U.S. patent number 10,385,983 [Application Number 15/716,840] was granted by the patent office on 2019-08-20 for burst disk assembly for high and ultra high vacuum containment vessels.
This patent grant is currently assigned to ACCU-GLASS PRODUCTS, INC.. The grantee listed for this patent is ACCU-GLASS PRODUCTS, INC.. Invention is credited to Andres L. Ligeti.
United States Patent |
10,385,983 |
Ligeti |
August 20, 2019 |
Burst disk assembly for high and ultra high vacuum containment
vessels
Abstract
An improved burst disc assembly for use in pressure relief
conduits for high vacuum and ultra-high vacuum containment vessels,
the assembly having a body with inlet and outlet openings connected
by an internal passage, a burst disc disposed within the internal
passage and connected therein to hermetically isolate the inlet and
outlet openings. The assembly further has a mounting structure
connected to the body and outwardly extending therefrom that may be
clamped between adjacent faces of a pair of metal seal flanges
provided in the relief conduit to secure the assembly in position
and hermetically seal the assembly in the conduit in a manner
prohibit the passage of gas molecules from the surrounding
environment into the containment vessel through the relief conduit.
The mounting structure is formed from a soft metal material having
substantially lower hardness value than that of the metal seal
flange faces to enable adequate sealing. The connection between the
mounting structure and the body further provides similar hermetic
seal. Upon rupture of the burst disc, the assembly alone must be
replaced while the metal seal flanges connecting the burst disc
assembly to the containment vessel may be reused.
Inventors: |
Ligeti; Andres L. (Livermore,
CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
ACCU-GLASS PRODUCTS, INC. |
Valencia |
CA |
US |
|
|
Assignee: |
ACCU-GLASS PRODUCTS, INC.
(Valencia, CA)
|
Family
ID: |
65808788 |
Appl.
No.: |
15/716,840 |
Filed: |
September 27, 2017 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20190093776 A1 |
Mar 28, 2019 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F16K
17/1606 (20130101); F16K 17/16 (20130101); F16K
17/403 (20130101); F16K 17/40 (20130101) |
Current International
Class: |
F16K
17/16 (20060101); F16K 17/40 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Nichols; P. Macade
Attorney, Agent or Firm: Patent Law Associates
Claims
Having thus described the invention, what is claimed is:
1. An improved burst disc assembly for use in high vacuum and
ultra-high vacuum containment vessels, the assembly comprising: a
body having an external surface and internal passage therethrough
connecting an inlet opening and an outlet opening; a burst disc
disposed within the internal passage between the inlet and outlet
openings, the burst disc hermetically sealed within the internal
passage; and a mounting gasket extending radially outwardly from
the external surface of the body, the mounting gasket configured to
be disposed between adjacent parallel faces of a pair of
selectively separable connection flanges, each face having a knife
edge sealing structure projecting therefrom to engage the mounting
gasket, support the burst disc assembly entirely within a pressure
relief conduit fluidly connected to the containment vessel and to
hermetically seal the burst disc assembly within the pressure
relief conduit to preclude leakage into the containment vessel.
2. The burst disc assembly of claim 1, wherein the mounting gasket
is formed of a material having a hardness that is significantly
less than the material hardness of the knife edges and the
adjacently disposed faces.
3. The burst disc assembly of claim 2, wherein the mounting gasket
material is copper and the adjacently disposed faces and the knife
edges are formed from stainless steel.
4. The burst disc assembly of claim 1, wherein the mounting gasket
is bonded to the body, the bond creating a hermetic seal
therebetween.
5. The burst disc assembly of claim 4, wherein the gasket is bonded
to the body by fusing, brazing, or welding.
6. The burst disc assembly of claim 1, further comprising a
protective cover connected to the outlet opening and configured to
prevent contact with the burst disc by rigid objects outside of the
containment vessel, the protective cover further permitting the
passage of gas from the containment vessel to the surrounding
atmosphere upon rupture of the burst disc cause by an overpressure
condition in the containment vessel.
