TP32-160/2 Shaft Seals Manual

Shaft seals
22
Materials of
secondary seals
Secondary seals
The choice of materials for secondary seals, i.e. rubber
components such as O-rings and bellows, is just as
important as the choice of seal face combinations. Both
are essential to the functioning of the mechanical shaft
seal. The Grundfos seals are intended to cover a wide
application field with few materials.
The sections below indicate main material properties as
regards temperature and resistance to principal liquid
groups. In case of doubt and where special liquids are
involved, please contact Grundfos.
NBR
Widely used for all-round applications, NBR (nitrile)
rubber covers a wide range of liquids at relatively low
temperatures (below +100°C).
• Good mechanical properties at high and low tem-
peratures
• Heat resistant up to +100°C; for short periods up to
+120°C, depending on the ambient environment
• Resistant to water up to +80°C
• Resistant to diesel oil, various mineral oils, grease
and vegetable oils
• Resistant to weak acids and alkalis
• Not resistant to polar solvents (alcohols, ketones
and esters)
• Not resistant to ozone and weather.
EPDM
EPDM is a rubber quality especially suitable for water
and aqueous solutions, but non-resistant to mineral
oils.
• Good mechanical properties at low temperatures
• Heat resistant up to +150°C
• Resistant to water up to +140°C
• Resistant to polar solvents (alcohols, ketones and
esters)
• Resistant to ozone and weather
• Resistant to glycol
• Partly resistant to vegetable oils at low tempera-
tures
• Not resistant to mineral oils.
FKM
FKM rubber covers a very wide range of liquids and
temperatures.
• Poor mechanical properties at low temperatures
• Heat resistant up to +200°C
• Resistant to water up to +90°C
• Resistant to acids and saline solutions
• Resistant to mineral oils and vegetable oils
• Resistant to most solvents (toluene, petrol, trichlo-
roethylene, etc.)
• Resistant to ozone and weather
• Not resistant to certain polar solvents (for instance
alcohols, ketones and esters)
• Not resistant to alkaline liquids at high tempera-
tures.
FFKM
FFKM (perfluoroelastomer) is chemically resistant to a
wide range of liquids. FFKM rubber corresponds to
PTFE, but offers considerably better mechanical prop-
erties.
• Good mechanical properties
• Resistant to water up to +150°C
• Especially suitable for use in chemical processing
plants, in the production of dyes, paints, varnishes,
solvents, nitric acid, etc.
• Resistant to ozone and weather
• Not entirely resistant to amines and strongly alka-
line liquids at high temperatures.