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.................................................................. Stuffing Box Sealing

I
I I
( g \

sJc lo l

ION
FROM
SEAL

Figure 6.17 Recirculation to suction diagram

would tend to solidify and cause hang-up of the seal faces. It usually
incorporates a disaster bushing to keep the quench in the seal area.
Liquid quenches are often used to dissolve and flush out crystalline
products, such as from Caustic solutions.
A Steam Quench is frequently used in high temperature applications, to
cool the seal faces and prevent coking of leakage residues.

6.4.4 Barrier fluid systems
Barrier fluid systems are required with all types of double seals. They
are usually external closed loop systems containing a fluid that is
normally different, but compatible, with the process liquid. The system
will contain a reservoir which should be as close as possible to the seal.
The design of these systems can vary widely. Some systems will use a
pumping ring in the seal while others will use a thermosyphon effect
where the difference in fluid temperature between the two legs in the
loop, will initiate a continuous flow around the system.

Auxiliary heating or cooling of the fluid is frequently added to the
pressure reservoir.
When the barrier fluid system is designed to operate at a pressure lower
than the stuffing box pressure, the process liquid will lubricate the
inboard set of faces. Any leakage from the inboard seal will flow into
the barrier system where it is vented or contained as may be
appropriate.
In this arrangement, the outboard seal is cooled and lubricated by the
barrier fluid at low pressure until the inboard seal fails. At this point,
the barrier fluid system should be isolated to allow process pressure to
build and be sealed by the outboard seal which will then carry the full
system load until shutdown.

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