7. The burst disc assembly of claim 6, wherein the protective cover
further includes a moveable indicator configured for movement
between a normal state and a burst state, movement from the normal
to the burst state being effected by an overpressure condition in
the containment vessel causing rupture of the burst disc.
8. A burst disc assembly for use in a pressure relief conduit for a
high vacuum or ultra-high vacuum containment vessel, the assembly
comprising: a body having an external surface configured for
insertion into the pressure relief conduit, the body having an
inlet opening and an outlet opening connected by an internal
passage; a burst disc disposed within the internal passage between
the inlet and outlet openings, the burst disc being hermetically
sealed within the internal passage to prevent the passage of gas
between the inlet opening and the outlet opening; and a mounting
structure extending radially outwardly from the body, the mounting
structure interfacing with adjacent flange faces disposed in the
relief conduit to position the mounting structure between the
adjacent flange faces, the flange faces each having a sealing
structure comprising a knife edge projecting from the flange face
toward the mounting structure, the mounting structure interface
with the sealing structures hermetically sealing the interface to
prevent the passage of gas into the relief conduit through the
interface between the flange faces and the mounting structure and
retaining the assembly in a fixed position within the relief
conduit, the mounting structure connection to the body further
being hermetically sealed to preclude the passage of gas through an
annular space between the external surface and the relief
conduit.
9. The burst disc assembly of claim 8, wherein the mounting
structure is formed of a material having a hardness that is
significantly less than the material hardness of the adjacent
flange faces.
10. The burst disc assembly of claim 9, wherein the mounting
structure material is copper and the adjacent flange face material
is a stainless steel.
11. The burst disc assembly of claim 9, wherein the mounting
structure is bonded to the body using a bonding method which
creates a hermetic seal therebetween.
12. The burst disc assembly of claim 11, wherein the bonding method
includes fusing, brazing, or welding.
13. The burst disc assembly of claim 8, further comprising a
protective cover connected to the outlet opening and configured to
prevent contact with the burst disc by rigid objects outside of the
containment vessel, the protective cover further permitting the
passage of gas from the containment vessel to the surrounding
atmosphere upon rupture of the burst disc cause by an overpressure
condition in the containment vessel, the protective cover further
including a moveable indicator configured for movement between a
normal state and a burst state, movement from the normal to the
burst state being effected by an overpressure condition in the
containment vessel causing rupture of the burst disc.
Description
BACKGROUND OF THE INVENTION
This invention relates generally to pressure protection of high
vacuum and ultra-high vacuum containment vessels, and more
particularly to a cartridge-style rupture disc for installation
between a mating pair of CF type metal seal flanges.
Burst discs are commonly used in high vacuum (HV) and ultra-high
vacuum (UHV) systems as a means of protecting a vacuum vessel or
chamber against accidental over-pressurization. They are designed
to burst or rupture at a predetermined and calibrated relief
pressure when the pressure inside the protected vacuum vessel
exceeds the specified relief pressure. Burst discs are one-time use
safety devices which must be discarded and replaced after use
(failure).
The conventional method for incorporating a burst disc in a HV or
UHV system is to provide a burst disc mounted in a fixture
incorporating an industry standard ConFlat.RTM. (CF) type metal
seal flange which allows connection to a CF flange provided on the
containment vessel. Once the burst disc is ruptured the entire
assembly, including the CF metal seal flange, must be scrapped as
it is no longer serviceable even though the metal seal flange
itself remains undamaged. Advantages would be realized by a burst
disc assembly that could be installed in a conventional CF flange
interface in a manner that prevented the leakage of gas at the
molecular level necessary for HV and UHV applications while
minimizing the material to be scrapped upon rupture of the disc.
Additional advantages would be realized by a burst disc assembly
that could be easily installed within existing containment vessel
relief piping without the need to modify the piping or
connections.
