CA2184864C - Method of forming a metal-to-metal seal in high pressure applications with low contact stress - Google Patents
Method of forming a metal-to-metal seal in high pressure applications with low contact stress Download PDFInfo
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- CA2184864C CA2184864C CA002184864A CA2184864A CA2184864C CA 2184864 C CA2184864 C CA 2184864C CA 002184864 A CA002184864 A CA 002184864A CA 2184864 A CA2184864 A CA 2184864A CA 2184864 C CA2184864 C CA 2184864C
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- Prior art keywords
- containment member
- extension sleeve
- thin walled
- pressure
- pressure containment
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L27/00—Adjustable joints, Joints allowing movement
- F16L27/12—Adjustable joints, Joints allowing movement allowing substantial longitudinal adjustment or movement
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- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Gasket Seals (AREA)
Abstract
A method of forming a metal-to-metal seal in high pressure applications with low contact stress. Firstly, providing a first elongate pressure containment member having a surface of revolution. Secondly, providing a second elongate pressure containment member having an exterior surface, an interior surface, a remote end, and a thin walled extension sleeve having a first end and a second end. The first end of the thin walled extension sleeve is conjoined with the second elongate pressure member at the remote end.
The second elongate pressure containment member is of a greater thickness than the sleeve. Thirdly, coupling the first elongate pressure containment member and the second elongate pressure containment member with the sleeve positioned in close relation to the surface of revolution.
Fourthly, placing the first elongate pressure containment member and the second elongate pressure containment member in an environment in which fluid pressure tends to cause a flow of fluids from the second end to the first end of the sleeve along an interfacial region between the sleeve and the surface of revolution. Fluid pressure tends to constrict and set up a pressure gradient which promotes sealing along the interfacial region.
The second elongate pressure containment member is of a greater thickness than the sleeve. Thirdly, coupling the first elongate pressure containment member and the second elongate pressure containment member with the sleeve positioned in close relation to the surface of revolution.
Fourthly, placing the first elongate pressure containment member and the second elongate pressure containment member in an environment in which fluid pressure tends to cause a flow of fluids from the second end to the first end of the sleeve along an interfacial region between the sleeve and the surface of revolution. Fluid pressure tends to constrict and set up a pressure gradient which promotes sealing along the interfacial region.
Description
T:L'i'I~ UE' 'I'f~E TNVEN'i ION
Metluod of fr->rmi rnc~ ~ nwt v a -t.:c~~-mc~~ta.i _~'~~.1 i n hi. gtv t~rEessure at:y~l.icat~ on; w~ tlu .3 ~~~'~.1 c~omari: ;;true <,>;~
_'~
FIELD OF TFiE INVENTION
The present irvvernt:ion rc:~.atcr~;~ t:i> a rue~ttuod of forming a 7_C)metal-to-metal seal. in Zzsc~h tr:e;~;~urc~ ~zp~e3icv:~tvions ~~~ith lava contact ;tress incc:>rporf~t :i.rzc~ i~-v.i:i ~t: t:o L~~z:°~rnt:
~>scc.7nclary control of leakage rates. 'This Fr~et:luad iras pax°ticular applicatian far connections between i:ubu7.a:r: r~t~m2~~~r. s, ~ra~erc~ ttrere i s relative movJement l:~et~aeen tine tubulai: merr~:ac:ru .
Tn xuigiu tpr_ess~m: c~ apt3l~ ~ ':z t: i cirrus , ~!uc~~ta~ ).-to-metal contact seals arc preien~recl ovar k~la~~t~irn~x°i~: .z~.als. 'I'o achieve ad~,c~uate seal_irag, cc_~rit:act. se<.1~, t:y~.rt..c,~,~:1:L~ z~~quire tk~.at the cantact: st:z_ess e;~:c:.f~e=oa t~~c~' ~,z ~ :,>nr.~:::~ 1 c:~ ) ~c:
c°mntair~ed over a 20 gi~~en sealing wic:itlu. Contact: ::aca:l s use~~ in high t_~ressure tui~ular f i tt:inq ,, t:y.~~i.ca . i.y )~<v,vr<::: i. rui.t ~ ru.L m::'>:e.-~zp i.ntk,:~verencc~
c~o~:~t:aet .>L.La~se:~ «t. te~i;.-~i_ ,:..~zi ~.:jz c.lE~z:: of ana~yiit.'~:de greater than the maximum pressure to be c.i~nt:::~x~necx ~uu:i cai~.~t:ri.t~uted o~rer very narrow wt dths to obtain adec~uaf..c=~ r ~,T). i~zl,:i 1. i 1:3.,% .
~alc~al~~t: ions c~f 25 thE, necc~s~~ary c::ornt~mt: ut:rE:ss a~:4~ t:wrtzt.:i.~m_:y petfc.~z~ne~:
using stress ana~_ysis me~hC>cls s~.zc;.h as f':irz:it::e cet.ernent analysis.
