Title: Non-fragmenting pressure relief apparatus
Abstract: Non-fragmenting pressure relief apparatus includes at least one circular rupture disc having a central asymmetric bulged section and a peripheral flange portion. A semi-circular line of weakness extends around the periphery of the bulged section and presents a hinge portion between the ends of the line of weakness. A hold-down member for the rupture disc having an inner opening surrounding the bulged section of the disc is provided with a unitary segment that extends into the inner opening of the hold-down member. The spaced end extremities of the line of weakness extend beneath the hold-down member segment. The hinge portion of the disc upon rupture of the disc bends about a fulcrum defined by the outer margin of the hold-down segment, which in conjunction with deflection of the segment of the hold-down member contributes to anti-fragmentation of the disc.
Patent Number: 7,017,767 Issued on 03/28/2006 to Eijkelenberg, et al.
| Inventors:
|
Eijkelenberg; Tom (Westerlo, BE);
Dom; Guido (Olen, BE)
|
| Assignee:
|
Fike Corporation (Blue Springs, MO)
|
| Appl. No.:
|
712179 |
| Filed:
|
November 13, 2003 |
| Current U.S. Class: |
220/89.2; 137/68.19 |
| Current Intern'l Class: |
B65D 90/36 (20060101) |
| Field of Search: |
220/892,203.18
137/6819-6828
|
References Cited [Referenced By]
U.S. Patent Documents
| 3526336 | Sep., 1970 | Wood.
| |
| 4067154 | Jan., 1978 | Fike, Jr.
| |
| 4404982 | Sep., 1983 | Ou.
| |
| 4512171 | Apr., 1985 | Mozley.
| |
| 4512491 | Apr., 1985 | DeGood et al.
| |
| 4662126 | May., 1987 | Malcolm.
| |
| 4669626 | Jun., 1987 | Mozley.
| |
| 4759460 | Jul., 1988 | Mozley.
| |
| 4777974 | Oct., 1988 | Swift et al.
| |
| 4821909 | Apr., 1989 | Hibler et al.
| |
| 5036632 | Aug., 1991 | Short, III et al.
| |
| 5154202 | Oct., 1992 | Hibler et al.
| |
| 5267666 | Dec., 1993 | Hinrichs et al.
| |
| 5305775 | Apr., 1994 | Farwell.
| |
| 5467886 | Nov., 1995 | Hinrichs.
| |
| 6070365 | Jun., 2000 | Leonard.
| |
| 6494074 | Dec., 2002 | Cullinane et al.
| |
| 6540029 | Apr., 2003 | Snoeys et al.
| |
| 2004/0189020 | Sep., 2004 | Krebill et al.
| |
| Foreign Patent Documents |
| 957849 | Dec., 1947 | FR.
| |
Primary Examiner: Ngo; Lien M.
Attorney, Agent or Firm: Hovey Williams LLP
Claims
What is claimed is:
1. Non-fragmenting, forward-acting overpressure relief apparatus comprising:
a rupture disc having a central section provided with an overpressure receiving
face and a peripheral flange section, said central section of the rupture disc
having a bulged portion, said bulged portion of the central section of the disc
being of generally asymmetric shape;
said central section of the disc having a line of weakness extending around a
part of the central section, said line of weakness having opposed end regions in
spaced relationship that define a unitary hinge portion therebetween, each of said
end regions having an outermost end,
said line of weakness defining a part of the central section of the disc that
ruptures and opens upon application of a forward-acting force of at least predetermined
magnitude to said overpressure receiving face of the central section,
a hold-down member mounted on and engaging the peripheral flange section of the
rupture disc on the side thereof opposite the overpressure receiving face of the
central section of the disc, said hold-down member having an inner opening in generally
circumscribing relationship to the central section of the disc,
said hold-down member being provided with a unitary segment that extends into
the inner opening of the hold-down member thereof,
said segment of the hold-down member overlying and engaging the hinge portion
of the disc in disposition overlying said end regions of the line of weakness,
said segment having an innermost linear margin extending between opposed end
regions of the line of weakness in inwardly spaced relationship from respective
outermost ends of the line of weakness,
said segment of the hold-down member undergoing deflection in the direction of
a forward-acting overpressure force applied to the central section of the disc
to absorb and divert a part of the overpressure force away from the portion of
the hinge extending between respective outermost end regions of the line of weakness
and thereby contribute to prevention of separation of the central section of the
disc from the peripheral portion of the disc.
2. Apparatus as set forth in claim 1, wherein said segment of the hold-down member
has a generally rectilinear outer margin.
3. Apparatus as set forth in claim 2, wherein said segment of the hold-down member
is of generally planar configuration.
4. Apparatus as set forth in claim 1, wherein said central section of the rupture
disc is of generally planar configuration.
5. Apparatus as set forth in claim 1, wherein the portion of the central section
of the rupture disc between engaged by said segment of the hold-down member is
of generally flat configuration.
6. Apparatus as set forth in claim 1, wherein said margin of the hold-down member
segment is generally rectilinear and has opposed extremities that overlie and extend
beyond opposite respective portions of the line of weakness.
