To facilitate welding of closed vessels, a metal backup strip is used at the junction inside the vessel. After welding from the outside, this strip is dissolved by a chemically reactive solvent poured through a filler hole into the vessel

Freeman, R.

Levoe, C.

English

NASA Technical Reports Server

NASA TECH BRIEF 
/ .
Detail "A" 
Junctic 
,ckup 
Weld 
May 1964	 Brief 63-10139 
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. 
Method of Welding Joint in Closed Vessel Improves Quality of Seam 
The problem: Closed vessels of various shapes, 
assembled by welding, may often be designed with 
only a few small access holes. They can therefore be 
welded only from the outside. But in single-side weld-
ing, without a backup bar to absorb heat, it is difficult 
to prevent burning of holes through the vessel or 
weakening of some wall areas. 
The solution: Use a metal backup strip at the junc-
tion inside the vessel and, after welding from the out-
side, dissolve the metal backup strip by a chemically 
reactive solvent (one which does not attack the vessel) 
poured through an orifice or filler hole into the vessel. 
How it's done: The two sections of the vessel to be 
welded together, for example two hemispheres, are
shown in position for welding. A metal backup strip 
is first fitted into one of the sections in the form of a 
band on the inside periphery of the vessel. Approxi-
mately half the width of the backup strip, or band, is 
placed to fit snugly into the selected section of the ves-
sel. The band not only serves as a backup strip, but 
also as a means for positioning the two sections. The 
exterior is then welded in a conventional manner 
around the junction between the two sections. 
After the welded vessel has cooled, a chemically 
reactive solvent for the backup band is poured through 
the small opening into the vessel and allowed to react 
with the band. When the band has completely dis-
solved, the spent liquid is drained from the vessel. 
(continued overleaf) 
This document was prepared under the sponsorship of the National 	 this document, or that the use of any information, apparatus, method, 
Aeronautics and Space Administration. Neither the United States Govern- 	 or process disclosed in this document may not infringe privately-owned 
ment, nor NASA, nor any person acting on behalf of NASA: A. Makes	 rights; or B. Assumes any liabilities with respect to the use of, or for 
any warranty or representation, express or implied, with respect to the	 damages resulting from the use of, any information, apparatus, method, 
accuracy, completeness, or usefulness of the information contained in 	 or process disclosed in this document.
https://ntrs.nasa.gov/search.jsp?R=19630000014 2020-03-11T16:45:11+00:00Z
Notes: 
1. For a 2014-T6 aluminum vessel the backup strip 
may be made of copper. In this case nitric acid may 
be used for dissolving the copper without attacking 
the aluminum. If the vessel is made of stainless 
steel, a backup band of aluminum may be used. A 
caustic soda solution will dissolve the aluminum 
band, while the stainless steel remains inert to this 
reagent. 
2. The backup band may be split to permit insertion 
into the vessel during assembly. 
3. A metal having good heat conductivity should be 
selected for the backup strip. 
4. A vent through which the solvent may be added to 
or drained from the vessel may be fitted to one of 
the sections prior to or after welding of the two 
sections.
5. This technique is suitable for any application 
involving tankage having access holes too small 
to permit entry of a welding tool. Small vessels 
whose interior dimensions must be accurately 
controlled, as for some nuclear-related compo-
nents, represent a specialized application. 
6. For further information about this innovation 
inquiries may be directed to: 
Technology Utilization Officer 
Jet Propulsion Laboratory 
4800 Oak Grove Drive 
Pasadena, California 91103 
Reference: B63-10139 
Patent status: NASA encourages commercial use 
of this innovation. No patent action is contemplated. 
Source: Clarence Levoe and Robert Freeman 
(J PL- l70)
. 
. 
LI 
Brief 63-10139


Method of welding joint in closed vessel improves quality of seam

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