SUMMARY OF THE INVENTION
Accordingly, the present invention, in any of the embodiments
described herein, may provide one or more of the following
advantages:
It is an object of the present invention to provide an improved
burst disc assembly for use on a vacuum containment vessel
subjected to high vacuum or ultra-high vacuum conditions that may
be installed using conventional metal seal flanged connections
without requiring the flanged connections to be scrapped upon
rupture of the burst disc.
It is another object of the present invention to provide a burst
disc assembly having a body with a burst disc that may be disposed
entirely within a relief conduit for a vacuum containment vessel,
the assembly further having a mounting structure outwardly
extending from the body that may be clamped and sealed between
adjacent faces of a pair of CF metal seal flanges wherein the
installed assembly prohibits the passage of gas molecules from the
surrounding environment to the vacuum containment vessel. The
mounting structure is formed from a soft metal material having
substantially lower hardness value than that of the flange seal
faces to enable UHV hermetic sealing. The connection between the
mounting structure and the body must also provide similar
molecular-level gas sealing.
It is a further object of the present invention to provide a burst
disc assembly for high vacuum and ultra-high vacuum containment
vessels that is easily removed following rupture and replaced with
an assembly that is easy to install with consistent leakage
performance.
It is a still further object of the present invention to provide an
improved burst disc assembly for high vacuum and ultra-high vacuum
containment vessels that minimizes waste following a disc rupture
thereby improving economic efficiency. Eliminating a metal seal
flange from the assembly achieves this objective.
It is a still further object of the present invention to provide an
improved burst disc assembly for high vacuum and ultra-high vacuum
containment vessels that is durable in construction, inexpensive of
manufacture, carefree of maintenance, easily assembled, and simple
and effective to use.
These and other objects are achieved in accordance with the present
invention by a burst disc assembly having a body with a burst disc
contained therein that may be disposed entirely within a relief
conduit for a vacuum containment vessel. The assembly further has a
mounting structure connected to the body and outwardly extending
therefrom that may be clamped between adjacent faces of a pair of
metal seal flanges provided in the relief conduit to secure the
assembly in position and prohibit the passage of gas molecules from
the surrounding environment to the containment vessel. The mounting
structure is formed from a soft metal material having substantially
lower hardness value than that of the flange seal faces to enable
UHV hermetic sealing. The connection between the soft metal
mounting structure and the body further provides similar
molecular-level gas sealing. Upon rupture of the burst disc, the
assembly alone must be replaced while the flanges connecting the
assembly to the vessel may be reused.
BRIEF DESCRIPTION OF THE DRAWINGS
The advantages of this invention will be apparent upon
consideration of the following detailed disclosure of the
invention, especially when taken in conjunction with the
accompanying drawings wherein:
FIGS. 1 and 2 illustrate a conventional burst disc assembly for use
in a high vacuum or ultra-high vacuum containment vessel;
FIG. 3 an exploded view of the improved burst disc assembly
invention as it is installed in a relief conduit for a high vacuum
or ultra-high vacuum containment vessel;
FIG. 4 is a side view of the improved burst disc assembly;
FIG. 5 is a cut-away view of the improved burst disc assembly of
FIG. 4;
FIG. 6 is cut-away view of the improved burst disc assembly as it
is installed in a relief conduit for a high vacuum or ultra-high
vacuum containment vessel;
FIG. 7 provides a detail view of the mount and seal interface
between the burst disc assembly and the relief conduit; and
FIG. 8 provides an alternate installation the burst disc assembly
as used in a closed venting system in which the outboard piping is
directed to a secondary containment vessel or container.
DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
Many of the fastening, connection, processes and other means and
components utilized in this invention are widely known and used in
the field of the invention described, and their exact nature or
type is not necessary for an understanding and use of the invention
by a person skilled in the art, and they will not therefore be
discussed in significant detail. Also, any reference herein to the
terms "up" or "down," or "top" or "bottom" are used as a matter of
mere convenience, and are determined with reference to ground.
Furthermore, the various components shown or described herein for
any specific application of this invention can be varied or altered
as anticipated by this invention and the practice of a specific
application of any element may already be widely known or used in
the art by persons skilled in the art and each will likewise not
therefore be discussed in significant detail. When referring to the
figures, like parts are numbered the same in all figures.