7. Apparatus as set forth in claim 1, wherein a transverse portion of the segment
of the hold-down member extending inwardly in a direction away from said margin
of the segment is deflected by the hinge portion of the central section of the
disc during rupture of the central section of the disc along substantially the
full length of the line of weakness, said deflected transverse portion of the segment
of the hold-down member absorbing a part of said rupture force applied to the central
section of the disc to divert said part of the force away from the part of said
hinge portion extending between respective outermost ends of the line of weakness.
8. Apparatus as set forth in claim 7, wherein said deflected transverse portion
of the segment of the hold-down member presents a generally inclined outwardly
facing surface engaged by the hinge portion of the disc, which in conjunction with
the force absorbed by the deflected transverse portion of the hold-down member
segment contributed to prevention of separation of the central section of the disc
from the peripheral flange section thereof at the hinge portion of the disc.
9. Apparatus as set forth in claim 1, said opposed end regions of the line of
weakness converging toward one another and located beneath the hold-down member segment.
10. Apparatus as set forth in claim 1, wherein said line of weakness is defined
by a series of elongated, end-to-end, spaced slits extending through the central
section of the rupture disc, said slits being separated from one another by individual
webs that are unitary with the remainder of the central section of the disc.
11. Apparatus as set forth in claim 10, wherein each of said slits is of substantially
greater length than the width of each web between respective ends of adjacent slits.
12. Apparatus as set forth in claim 1, wherein the central section of said rupture
disc has an outer edge portion that is generally circular, said hold-down member
being of generally annular configuration with the inner opening thereof surrounding
the circular edge portion of the central section of the disc.
13. Apparatus as set forth in claim 12, wherein the central section of the disc
has a major bulged portion and a unitary minor relatively flat portion, said flat
portion of the disc being in engagement with said segment of the hold-down member.
14. Apparatus as set forth in claim 1, wherein the line of weakness in the central
section of the disc is configured and sized and the segment of the hold-down member
engaging the central section of the disc is oriented with respect to the end regions
of the line of weakness such that upon rupture of the central section of the disc
along the line of weakness, the hinge portion of the central section of the disc
defined by the end regions of the line of weakness bends around the outer margin
of the segment of the hold-down member thus precluding separation of said hinge
portion and thereby the central section of the disc from the peripheral flange
section thereof along an imaginary line between said outermost ends of the end
regions of the line of weakness.
15. Apparatus as set forth in claim 10, wherein is provided a pair of said discs,
said discs being positioned with one disc overlying the other disc, there being
a layer of material therebetween precluding passage of fluid through the slits
until rupture of the webs between the slits of each line weakness of respective
discs resulting in rupture of the central section of both of the discs.
16. Apparatus as set forth in claim 15, wherein each of the discs is of sheet
material, the thickness of the sheet material of one of the discs being greater
than the thickness of the material of the other disc.
17. Non-fragmenting, forward-acting overpressure relief apparatus comprising:
a rupture disc having a central section provided with a overpressure receiving
face and a peripheral flange section,
the central section of the rupture disc having a major bulged portion and a unitary
minor relatively flat portion, the central section of the rupture disc having an
outer edge portion that is generally semicircular,
said central section of the disc having a line of weakness extending around a
part of the central section, said line of weakness having opposed end regions in
spaced relationship that define a unitary hinge portion therebetween, each of said
end regions having an outermost end,
said line of weakness defining a part of the central section of the disc that
ruptures and opens upon application of a forward-acting force of at least predetermined
magnitude said overpressure receiving face of the central section,
a generally annular hold-down member mounted on and engaging the peripheral flange
section of the rupture disc on the side thereof opposite the overpressure receiving
face of the central section of the disc, said hold-down member having an inner
opening in generally circumscribing relationship to the semicircular edge portion
of the central section of the disc,
said hold-down member being provided with a unitary segment that extends into
the inner opening of the hold-down member thereof, said segment of the hold-down
member being in engagement with said flat portion of the disc,
said segment of the hold-down member overlying and engaging the hinge portion
of the disc in disposition overlying said end regions of the line of weakness,
said segment having an innermost linear margin extending between opposed end
regions of the line of weakness in inwardly spaced relationship from respective
outermost ends of the line of weakness,
said segment of the hold-down member undergoing deflection in the direction of
a forward-acting overpressure force applied to the central section of the disc
to absorb and divert a part of the overpressure force away from the portion of
the hinge extending between respective outermost end regions of the line of weakness
and thereby contribute to prevention of separation of the central section of the
disc from the peripheral portion of the disc.
