Helical seal is used to seal bolted flange joints in a high temperature environment. The seal design incorporates a new cross-sectional shape, a metal strip with a slight radius, and the use of premolded asbestos. It provides equal load distribution under compression loads, allows for minimum loss and recovery values, and increases the temperature range

Held, C.

English

NASA Technical Reports Server

OLD
CONFIGURATION
Preformed High Temper-
ature Filler and 
NEW
CONFIGURATION 
December 1967	 Brief 67-10655 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Development of Helical Seal for High Temperature (20000 F) Application 
The problem: 
To design a helical seal to be used to seal bolted 
flange joints in a high temperature (2000°F) environ-
ment. Commercially available seals have not been 
satisfactory in high temperature applications (1400°F). 
In use, the seal is compressed between two flanges and 
upon loosening the flange bolts, the seal is incapable 
of recovering its original state. 
The solution: 
A seal design incorporating a new cross-sectional 
shape, a metal strip with a slight radius, and the use of 
premolded asbestos. 
How it's done: 
The proposed helical seal may be constructed as 
follows: Feed a 1/4-inch by 0.010-inch thick steel strip 
through a tooling setup in a manner to bend the strip 
on a 0.075 radius. Immediately after bending, cut the 
strip at approximately 40 degrees. Then spiral wind the
strip in a fixture to a diameter equal to a specific sealing-
area flat, dependent upon the environment in which it 
is used. This winding process includes from 5 to 10 
winds, after which an asbestos strip saturated with a 
high-temperature sealant is coiled with the curved strip, 
resulting in a high-temperature expansion strip between 
each metal strip after the 5 to 10 initial winds. The 
asbestos stripping is then cut prior to the last 5 to 10 
winds. The solid winds at the beginning and end of each 
wind should create a sufficient thickness of material 
for tack welding the assembly to prevent any unwinding 
during the life or use of the seal. The asbestos used 
between windings is molded, rolled, or extruded to a 
configuration matching that of its mating metal strip. 
Notes: 
1. This new design may provide equal load distribution 
under compression loads, allow for minimum loss 
and recovery values, and increase temperature 
range from 1400 0
 to 2500° F. (nnndnr1.'nfl 
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=19670000654 2020-03-11T21:39:46+00:00Z
This development is in conceptual stage only, and 
as of date of publication of this Tech Brief, neither 
a model nor prototype has been constructed. 
Inquiries concerning this concept may be di-
rected to:
Technology Utilization Officer 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: B67-10655
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: C. Held

of North American Aviation, Inc.

under contract to

Marshall Space Flight Center

(MFS-13304) 
IS—CAS..42111 
RM. 1313	 KSC HQS. 
Brief 67-10655	
-	 Category 05


Development of helical seal for high temperature /2000 degrees F/ application

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