~184Ff 1 Unfortunately, there are many applications in which it is desirable that the contact stress be minimized in order to facilitate assembly, sliding, rotation or other operations.
5In such applications, the high contact stress of metal-to-metal contact seals make them undesirable, as it inevitably leads to higher friction forces during relative movements and greatly increased potential for galling or other damage which can initiate seal failure.
S~UI~lP~RY OF THE INVENTION
What is required is a method of forming a metal-to-metal seal in high pressure applications with low contact stress.
According to the present invention there is provided a method of forming a metal-to-metal seal in high pressure applications with low contact stress. Firstly, providing a first elongate pressure containment member having a surface of revolution. Secondly, providing a second elongate pressure containment member having an exterior surface, an interior surface, a remote end, and a thin walled extension sleeve having a first end and a second end. The first end of the thin walled extension sleeve is conjoined with the second elongate pressure member at the remote end. The second elongate pressure containment member is of a greater thickness than the sleeve. Thirdly, coupling the first elongate pressure containment member and the second elongate pressure containment member with the sleeve positioned in close 218~a~
Metluod of fr->rmi rnc~ ~ nwt v a -t.:c~~-mc~~ta.i _~'~~.1 i n hi. gtv t~rEessure at:y~l.icat~ on; w~ tlu .3 ~~~'~.1 c~omari: ;;true <,>;~
_'~
FIELD OF TFiE INVENTION
The present irvvernt:ion rc:~.atcr~;~ t:i> a rue~ttuod of forming a 7_C)metal-to-metal seal. in Zzsc~h tr:e;~;~urc~ ~zp~e3icv:~tvions ~~~ith lava contact ;tress incc:>rporf~t :i.rzc~ i~-v.i:i ~t: t:o L~~z:°~rnt:
~>scc.7nclary control of leakage rates. 'This Fr~et:luad iras pax°ticular applicatian far connections between i:ubu7.a:r: r~t~m2~~~r. s, ~ra~erc~ ttrere i s relative movJement l:~et~aeen tine tubulai: merr~:ac:ru .
Tn xuigiu tpr_ess~m: c~ apt3l~ ~ ':z t: i cirrus , ~!uc~~ta~ ).-to-metal contact seals arc preien~recl ovar k~la~~t~irn~x°i~: .z~.als. 'I'o achieve ad~,c~uate seal_irag, cc_~rit:act. se<.1~, t:y~.rt..c,~,~:1:L~ z~~quire tk~.at the cantact: st:z_ess e;~:c:.f~e=oa t~~c~' ~,z ~ :,>nr.~:::~ 1 c:~ ) ~c:
c°mntair~ed over a 20 gi~~en sealing wic:itlu. Contact: ::aca:l s use~~ in high t_~ressure tui~ular f i tt:inq ,, t:y.~~i.ca . i.y )~<v,vr<::: i. rui.t ~ ru.L m::'>:e.-~zp i.ntk,:~verencc~
c~o~:~t:aet .>L.La~se:~ «t. te~i;.-~i_ ,:..~zi ~.:jz c.lE~z:: of ana~yiit.'~:de greater than the maximum pressure to be c.i~nt:::~x~necx ~uu:i cai~.~t:ri.t~uted o~rer very narrow wt dths to obtain adec~uaf..c=~ r ~,T). i~zl,:i 1. i 1:3.,% .
~alc~al~~t: ions c~f 25 thE, necc~s~~ary c::ornt~mt: ut:rE:ss a~:4~ t:wrtzt.:i.~m_:y petfc.~z~ne~:
using stress ana~_ysis me~hC>cls s~.zc;.h as f':irz:it::e cet.ernent analysis.
~184Ff 1 Unfortunately, there are many applications in which it is desirable that the contact stress be minimized in order to facilitate assembly, sliding, rotation or other operations.
5In such applications, the high contact stress of metal-to-metal contact seals make them undesirable, as it inevitably leads to higher friction forces during relative movements and greatly increased potential for galling or other damage which can initiate seal failure.
S~UI~lP~RY OF THE INVENTION
What is required is a method of forming a metal-to-metal seal in high pressure applications with low contact stress.
According to the present invention there is provided a method of forming a metal-to-metal seal in high pressure applications with low contact stress. Firstly, providing a first elongate pressure containment member having a surface of revolution. Secondly, providing a second elongate pressure containment member having an exterior surface, an interior surface, a remote end, and a thin walled extension sleeve having a first end and a second end. The first end of the thin walled extension sleeve is conjoined with the second elongate pressure member at the remote end. The second elongate pressure containment member is of a greater thickness than the sleeve. Thirdly, coupling the first elongate pressure containment member and the second elongate pressure containment member with the sleeve positioned in close 218~a~
relation to the surface of revolution. Fourthly, placing the first elongate pressure containment member and the second elongate pressure containment member in an environment in which fluid pressure tends to cause a flow of fluids from the second end to the first end of the sleeve along an interfacial region between the sleeve and the surface of revolution.