18. Apparatus as set forth in claim 17, wherein the part of the bulged portion
of the central section of the rupture disc remote from the hinge portion of the
disc is of greater three dimensional curvature than the three dimensional curvature
of the bulged portion of the central section of the rupture disc that approaches
and merges into the flat portion of the central section of the rupture disc.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to non-fragmenting, forward-acting pressure relief apparatus
used to protect processing equipment, pressure vessels, piping and structures from
high pressure events and/or to vent such equipment when destructive and catastrophic
overpressures result from any media where an explosion is a risk such as gas and
dust particle explosions. Explosion hazards exist in connection with various types
of gases and dust particles such as coal, flour, sugar, metal, and plastics. In
particular, the invention concerns a single pressure relief rupture disc and composite
rupture disc apparatus designed to rupture and vent a protected area, process or
equipment whenever an overpressure condition occurs that exceeds a preselected
value. The pressure relief rupture disc apparatus incorporates a rupture disc or
rupture disc assembly which ruptures and vents an area when overpressure condition
or explosion occurs wherein the section of the rupture disc or sections of the
rupture disc assembly open fully for pressure relief without fragmentation or separation
of the ruptured sections of the disc or composite sections of the disc assembly
from the remaining flange portion or portions of the assembly.
The non-fragmenting pressure relief apparatus is adapted for use in a variety
of applications including those where cycling between positive and negative pressure
in the protected system must be accommodated without rupturing of the disc or disc
assembly and opening of the rupturable section of the disc or the rupturable sections
of the disc assembly occurs only when a predetermined pressure value is exceeded
in the protected zone.
2. Description of the Prior Art
Many industrial processes involve handling and processing of materials that
under certain conditions can create hazardous overpressures resulting from explosive
conflagrations, or rapid rise in pressure from runaway processes, failure of protective
devices such as pressure regulating valves, and similar unpredictable mishaps.
Exemplary in this respect are processes involving gases or dust particles in contained
vessels or piping which can spontaneously ignite or produce an explosion from untoward
events such as a spark or the like and that result in dangerous pressure build-ups
within an enclosure, piping or containment vessels. Single rupture discs and composite
rupture discs usually having two separate rupture discs have long been employed
to protect vessels, pipes, conduits, and structures or areas from overpressure
of a predetermined value.
Explosion vents have been provided for many years to cover relief openings
in vessels, tanks, bag houses, and piping associated with such equipment, to relieve
excess pressure before the excessive pressure damages equipment, components, or
structures where the equipment is in operation. Bag houses or the like that are
constantly at risk of explosions by virtue of the high concentration of dust within
the bag house. Typically bag houses are constructed with one or more pressure relief
openings having explosion vents closing each relief opening. The explosion vents
seal the openings when the bag houses operate at normal positive or negative pressures
and then burst or open when the bag houses are subjected to a pressure build up
of a predetermined excess magnitude to uncover the openings and thus vent the interior
of the bag houses. To prevent premature or a late bursting, explosion vents must
be designed to consistently burst at a particular pressure level. The same type
of hazard must also be safely controlled in connection with processing equipment
involving combustible gases or dust particles, pipes conveying gases or dust laden
fluids from one part of a process to another or to a collection area, processing
vessels in which a runaway reaction or untoward build-up of pressure in the vessel
can occur without warning, and other industrial processes where an uncontrolled
explosion or excessive build-up of pressure is a continuing safety hazard.
Pressure relief apparatus also must accommodate cycling between positive
and negative pressure conditions in the equipment, piping, or vessels that require
overpressure protection. To this end, it has been conventional to provide rupture
disc apparatus in which a rupturable section of the apparatus includes a central
bulged area presenting opposed convex concavo surfaces with the concave surface
facing the protected zone. This forward acting bulge rupture disc is better able
to withstand vacuum conditions within the protected zone than is the case with
a flat rupture disc. In addition, pressure relief rupture disc assemblies have
included a pair of rupturable central areas with one of the rupture discs being
of thicker material than the other rupture disc. In the case of bulged rupture
discs, the concavo-convex areas of the discs are in complemental aligned relationship.
Many of the pressure relief devices in the past and present use have been provided
with lines of weakness defining the rupturable section of both flat and bulged
discs. The lines of weakness are semi-circular in the case of circular discs and
rectangular in the instance of rectangular rupture discs. The lines of weakness
have been either score lines in one surface of a respective disc defining the rupture
area thereof, or a series of elongated slits extending through the rupture disc
material with unitary disc webs separating the ends of adjacent elongated slits.
Where slits through the disc material are provided defining lines of weakness,
a layer of rupturable material, usually a flexible synthetic resin film or the
like, is positioned in overlying relationship to the series of slits in order to
prevent leakage of fluid therethrough until such time as rupture of the section
of the disc defined by the line of weakness occurs. Exemplary pressure relief rupture
disc structures in this respect have been provided with two rupture discs in complemental
overlying relationship with a layer of flexible material interposed between adjacent
surfaces of the rupture discs and an additional strip of flexible material directly
overlying a corresponding line of weakness.
The lines of weakness, whether in the form of a score line, or a series of elongated
slits defining a line of weakness, do not extend around the entire perimeter of
the rupture portion of the disc defined by the line of weakness, but have opposed
ends in spaced relationship which present a unitary hinge for the rupturable section
of the disc to retain the ruptured portion of the disc with the flange portion
thereof, and thereby avoid fragmentation of the disc with attendant released metal
fragment hazards in the area surrounding the location of the pressure relief apparatus.
