U.S. patent application number 15/972852 was filed with the patent office on 2018-09-06 for membrane potting methods.
This patent application is currently assigned to Evoqua Water Technologies LLC. The applicant listed for this patent is Evoqua Water Technologies LLC. Invention is credited to Peter Breffni Ackland, Michael Collignon, Ying Hao Teo.
Application Number | 20180250853 15/972852 |
Document ID | / |
Family ID | 50338089 |
Filed Date | 2018-09-06 |
United States Patent
Application |
20180250853 |
Kind Code |
A1 |
Ackland; Peter Breffni ; et
al. |
September 6, 2018 |
Membrane Potting Methods
Abstract
Apparatus and methods are disclosed which reduce stress
formation in potting heads for porous hollow filtration membranes.
In one example, there is disclosed a potting sleeve for forming a
potting head which includes a first fixed portion and a second
portion which is movable relative to the first fixed portion to
reduce a peripheral extent thereof. In another example, a method of
mounting a porous hollow membrane in a membrane filtration
apparatus includes positioning a portion of porous hollow membranes
within a mold and introducing a curable potting material into the
mold so as to immerse the portion of the porous hollow membranes
and at least part of one or more deformable members in the potting
material. The method further includes at least partially curing the
potting material to form a potting head and removing the potting
head and the one or more deformable members from the mold.
Inventors: |
Ackland; Peter Breffni;
(Seven Hills, AU) ; Collignon; Michael;
(Annagrove, AU) ; Teo; Ying Hao; (Carlingford,
AU) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Evoqua Water Technologies LLC |
Pittsburgh |
PA |
US |
|
|
Assignee: |
Evoqua Water Technologies
LLC
Pittsburgh
PA
|
Family ID: |
50338089 |
Appl. No.: |
15/972852 |
Filed: |
May 7, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14033968 |
Sep 23, 2013 |
9962865 |
|
|
15972852 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01D 63/022 20130101;
B29C 39/10 20130101; B01D 2313/21 20130101; B01D 63/02
20130101 |
International
Class: |
B29C 39/10 20060101
B29C039/10 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 26, 2012 |
AU |
2012904203 |
Sep 23, 2013 |
AU |
2013231145 |
Claims
1. A potting sleeve for use in forming a potting head having a
porous hollow membrane mounted therein, the potting sleeve
including a first fixed portion and a second portion which is
movable relative to the first fixed portion to reduce a peripheral
extent of the second portion.
2. The potting sleeve of claim 1, wherein the second portion of the
potting sleeve is inwardly deformable to reduce the peripheral
extent thereof.
3. The potting sleeve of claim 2, wherein the second portion of the
potting sleeve includes structurally weakened regions configured to
provide for the second portion of the potting sleeve to be inwardly
deformable.
4. The potting sleeve of claim 1, wherein the potting sleeve
includes one or more openings in a wall of the potting sleeve.
5. The potting sleeve of claim 4, wherein the openings are
slots.
6. The potting sleeve of claim 1, wherein the second portion of the
potting sleeve is formed of a flexible material.
7. A method of mounting a porous hollow membrane in a potting head
of a membrane filtration apparatus, the method comprising:
providing a mold for receiving potting material; positioning a
potting sleeve within the mold, the potting sleeve including a
first fixed portion and a second portion which is movable relative
to the first fixed portion to reduce a peripheral extent of the
second portion; positioning a portion of the porous hollow membrane
to be mounted in a region of the mold encompassed by the potting
sleeve; introducing a curable potting material into the region to
immerse the portion of the porous hollow membrane in the potting
material; at least partially curing the potting material to form
the potting head; and removing the potting head and the potting
sleeve from the mold.
8. The method of claim 7, wherein the second portion of the potting
sleeve is inwardly deformable to reduce the peripheral extent
thereof.
9. The method of claim 8, wherein the second portion of the potting
sleeve includes structurally weakened regions configured to provide
for the second portion of the potting sleeve to be inwardly
deformable.
10. The method of claim 7, wherein the potting sleeve is provided
with one or more openings in a wall of the potting sleeve.
11. The method of claim 10, wherein the openings are slots.
12. The method of claim 7, wherein the second portion of the
potting sleeve is formed of a flexible material.
13. A method of mounting a porous hollow membrane in a support
structure of a membrane filtration apparatus, the method
comprising: providing a mold for receiving potting material;
positioning one or more deformable members within the mold;
positioning a portion of the porous hollow membrane to be mounted
within the mold; introducing a curable potting material into the
mold to immerse the portion of the porous hollow membrane and at
least part of the one or more deformable members in the potting
material; at least partially curing the potting material to form
the potting head; and removing the potting head and the one or more
deformable members from the mold.
14. The method of claim 13, wherein the deformable member comprises
a cylindrical plug.
15. The method of claim 14, wherein the plug is hollow and
collapsible.
16. The method of claim 13, wherein the deformable member is formed
of a flexible material.