Fluid pressure tends to constrict and set up a pressure gradient which promotes sealing along the interfacial region.
With seals normally used in high pressure applications, high contact stress is concentrated over a narrow sealing width. With the present method, the teaching is exactly the opposite; a comparatively low contact stress is distributed over a wide sealing width. This teaching exploits the relationship between width and maximum contact stress. As the contact width is increased, the average contact stress is decreased. This teaching allows an interference fit to be provided, with a lower average contact stress.
Formulas necessary for the calculation of necessary contact stress in high pressure applications are published by the American Petroleum Institute. These formulas all teach that the initial contact stress must be greater than the pressure to be contained in order to avoid seal failure. In accordance with the teachings of the present method, the initial contact stress between the sleeve and the surface of revolution can be less than required to maintain contact stress greater than the contained pressure over the full intended pressure range. There can even be an initial gap, 30that is closed and sealed by fluid pressure.
There are numerous ways of securing the sleeve to the second pressure containment member. Sleeve can be secured by welding, clamping, or with various fasteners. In view of the 2~8~~6~
Fluid pressure tends to constrict and set up a pressure gradient which promotes sealing along the interfacial region.
With seals normally used in high pressure applications, high contact stress is concentrated over a narrow sealing width. With the present method, the teaching is exactly the opposite; a comparatively low contact stress is distributed over a wide sealing width. This teaching exploits the relationship between width and maximum contact stress. As the contact width is increased, the average contact stress is decreased. This teaching allows an interference fit to be provided, with a lower average contact stress.
Formulas necessary for the calculation of necessary contact stress in high pressure applications are published by the American Petroleum Institute. These formulas all teach that the initial contact stress must be greater than the pressure to be contained in order to avoid seal failure. In accordance with the teachings of the present method, the initial contact stress between the sleeve and the surface of revolution can be less than required to maintain contact stress greater than the contained pressure over the full intended pressure range. There can even be an initial gap, 30that is closed and sealed by fluid pressure.
There are numerous ways of securing the sleeve to the second pressure containment member. Sleeve can be secured by welding, clamping, or with various fasteners. In view of the 2~8~~6~
high pressure applications for which the present method is intended, it is preferred that the sleeve be intregally formed as part of the second elongate pressure containment member.
It is important that there be a clear differentiation in the thickness of the sleeve and the thickness of the second elongate pressure containment member. The sleeve cannot merely be a gradually tapered extension of the second elongate pressure containment member, and still work as intended. It l0is, therefore, preferred that the first end of the sleeve be conjoined to the remote end of the second elongate pressure containment member over an interval of length not greater than one thickness of the second elongate pressure containment member.
Although beneficial effects may be obtained through the use of the method, as described above, where there is a gap, a portion of the length of the sleeve is required to compensate for the gap and this can adversely effect the sleeves ability to seal in response to fluid pressure. Even more beneficial 20effects may, therefore be obtained when a circumferential notch is placed near the remote end of the second elongate pressure containment member on the side where the fluid pressure is less. The notch provides for some additional flexibility which makes the sleeve more responsive to fluid pressure.
In accordance with another aspect of the present invention there is provided a seal assembly which includes a first elongate tubular member having a surface of revolution.
A second elongate tubular member is provided having an exterior surface, an interior surface and a remote end. A
thin walled extension sleeve is provided having a first end and a second end. The first end of the thin walled extension sleeve is conjoined with the remote end. The second elongate 2184;~~~
tubular member is telescopically received within the first elongate tubular member with the sleeve positioned in close relation to the surface of revolution.
It is important that there be a clear differentiation in the thickness of the sleeve and the thickness of the second elongate pressure containment member. The sleeve cannot merely be a gradually tapered extension of the second elongate pressure containment member, and still work as intended. It l0is, therefore, preferred that the first end of the sleeve be conjoined to the remote end of the second elongate pressure containment member over an interval of length not greater than one thickness of the second elongate pressure containment member.
Although beneficial effects may be obtained through the use of the method, as described above, where there is a gap, a portion of the length of the sleeve is required to compensate for the gap and this can adversely effect the sleeves ability to seal in response to fluid pressure. Even more beneficial 20effects may, therefore be obtained when a circumferential notch is placed near the remote end of the second elongate pressure containment member on the side where the fluid pressure is less. The notch provides for some additional flexibility which makes the sleeve more responsive to fluid pressure.
In accordance with another aspect of the present invention there is provided a seal assembly which includes a first elongate tubular member having a surface of revolution.
A second elongate tubular member is provided having an exterior surface, an interior surface and a remote end. A
thin walled extension sleeve is provided having a first end and a second end. The first end of the thin walled extension sleeve is conjoined with the remote end. The second elongate 2184;~~~
tubular member is telescopically received within the first elongate tubular member with the sleeve positioned in close relation to the surface of revolution.