Notwithstanding the provision of anti-fragmentation hinge portions
of the rupture discs structures of previous designs, the construction of such hinge
areas has not been totally satisfactory to accommodate a multiplicity of overpressure
events and conditions. If the width of the hinge area is too great, the pressure
value at which the rupturable section gives way is often times compromised resulting
in failure of the rupture disc to open at a pre-selected value. On the other hand,
if the hinge area is narrowed in order to assure full opening of a rupture disc
at a prescribed pressure value, the unitary hinge area tends to also rupture allowing
the section of the disc which opens to tear away from the surrounding remaining
flange portion of the disc and thereby produce a resultant dangerous metal projectile
escaping from the rupture disc assembly at high velocity.
Therefore, there has been and continues to be a need for pressure relief
rupture disc apparatus which will reliably open at a preset overpressure value
yet is resistant to fragmentation of the ruptured area of the disc upon opening
of the disc. It is also desirable that the design of the explosion protection rupture
disc assembly be applicable to a wide range of vent openings and different prescribed
rupture pressures dependent solely upon materials of construction, thickness of
the material and whether the central section is bulged or not, without it being
necessary to provide a multiplicity of specifically engineered hinge construction
designs in order to prevent fragmentation of the rupturable section of the disc.
SUMMARY OF THE INVENTION
Non-fragmenting, forward-acting pressure relief apparatus in accordance
with this invention includes either a single rupture disc, or a pair of rupture
discs, each having a central section and a peripheral flange section. The apparatus
is adapted to be clamped between annular inlet and outlet support members in certain
high pressure applications. A line of weakness that extends around a central part
of the central section of each of the discs defines the rupturable portion of that
disc. The line of weakness has opposed end regions in spaced relationship presenting
a unitary hinge portion therebetween that prevents the central section of each
disc from tearing away from the peripheral flange section of a respective disc
upon rupture of the central section thereof. Each line of weakness in a preferred
form of the invention comprises a line of elongated, end-to-end, spaced slits having
terminal ends which define the hinge portion of the disc.
A hold-down member is provided for the rupture disc in a single disc embodiment
and for both discs in a composite rupture disc assembly. The hold-down member has
an inner opening in generally circumscribing relationship to the rupturable central
section of the adjacent disc in close proximity to the line of weakness in the
disc. The hold-down member has an elongated unitary segment that extends into the
inner opening of the hold-down member in disposition engaging the hinge portion
of the adjacent disc and overlying respective opposed end regions of the line of
weakness. The unitary segment of the hold-down member overlying the hinge portion
of the rupture disc has an innermost margin extending between opposed end regions
of the line of weakness in inwardly spaced relationship from respective outermost
ends of the line of weakness.
Upon application of a force against the central rupturable section of a single
disc or the rupturable sections of a pair of complemental discs sufficient to tear
the unitary webs of disc material between adjacent ends of the slits defining the
line of weakness, the rupturable sections of the discs open to vent the area protected
by the pressure relief apparatus. Although the line of weakness tears along the
full length thereof upon rupture of the central section of a respective disc, the
hinge portion of the central section of the disc bends along the outer margin of
the inwardly extending segment of the hold-down member, rather than about an imaginary
line extending between the outermost opposed, spaced extremities of the line of
weakness. The hinge portions of the discs therefore bend along a line of greater
length than the distance between the opposed outermost extremities of corresponding
lines of weakness. The outer margin of the inwardly extending segment of the hold-down
member functions as an elongated fulcrum edge for the hinge portion of the disc
or discs to more evenly distribute the bending forces on the hinge portion of the
disc across an area spaced inwardly from the narrowest zone of the hinge portions
of the central sections of the disc. In addition, a transverse portion of the inwardly
extending segment of the hold-down member extending in a direction away from the
outer margin of that segment is deflected by the hinge portion of the central section
of the discs during rupture of the central sections of the disc or discs along
substantially the full length of the line of weakness. The deflected transverse
portion of the segment of the hold-down member absorbs a part of the rupture force
applied to the central section of the disc or discs thus diverting part of the
force away from the hinge portions extending between respective outermost ends
of the lines of weakness. As the transverse portion of the segment of the hold-down
member is deflected by the hinge portions of the central section or sections of
the disc or discs during rupture of the central sections thereof, the deflected
portion of the segment of the hold-down member is bent into a transversely inclined
or generally curved configuration along a substantial portion of the length of
the hold-down member segment. Deflection of the transverse portion of the hold-down
member segment contributes to prevention of separation of the central section of
the disc or discs from the peripheral flange portions thereof at the hinge portion
of the disc during rupture of the disc, by virtue of the fact that the hinge portion
of the disc or discs bend around an inclined or curved surface defined by the deflected
transverse portion of the segment of the hold-down member, rather than bending
around an abrupt corner that could contribute to tearing of the hinge portions
of the disc along a straight line defined by that corner.