17. The method of claim 13, wherein the deformable member is formed
of a material selected from the group consisting of a soft resin
material and rubber.
18. The method of claim 13, wherein an outer surface of the
deformable member is provided with engagement formations.
19. The method of claim 18, wherein the engagement formations
comprise one or more of a groove, a rib, a shoulder, and a fin.
20. The method of claim 18, wherein the engagement formations
extend axially from a central body of the deformable member.
21. The method of claim 18, wherein the engagement formations
extend circumferentially from a central body of the deformable
member.
22. A structural element for supporting a potting head having a
porous hollow membrane mounted therein and extending from a first
surface of the potting head, the structural element comprising a
cap configured to engage with a potting sleeve of the potting head,
the cap having a bearing surface which supports a second surface of
the potting head opposite to the first surface of the potting head
when the cap is engaged with the potting sleeve.
23. The structural element of claim 22, wherein the cap is
generally cylindrical and the bearing surface includes one or more
radially extending ribs.
24. The structural element of claim 22, wherein the structural
element extends into the second surface of the potting head.
25.-29. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a division of and claims benefit under
35 U.S.C. .sctn. 120 to co-pending U.S. patent application Ser. No.
14/033,968, titled MEMBRANE POTTING METHODS, filed on Sep. 23,
2013, which claims foreign priority benefits under 35 U.S.C. .sctn.
119(a)-(d) or 35 U.S.C. .sctn. 365(b) from Australian application
no. 2012904203, filed Sep. 26, 2012, each of which is incorporated
herein by reference in its entirety for all purposes.
BACKGROUND
1. Technical Field
[0002] Aspects and embodiments disclosed herein relate generally to
methods and apparatus for mounting porous hollow filtration
membranes in a membrane filtration system.
2. Discussion of Related Art
[0003] Any discussion of the prior art throughout the specification
should in no way be considered as an admission that such prior art
is widely known or forms part of common general knowledge in the
field.
[0004] Synthetic polymeric membranes are well known in the field of
ultrafiltration and microfiltration for a variety of
implementations, including desalination, gas separation,
filtration, and dialysis. The properties of the membranes vary
depending on the morphology of the membranes, for example,
depending on parameters such as symmetry, pore shape, and pore
size, and the chemical nature of the polymeric material used to
form the membrane.
[0005] A large membrane surface area may be provided when a large
filtrate flow is desired. In commercial embodiments, a large number
of hollow porous membranes may be mounted together and housed in
filtration modules. A commonly used technique to reduce the size of
the filtration apparatus is to form the hollow porous membranes in
the shape of hollow porous fibers. The hollow porous membranes act
in parallel to filter a feed liquid, for example, water for
purification. By producing a pressure differential across the
membrane walls, the liquid is forced to flow through the pores of
the walls of each of the hollow porous membranes while contaminants
remain trapped on one side of the membranes and filtrate is
withdrawn from the other side. In systems where feed liquid is
applied to the outer walls of the membranes (outside-in
filtration), the filtrate collects inside the hollow regions,
cavities or channels (known as lumens) within the porous hollow
membranes and is drawn off through ends of the lumens.
[0006] By sealing the ends of a porous hollow membrane in a module
pot an impenetrable barrier may be formed between the feed and the
filtrate. It is desirable that the seal formed by the barrier
between the feed and filtrate be maintained to avoid contamination
of the filtrate with feed. It is thus desirable that such module
pots be designed to withstand forces such as hydraulic pressure
from fluid flow inside the filtration module which might otherwise
compromise the seal between the feed and the filtrate.
[0007] In addition to sealing the ends of porous hollow membranes,
a module pot may be designed to perform further functions including
structurally supporting and mounting the membranes within a module
or otherwise within a filtration system. In some filtration
arrangements, filtrate is withdrawn only from one end of the
membranes and the other ends are merely sealed and supported by a
potting head. In other arrangements, only one potting head is
provided with the membranes being looped with both open ends
located in the same potting head.
[0008] In some potting arrangements, the porous membrane ends may
be sealingly potted using a curable resin material with the porous
membrane ends being positioned within the resin material in its
liquid non-cured state. The resin material may be allowed to cure
to form a generally solid potting head. The curable resin material
may be surrounded by a potting sleeve. The potting sleeve may be
used to provide an interface between the potting head formed by the
cured resin material and associated equipment such as headers and
mounting apparatus.
SUMMARY
[0009] It has been found that some curable potting materials which
may be used to secure filtration membranes within a potting head
disposed in a potting sleeve may shrink during the curing process.
This shrinkage may result in the formation of residual tensile
stress within the potting head due to resistance of the potting
sleeve to such shrinkage. Residual tensile stress in potting
materials has been found to not only decrease fracture strength and
toughness but also to reduce the fatigue life of the materials. The
residual tensile stress may cause cracking, splitting, and/or
breaking of the potting head. This can result in compromising the
separation between the feed liquid and the filtrate stream in a
filtration system and possible undesirable contamination of
filtrate.
