Rotating shaft seals used in space power systems have spiral grooves in one or both of the opposing seal faces. These grooves induce a pumping action which displaces the intervening fluid radially inward toward the shaft and counters the centrifugal forces which tend to displace the fluid outward

Allen, G. P.

Johnson, R. L.

Ludwig, L. P.

Strom, T. N.

English

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July 1968	 Brief 68-10270 
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AEC—NASA TECH BRIEF
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1MI 
AEC-NASA Tech Briefs describe innovations resulting from the research and development program 
of the U.S. AEC or from AEC-NASA interagency efforts. They are issued to encourage commercial 
application. Tech Briefs are published by NASA and may be purchased, at 15 cents each, from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Spiral-Grooved Shaft Seals Substantially Reduce Leakage and Wear 
	
Rotating shaft seals for use in space power systems
	 To overcome these problems, seals have been devel-
	
must operate reliably for periods of several years with-
	 oped which incorporate spiral grooves, as shown 
	
out maintenance or attention. Leakage and wear must
	 above, in one or both of the opposing seal faces. These 
	
be minimized. In addition, they must be suitable for
	 grooves induce a pumping action which displaces the 
	
use at extreme temperatures, simple and light in
	 intervening fluid radially inward toward the shaft and 
	
weight, and capable of containing pumped fluids such
	 counters the centrifugal forces which tend to displace 
as liquid sodium or potassium.
	 the fluid outward. The net effect maintains hydrody-
	
Conventional shaft seals are not adequate. Leakage
	 namic separation of the seal faces, thus preventing seal 
	
rates are too high; thermal and pressure distortions
	 face contact and wear (see the figure overleaf). 
	
cause rubbing contact which results in wear, scoring,
	 Spirally-grooved seals have been tested against corn-
and increased leakage rates,
	 parable conventional seals for use in a liquid sodium 
(continued overican 
	
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Administration. Neither the United States Government nor any per- 	 method, or process disclosed in this document may not infringe pri-

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Liquid Sodium, 20 psig (29 N/cm 2
 Gage) 
Argon, 1 psig 
(0.7 N/cm2 Gage)	 Bellows 
Shaft Centerline  
pump operating at over 1300°F and 20 psig. The re-
suits showed that: 
1. The spirally-grooved seals leaked at a rate less than 
the detectable limit of 0.02 cubic inch per hour with 
generally no detectable increase in leakage after 
prolonged operation. Comparatively, the conven-
tional seals had initial leakage rates up to 27 cuhi" 
inches per hour which increased to as mucn as 57 
cubic inches per hour with prolonged operation. 
2. The spirally-grooved seals showed negligible wear 
at the completion of the test run. 
3. Static leakage of the spirally-grooved seals was 
comparable to that of the conventional seals. 
Notes: 
1. This technique of machining rotating shaft seals 
with spirally-grooved faces appears applicable to a 
wide variety of uses.
2. Inquiries concerning this invention may be directed 
to:
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B68-10270 
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to NASA, Code 
GP, Washington, D.C. 20546. 
Source: T. N. Strom, L.P. Ludwig,

G. P. Allen, and R. L. Johnson

(LEW- 10397) 
Brief 68-10270	 Category 05


Spiral-grooved shaft seals substantially reduce leakage and wear

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