5 Although beneficial effects may be obtained through the seal assembly, as described above, even better performance may be obtained from the seal assembly when the second elongate tubular member has a notch in the exterior surface adjacent the remote end.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features of the invention will become more apparent from the following description in which reference is made to the appended drawings, wherein:
FIGURE 1 is a side elevation view, in section, of a metal-to-metal seal constructed in accordance with the teaching of the present invention.
FIGURE 2 is a side elevation view, in section, of the metal-to-metal seal illustrated in FIGURE 1, undergoing pressure testing.
FIGURE 3 is a graph setting forth seepage rates at applied pressures when the metal-to-metal seal is subjected to pressure testing, as illustrated in FIGURE 2.
FIGURE 4 is a graph setting forth friction loads at applied pressures when the metal-to-metal seal is lubricated and then subjected to pressure testing, as illustrated in FIGURE 2.
FIGURE 5 is a magnified view of the metal-to-metal seal illustrated in FIGURE 1, deformed by applied pressure.
~1848~1~
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features of the invention will become more apparent from the following description in which reference is made to the appended drawings, wherein:
FIGURE 1 is a side elevation view, in section, of a metal-to-metal seal constructed in accordance with the teaching of the present invention.
FIGURE 2 is a side elevation view, in section, of the metal-to-metal seal illustrated in FIGURE 1, undergoing pressure testing.
FIGURE 3 is a graph setting forth seepage rates at applied pressures when the metal-to-metal seal is subjected to pressure testing, as illustrated in FIGURE 2.
FIGURE 4 is a graph setting forth friction loads at applied pressures when the metal-to-metal seal is lubricated and then subjected to pressure testing, as illustrated in FIGURE 2.
FIGURE 5 is a magnified view of the metal-to-metal seal illustrated in FIGURE 1, deformed by applied pressure.
~1848~1~
FIGURE 6 is a graph setting forth seal contact stress distribution when the metal-to-metal seal is subjected to pressure testing, as illustrated in FIGURE 2.
FIGURE 7 is a graph setting forth average contact stress as a function of applied pressure when the metal-to-metal seal is subjected to pressure testing, as illustrated in FIGURE 2.
FIGURE 8 is a side elevation view, in section, illustrating a first alternative sealing assembly constructed in accordance with the teachings of the present method.
FIGURE 9 is a side elevation view, in section, illustrating a second alternative sealing assembly constructed in accordance with the teachings of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED E~DIMENT
The preferred method of forming a metal-to-metal seal in high pressure applications with low contact stress will now be described with reference to FIGURES 1 through 7.
Firstly, provide a first elongate pressure containment member 12 having a surface of revolution 14.
Secondly, provide a second elongate pressure containment member 16 having an exterior surface 17, an interior surface 19 and a remote end 18. In FIGURE 1, first elongate pressure containment member 12 and second elongate pressure containment member 16 are tubular members. This is a typical application z~s~ ~~~
FIGURE 7 is a graph setting forth average contact stress as a function of applied pressure when the metal-to-metal seal is subjected to pressure testing, as illustrated in FIGURE 2.
FIGURE 8 is a side elevation view, in section, illustrating a first alternative sealing assembly constructed in accordance with the teachings of the present method.
FIGURE 9 is a side elevation view, in section, illustrating a second alternative sealing assembly constructed in accordance with the teachings of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED E~DIMENT
The preferred method of forming a metal-to-metal seal in high pressure applications with low contact stress will now be described with reference to FIGURES 1 through 7.
Firstly, provide a first elongate pressure containment member 12 having a surface of revolution 14.
Secondly, provide a second elongate pressure containment member 16 having an exterior surface 17, an interior surface 19 and a remote end 18. In FIGURE 1, first elongate pressure containment member 12 and second elongate pressure containment member 16 are tubular members. This is a typical application z~s~ ~~~
for this method of sealing, although there are some applications in which they need not be tubular members.
Second elongate pressure containment member 16 has a thin walled extension sleeve 20 having a first end 22 and a second end 24. First end 22 of thin walled extension sleeve 20 is conjoined with remote end 18 of second elongate pressure member 16. Sleeve 20 can be conjoined with second elongate member 16 by welding and forming or machining from a single piece of material. In view of the intended high pressure applications, it is preferred that sleeve 20 be integrally formed as part of second elongate pressure member 16 by machining from a single piece of material. Second elongate pressure containment member 16 is of a greater thickness than sleeve 20. Second end 24 of sleeve 20 projects past remote end 18. Depending on the requirements of the application a notch 30 may be provided near remote end 18. Notch 30 is placed so that it is exposed to the low pressure. In the intended application, as will be further described in relation to FIGURE 2, interior surface 19 is subjected to fluid pressure that is high when compared to exterior surface 17. Notch 30 is, therefore, illustrated on exterior surface 17 adjacent remote end 18.