[0010] It would be desirable to provide an arrangement of a potting
head and potting sleeve in which the formation of residual stress
within the potting head during curing of the potting material is
reduced as compared to prior known methods.
[0011] According to one aspect, there is provided a potting sleeve
for use in forming a potting head having a porous hollow membrane
mounted therein. The potting sleeve includes a first fixed portion
and a second portion which is movable relative to the first fixed
portion to reduce a peripheral extent of the second portion.
[0012] In some embodiments, the second portion of the potting
sleeve is inwardly deformable to reduce the peripheral extent
thereof. The second portion of the potting sleeve may include
structurally weakened regions configured to provide for the second
portion of the potting sleeve to be inwardly deformable. The second
portion of the potting sleeve may be formed of a flexible
material.
[0013] In some embodiments, the potting sleeve includes one or more
openings in a wall of the potting sleeve. The openings may be
slots.
[0014] In accordance with another aspect, there is provided a
method of mounting a porous hollow membrane in a potting head of a
membrane filtration apparatus. The method comprises providing a
mold for receiving potting material and positioning a potting
sleeve within the mold. The potting sleeve includes a first fixed
portion and a second portion which is movable relative to the first
fixed portion to reduce a peripheral extent of the second portion.
The method further comprises positioning a portion of the porous
hollow membrane to be mounted in a region of the mold encompassed
by the potting sleeve, introducing a curable potting material into
the region to immerse the portion of the porous hollow membrane in
the potting material, at least partially curing the potting
material to form the potting head, and removing the potting head
and the potting sleeve from the mold.
[0015] In some embodiments, the second portion of the potting
sleeve is inwardly deformable to reduce the peripheral extent
thereof. The second portion of the potting sleeve may include
structurally weakened regions configured to provide for the second
portion of the potting sleeve to be inwardly deformable. The second
portion of the potting sleeve may be formed of a flexible
material.
[0016] In some embodiments, the potting sleeve is provided with one
or more openings in a wall of the potting sleeve. The openings may
be slots.
[0017] In accordance with another aspect, there is provided a
method of mounting a porous hollow membrane in a support structure
of a membrane filtration apparatus. The method comprises providing
a mold for receiving potting material, positioning one or more
deformable members within the mold, positioning a portion of the
porous hollow membrane to be mounted within the mold, introducing a
curable potting material into the mold to immerse the portion of
the porous hollow membrane and at least part of the one or more
deformable members in the potting material, at least partially
curing the potting material to form the potting head, and removing
the potting head and the one or more deformable members from the
mold.
[0018] In some embodiments, the deformable member comprises a
cylindrical plug.
[0019] The plug may be hollow and collapsible. The plug may be
expandable.
[0020] In some embodiments, the deformable member is formed of a
flexible material. The deformable member may be formed of a
material selected from the group consisting of a soft resin
material and rubber.
[0021] In some embodiments, an outer surface of the deformable
member is provided with engagement formations. The engagement
formations may comprise one or more of a groove, a rib, a shoulder,
and a fin. The engagement formations may extend axially from a
central body of the deformable member. The engagement formations
may extend circumferentially from a central body of the deformable
member.
[0022] In accordance with another aspect, there is provided a
structural element for supporting a potting head having a porous
hollow membrane mounted therein and extending from a first surface
of the potting head. The structural element comprises a cap
configured to engage with a potting sleeve of the potting head, the
cap having a bearing surface which supports a second surface of the
potting head opposite to the first surface of the potting head when
the cap is engaged with the potting sleeve.
[0023] In some embodiments, the cap is generally cylindrical and
the bearing surface includes one or more radially extending ribs.
The structural element may extend into the second surface of the
potting head. In accordance with another aspect, there is provided
a potting sleeve for use in forming a potting head having a porous
hollow membrane mounted therein. The potting sleeve includes at
least one reinforcement member positioned between inner walls of
the potting sleeve, the reinforcement member having opposed sides
extending axially of the potting sleeve between a first end portion
and an opposed second end portion of the reinforcement member. The
reinforcement member is connected to an internal wall of the
potting sleeve at connection points on each of the opposed sides of
the first end portion and the reinforcement member is free of
engagement with the potting sleeve apart from at the connection
points.
[0024] In some embodiments, the reinforcement member is plate-like.
The reinforcement member may be located along a diameter of the
potting sleeve.
[0025] In some embodiments, the first end portion of the
reinforcement member is spaced axially from one end of the potting
sleeve.
[0026] In some embodiments, the reinforcement member apart from
adjacent the connection points is, in use, positioned within the
potting head.
BRIEF DESCRIPTION OF DRAWINGS
[0027] The accompanying drawings are not intended to be drawn to
scale. In the drawings, each identical or nearly identical
component that is illustrated in various figures is represented by
a like numeral. For purposes of clarity, not every component may be
labeled in every drawing. In the drawings:
[0028] FIG. 1 is an elevational view of a top potting sleeve for a
membrane sub-module;
[0029] FIG. 2 is a plan view of the potting sleeve of FIG. 1;
[0030] FIG. 3A is an elevational section view of the potting sleeve
of FIG. 1 taken along section B-B of FIG. 2;
[0031] FIG. 3B is a similar side elevational sectional view as FIG.
