The double mechanical seals fitted to
Hy~Line and Ultima provide the facility to
contain a high pressure fluid behind the
primary seal. This allows the pump to be
used for applications where the single seal
is unsuitable. Double seals Codes 1 and 4
are run with a fluid between the primary and
secondary mechanical seals to form a
barrier between the pump and the
atmosphere.
For LH32 and LH34 Pumps:
Double mechanical shaft seals are not
available on the LH32 or LH34 size pumps.
They are used with:
Double Mechanical Seal with a low
pressure liquid flush when:
• The pumped fluid is toxic or hazardous
and must not escape from pump even in
minute quantities.
• The system can be installed as in figure
4a but must be capable of withstanding
the full pressure within the pumped fluid
pipe system.
Double Mechanical Seal with a high
pressure liquid flush when:
• The pumped fluid has no lubricating
properties and cannot be allowed onto
seal faces
• Pumped fluid is highly viscous, i.e. over
150,000 cps.
• A high pressure sterile liquid barrier is
required.
When the double seal is used with a high-
pressure liquid flush for the reasons
described above, a flushing system must be
installed as follows:
• The flushing liquid used must itself be
compatible with the pumped fluid and
must itself not require a complex seal, i.e.
must be non hazardous, non abrasive and
lubricating.
• Flush liquid must be at a pressure of 1 bar
(15psi) above the discharge pressure of
the Jabsco lobe pump and should flow at
35 to 55 litres/hour (10 to 15 US gal/hour)
per seal.
Page 11
Hy~Line and Ultima Lobe Pumps
07/03
Figure 4a: Suggested Low Pressure
Flushing System
Figure 5:
Double
Mechanical
Seal
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