Scheme measures sliding support friction forces and incorporates them into software programs which are used to analyze piping flexibility

Parker, C. S.

English

NASA Technical Reports Server

ABend No. 2
Frictional 
Bend No. 1 Restraints 
Curvature 
Radius 
Frictional 
Restraints 
B
Anchor 
Virtual Stop 
Upper Support 
Anchor 
..
Benc
orts 
May 1972
	
B72-10103 
NASA TECH BRIEF 
Marshall Space Flight Center 
NASA Tech Briefs announcenew technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Longitudinal Friction Forces in Piping Design 
n II Bend No. 2 
Thermal Movement
No Restraints
* Slide Supports
C 
.
The problem: 
Computer programs available to expedite the solution 
of piping analysis, and methods of reducing deformation 
do not consider sliding support friction forces. 
The solution: 
A scheme has been developed to measure longitudinal 
friction forces, and to incorporate them into the soft-
ware programs which are used to analyze piping flex-
ibility.
How it's done: 
Friction restraint usually starts without any initial 
value, but develops any value up to a limit of the friction 
coefficient times the thrust between the sliding surfaces. 
Considering a model of a "Z" bend as indicatl in 
the diagram: 
In figure A, the frictional force component does not 
restrain the thermal movement, the radius of curvature 
remaining relatively large. Bend #1 stretches about five 
times as much as bend #2. 
• 
(continued overleaf) 
This document was prepared under the sponsorship of the National
	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately owned rights. 
https://ntrs.nasa.gov/search.jsp?R=19720000103 2020-03-17T03:24:59+00:00Z
In figure B, however, due to frictional restraint, as 
indicated by the lines crossing the pipe, the radius of 
curvature of bend #1 is smaller. This results in forces 
which put a greater strain on bend #2. 
Utilizing external restraints, whose loads were cal-
culated from computer tables, flexibility constants were 
modified until the loading matched the limitation of 
friction. These external loads for an empty pipe line, 
combined with the limited flexibility of bend #2, caused 
a decrease in the displacement of the upper support. 
When the pipe line was loaded with LN 2 (Liquid Nitrogen), 
the resulting forces were enough to make a virtual stop 
at the upper support as shown in figure C. 
The restraining forces were varied from 35 to 45 per 
cent of the weight of the support. This numerical vari-
ation was necessary to obtain the calculated results. 
These results were documented in equation form, and 
are a necessary addition to the computer program for a 
more accurate analysis of piping design.
Note: 
Requests for further information may be directed to: 
Technology Utilization Officer 
Marshall Space Flight Center 
Code A & TS-TU 
Huntsville, Alabama 35812 
Reference: B72-10103 
Patent status: 
No patent action is contemplated by NASA. 
Source: C. S. Parker of

General Electric Company 
under contract to

Marshall Space Flight Center

(MFS-1 3754)
. 
B-72-10103	 Category 01


Longitudinal friction forces in piping design

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server