3A with the potting sleeve positioned in a potting mold;
[0032] FIG. 4 is a broken elevational view of a membrane sub-module
according to another embodiment;
[0033] FIG. 5 is an underside perspective view of the lower potting
sleeve of the sub-module of FIG. 4;
[0034] FIG. 6 is an elevational view of the lower potting sleeve of
the sub-module of FIG. 4;
[0035] FIG. 7 is an elevational view of a deformable member
according to another embodiment;
[0036] FIG. 8 is a cross-sectional elevational view of the
deformable member of FIG. 7;
[0037] FIG. 9 is a top perspective view of a deformable member
according to another embodiment;
[0038] FIG. 10A is a cross-sectional elevational view of a potting
mold with the deformable member of FIG. 7 positioned in use in the
potting material together with filtration membranes;
[0039] FIG. 10B is a similar view as FIG. 10A of the deformable
member of FIG. 7 positioned in use in a potting head;
[0040] FIG. 11 is a top perspective view of a potting sleeve with
structural extension according to another embodiment;
[0041] FIG. 12 is a top perspective cross sectional view taken
along a diameter of the potting sleeve of FIG. 11;
[0042] FIG. 13 is an exploded top perspective view of an upper
portion of a membrane sub-module employing the potting sleeve
according to the embodiment of FIGS. 11 and 12;
[0043] FIG. 14 is a top perspective cross sectional view taken
along a diameter of the membrane sub-module of FIG. 13 in assembled
form;
[0044] FIG. 15 is a cross sectional elevational view of the
sub-module of FIG. 14;
[0045] FIG. 16 is an elevational view of an upper potting sleeve
according to another embodiment;
[0046] FIG. 17 is a top perspective cross sectional view taken
along a diameter of the potting sleeve of FIG. 16 with potting
resin in the potting sleeve; and
[0047] FIG. 18 is a top perspective cross sectional view taken
along a diameter of the potting sleeve of FIG. 16 without potting
resin in the sleeve.
DETAILED DESCRIPTION
[0048] Aspects and embodiments disclosed herein are not limited to
the details of construction and the arrangement of components set
forth in the following description or illustrated in the drawings.
Aspects disclosed herein are capable of other embodiments and of
being practiced or of being carried out in various ways. Also, the
phraseology and terminology used herein is for the purpose of
description and should not be regarded as limiting. The use of
"including," "comprising," "having," "containing," "involving," and
variations thereof herein is meant to encompass the items listed
thereafter and equivalents thereof as well as additional items.
[0049] Aspects and embodiments disclosed herein are directed to
filtration modules or sub-modules and to methods of forming same.
Aspects and embodiments disclosed herein provide for a reduced
amount of residual stress in potting material of the potting heads
of the filtration modules or sub-modules after formation of the
potting heads as compared to prior known methods and apparatus.
This reduction in residual stress may reduce the chances of
mechanical failure of the potting head, for example, delamination
of membranes from the potting material in which they are retained,
delamination of the potting material from a potting sleeve in which
it may be disposed, cracking of the potting material, or other
forms of mechanical failure. Aspects and embodiments disclosed
herein also provide for a membrane module to include a potting head
having a potting material layer thickness with a strength greater
than prior known potting heads having potting material layers of
equivalent thicknesses.
[0050] In some embodiments, a potting sleeve for use in forming a
filtration membrane module may be provided with one or more
features to at least partially alleviate mechanical stresses which
may develop within a potting material during curing of the potting
material in the potting sleeve. Many potting materials shrink upon
curing, resulting in tensile stresses forming in the potting
material if the potting material is constrained to maintain set
dimensions during curing. In some embodiments disclosed herein a
potting sleeve into which a potting material may be introduced and
then cured includes one or more features which provide for one or
more dimensions of one or more portions of the potting sleeve to
decrease during the curing of the potting material. The decrease in
the one or more dimensions of the potting sleeve during curing of
the potting material accommodates at least some of the shrinkage of
the potting material thus reducing the tendency for tensile
stresses to develop in the curing potting material.
[0051] In other embodiments one or more stress relieving features
may be disposed in the curing potting material in a potting sleeve.
The one or more features may expand or be displaced during the
curing of the potting material, relieving mechanical stresses which
might otherwise develop in the curing potting material.
[0052] Referring to FIGS. 1 to 3 there is shown one embodiment of
an upper or top potting sleeve for a membrane sub-module 4. The
potting sleeve 5 is generally cylindrical though it will be
appreciated that the cross-sectional shape of the potting sleeve is
not critical and many suitable cross-sectional shapes may be used
depending on the desired geometric shape of the potting head. For
example, in various embodiments, the potting sleeve 5 may have an
elliptical, square, rectangular, or triangular cross-section.