Referring to FIGS. 1 and 2, a conventional burst disc assembly 10
used for over-pressure protection of a high vacuum (HV) or
ultra-high vacuum (UHV) is illustrated. The prior art assembly 10
includes a burst disc membrane 11 mounted in an internal conduit 13
extending through a body 12. The connection between the disc
membrane 11 and the body creates a hermetic seal that prevent the
passage of gas through the conduit while the membrane remains
intact. The body 12 further includes a metal seal flange 15 which
enables the assembly 10 to be connected to a matching metal seal
flange (not shown) provided on a pressure relief conduit of a
containment vessel (not shown) in a manner positioning the disc
membrane in fluid communication with the containment vessel
interior. Mechanical connections to vacuum containment vessels are
unique to high vacuum service applications as they are required to
create a hermetic seal between the containment vessel and the
surrounding environment. One exemplar mechanical connection is the
ConFlat.RTM. (CF) type metal seal flange which utilized opposing
parallel faces, each having a sealing structure encircling the
internal opening in the flange, and a gasket compressed between the
faces. The sealing structure is in the form of a knife edge
projecting from the flange face. The gasket is formed from a
comparatively softer material so that the knife edges plastically
deform the gasket material as the flanges are drawn together to
create the seal. Following an overpressure event in the containment
vessel that causes actuation of the burst disc membrane 11, the
entire burst disc assembly 10 must be scrapped.
Referring now to FIGS. 3 through 8, there is shown a pressure
relief conduit connection 18 to a HV or UHV containment vessel
which includes an inboard metal seal flange 16. An improved burst
disc assembly 20 embodiment of the present invention comprises a
generally hollow cylindrical body 22 with an inlet opening 23 and
an outlet opening 24, the body 22 configured to fit within the
interior space 19 of the relief conduit 18. An exemplar relief
conduit comprises a relief conduit of a nominal 1.5-inch outside
diameter pipe having a nominal 0.06-inch wall thickness. The
exemplar body has an outside diameter of 1.35 inches which allows
it to fit inside the conduit. The improved burst disc assembly 20
may be scaled to fit applications in both larger and smaller
diameter piping connections.
The illustrated pressure vacuum containment relief configuration in
FIGS. 3 and 6 is shown venting to atmosphere as might be used when
non-hazardous gasses are involved. The burst disc assembly 20 may
also be used in closed venting configurations in which the vent
conduit is directed to a receiving vessel to prevent release of
potentially hazardous gasses. The design of the improved burst disc
assembly may be installed in either configuration, requiring only a
mating pair of metal seal flanges 16, 17 for installation, further
enhancing the utility of the invention. FIG. 8 illustrates
installation of the burst disc assembly 20 in a closed venting
system in which the outboard piping 13 is directed to a secondary
containment vessel or container.
The burst disc assembly 20 further includes a mounting structure 26
extending radially outwardly from the body 22. The mounting
structure 26 is configured to be clamped between adjacent faces
161, 171 of inboard and outboard metal seal flanges 16, 17,
respectively, which secure the burst disc assembly 20 in position
within the relief conduit 18 against the pressure forces subjected
on the burst disc membrane. The mounting structure 26 also seals
the interface between the inboard and outboard metal seal flanges
16, 17.
The inboard and outboard seal flanges 16, 17, and the burst disc
assembly body 22 are preferably formed from stainless steel, a
preferred material in high vacuum applications. The mounting
structure 26 is formed from a relatively soft metal material, such
as oxygen free copper (OFE copper), which enables it to function as
a sealing gasket between the inboard and outboard metal seal
flanges 16, 17 to create a hermetic seal. The hermetic seal
prevents the passage of gas molecules from the surrounding
environment into the normal vacuum conditions within the relief
conduit interior space 19. The seal flange faces 161, 171 each have
a sealing structure 163, 173 encircling the internal opening in the
flange face. The sealing structures 163, 173 deform the material of
the gasket as the flanges are drawn together by clamping fasteners
180. The sealing structures 163, 173 may be in the form of a knife
edge projecting from the flange face 161, 171. Both of the metal
seal flanges are preferably in the form of a knife-edge encircling
the conduit, the knife edge locally deforming the relatively softer
copper material of the mounting structure 26 to assure a leak-tight
seal capable of preventing the passage of gasses at the molecular
level.