In accordance with a preferred embodiment of the present invention, the pressure
relief apparatus is provided with a pair of centrally bulged discs in overlying
relationship each of which has a line of weakness defined by a series of end to
end spaced slits, with one of the discs being of greater thickness than the other
disc. The lines of weakness in opposed discs are in aligned relationship. A hold-down
member is provided in overlying relationship to the normally uppermost or outermost
disc of the assembly while a support ring is optionally located against the inner
or inboard surface of the other rupture disc. The hold-down member and the ring
each have an inwardly extending, unitary segment located in aligned relationship
to the hinge portion of each of the discs. The inwardly extending segment of the
hold-down member against the upper or outermost disc protects against fragmentation
of the hinge portions of both of the discs upon forward opening of the discs by
an overpressure condition, while the segment of the support ring underlying the
innermost rupture disc of the assembly assists in presenting fragmentation of the
central rupturable sections of the discs when a vacuum condition prevails of sufficient
magnitude to cause inward rupture of the central rupturable sections of the two discs.
It is of importance to note that the line of weakness in each of the rupture
discs
in the case of a pair of superimposed rupture discs, or where only a single rupture
disc is provided, is oriented relatively and of a length such that outermost end
regions of the line of weakness in each of the discs extend inwardly in spaced
relationship from the outermost margin of the inwardly extending segment of a respective
hold-down member. Upon rupture of a central section of the disc or discs along
a line defined by the line of weakness of a corresponding disc, the central section
will rupture along the entire length of a respective line of weakness, but the
hinge portions of the discs bend around the inner elongated margin of the inwardly
extending segment of the hold-down member thus protecting the hinge portions from
tearing, which would result in separation of the central sections of the discs
from the flange portion thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of composite domed disc structure having a pair
of centrally bulged rupture discs forming a part of the non-fragmenting, forward-acting
pressure relief apparatus of this invention, with each of the rupture discs being
provided with a slit defining line of weakness;
FIG. 2 is a top plan view of the composite disc structure as shown in FIG. 1;
FIG. 3 is a bottom view of the composite disc structure as shown in FIG. 1;
FIG. 4 is an enlarged fragmentary horizontal cross-sectional view taken substantially
on the line 4—4 in FIG. 2 and looking in the direction of the arrows;
FIG. 5 is an enlarged fragmentary plan view of opposed ends of slits defining
a line of weakness and illustrating circular cutouts at the end of each slit;
FIG. 6 is an enlarged fragmentary cross-sectional view taken substantially on
the line 6—6 of FIG. 2, and in addition showing an annular
hold-down member overlying the upper bulged disc, a vacuum support ring against
the concave face of the bottom disc, and a support ring underlying the bottom bulged disc;
FIG. 7 is a schematic cross-sectional view through one of the bulged rupture
discs in illustrating the asymmetric configuration of the bulged area of the disc;
FIG. 8 is an enlarged essentially schematic representation of the segment of
the annular hold-down ring which extends into the center of the ring and showing
the manner in which the outermost margin of the segment is deflected and bent upwardly
by the hinge portion of the rupture disc during rupture thereof;
FIG. 9 is an enlarged schematic cross-sectional view taken on the line 9—9
of FIG. 8 and looking in the direction of the arrows;
FIG. 10 is an exploded perspective view of the embodiment of the invention having
bulged rupture discs;
FIG. 11 is a top plan view of the rupture disc assembly of FIG. 1 and showing
the general shape of the opened ruptured bulged sections of the disc upon actuation
of the pressure relief apparatus; and
FIG. 12 is a perspective view of alternate non-fragmenting pressure relief apparatus
having an essentially flat rupture disc, with the opening in the hold-down ring
indicated by dashed lines.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Non-fragmenting, forward-acting composite pressure relief apparatus
in accordance with a preferred embodiment of this invention as shown in FIGS. 1-11
of the drawings and generally designated
20. Pressure relief apparatus
20
is optionally adapted to be clamped between conventional inlet and outlet support
members
80 and
82 as shown in FIG. 6. Apparatus
20 is especially
useful for protecting processing equipment, pressure vessels, piping and structures
including bag houses and the like from overpressures resulting from explosions
and other potentially destructive and catastrophic high pressure events. Although
apparatus
20 as illustrated in the drawings is of circular configuration,
the principals hereof are also applicable to rectangular non-fragmenting pressure
relief apparatus.
Composite pressure relief apparatus
20 includes a topmost or outermost
rupture disc
22 normally constructed of a relatively thin corrosion resistant
metal material such as stainless steel. Disc
22 in its circular embodiment
includes an annular flange
24 generally provided with a series of circumferentially
extending, spaced openings
26 oriented to receive respective bolts
28
(FIG. 6) which serve to optionally clamp apparatus
20 between inlet and
outlet support members
80 and
82 forming a part of or connected to
structure or equipment to be protected from an untoward overpressure event or condition
such as an explosion. Support members such as
80 and
82 are not a
requirement in certain overpressure protection applications of apparatus
20.
An annular, generally planar hold-down member
36 that overlies disc
22
and that is best shown in FIG. 10 has an inner, semi-circular edge
38 defining
an interior opening
40 of member
36. A series of peripherally positioned
bolt receiving openings
42 are provided in hold-down member
36, which
correspond to and are aligned with openings
26 in flange
24 of rupture
disc
22. A unitary, initially planar segment
44 of hold-down member
36 projects into the opening
40 of hold-down member
36 and
has an elongated, rectilinear margin
46 that extends between and merges
with opposed end extremities of inner semi-circular edge
38 of hold-down
member
36. It is to be seen from FIG. 10 for example, that the length of
margin
46 of hold-down member
36 is somewhat (e.g. about 55%-60%)
greater than the radius of central section
30 of disc
22.