[0053] The outer surface 6 of the potting sleeve 5 may be provided
with a number of engagement formations. The engagement formations
may comprise, for example, circumferentially extending grooves,
shoulders, or ribs on outer surface 6 of the potting sleeve 5. It
will be appreciated by those in the art that, depending on specific
implementations, a variety of different forms and shapes of
formation may be used to provide for engagement of the potting
sleeve 5 and its associated potting head with other components of
the membrane sub-module 4.
[0054] A lower portion of the potting sleeve 5 is provided with a
circumferential, outwardly extending rib 7 which, in use, is
supported on a shoulder provided in the housing of the sub-module
(not shown). Above the rib 7, two axially spaced rows of
circumferentially spaced through-openings 8 and 9 are provided in
the wall of the potting sleeve 5. The openings 8, 9 are shown are
circular holes but it will be appreciated the shape and size of the
openings is not critical and, in embodiments where openings are
desired, any suitable form of opening may be used. For example, the
openings 8, 9 may be in the form of circular holes, oval holes,
slits, slots, or other shapes.
[0055] Above the openings 8, 9, a pair of circumferential,
outwardly extending ribs 10 and 11 form a groove 12 which, in use,
accommodates a sealing O-ring (not shown). A further
circumferential, outwardly extending rib 13 is provided above and
vertically spaced from the ribs 10 and 11 to define a supporting
shoulder 13'. In some embodiments, it may be desirable to provide
ribs 10, 11, and 13 in a region of the potting sleeve 5 which is
substantially rigid to ensure the integrity of any mounting or
sealing arrangements or structures.
[0056] An upwardly extending skirt portion 14 is provided above the
rib 13. The skirt portion 14 includes a circumferential groove 15
in its base portion 16 and a reduced diameter inset upper portion
17 with a further circumferential groove 18 positioned between the
base portion 15 the upper extent of the inset portion 17. This
groove 18 serves to form an outwardly extending lip 19 at the upper
extent of the inset portion 17. The lip 19 may be used to engage
with a lifting mechanism (not shown) to remove the sub-module from
the filtration apparatus.
[0057] The skirt portion 14 forms a portion of the potting sleeve 5
which it movable relative to the fixed lower portion of the sleeve.
The skirt portion 14 may be utilized to reduce the peripheral
extent of the movable portion of the potting sleeve 5. The skirt
portion 14 may include a plurality of circumferentially spaced,
vertically extending slots 20 formed therein to define deformable
or flexible finger portions 21 therebetween.
[0058] As best shown in FIGS. 3A and 3B, in use, the upper potting
sleeve 5 is positioned in a potting mold 23, together with the
membranes 24 to be potted, and is filled with potting material 22
from a level just below the upper set of through-openings 9 to
above the upper extent of the potting sleeve 5. The potting
material 22 may include any material which may retain filtration
membranes 24 within the potting sleeve 5. The potting material 22
may include, for example, urethane, resin, epoxy, or other suitable
materials. In some embodiments, the membrane pot may be formed from
more than a single layer of potting material, for example, as
disclosed in co-pending U.S. patent application Ser. No.
13/087,548, which is incorporated herein by reference in its
entirety for all purposes. When more than one layer of potting
material is used the layers may be formed of different materials.
For example a lower layer distal from the side of the potting head
from which the membranes 24 emerge may be formed of a material
which strongly adheres to the membranes 24 but is relatively rigid,
for example, an epoxy material. A softer potting material, for
example, a urethane material may form a layer above the rigid
layer. The membranes 24 may emerge from the softer potting
material. The softer potting material may flex in use providing for
the membranes 24 to move slightly at the point they enter the
softer potting material, which may decrease the chances for the
membranes 24 to shear from the potting head.
[0059] In some embodiments, the inner surface of the potting sleeve
5 may include one or more layers of material which may promote
adhesion of the potting material 22 to the potting sleeve, and/or
which may elastically deform to facilitate the reduction in
mechanical stresses in the cured potting material 22. The one or
more layers of material may include, for example, a layer of a
urethane material.
[0060] As the potting material 22 cures and contracts, the wall of
the portion of the potting sleeve 5 defined by the flexible finger
portions 21 may deform radially inward to reduce the peripheral
extent of skirt portion 14 of the potting sleeve 5 and reduce or
eliminate mechanical stresses which might otherwise form within the
cured potting material.
[0061] It will be appreciated that although slots 20 may be
utilized in some embodiments to weaken the skirt portion 14 and
provide a movable portion of the potting sleeve 5 to reduce the
peripheral extent thereof by inward deformation of the sleeve wall,
a variety of other configurations may be used to achieve a similar
result in providing for deformability of the potting sleeve. The
slots 20 may be replaced by or augmented with thin flexible regions
which enable the finger portions 21 to flex inwardly. Further, in
some embodiments, the potting sleeve 5 or a portion of the potting
sleeve may be formed from a deformable or flexible material. The
flexible material may be any material which may adhere to potting
material 22 which may be used to retain filtration membranes within
the potting sleeve 5 and which has sufficient flexibility to
contract along with the potting material 22 upon curing. The
flexible material may include, for example, urethane or rubber. In
some embodiments, the flexible material may be urethane including a
flexibilizing agent.
