A low-cost fitting, fabricated from standard connectors, is used for disconnecting flow lines in cryogenic systems. Utilizing vacuum-jacketed lines made from two sizes of tubing welded at the ends, the connectors are stronger and setup time is reduced

Calvert, H. F.

English

NASA Technical Reports Server

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May 1964	 Brief 63-10367 
NASA TECH BRIEF 
This NASA Tech Brief is issued by the Technology Utilization Division to acquaint industry 
with the technical content of an innovation derived from the NASA space program. 
Connector for Vacuum-Jacketed Lines Cuts Tubing System Cost 
Tube-To Tube Fitting
Weld 
Note: Standard pin fittings are used as an example 
for this typical assembly sketch. 
The problem: Design of a low-cost connector for 
disconnecting vacuum-jacketed flow lines, as used in 
cryogenic systems. Cryogenic systems generally re-
quire many disconnect fittings. Available connectors 
are only suited to low pressures, are large in size, 
and are quite expensive. They utilize small line sizes 
that are unsatisfactory for liquid hydrogen applica-
tions because of too great a heat loss. 
The solution: An improved fitting fabricated from 
standard connectors and utilizing vacuum-jacketed 
lines made from two sizes of tubing that have been 
welded at the ends. The improved connectors are in-
expensive and yet are more satisfactory than those 
generally available. Strength is excellent. Connec-
tors assembled with copper tubing have been proof-
tested to more than 5,000 psi. 
How it's done: Various combinations of tubing and 
fitting sizes may be utilized in fabricating the low 
cost vacuum-jacketed line connector. In this case,
3/8-inch tubing is placed inside 5/8-inch tubing and 
the ends are welded together. This forms a sealed 
space for the vacuum. A standard tube-to-tube fitting 
is drilled to fit the outside of one end of the vacuum 
line and welded in place by the inert gas-shielded arc 
method. A flared sleeve, made from 3/4-inch tubing, 
is welded to the other vacuum line. A standard nut 
and sleeve are placed over the vacuum line before the 
flared sleeve is assembled and welded in place. 
Connections can be made or broken in the. same 
manner as a standard tubing assembly. Setup time is 
reduced, as compared with the conventional aluminum 
gasket type while replacement of parts in the system 
is greatly simplified. 
Notes: 
1. If a large number of connectors are needed, as in 
industrial systems, cost savings can be large. Con-
ventional vacuum connectors may cost up to $400 
(continued overleaf) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States Gosern-
ment, nor NASA, nor any person acting on behalf of NASA: A. Makes 
any warranty or representation, express or implied, with respect to the 
accuracy, completeness, or usefulness of the information contained in
this document, or that the use of any information, apparatus, method, 
or process disclosed in this document may not infringe privately-owned 
ri g hts; or B. Assumes any liabilities with respect to the use of, or for 
dama g es resulting from the use of, any information, apparatus, method, 
or process disclosed in this document.
https://ntrs.nasa.gov/search.jsp?R=19630000063 2020-03-11T16:47:52+00:00Z
each, while this innovation can be fabricated for 
approximately $25 per fitting. 
2. When maximum strength is needed, the vacuum 
tubing can be made from stainless steel. It would 
have all of the advantages of the copper tubing yet 
be useful in pressure levels above 5,000 psi. An-
other variation would be to install tube-to-tube
fittings at both ends of the vacuum line. For prop-
erly equipped valves, one length of tubing would 
then be interchangeable with another. 
Patent status: NASA encourages commercial use 
of this innovation. No patent action is contemplated. 
Source: Howard F. Calvert 
Lewis Research Center (Lewis-66) 
Brief 63-10367


Connector for vacuum-jacketed lines cuts tubing system cost

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