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The Practical Pumping Handbook .......................................................................................................................................... 7o_ -T .......... 7m

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Figure 6.1: Packed stuffing box

When abrasive liquids arc being pumped, a lantern ring is installed to
accommodate the introduction of a clean sealing liquid that will replace
the pumpagc in the stuffing box. This sealing liquid is normally
introduced at 10 to 15 p.s.i, above the pressure, behind the impeller at
the bottom of the stuffing box. This allows the scaling liquid to provide
all thc cooling and lubrication needed between the shaft and the
packing and restricts the entry of the pumpage into the stuffing box
area.
The lantern ring is normally inserted about 2 or 3 rings from the
bottom of the box where it will connect with the flush port in the
stuffing box. However, for extremely abrasive pumpages in a situation
where product contamination is acceptable, the lantern ring can be
positioned at the bottom of the stuffing box. With appropriate
relocation of the flush port, this takes the pressurized sealing water
straight into the pumpage and prevents it from damaging the pacldng.

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Figure 6.2: Packed stuffing box with bottom lantern ring

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