Thirdly, couple first elongate pressure containment member 12 and second elongate pressure containment member 16 with sleeve 20 positioned in close relation to surface of revolution 14. In the illustrated embodiment, second elongate pressure containment member 16 has been telescopically inserted into first elongate pressure containment member 12.
Contrary to API recommended practice guidelines for sealing between overlapping 'cylindrical' members, the initial contact stress between sleeve 20 and surface of revolution 14 may be less_than required to maintain contact stress greater than the zl~~~ ~~
Second elongate pressure containment member 16 has a thin walled extension sleeve 20 having a first end 22 and a second end 24. First end 22 of thin walled extension sleeve 20 is conjoined with remote end 18 of second elongate pressure member 16. Sleeve 20 can be conjoined with second elongate member 16 by welding and forming or machining from a single piece of material. In view of the intended high pressure applications, it is preferred that sleeve 20 be integrally formed as part of second elongate pressure member 16 by machining from a single piece of material. Second elongate pressure containment member 16 is of a greater thickness than sleeve 20. Second end 24 of sleeve 20 projects past remote end 18. Depending on the requirements of the application a notch 30 may be provided near remote end 18. Notch 30 is placed so that it is exposed to the low pressure. In the intended application, as will be further described in relation to FIGURE 2, interior surface 19 is subjected to fluid pressure that is high when compared to exterior surface 17. Notch 30 is, therefore, illustrated on exterior surface 17 adjacent remote end 18.
Thirdly, couple first elongate pressure containment member 12 and second elongate pressure containment member 16 with sleeve 20 positioned in close relation to surface of revolution 14. In the illustrated embodiment, second elongate pressure containment member 16 has been telescopically inserted into first elongate pressure containment member 12.
Contrary to API recommended practice guidelines for sealing between overlapping 'cylindrical' members, the initial contact stress between sleeve 20 and surface of revolution 14 may be less_than required to maintain contact stress greater than the zl~~~ ~~
contained pressure over the full pressure range. In fact, there may be a gap 26 between sleeve 20 and surface of revolution 14, as will hereinafter be further described.
Fourthly, place first elongate pressure containment member 12 and second elongate pressure containment member 16 in an environment in which fluid pressure tends to cause a flow of fluids from second end 24 to first end 22 of sleeve 20 along an interfacial region 28 between sleeve 20 and surface l0of revolution 14. Fluid pressure tends to constrict and set up a pressure gradient along interfacial region 28 sufficient to seal interfacial region 28. Where a notch 30 is included, fluid pressure, acting largely in the axial direction, has the further tendency to constrict the interfacial region and control the sealing contact stress distribution.
Once the underlying principles of the described method are understood, it will be appreciated that the length and thickness of sleeve 20 required to achieve the desired result will vary with the application, as will the width and depth of the notch 30 if included. Certain of these variables can, however, be reduced to a formula:
L > Lt here LI 021 , without notch and Ll ~ 0.051 with not ch, where t = b = character istic shel 1 waveleng th, 3 1- n Z~
= rzt~ for cylin ders , r = average s leeve radi us, t = sleeve w all thiclai ess, and n = Poisson' s ratio With this method of sealing there can actually be an initial gap 26, as illustrated in FIGURE 1, between first elongate pressure containment member 12 and sleeve 20. Where such a gap exists an initial flow through the gap must be provided for and small gap sizes may be accounted for using laminar flow assumptions in the formula:
L2 > 3dP where, Q~ 6m g = gap size dependent on presser a induced deformatio ns, m = viscosity , P = annular p ressure, Q~ = maximum a llowable s eapage flo w rate, and Po = applied d i~erentia 1 pressure for maxim um flow wi thin opera ting press ere range.
Sealing can be enhanced, as it is in other sealing applications, by providing a weak solid interface compound, such as grease, in interfacial region 28. This alters the flow behaviour of the annular material from that of a fluid to a weak solid which mechanism may be described by the formula:
Ip L ~ > 2 ~dP where, g = gap size dependent on presser a induced deformatio ns, t = allowable static sh ear streng th of irate rfacial ma terial, P = annular p ressure, and Po = maximum a pplied dif ferential pressure.
Care must be taken in having a clear differentiation between sleeve 20 and the balance of second elongate pressure containment member 16. If the transition in thickness is gradual, there is a danger that sleeve 20 will not function as intended. Sleeve 20 has to be sufficiently thin that it will deform to seal interfacial region 28 when subjected to the pressures of the intended application. It is, therefore, to be ~18~~6~
preferred that first end 22 of sleeve 20 be connected to remote end 18 of second elongate pressure containment member 16 over an interval of length not greater than one thickness of second elongate pressure containment member 16.
The physical testing of the prototype will now be described to illustrate the utility of the present invention.
The seal will be referred to as MICS seal; MICS being an acronym for Minimal interfacial contact stress.
