Page 256 - The Tribology Handbook

Selection of seals 619

Check-Uist for seal selection Fluid compatibility: check all materials which may be ex-
posed to the fluid, especially rubbers.
Ternjmature (s'ee Figure 19.12): seals containing rubber, Abrasion resistance: harder sliding contact materials are
natural filbres or plastic (which includes many face seals) usually better but it is preferable to keep abrasives away
may have severe temperature limitations, depending on from the seal if at all possible, for example by flushing with
the material, for example: a clean fluid.
Polyurethane and natural rubber are particularly abra-
Natural rubber -50 to +80"C sion resistant polymers. Where low friction is also necess-
Nitrile rubber -40 to +I30 ary filled PTFE may be considered.
Fluorocarbon rubber -40 to +200 Vibration: should be minimised, but rubber seals are
Perfluorocarbon rubber -10 to +300 likely to function better than hard seals.
PTFE, plastic -100 to +280
At low temperatures, certain of the fluoroelastomers may
become less 'rubbery' and may seal less well at high
pressure.
Speed (see Figure 19.13)
Pressure (see Figure 19.13)
Sire (see Figure 19.14)
Leakage (see Figure 19.15)
After making an initial choice of a suitable type of seal,
the section of this handbook which relates to that type of
sealshould be studied. Discussion with seal manufacturers
is also recommended.

1200
1100
I000
u
g 900
3
ii 800
a
W
2 700
W
In
IL 600
0
$ 500
2
Q 400
E
w
a MECHANICAL
300
W
c
200
100
0
figure 19.12 Approximate upper temperature limits for seals

B19.5