SSI America BINARY SOLVENT DELIVERY MODULE 90-2581 REV B - Manual (Page 6)

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1.1.4 Self-Flush and Seal Life
It is recommended that the Self Flush feature be used to improve
seal life in a number of applications. In particular, (as stated above) if
pumping Buffers, Acids/Bases or any inorganic solution near
saturation, the pump should utilize the Self Flush feature. With every
piston stroke, an extremely thin film of solution is pulled back past the
seal. If this zone is dry (without use of Self Flush), then crystals will
form with continuous operation, which will ultimately damage the
seal.
Another application where Self Flush is highly recommended is
when pumping Tetrahydrofuran (a.k.a. THR, Diethylene Oxide) or
other volatile solvents such as acetone (Note: THF and most solvents
are compatible only with all-Stainless Steel systems. THF will attack
PEEK). Volatile solvents will dry rapidly behind the seal (without the
use of Self Flush), which will dry and degrade the seal.
IPA, Methanol, 20% IPA/water mix or 20% Methanol/water mix
are good choices for the flush solution. Consult the factory for
specific recommendations.