Referring to FIGURE 2, a prototype seal assembly, generally indicated by reference numeral 10, was constructed according to the teaching of the present invention. Seal assembly 10 was the subjected to physical tests designed to verify the performance of seal 10 under the application of pressure, and friction loads associated with axial sliding along the seal surfaces.
Referring to FIGURE 2, seal assembly 10 consists of first 20pressure containment member 12 and second pressure containment member 16. Pressure containment members 12 and 16 were formed from bars and machined long internal bore cavities. They were then telescopically connected to form a fully enclosed pressure containment unit upon assembly. Second pressure containment member 16 was machined to incorporate a 12 inch long thin walled sleeve 20 at one of its ends, remote end 18.
A radial clearance gap 26 of 0.0004 inches was provided between an outside surface of sleeve 20 and inside surface of revolution 14 of first pressure containment member 12; both of which surfaces constitute the seal area. Two holes 32 and 34 ~1~~~~~
were drilled through first pressure containment member 12 and second pressure containment member 16 in order to accommodate fixtures for hydraulic lines supplying pressure fluid and connecting pressure measuring instrumentation.
Test were conducted on both a "dry" specimen and also on a specimen having seal surfaces which were lubricated with grease. First pressure containment member 12 was then lowered onto second pressure containment member 16 to a predetermined depth. The unit was placed vertically between the a top compression plate 36 and a bottom compression plate 38 of a testing machine (not shown). A fluid containment vessel 40 was attached to bottom compression plate 38 to collect leaked fluid.
The specimen was filled with water pumped into inside cavity 42 through the lower of the access holes, access hole 32. Internal pressure was applied first by adding extra pressure fluid. At each given threshold pressure the inflow 201ine was shut off. The specimen was then compressed by the testing machine, with inside pressure building up. After the peak value was reached, the testing machine stroke was reversed, and the specimen was allowed to expand back until it reached the original threshold pressure. More water was pumped 25inside the specimen to bring up the pressure to the next threshold value, at which point the load cycle was repeated.
~18~b~
During testing, no leak was detected from the lubricated specimen at any pressure during static pressure increases, nor during load cycles with sliding up to a pressure of approximately 5,500 psi. Above this pressure, seepage was observed during compression and expansion sliding driven by the testing machine, of magnitude less than 0.15 bbl/day.
Seepage rates detected from the unlubricated test under static conditions, shown in FIGURE 3, exhibit an approximately linear dependence on the pressure above the activation pressure of approximately 2000 psi, with estimated leakage magnitude approximately 1 bbl/day at 8,000 psi. which is considered to be within acceptable limits.
FIGURE 4, represents friction loads obtained during the compression of the lubricated specimen. The abscissa represents the inside pressured the ordinate corresponds to the difference between the total sliding load and end pressure load, and is therefore a measure of friction load. Based on the above values, the friction coefficient determining 20friction along lubricated surfaces was estimated at 0.088.
Test data obtained during specimen expansion showed a relatively smaller difference between total load and the product of inside pressure times cross-section area, indicating smaller friction loads, especially under higher pressures. Friction coefficient for dry specimen was estimated in a similar manner and found equal to approximately 0.33, with friction loads up to 30,000 lbf.
The tests verified the ability of the MICS seal to ensure 30pressure integrity between two tubular members subjected to internal pressures up to 9,000 psi and relative axial movement ~18.~~~
of the seal surfaces. Seepage rates obtained from the lubricated specimen during load cycles under high pressures and from the dry specimen, were very low. Friction loads associated with axial compression or expansion of the assembly under pressure were small, confirming that metal-to-metal sealing in combination with the further tendency of the largely axial fluid pressure load between the pressured surfaces and the unpressured notch cavity to constrict the interfacial region and control the sealing contact stress distributionwas achieved with minimized contact stress yielding acceptably low overall friction sliding loads for full scale applications.
A seal geometry incorporating notch 30 but otherwise similar to that used for the physical tests, as shown in FIGURE 2, was analyzed using the finite element analysis (FEA) method. The mesh for the model constructed provided an initial notch of 0.00025 inches. The analysis considered the tendency of pressure to penetrate the contact region so that pressure 20was applied to all inside surfaces up to the seal location.
FIGURE 5, shows the deformed mesh in the seal region after seal contact has been activated by flow or stress gradients in the grease along the interfacial region. The deformations are exaggerated to better visualize the ability of the gap to control the contact region geometry and hence contact stress distribution under pressure loading.
