Filter senses increasing pressure drop and uses this to compress bellows. Compression of bellows stores energy in spring until predetermined pressure-drop level is reached. At this point, bellows and spring are released. Relaxation of spring is used to move a clean area of screen into position across fluid stream

Winzen, J. P.

English

NASA Technical Reports Server

ellows	 Cartridge 
Splowo l o
Aperture 
Clean 
Screen 
Spool 
Section A-A 
itlet 
.
Ir
Indicator
Figure 1. Sequential Strip Filter 
December 1973
	 B73-10430 
•	 NASA TECH BRIEF 
Lyndon B. Johnson Space Center 
NASA Tech Briefs announce new 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. 
Sequential-Strip and Sequential-Disk Filters 
The problem: 
Current liquid and gas filters have limited life 
because of their finite contaminant capacities. As the 
filter unit reaches its maximum capacity, the pressure 
drop across it increases exponentially. At this point, a 
valve is actuated to bypass the filter, or the downstream 
pressure capability is severely limited. This condition is 
corrected by shutting the system down to clean the
filter element or by replacing the element. Because of 
the wide variations in system fluid cleanliness, the 
operational time span of a filter can never be predicted. 
The end of the useful filter service normally is indicated 
by a popup differential pressure switch or by a differ-
ential pressure gauge, both of which require frequent 
monitoring that is difficult in remote inaccessible 
installations. 
Thisdocumentwas 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
The solution: 
Sequential-strip and sequential-disk filters do not 
require frequent monitoring. 
How it's done: 
The sequential-strip filter (see Figure 1) senses 
increasing pressure drop and uses this to compress a 
bellows. The compression of the bellows stores energy 
in a spring until a predetermined pressure-drop level is 
reached. At this point, the bellows and spring are 
released. The relaxation of the spring is used to move a 
clean area of screen into position across the fluid 
stream. In section A-A of Figure 1, the clean screen is 
shown in position across the flow aperture. The dirty 
screen is taken up on a windup spool, and the clean 
screen is stored on a cartridge spool. The number of 
screen frames used is shown on a mechanical indicator. 
This indication can be converted readily to an electrical 
signal, capable of remote readout. 
The sequential-disk filter (see Figure 2) consists of a 
series of screen disks stacked on top of each other, 
with suitable seals between their mating surfaces. Each 
disk has a built-in spring-assisted burst diaphragm. Fluid 
flows into the filter at the top and from inside to 
outside on the first screen disk. As contamination builds 
up on the first disk, the pressure drop across the disk 
increases until the failure point of the burst diaphragm 
is reached. Failure of the diaphragm allows system fluid 
(continued overleaf) 
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=19730000430 2020-03-17T07:30:27+00:00Z
Burst Diaphragm 
Screen Disks 
Figure 2. Sequential-Disk Filter
. 
to flow into the second screen disk, and the process 
repeats itself. A piston-operated mechanical counter 
displays the number of the disk in use. This indication 
can also be converted to an electrical-signal remote 
readout. 
Note: 
No further documentation is available. Specific ques-
tions, however, may be directed to: 
Technology Utilization Officer 
Johnson Space Center 
Code JM7 
Houston, Texas 77058 
Reference: B73.10430
Patent status: 
Inquiries concerning rights for the commercial use of 
this invention should be addressed to: 
Technology Utilization Officer 
Johnson Space Center 
Code AM 
Houston, Texas 77058
Source: J. P. Winzen of

Brunswick Corp.
under contract to

Johnson Space Center
(MSC-14592)
S 
B73-10430	 Category 06
	
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Sequential-strip and sequential-disk filters

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