[0062] In another embodiment, the wall of the potting sleeve or a
portion thereof may be formed of a number of radial segments which
move circumferentially relative to one another to produce an
inwardly collapsible configuration. Further, although the slots 20
are shown as extending generally vertically, it will be appreciated
that they may extend at an angle to vertical, if desired. For
example, the slots may extend horizontally, breaking the skirt 14
into a plurality of horizontal finger-like segments or may form a
spiral in the skirt 14.
[0063] Referring to FIGS. 4 to 6, there is shown an embodiment of a
lower potting sleeve 30. The lower potting sleeve 30 is generally
similar in configuration to the upper potting sleeve 5 described
above and may include any one or more of the features of the upper
potting sleeve 5.
[0064] FIG. 4 shows a broken perspective view of a membrane
sub-module 4 with an upper potting sleeve 5 and a lower potting
sleeve 30.
[0065] As shown in FIGS. 5 and 6, the lower potting sleeve 30 has a
smooth-walled fixed upper portion 31 divided from a fixed middle
portion 32 by a circumferential outwardly extending or protruding
locating shoulder 33. In a similar manner to the upper potting
sleeve 5, the middle portion 32 of the lower potting sleeve wall 34
is provided with a series of vertically spaced rows of
through-openings 35. The through-openings 35 in each row are
circumferentially spaced from one another and formed in
circumferentially spaced groups 36 consisting of a number of rows
of through-openings 35. The through-openings 35 are illustrated as
are rounded slots, however, it will be appreciated the form, shape,
size, and number of the through-openings 35 is not critical and any
suitable form or number of through-openings 35 may be employed. In
use, these openings 35 provide for fluid communication with the
membranes mounted in the potting head.
[0066] The lower extent of the middle portion 32 of the sleeve 30
is defined by a further circumferential, outwardly extending
locating shoulder 37. Adjacent and above the locating shoulder 37,
a further row of circumferentially spaced slot openings 38 are
provided in the sleeve wall. It will be appreciated the form,
shape, size, and number of the openings 38 is not critical and any
suitable form or number of openings 38 may be employed.
[0067] A lower skirt 39 extends downwardly below the shoulder 37
and has a circumferential groove 40 formed therein. In a similar
manner to the skirt 14 of the upper potting sleeve 5, the lower
skirt 39 is movable relative to the fixed upper portion 31 and the
fixed middle portion 32 of the lower porting sleeve 30. The lower
skirt 39 includes a plurality of circumferentially spaced,
vertically extending slots 41 formed therein to define deformable
or flexible finger portions 42 therebetween. The lower skirt 39
thus forms a movable portion of the potting sleeve to reduce the
peripheral extent thereof by deformation of the flexible finger
portions 42. As potting material disposed within the potting sleeve
30 cures and contracts, the wall 34 of the lower potting sleeve 30
defined by the flexible finger portions 42 can move radially inward
to reduce the peripheral extent of skirt 39 of the potting sleeve
30 to reduce or eliminated stresses which might otherwise be formed
within the cured potting head.
[0068] Although the embodiments described above include openings in
the potting sleeves and a variety of engagement formations formed
in the outer surfaces of the potting sleeves, it will be
appreciated these features are not critical and embodiments
comprising a simple plain potting sleeve without openings or
particular engagement formations could be employed provided the
potting sleeve includes a movable portion which enables the
peripheral extent of the potting sleeve to be reduced when the
potting material shrinks during curing, thus reducing the potential
for mechanical stresses to develop within the potting material.
[0069] Referring to FIGS. 7 to 10B, another embodiment of a potting
head 52 is illustrated. In this embodiment a deformable member 50
is positioned in the potting material 51 during the potting process
so as to relieve stresses produced during the curing of the potting
material 51.
[0070] As will be appreciated, a variety of different forms of
deformable member 50 may be used to achieve the desired function.
Embodiments disclosed herein are not limited to the type of
deformable member 50 illustrated in FIGS. 7 to 10B. Further,
although a single deformable member 50 is shown in FIGS. 10A and
10B, it will be appreciated that a number of deformable members 50
may be positioned as desired throughout the potting head 52.
