaning. Dynamic pressure dry gas seal ring groove machined end face, using tungsten carbide ring (WC) material, which has a high surface hardness, wear resistance, thermal conductivity coefficient, etc.; static ring using impregnated graphite material, which has high strength, good lubricating properties and high temperature, etc. from.
Seal gas is nitrogen, provided by external network, the maximum pressure is 0.7MPa, the normal operating pressure of 0.5-0.6MPa, the minimum pressure of 0.4MPa, the nitrogen flow is greater than l0 standard m3 / h.
0.7MPa nitrogen is passed through the filtration unit under reduced pressure to 0.5 MPa, into the sealed chamber through a flow meter. To prevent the pipe network in the nitrogen pressure fluctuations for emergency spare bottle with nitrogen gas source, alternate air source can supply 2h. Dry gas seal leakage from the flow meter showed normal operation, the nitrogen leak kept within a stable range,identification cable ties if the leakage continues to increase, the seal chamber pressure will drop, when the pressure drops Bian 0.3MPa, interlock parking to Centrifuge ensure safety. From the actual operation situation, the nitrogen pressure in the 0.5MPa, to ensure the good functioning at this time, nitrogen consumption was 0.48 standard m3 / h, less than the design of a standard m3 / h.