Mylar lip type back-up ring installed in combination with three rubber O-rings seal the junctions between a tube stub and an adapter during high pressure gas flow at cryogenic to room temperatures. Mylar seals should not be used with oxygen under pressure or in the liquid state

Funk, G. M.

English

NASA Technical Reports Server

S
Cryog 
Tut
June 1966	 Brief 66-10278 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U. S. space 
program and to encourage their commercial application. Copies are available to the public from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
0-Rings with Mylar Back-Up Provide High-Pressure Cryogenic Seal 
0-Ring Spacer
4 Gas Flow 
Mylar Cryogenic Seal 	 Room Temperature Seal 
The problem: 
Sealing the junction between a tube stub and an 
adapter during high pressure gas flow at cryogenic to 
room temperatures. Leaks occur when rubber 0-rings 
are used because they harden and shrink at cryogenic 
temperature. 
The solution: 
A Mylar lip type back-up ring installed in combina-
tion with three rubber 0-rings. Contraction pressure 
on the Mylar lip from one of the rings provides the 
low temperature seal, and the normal function of 
another of the seals, in conjunction with a third spacer 
ring, provides the ambient seal. 
How it's done: 
The lip of the Mylar seal is installed on the tube 
stub with the disk portion resting against the end of
the adapter. The first 0-ring, the cryogenic seal assist, 
is placed over the Mylar lip. The spacer 0-ring is then 
placed on the tube stub adjacent to the cryogenic seal 
assist, and the room temperature seal 0-ring is placed 
on the tube adjacent to the spacer. 
Under cryogenic gas flow conditions, the cryogenic 
seal assist contracts, forcing the still resilient Mylar 
lip firmly against the tube for an effective seal. Axial 
gas pressure forces the cryogenic assist ring and the 
disk portion of the Mylar against the adapter end for 
further sealing. 
Under room temperature gas flow, the ambient seal 
functions as a normal 0-ring. The spacer prevents the 
room temperature seal from riding on the Mylar lip 
and thus losing good sealing contact with the tube 
stub. 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19660000277 2020-03-11T17:38:26+00:00Z
Notes: 
1. This design provides a leakproof seal for helium 
flow at 1000 psig, ranging from room temperature 
to —320°F. 
2. Mylar seals should not be used with oxygen under 
pressure or in the liquid state. 
3. The tube stub surface finish as it comes from stock 
is sufficient for effective sealing by this method. 
4. Inquiries concerning this invention may be directed 
to:
Technology Utilization Officer 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: B66-10278
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: G. M. Funk
of North American Aviation, Inc.

under contract to

Marshall Space Flight Center

(M-FS-603)
. 
. 
Brief 66-10278	 Category 05


O-rings with mylar back-up provide high- pressure cryogenic seal

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