Buffered shaft seal

A steam buffered shaft seal shall be provided to ensure that hot flue gas cannot escape from the casing at any specified operating condition. The steam supply shall be controlled by... 

The shaft seal (see subsection Shaft Seals ) generally is a close-clearance labyrinth-type seal. It is desirable that there be available a suitable pressurized buffer gas for injection into the intermediate point in the seal, such gas to be available at an absolute pressure well above the highest shaft pressure to be sealed. Then the seal-gas system may consist of only a filter, a flow-indicating device, and a throttle... 

A buffered oil seal shall be provided at the shaft and bearing ease interfaee to ensure that oil does not eseape from the bearing ease at any operating eondition. 

A typical mechanical contact shaft seal has two major elements, as seen in Figure 13-30. These are the oil-to-pressure-gas seal and the oil-to-unconta-minated-seal-oil-drain seal or breakdown bushing. This type of seal will normally have buffering via a single ported labyrinth located inboard of the seal and a positive shutdown device, which will attempt to maintain gas... 

Care must be taken in the assembly of the buffered shaft end seals, particularly in the area of the secondary o-ring seals. A cut or damaged ring can allow more oil to be bypassed than from a damaged main seal. 

Sleeves at Shaft Seals Inter Oil Leakage Buffer Gas Flow (Per Seal)... 

Tape recorder drive wheels Anti-vibration buffers Bearing shaft seals... 

In dry compressors, shaft end seals are generally one of five type.s. These are labyrinth, restrictive ring, mechanical contact, liquid film, and dry gas seal. The labyrinth type is the most simple but has the highest leakage. The labyrinth seal is generally ported at an axial point between the seals in order to use an eductor or ejector to control leakage and direct it to the suction or a suitable disposal area. Alternatively, a buffer gas is used to prevent the loss of process gas. Appendix D presents a calculation method for use with labyrinth seals. 

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