A backup bar designed to use both vacuum and air pressure provides a method of sealing the weld root of a faulty section of seam weld. With slight redesign, the bar can be made sufficiently flexible to fit any large cylindrical surface

Carmody, R. J.

English

NASA Technical Reports Server

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August 1964	 Brief 63-10384 
NASA TECH BRIEF	
-I& 
This NASA Tech Brief is issued by the Technology Utilization Division to acquaint 
industry with the technical content of an innovation derived from the space program. 
Vacuum-Type Backup Bar Speeds Weld Repairs 
Vacuum Chamber
Stainless Steel Inserts FIGURE 1
FIGURE 2 
The problem: When a faulty section of seam weld is 
detected in a completed welded metal structure such as 
a large steel tank, it is necessary to repair the weld sec-
tion in place. This involves backing up the root of the 
weld to retain the molten metal. Conventional tech-
niques consume much time and involve fabrication of 
a backup device and the use of clamps, supports, and 
other mechanical fixtures.
How it's done: A backup bar is fabricated with a 
tube system, a rubber seal, fiberglass vacuum chambers, 
and a row of small, grooved, stainless-steel inserts 
mounted in a channel containing a rubber tube at-
tached to an air fitting. The backup bar is curved and 
is slightly flexible to adapt to a limited size range of 
surfaces. 
The bar is placed against the weld seam to be re-
The solution: A backup bar designed to use both	 paired and a vacuum source applied to remove the air 
vacuum and air pressure to seal the weld root in a 	 from the vacuum chambers in a matter of seconds. 
matter of seconds. 	 The bar will cling tightly to the structure as long as 
(continued overleaf) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States Govern-
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 
rights; or B. Assumes any liabilities with respect to the use of, or for 
damages resulting from the use of, any information, apparatus, method, 
or process disclosed in this document.
https://ntrs.nasa.gov/search.jsp?R=19630000067 2020-03-11T16:47:46+00:00Z
the vacuum is maintained. Compressed air is intro-
duced into the rubber tube behind the inserts, pressing 
them tightly against the weld root. The reverse side of 
the bar is of fiberglass and mounts two carrying 
handles. 
Notes: 
I. The backup bar is 3 feet long, about 8 inches wide, 
and 1 inch thick, with a weight of about 30 
pounds. The same basic design could be used for 
smaller or larger units. 
2. With slight redesign the bar could be made suf-
ficiently flexible to fit any large cylindrical surface.
For further information about this innovation in-
quiries may be directed to: 
Technology Utilization Officer 
Marshall Space Flight Center 
Huntsville, Alabama, 35812 
Reference: B63-10384 
Patent status: NASA encourages commercial use 
of this innovation. No patent action is contemplated. 
Source: R. J. Carmody 
(M-FS- 12) 
Brief 63-10384


Vacuum-type backup bar speeds weld repairs

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