[0071] One embodiment of a suitable deformable member 50 is shown
in FIGS. 7 and 8. The deformable member 50 comprises a generally
cylindrical, hollow, elongate plug 55. One end of the plug 55 is
formed with a conical head 56 while the other end is formed with an
enlarged diameter base portion 57. The outer wall of the elongate
plug 55 is provided with outwardly extending engagement formations
for providing engagement with the potting material of the potting
head. The engagement formations may comprise longitudinally
extending fins 58 spaced at 90.degree. intervals around the
circumference of the plug 55. It will be appreciated that more or
fewer than four longitudinally extending fins 58 may be utilized
and that these fins 58 need not be spaced at 90.degree. intervals
but may be spaced at any particular angular interval or intervals
desired. Further, in some embodiments, the fins 58 need not extend
along the lateral extent of the deformable member 50 as
illustrated, but may alternatively or additionally be in the form
of rings or tabs extending from a central body of the deformable
member with surfaces arranged normal to the lateral extent of the
central body of the deformable member 50 or at other angles as
desired. It will be appreciated that any suitable form of
engagement formation may be used, for example, grooves, ribs,
shoulders, dimples, or formations of other shapes.
[0072] The embodiment shown in FIG. 9 illustrates another form of
the engagement formations. In this embodiment the outer wall or
surface of the plug is provided with a series of axially spaced
circumferential grooves 59. It will be appreciated that in other
embodiments, the deformable member 55 may assume even additional
shapes. For example, the central body of the deformable member need
not by cylindrical as illustrated, but may rather be formed with a
square, rectangular, oval, or polygonal cross section, or any other
cross section as desired. Further, the cross-sectional area of the
central body of the deformable member 55 may vary along its lateral
extent, for example, expanding or decreasing from a base to a tip
of the deformable member 55.
[0073] The plug 55 may be hollow and may be made of thin molded
plastic material. In use, the thin plastic material may deform due
the heat released by the exothermic reaction which occurs during
curing of the potting material 52. In other embodiments, the
deformable plug may be formed of pre-molded rubber which can
readily adhere to the potting material.
[0074] In another embodiment, the deformable plug 55 can be molded
from a soft resin material, for example, urethane a short time (for
example, about 30 minutes) before pre-potting of the membranes. The
soft urethane plug can then be located in the potting material to
ensure chemical bonding between the plug and the potting material
of the potting head. The soft resin material provides a readily
deformable plug.
[0075] The deformable plug 55 may be molded in a mold coated with
polytetrafluoroethylene or another non-stick material to ensure the
outer surface of the plug is free of mold release agent which could
hinder the chemical bond between the plug 55 and the potting
material of the potting head.
[0076] FIGS. 10A and 10B show one embodiment of the deformable plug
55 located within a potting head 52.
[0077] In use, the plug 55 is attached by means of the enlarged
base portion 57 to a pre-potting dish 59'. The plug 55 is then
located within the potting mold 23 together with the membranes 24
to be potted, the potting sleeve 5 and potting material 51
introduced into the potting mold 23. The conical head 56 of the
plug 55 assists deflection of the membranes 24 away from the plug
55 during the insertion of the membranes into the potting mold 23.
The mold 23 may be centrifuged to facilitate correct distribution
of the potting material 51 around the membranes 24. Following
curing of the potting material 51, the base 57 of the plug may be
sliced off leaving the plug 55 flush with the top of the potting
head 52.
[0078] The soft core or cores created within the potting head 52 by
the deformable plug 55 will stretch or otherwise deform allowing
the potting material 51 to shrink as it cures, avoiding much of the
residual stress which might otherwise be produced by the shrinkage.
The reduction in residual stresses within the potting head 52 may
lead to a reduction in stress at the membrane-potting material
interface.
[0079] FIGS. 11 to 14 show a further embodiment of a potting head
arrangement including a mechanism for mechanically reinforcing the
potting head. In some prior methods as the size of a potting head
increases, the thickness of the potting head is increased to resist
fluctuating pressures within the membrane sub-module during use.
The increased thickness of the potting head results in excessive
usage of potting material and the consequent increase in weight of
the sub-module. Further, the increased thickness of the potting
head may result in an undesirable lumen pressure drop in the length
of the membrane as the length of the membrane operating at maximum
flow may be substantially increased. Accordingly, where possible,
it is desirable to minimize the thickness of the potting head while
maintaining its mechanical strength.
[0080] It has been recognized that increasing the size of a potting
head may increase the desirability of providing a structure to
reinforce the potting head to reduce deflection of the potting
material and prevent breakage and cracking of the potting material
or potting head during use. Incorporating reinforcing elements such
as ribs within the potting head, however, may result in a pot
structure which is rigid and stiff and which may resist the
shrinkage of potting material during curing, thus providing for the
formation of residual mechanical stresses in the cured potting
material. It has been found that where there is no connection
between the reinforcing elements and the potting sleeve surrounding
the potting material, a large shear stress may be produced between
the internal walls of the potting sleeve and the potting material
during curing. Alternatively, where no reinforcing elements are
provided, deflection of the potting head and/or potting material
during use when exposed to high pressures in a filtration system
may be undesirably large. It has been found desirable to provide
reinforcement of the potting material without producing excessive
stress between the potting material and the potting sleeve during
curing. Further, by providing a supporting structural element, the
mechanical integrity of the potting head can be maintained while
providing a potting material layer which is more resistant to
deformation than a potting material layer of an equivalent
thickness which is not reinforced with a supporting structural
element.