The bulged portion of central section
30 lies within opening
40
of hold-down member
36 when the latter is positioned in overlying relationship
to flange
24 of rupture disc
22. The transition zone
48 between
flange
24 of rupture disc
22 and the bulged portion of central section
30 of disc
22 is located just inside of the semi-circular edge
38
of hold-down member
36 when hold-down member
36 is positioned against
and in overlying relationship to a bulged disc
22. The bulged portion of
central section
30 of disc
22 is formed by bulging the disc in a
tool (not shown) that has an inner opening generally conforming to the configuration
of edge
38 and margin
46 of hold-down member
36. Accordingly,
the bulge formed in the central section
30 of disc
22 is of asymmetric
configuration as illustrated schematically in FIG. 7.
The bulged portion of central section
30 of disc
22 is provided
with a semi-circular line of weakness generally designated
50 and preferably
comprised of a series of arcuate, separate, end-to-end slits
52 each of
which extends through the full thickness of the bulged portion of central section
30 of disc
22. As depicted schematically in the fragmentary enlarged
view of FIG. 5, each of the slits
52 terminates in a circular opening
54
communicating with a corresponding slit
52 and of substantially greater
diameter than the width of each slit
52. Adjacent openings
54 are
in spaced relationship presenting a web of material
56 unitary with the
material of the bulged portion
30b of section
30. It can be
seen from FIG. 4, that the line of weakness
50 in the bulged portion of
section
30 of disc
22 defined by slits
52 is of a length such
that the endmost slits
52a and
52b of line of weakness
50 define end regions that are in spaced relationship from one another but
extend beneath segment
44 of hold-down member
36 overlying the bulged
portion of section
30 disc
22. The spaced terminal ends
52c
and
52d of end slits
52a and
52b define
a unitary hinge portion
58 of central section
30 of bulged disc
22.
The margin
46 of segment
44 is located inwardly from an imaginary
line between the respective outermost extremities
52c and
52d
of line of weakness
52 and therefore the outer extremities of margin
46 intersect end slits
52a and
52b adjacent
the innermost ends of end slits
52a and
52b. The distance
from an imaginary line between the extremities
52c and
52d
of line of weakness
52 and the mid-point of margin
46 of segment
44 measured along the dashed section line
6—
6 of FIG.
2 for example is approximately one third of the distance from margin
46
to the outer peripheral edge of disc
22 measured along section line
6—
6.
Thus, the major depth of segment
46 is approximately one third of the width
of the flange
24 of disc
22.
The bulged portion of section
30 of disc
22 is formed by bulging
a blank disc into the cavity of a tool having an inner margin that conforms to
the configuration of the inner circular edge
38 of the opening
40
in hold-down member
36. Accordingly, the bulged portions of the central
section
30 of disc
22 is of asymmetric cross-sectional configuration
with the curvature of the bulge opposite hinge portion
58 being of greater
curvature than the portion of the bulge which merges into hinge portion
58.
The asymmetric cross-sectional shape of the bulged portion of section
30
is illustrated in the cross-sectional view of FIG. 7 wherein it can be seen that
the cross-sectional curvature of the bulged section
30 is of greater curvature
from outer point A at flange
24 to central point B, than from point B to
point C, which represents the area of bulged section
30 contacting the central
part of margin
46 of segment
44 of hold-down member
36. Accordingly,
disc
22 has a relatively flat portion
60 which conforms generally
to the overall shape of segment
44 of hold-down member
36.
As is best shown in the exploded view of FIG. 10, apparatus
20 includes
a second rupture disc
122 which is of identical shape and overall dimensions
disc
22, but preferably is constructed of somewhat thicker stainless steel
material. Furthermore, an annular clamping member
262 is provided against
the underside or innermost side of disc
122. The bulged portion of the central
section
130 of disc
122 has a line of weakness
50, which preferably
has the same number of slits
152 as slits
52 of weakness
50
of disc
22. Furthermore, the slits
152 of line of weakness
150
of disc
122 align with and are of same length as respective slits
52
of line of weakness
50 in rupture disc
22.
A layer
64 of synthetic material such as Teflon or Mylar is interposed
between
disc
22 and disc
122 for blocking leakage of air or other fluids
through the slits of lines of weakness
52 and
152 and each of the
discs
22 and
122. Desirably, relatively narrow semi-circular strips
66 and
68 of synthetic resin material such as Teflon are positioned
between layer
64 and disc
22 and disc
122 respectively in
alignment with respective lines of weakness
50 and
50′. Strips
66 and
68 may be adhesively secured to respective opposed surfaces
of central sections
30 and
130 of rupture discs
22 and
122.
It is to be noted from FIG. 10 that the flange
124 of disc
122
has
a series of bolt receiving openings
126 that align with openings
26
in disc
22 and with openings
42 in hold-down member
36. Disc
122 has a hinge portion
158 that is of the same dimensions and is
aligned with hinge
58 of disc
22.
