Page 255 - The Tribology Handbook

BI9 Selection of seals

SEAL SELECTION
Table 79.3 The use of dynamic contact seals in the six dynamic sealing situations

Con&uration
(see diagram) Multiple seal
Satisfactory unless:
(i) no contamination permissible Buffer fluid = gas or vacuum: pB >pi, p2 or pB <<pi, p2
64 IPl - P21 large Buffer fluid = liquid 1 or 2: pB (PI + p2)/2
(iii) liquids both poor lubricants Buffer fluid = good lubricant: pe >pi, p2
(in) abrasive present Buffer fluid = clean liquid: p~ > PI or p2, subject to abrasive location
Satisfactory unless:
(i) no contamination permissible Buffer fluid = gas or vacuum: p~ > p1 or pB > p2 or pB > pl, p2 or pB <PI,
(4 IPI - P21 large P2
(zii) the liquid is a poor lubricant Buffer fluid = liquid: PB @I + p2)/2
(iv) abrasive present Buffer fluid = good lubricant: p~ >pi, p2
Buffer fluid = clean liquid: p~ > PI or p2, subject to abrasive location
(c) Satisfactory unless: Buffer fluid = compatible
(i) no contamination of vacuum liquid or gas; alternatively
permissible use clearance seal(s) and
(4 PZ * PZ evacuate buffer zone PB a PI
(iii) the liquid is a poor lubricant
(iv) abrasive present in liquid Buffer fluid = clean liquid: pB >pi
(4 Unsatisfactory Buffer fluid = compatible
liquid lubricant: PB>PI,P2
(e) Unsatisfactory Buffer fluid = compatible
liquid lubricant: PB>Pl
(r) Unsatisfactory Buffer liquid = compatible
liquid lubricant: PB>PI>P2

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VACUUM 1 n VACUUM 2
'1 (e)
B19.4