Seal for separation device

A spiral wound liquid separation device enclosed within a housing and a cover for the housing is provided with a seal which separates liquid feed to the device from liquid retentate produced by the device. The seal is of unitary construction with one end sealed to the outside surface of the spiral wound separation device and with a second end positioned between the housing and the cover under compression.

BACKGROUND OF THE INVENTION 
This invention relates to a sealing means for a spiral wound filtration 
apparatus such as in reverse osmosis or ultrafiltration apparatus. 
At the present time, liquid separation apparatus such as filtration or 
reverse osmosis apparatus including a spiral wound cartridge are utilized 
in separation processes for liquids. The spiral wound cartridge is formed 
by interleaving one or more membrane layers, one or more spacer layers and 
one or more liquid impermeable layers about a central hollow core which 
functions as an outlet for permeate. The cartridge includes a sealing 
configuration which prevents admixture of permeate with either feed or 
retentate. The cartridge is positioned within a housing wherein feed is 
introduced axially into the cartridge, retentate is removed axially from 
the cartridge and permeate is recovered by way of the central hollow core 
which is in fluid communication with a fluid outlet in a cover which also 
seals the cartridge within the housing. At the present time, the feed is 
sealed from the retentate by a chevron-shaped elastomeric seal which is 
interposed between the outside surface of the cartridge and the inside 
surface of the housing for the cartridge in a manner to seal the feed 
inlet from the retentate outlet. An O-ring, spaced apart from the 
chevron-shaped seal, is positioned between the cover for the housing and 
the housing to prevent feed leakage from the housing prior to its being 
passed through the spiral wound cartridge. Unfortunately, the 
chevron-shaped seal has a tendency to fail under the normal operating 
conditions of pressure and fluid flow primarily due to incomplete sealing 
at the inside wall of the housing and the seal surface contacting the 
inside wall of the housing. 
U.S. Pat. No. 4,594,161 describes a seal structure for a reverse osmosis 
apparatus wherein a seal is effected between a housing for a spiral wound 
cartridge and a cover for the housing. 
Accordingly, it would be desirable to provide a sealing means which 
prevents a feed liquid from by-passing a liquid separation means prior to 
being removed as retentate. Such as sealing means would permit more 
efficient liquid separation processes which utilize a spiral wound 
separation cartridge. 
SUMMARY OF THE INVENTION 
The present invention provides a seal for use in conjunction with a spiral 
wound liquid separation device which includes a filtration membrane such 
as an ultrafiltration membrane or a semipermeable reverse osmosis 
membrane. The spiral wound separation device is positioned with a housing, 
and a cover for the housing that cooperates with the housing and the seal 
to effect desired fluid flow through the separation device. The seal 
prevents admixture of a feed liquid to be passed through the separation 
device and retentate liquid removed from the separation device. One end of 
the seal is adhered to the outside surface and about the entire 
circumference of the spiral wound separation device adjacent a fluid inlet 
within a cover. A second end of the seal is positioned between a top 
surface of the housing and the cover. The seal prevents incoming liquid 
feed to by-pass the separation device prior to being removed from the 
housing. The second end of the seal preferably has a generally O-ring 
shaped cross section and is maintained in a sealing relationship between 
the cover and the housing under a compressive force.

DESCRIPTION OF SPECIFIC EMBODIMENTS 
The seal of this invention is useful in conjunction with spiral wound 
liquid separation devices such as are utilized in reverse osmosis or 
ultrafiltration. Examples of spiral wound liquid separations devices are 
disclosed in U.S. Pat. Nos. 3,966,616; 4,548,714; 4,842,736 and 4,906,372 
which are incorporated herein by reference. The separation device is 
enclosed within a housing and a cover for the housing. The seal of this 
invention seals a feed liquid from a retentate liquid and also seals feed 
liquid, retentate liquid and permeate liquid from the environment 
surrounding the liquid separation device utilizing the seal. The seal is 
of unitary construction and has a first surface adhered to an outside 
surface of the spiral wound liquid separation device and has a free end 
positioned between the housing and the cover under a compressive force. In 
a preferred form of the invention, the free end of the seal has an 
essentially O-ring cross section. 
Referring to the figures, the seal 10 of this invention is formed of a 
unitary construction and includes a first end 12 which is adhered to the 
outside surface 14 of a spiral wound liquid separation device 16. The 
first end 12 can be adhered by any conventional means such as with an 
adhesive composition or a tape including an adhesive layer. The first 
surface 12 is adhered about the entire circumference of the outside 
surface 14 so that volume 18 is sealed from volume 20. The free end 22 of 
seal 10 is positioned on the surface 24 of flange 26 of housing 28. The 
surface 24 can include a recess to accommodate a portion of the 
cross-section of the free end 22 of the seal 10. The free end 22 is 
positioned between the surface 24 of the housing 28 and the surface 30 of 
the cover 32 such as with conventional nuts and bolts extending through 
pathways 34 and 36. The cover is provided with a feed inlet 38 and a feed 
outlet 40 so that feed can be introduced into the spiral wound liquid 
separation device 16 which directs permeate into central pathway 42 while 
retentate is directed into volume 20. Retentate is removed from volume 20 
by retentate exit 44. Extension 46 of cover 32 has two O-rings 48 and 50 
which effect a seal between the feed inlet 40 and the permeate outlet 52. 
Permeate is directed through permeate outlet conduit 54 for recovery. 
The sealing means of the prior art is shown in FIG. 3. The sealing means 
comprises two distinct seals 58 and 60. Seal 58 comprises an O-ring which 
is positioned between a flap 26 of a housing 28 and is distinct and 
separated from seal 60. Seal 60 is adhered to the outside surface of a 
spiral wound liquid separation device (not shown) at area 62. The seal 60 
includes two leaves 64 and 65 which expand apart from each other under the 
pressure of a liquid feed introduced through a cover (not shown) similar 
to that described above with reference to FIG. 1. The expansion of the 
leaf 64 against inside surface 70 of housing 28 is intended to effect a 
seal between feed liquid and retentate liquid in volume 20 which is to be 
removed through retentate outlet conduit 44. These seals are undesirable 
since intimate contact between leaf 64 and surface 70 is not always 
achieved since, for example, the leaf 64 can become fluted under the 
liquid pressures encountered during use of the apparatus. In addition, the 
space between leaves 64 and 66 can become a dead space where essentially 
no liquid flow occurs. This can lead to the undesirable proliferation of 
microorganisms within the dead space. Therefore, the sealing means shown 
in FIG. 3 are undesirable.