An annular support ring
262 underlies disc
122 and is of the same
shape and configuration as hold-down member
36, but may be the same or of
greater thickness. The segment
244 of support ring
262 is aligned
with and conforms to the shape of segment
44 of hold-down member
36.
Bolt receiving holes in support ring
262 align with openings
42,
26 and
126.
When assembled, hold-down member
36 rests against rupture disc
22
with segment
44 resting on and in complemental engagement with the flat
area of disc
22 inboard of flange
24 of the disc. Strips
66
and
68 along with flexible layer
64 close the slits
52 and
152 of each of the bulged portions of central sections
30 and
130
of rupture discs
22 and
122.
The bulged portion of the central section
130 of rupture disc
122
rests within the bulged portion of central section
30 of rupture disc
22
and respective concave and convex faces thereof are separated only by Teflon layer
64 and strips
66 and
68.
It is desirable, but not mandatory in the case of the preferred embodiments of
non-fragmenting pressure relief apparatus
20, that a semi-circular vacuum
support ring
72 as shown in FIG. 4, be provided in underlying relationship
to the rupture disc
122 in alignment with slits
152 of line of weakness
150 of rupture disc
122. The opposed, spaced ends of ring
72
clear and do not overly the hinge portion of bulged portion of the section
130
of rupture disc
122. Ring
72 is preferably spot welded to the underside
of the bulged portion of central section and segment
130 of rupture disc
122. The semi-circular support ring
72 forming a part of apparatus
20 may be formed by bulging a blank disc and then cutting ring
72
from such disc with a laser beam or the like. Optionally, a series of spaced, radially
extending tabs
74 may be spot welded to ring
72 on the underside
of bulged portion of the central section
30 of rupture disc
122 in
partially supporting relationship, to thereby increase the reversal resistance
of bulged portions of central sections
30 and
130 of rupture discs
22 and
122 under vacuum conditions imposed on apparatus
20.
The composite non-fragmenting pressure relief apparatus
320 as illustrated
in FIG. 12 is the same as apparatus
20 except that the rupture discs
322
and
332 are flat, do not have central bulged sections, and are each provided
with a semi-circular circumferentially extending line of weakness
350. Otherwise,
the components of apparatus
320 are the same as the components of apparatus
20. Accordingly, an annular hold-down member
336 designated by dashed
lines, and that is identical to hold-down member
36, overlies the central
flat section
330 of rupture disc
322. The annular hold-down member
(not shown) that overlies the peripheral flange portion
324 of disc
322
has an inner opening
338 shown by dashed lines as well as an inwardly extending
segment similar to segment
44 of hold-down member
36 and thus presents
an inner straight margin indicated schematically by the dashed line
346
aligned with the hinge portion
358 of disc
322. A support ring identical
in configuration to support ring
262 may be provided if desired in underlying
relationship of the flange portion of disc
332. The support ring beneath
disc
332, if provided, preferably has a segment that conforms to segment
244 of hold-down member
262.
Although composite explosion protection apparatus
20 and
220
having a pair of superimposed complemental rupture discs is preferred for most
applications, a single scored bulged rupture disc or a single scored flat rupture
disc may be provided if deemed to be adequate for protecting a particular piece
of equipment, piping, conduits, or structures from an overpressure condition or
an explosion.
In operation, the assembled components of pressure relief apparatus
20
are mounted over a vent opening in structure or equipment requiring protection
from explosions or untoward overpressure events with bolts
28 serving to
fixedly secure apparatus
20 between optional flanges
80 and
82
in position over the exhaust opening. In the event of an overpressure event developing
that exceeds the burst pressure of the central section
30 of rupture disc
22 and central section
130 of rupture disc
122 as controlled
by the resistance to rupture of webs
66 between adjacent lines of weakness
slits
52 and
152, and the layer
64 of synthetic resin material
as well as strips
66 and
68, the central sections
30 and
130
of rupture discs
22 and
122 open instantaneously and bend about respective
hinges
58 and
158.
As shown schematically in FIG. 11, the central section
30 of rupture disc
22 and central section
130 of rupture disc
122 open as a unit
as the lines of weakness
50 and
150 tear along the full length thereof
including the endmost regions thereof defined by terminal end slits
52a
and
52b, as well as the corresponding endmost region slits of
line of weakness
150 of rupture
122, thus allowing full, unimpeded
opening of the central section
30 of rupture disc
22, and central
section
130 of rupture disc
122. However, notwithstanding full tearing
of the arcuate length of each of the lines of weakness
50 and
150
of central sections
30 and
130 of rupture discs
22 and
122,
the hinge portions
58 and
158 of central sections
30 and
130
respectively of rupture discs
22 and
122 bend about a fulcrum presented
by the margin
36 of segment
44 of hold-down member
36, and
not about an imaginary line in the zone extending between the terminal ends
52c
and
52d of lines of weakness
50 and
150.