FIGURES 6 and 7, provide evaluation of the contact pressure. As shown, a wide seal contact width is achieved so that the low contact stress condition required for sliding is w.I(.~~7 a C'V C'Cl , i~ l ~C) ~1:.~ ;-ul:l~;~l l . C1 ~" ~ E~,~.J~'s:~S ~ , f sW':c.ll;;it !' i(l 1)1 1.. 1..: 7. i"r J
lIlt.('I~f HrC:I'iCi.: 4lc~;i )a.'S(:'C~ < 7: : 1.1 V~zL..7.C~~I'1 ~:~ i't:
~;:1t~ C):~ i...'SFW ~Wa1~, requliz~EJd. Used w:i trl ilnv i l.~~w ~. cl).mrt ic~~Il.';, leil~_s va~.ue aJ.~..c;.»r.>
applwp?: iat:e sel or..t-iol: i ~i ~-io;; icln~ ~m ,)cicec_e ~,. __~
c~ovE.rn_ilmt ei.t:lle.r '_~ thG ~>ec.eparr,e i'.l.cw ~>)~ E~c>)nt>c~ ~a:l .>c;,a l z ~~clu.l l c:rni:W
:~.
S~dlZi ~_o FIGLIRF ~' ~.1 1 i,;t:.~:.~ < <; c.~I~~'. 1 :arum ~.:1 >ea.1 ~ In:;
assce:):)L;1 y,;
there cil~f'_ 8 ',TC3I l E.'t:y' 1:71.: c:.1 j a"I I r°:t.:L VE.
:~E.r.t_l.:LIl~ <),'a:eIllt).11'.'', t:~lat CaI1 be constructed using the t=E:a~i~7l~.m.~., ~>,L~ t.~l_E_~ ~r_e;>elzt:
r;uet::hod. I'n each case high PrEy ssux~Er~ct_,~ zzpcorl ~;3 e:evtv ~'Cj . In each case fluid a.t:tempt.:s to migz otc,v r:r_~In <zn 1 a~rA ot_ ruighi pressm:e ~)t..
:second ~-~rld 2~ of sl.<aevr:: a'Ci I cv~.~zr.c_~ t i r .~, E I~~i :''? . F.W
errillo FIGURE 8, there is 1. Lu ;t:.z°~t ~,:? a:~ Ir~ara-i~:z :Lr~ G,~2i.i~:i1 sleeve 20 c:~I:
he adapi_ed to seal ol~l ,HIV ),x1 Ekz..tclr s~zc°irc.c:. c~y:t: a tul:~ular member with pressure cami_nc~ frroln t~~~~ ~~3i1-eca~ia:aa:u~. Re:lei~ri.ng to FIGLTR.'~
9r there is i. 11.u stratcd ~ Inarlrzcx yII ~~rilieii t:wo o.f seal assemblies 10 can be ci:~mb~~rmad . tc~ Izuc:e L t:.he needs of an application in which prc~.:~.~ur~cv a,~ oil Laothl ~ _de.~;. Axis csi_ symne.tzy 51 earl be on e~_ther icicle of. ~;.'eevi:;a 2(7~ a:~ a.i..l_>nz-~tx~<~ted in Figure 1.
~?0 It will be appazent: t:o tzlnc:a :>i;i.~..:l.t-c'3than, art that in t:he present method teaches~.Iiufit~c_t-~r~~ Iz~Evt:'~wc'~afo:r~m~_ng a meta7-<:,}i to-metal seal in hicth far~~::ut.~, , ~y~~l ~,ai.t h l_o~
c:) ~ a:;"f ~ i>.)~:;contaca..
stress. It w~.l~. alsoh~e~)r>n u_1~)t to ,~rl~~~ .>ka.l:Led iIn tile ar:t tizat Inod:ifications i~-c~Inaua:~ t~.a t:llE:t~rat.ed.
enrl:zodiment:.
I.Iay il'u-a withoutdepart:inEl ' e~ ~>}i r i t: c~i t:he illvent.i.om from t~~zlz~a ,7c~o7~e a~~ herei_naft:er detilm~di t~iu :-.mn:, .
n
Fourthly, place first elongate pressure containment member 12 and second elongate pressure containment member 16 in an environment in which fluid pressure tends to cause a flow of fluids from second end 24 to first end 22 of sleeve 20 along an interfacial region 28 between sleeve 20 and surface l0of revolution 14. Fluid pressure tends to constrict and set up a pressure gradient along interfacial region 28 sufficient to seal interfacial region 28. Where a notch 30 is included, fluid pressure, acting largely in the axial direction, has the further tendency to constrict the interfacial region and control the sealing contact stress distribution.
Once the underlying principles of the described method are understood, it will be appreciated that the length and thickness of sleeve 20 required to achieve the desired result will vary with the application, as will the width and depth of the notch 30 if included. Certain of these variables can, however, be reduced to a formula:
L > Lt here LI 021 , without notch and Ll ~ 0.051 with not ch, where t = b = character istic shel 1 waveleng th, 3 1- n Z~
= rzt~ for cylin ders , r = average s leeve radi us, t = sleeve w all thiclai ess, and n = Poisson' s ratio With this method of sealing there can actually be an initial gap 26, as illustrated in FIGURE 1, between first elongate pressure containment member 12 and sleeve 20. Where such a gap exists an initial flow through the gap must be provided for and small gap sizes may be accounted for using laminar flow assumptions in the formula:
L2 > 3dP where, Q~ 6m g = gap size dependent on presser a induced deformatio ns, m = viscosity , P = annular p ressure, Q~ = maximum a llowable s eapage flo w rate, and Po = applied d i~erentia 1 pressure for maxim um flow wi thin opera ting press ere range.