[0081] FIGS. 11 and 12 show perspective views of an extension
fitting 60 for a potting sleeve 61. The extension fitting 60
includes structural element 62 for supporting a potting head 63
having one or more porous hollow membranes (not shown) mounted
therein and extending from a first surface thereof. The structural
element 62 comprises a cap 64 configured to engage with a potting
sleeve 61 of the potting head 63. The cap 64 has a bearing surface
65 which supports a second surface 66 of the potting head 63
opposite the first surface of the potting head 63 which forms an
interface with the porous hollow membranes disposed in the potting
head 63 when the cap 64 is engaged with the potting sleeve 61. The
bearing surface 65 may comprise the lower surfaces of a series of
radially extending ribs 67 which are equally spaced around the
circumference of an inner wall of the generally cylindrical cap 64.
The ribs 67 extend diametrically of the cylindrical cap 64. The
cylindrical cap 64 has a downwardly extending skirt portion 68
below the lower surface 65 of each rib 67 and engages with a
reduced diameter stepped portion 69 of the potting sleeve 61. It
will be appreciated that other forms of ribs 67 may additionally or
alternatively be included in the cap 64. For example, the ribs 67
may include one or more rings which may be disposed concentrically
within the cap, and/or may include ribs which are non-equally
spaced around the circumference of the inner wall of the cap
64.
[0082] FIGS. 13 and 14 show the use of the extension fitting in a
membrane module 70. In this embodiment, the potting sleeve 61 and
cap 64 slide into a generally cylindrical module housing 71,
although it will be appreciated that the module housing 71, potting
sleeve 61, and cap 64 may in other embodiments have alternative
cross sections, for example, square or rectangular cross sections.
The module cap 64 is removably engaged with the top of the module
housing 71 and applies an axial support force to the surface 66 of
the potting head 63 to prevent deflection thereof under fluctuating
pressure from within the sub-module during use.
[0083] It will be appreciated that although a bearing surface
comprising the lower surfaces of the series of radially extending
ribs 67 is shown in FIGS. 11 to 14 a variety of forms of bearing
surface could alternatively or additionally be used. For example, a
cylinder having a generally flat bearing surface corresponding to
the upper surface of the potting head could also or alternatively
be used.
[0084] FIGS. 16 to 18 show another embodiment of a potting sleeve.
The overall configuration of the potting sleeve is similar in
configuration to the sleeve shown in FIGS. 5 and 6. Designations
are the same for the same features in each embodiment.
[0085] The potting sleeve 30 includes at least one reinforcement
member 80 positioned between inner walls of the potting sleeve 30.
The reinforcement member 80 has opposed sides 82 and 83 extending
axially of the potting sleeve 30 between a first end portion 84 and
an opposed second end portion 85 of the reinforcement member 80.
The reinforcement member is connected to an internal wall of the
potting sleeve 30 at connection points 86, 87 on each of the
respective opposed sides 82 and 83 of the first end portion 84. The
reinforcement member 80 is free of engagement with the potting
sleeve 30 apart from at the connection points 86, 87.
[0086] As best shown in FIG. 17 the reinforcement member 80 is
generally plate-like and the connection points 86 and 87 are
outwardly extending portions at the lower ends of each opposed side
82 and 83 of the reinforcement member 80. In use, the upper
non-fixed portion of the reinforcement member 80 is embedded in the
potting head material 88. The non-fixing of this portion enables
the reinforcement member 80 to move during curing and shrinking of
the potting material 88 and thus undue stresses between the potting
head material 88 and the inner surface of the potting sleeve 30 are
reduced or avoided. It will be appreciated that a similar form of
potting sleeve could be employed for the upper potting sleeve of
the membrane sub-module. The form, shape and dimensions of the
reinforcement member 80 are not critical. For example, the
reinforcement member 80 may in alternate embodiments include more
than one plate-like member which may be parallel or which may
intersect the plate-like member illustrated. The reinforcement
member 80 may be in a shape other than the generally rectangular
shape illustrated, for example a semi-circular shape. In some
embodiments, one or more apertures may be defined in the
reinforcement member 80. Further, it will be appreciated that one
of more reinforcement members having the desired operational
attributes could be used. The reinforcement members may interengage
or intersect one another provided they have a portion or portions
free to move relative to the potting material 88.
[0087] Having thus described several aspects of at least one
embodiment, it is to be appreciated various alterations,
modifications, and improvements will readily occur to those skilled
in the art. For example, it is to be appreciated that any of the
features of any of the embodiments disclosed herein may be combined
or substituted for features of any other embodiment disclosed
herein. Such alterations, modifications, and improvements are
intended to be part of this disclosure, and are intended to be
within the scope of the disclosure. Accordingly, the foregoing
description and drawings are by way of example only.
* * * * *