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the mating surface; 5) O-ring (rubber, covered with a
Teflon film) sealing element; 6) coolant inlet and
outlet. of the housing and removal of heat generated by friction between the sealing rings and sealin
fluid. A seal with cooled housing is shown in Fig. ib while a seal with cooled lower section
in contact with the process fluid is shown in Fig. 2b.
Double axial Seals used for top-entry agitator are relatively large (longitudinally).
This complicates replacement of the seal or disassembly of the agitator during repair. Seal-
ing rings are located perpendicularly to the axis of rotation in double radial mechanical
seals (see Fig. 3). These seals are almost half the height of axial seals. Radial seals
are especially advantageous with large-diameter shafts.
The outer and inner sealing rings are pressed to a rotating sealing ring by cylindrical
springs in these bearings. Sealing fluid is supplied into the cavity between the sealing
ring. This cools the fretting surfaces. Additional cooling is provided through a special b
Fig. 3. Radial double mechanical sea2 for top-entry
agitator shafts: a) Crane Packing type 151; b) Paci-
fie type 556; I) inlet, outlet of the sealing fluid;
2, 4) outer and inner seal rings, respectively; 3)
rotating seal ring; 5) springs; 6) sealing elements;
7) coolant inlet and outlet; 8) sealing fluid leakage
drain. 'b
Fig. 4. Double mechanical seal for bottom-entry agitator shafts: a)
axial by Burgmann; b) radial by Pacific; i) seal fluid inlet; 2) helix;
3) seal fluid outlet and leakage drain; 4) rotating rings with grooves
on the fretting surface; 5) spring; 6) stationary ring.
connection in seals supplied by Pacific (see Fig. 3b). The sealing rings are fabricated of
Teflon as wedge-shaped rings in the seals supplied by Crane Packing (see Fig. 3a) while the
inner sealing ring is of filled Teflon.
Pacific and Burgmann have designed double seals for bottom-entry agitators (see Fig. 4).
Burgmann has based the design on an HS-D (see Fig. 4a) seal. Intensive circulation of the
cooling and sealing fluids directly in the contact zone of the sealing ring located on the
process fluid side is provided by a "screw pump" device. Sealing fluid, which also cools