During rapid full opening of the central sections
30 and
130
of rupture discs
22 and
122 as a result of a high pressure event
such as an explosion, the force of gases from the explosion or high pressure event
applied to the concave face of disc
122 and transferred to the concave face
of disc
22, also is applied to hinge portions
58 and
158 of
rupture discs
22 and
122. When the force applied to central sections
30 and
130 of rupture discs
22 and
122 as well as to
the hinge portions
58 and
158 of sections
30 and
130
of disc
22 and
122 is of sufficient magnitude to effect opening of
central sections
30 and
130, that force has also been found great
enough to deflect the outer part of segment
46 to a degree that is generally
proportional to the amount of disc breaking force applied to the central sections
30 and
130 of rupture discs
22 and
122, as shown schematically
in FIGS. 8 and 9. Referring to the schematic representation of deflected segment
44 in FIG. 8, the transverse deflected portion of the segment
44
of hold-down member
36 extends across substantially the full width of margin
46 of segment
44. The degree to which the segment
44 is deflected
is generally proportional to the force applied thereto by central section
30
of disc
22 during opening of the central section
30, with the disc
engaging surface
76 of the deflected portion of segment
44 being
either somewhat arcuate as shown in FIG. 9, or presenting a somewhat more transversely
linear inclined surface.
In all instances though, the deflected outer portion of segment
44 of
hold-down
member
36 resulting from opening of central sections
30 and
130
of rupture discs
22 and
122 absorbs a part of the rupture force applied
to the central sections
30 and
130 of rupture discs
22 and
122, thus diverting that part of the rupture force away from the zone of
the hinge portions
58 and
158 extending between respective outermost
ends
52c and
52d of lines of weakness
50 and
150. This diversion of a part of the rupture force applied to the central
sections
30 and
130 of rupture discs
22 and
122 contributes
to prevention of separation of central sections
30 and
130 of rupture
discs
22 and
122 from flange portions
24 and
124 thereof
during opening of the rupture discs. Another important factor serving to prevent
fragmentation of central sections
30 and
130 from flange portions
24 and
124 of rupture discs
22 and
122 results from
bending of hinge portions
58 and
158 about the fulcrum defined by
margin
46 of segment
44 in spaced relationship from the weakest zone
of the hinge portions
58 and
158 extending along an imaginary line
between the end extremities
52c and
52d of lines of
weakness
50 and
150. In addition, the inclined or curved surface
76 of the deflected part of segment
44 created during deflection
of the outer portion of segment
44 and which directly engages hinge portion
58 of central section
30 of disc
22, assures that the hinge
portion
58 and
158, as bend about margin
46 of the deflected
part of segment
44 are not required to bend about an abrupt transverse edge
which could contribute to fragmentation of the central sections
30 and
130
of rupture discs
22 and
122 during opening of the central sections
30 and
130.
As shown schematically in FIG. 11, the central sections
30 and
130
of rupture discs
22 and
122 upon opening lay back in a position generally
parallel to their initial closed positions to provide a maximum outlet for escape
of gases, but without separating from the flange portions of respective rupture
discs. Extension of the lines of weakness
50 and
150 beneath segment
44 of hold-down member
36 has been found to significantly contribute
to the non-fragmenting characteristics of central sections
30 and
130
of rupture discs
22 and
122, in that there is no tendency for the
hinge portions of central sections
30 and
130 of rupture discs
22
and
122 to commence tearing laterally along the length of margin
46
of segment
44 of hold-down member
36 as the hinge portions
58
and
158 bend about margin
46, rather than being required to bend
along an imaginary line between the end extremities
52c and
52d
of lines of weakness
50 and
150 that could result in separation
of central sections
30 and
130 from flange portions
24 and
124.
Vent apparatus
320 operates in the same manner as vent apparatus
20,
except in most instances, the central sections of rupture discs
322 and
332 having flat central sections are not capable of withstanding as high
vacuum conditions as is the case with bulged central section rupture discs
22
and
122.
Preferred embodiments of apparatus
20 or
320 may be from
about 250 mm in width to as much as about 1500 mm, and be constructed to burst
at anywhere from about 25 millibars to about 1 bar. For example, in the case of
apparatus
20 or
320 having an overall diameter of about 1015 mm,
the diameter of the line of weakness of the central section thereof may nominally
be about 775 to 780 mm. The diameter of the bulged section in this instance may
be about 797 mm. The rupture discs
22 and
322 are preferably fabricated
of 0.5 mm stainless steel, and may be from about 0.15 mm to about 1.5 mm in thickness.
The discs
122 and
332 are preferably constructed of 1.2 mm stainless
steel and maybe from about 0.8 mm to about 2 mm thick. The Teflon layer
64
and Teflon strips
66 and
68 are in each instance preferably of material
having a thickness of about 0.05 mm and may be from about 0.025 mm to about 0.25
mm in thickness. Each of the slits
52 and
152 are preferably about
100 mm in length, and may be from about 50 mm to about 150 mm long. The webs
56
between slits
52 and
152 are desirably about 3 mm in width. The circumference
of each of the lines of weakness
50 and
150 depends upon the overall
size of the rupture discs
22 and
122, but in all instances should
extend to at least about one third of the overall distance between the mid-point
of margin
46 of segment
44 and the outer periphery of hold-down member
36.
*