The mounting structure 26 is connected to the body 22 at a gasket
bond 29 using a connection means that provides a hermetic seal and
the mounting structure 26 and the body 22. Preferred means for
bonding the preferred copper material of the mounting structure 26
to the stainless steel of the body 22 include fusing, brazing,
welding, or other hermetically sealing method. The method must
allow sufficient control of the weld beam input to accommodate the
different melting points of the dissimilar materials of the
preferred embodiment. An electron beam welding process has been
shown to provide satisfactory structural bonding and sealing
performance without distorting the stainless-steel body or the
copper mounting structure to the point at which the sealing
performance of the flanged connection is affected. The bond 29 is
positioned adjacent to the body 22 in a location that is displaced
slightly from the interface between the flange sealing structures
163, 173 and the mounting structure 26.
The body 22 includes an internal bore 21 connecting the inlet and
outlet openings 23, 24 to allow the relief conduit 18 to vent to
atmosphere. A burst membrane 31 is disposed within the internal
bore 21 and joined to the body 22, preferably by welding, to
prevent the passage of gas at molecular level through the internal
bore past the membrane 31 while the membrane remains intact.
Overpressure conditions in the containment vessel cause the
material of the burst membrane to rupture, opening the vent path
between the inlet and outlet openings 23, 24, and venting the
containment vessel to atmosphere.
The burst disc assembly 20 may also include a protective cover 41
to protect the burst membrane 31 from unintentional contact with
foreign objects outside of the containment vessel that could cause
the membrane to rupture. The protective cover 41 is preferably
connected to the body 22 adjacent to the outlet opening 24 and may
extend outward of the outboard flange 17. The protective cover may
be connected to the body 22 by a threaded connection or by any
other means to secure the cover 41 to the body. The cover 41 is
sized to permit it to extend through an opening 175 in the outboard
flange so that it is exposed to the surrounding atmosphere or an
exhaust conduit. The cover 41 may be provided with a plurality of
vent openings 411 to permit the expulsion of gasses resulting from
an overpressure actuation of the burst disc.
The protective cover 41 may be provided with a visual indicator 43
to signal that a rupture of the burst disc membrane 31 has occurred
and that the burst disc assembly 20 requires replacement. In one
embodiment, the indicator 43 is moveably positioned in the cover 41
and moveable between a normal position and a burst indicating
position (shown in FIG. 6). In the normal position, the indicator
43 is substantially disposed within the cover 41 where it is not
outwardly visible to an outside observer. An overpressure condition
rupturing the burst disc pressurizes the volume inside of the
indicator and overcomes the slight friction fit between the
indicator and the cover. The pressure forces acting on the interior
side 432 of the indicator 43 displace the indicator toward the
burst indicating position. In this position, at least a portion of
the indicator 43 projects outwardly from the cover 41 where it
become visible to an outside observer indicating that an
overpressure condition has occurred in the containment vessel and
the burst disc assembly 20 requires replacement. The indicator 43
may be differently colored than the cover 41 to improve the visual
indication.
Naturally, the invention is not limited to the foregoing
embodiments, but it can also be modified in many ways without
departing from the basic concepts. Changes in the details,
materials, steps and arrangements of parts which have been
described and illustrated to explain the nature of the invention
will occur to and may be made by those skilled in the art upon a
reading of this disclosure within the principles and scope of the
invention. The foregoing description illustrates the preferred
embodiment of the invention; however, concepts, as based upon the
description, may be employed in other embodiments without departing
from the scope of the invention.
* * * * *