Sealing can be enhanced, as it is in other sealing applications, by providing a weak solid interface compound, such as grease, in interfacial region 28. This alters the flow behaviour of the annular material from that of a fluid to a weak solid which mechanism may be described by the formula:
Ip L ~ > 2 ~dP where, g = gap size dependent on presser a induced deformatio ns, t = allowable static sh ear streng th of irate rfacial ma terial, P = annular p ressure, and Po = maximum a pplied dif ferential pressure.
Care must be taken in having a clear differentiation between sleeve 20 and the balance of second elongate pressure containment member 16. If the transition in thickness is gradual, there is a danger that sleeve 20 will not function as intended. Sleeve 20 has to be sufficiently thin that it will deform to seal interfacial region 28 when subjected to the pressures of the intended application. It is, therefore, to be ~18~~6~
preferred that first end 22 of sleeve 20 be connected to remote end 18 of second elongate pressure containment member 16 over an interval of length not greater than one thickness of second elongate pressure containment member 16.
The physical testing of the prototype will now be described to illustrate the utility of the present invention.
The seal will be referred to as MICS seal; MICS being an acronym for Minimal interfacial contact stress.
Referring to FIGURE 2, a prototype seal assembly, generally indicated by reference numeral 10, was constructed according to the teaching of the present invention. Seal assembly 10 was the subjected to physical tests designed to verify the performance of seal 10 under the application of pressure, and friction loads associated with axial sliding along the seal surfaces.
Referring to FIGURE 2, seal assembly 10 consists of first 20pressure containment member 12 and second pressure containment member 16. Pressure containment members 12 and 16 were formed from bars and machined long internal bore cavities. They were then telescopically connected to form a fully enclosed pressure containment unit upon assembly. Second pressure containment member 16 was machined to incorporate a 12 inch long thin walled sleeve 20 at one of its ends, remote end 18.
A radial clearance gap 26 of 0.0004 inches was provided between an outside surface of sleeve 20 and inside surface of revolution 14 of first pressure containment member 12; both of which surfaces constitute the seal area. Two holes 32 and 34 ~1~~~~~
were drilled through first pressure containment member 12 and second pressure containment member 16 in order to accommodate fixtures for hydraulic lines supplying pressure fluid and connecting pressure measuring instrumentation.
Test were conducted on both a "dry" specimen and also on a specimen having seal surfaces which were lubricated with grease. First pressure containment member 12 was then lowered onto second pressure containment member 16 to a predetermined depth. The unit was placed vertically between the a top compression plate 36 and a bottom compression plate 38 of a testing machine (not shown). A fluid containment vessel 40 was attached to bottom compression plate 38 to collect leaked fluid.
The specimen was filled with water pumped into inside cavity 42 through the lower of the access holes, access hole 32. Internal pressure was applied first by adding extra pressure fluid. At each given threshold pressure the inflow 201ine was shut off. The specimen was then compressed by the testing machine, with inside pressure building up. After the peak value was reached, the testing machine stroke was reversed, and the specimen was allowed to expand back until it reached the original threshold pressure. More water was pumped 25inside the specimen to bring up the pressure to the next threshold value, at which point the load cycle was repeated.
~18~b~
During testing, no leak was detected from the lubricated specimen at any pressure during static pressure increases, nor during load cycles with sliding up to a pressure of approximately 5,500 psi. Above this pressure, seepage was observed during compression and expansion sliding driven by the testing machine, of magnitude less than 0.15 bbl/day.
Seepage rates detected from the unlubricated test under static conditions, shown in FIGURE 3, exhibit an approximately linear dependence on the pressure above the activation pressure of approximately 2000 psi, with estimated leakage magnitude approximately 1 bbl/day at 8,000 psi. which is considered to be within acceptable limits.
FIGURE 4, represents friction loads obtained during the compression of the lubricated specimen. The abscissa represents the inside pressured the ordinate corresponds to the difference between the total sliding load and end pressure load, and is therefore a measure of friction load. Based on the above values, the friction coefficient determining 20friction along lubricated surfaces was estimated at 0.088.
Test data obtained during specimen expansion showed a relatively smaller difference between total load and the product of inside pressure times cross-section area, indicating smaller friction loads, especially under higher pressures. Friction coefficient for dry specimen was estimated in a similar manner and found equal to approximately 0.33, with friction loads up to 30,000 lbf.
The tests verified the ability of the MICS seal to ensure 30pressure integrity between two tubular members subjected to internal pressures up to 9,000 psi and relative axial movement ~18.~~~
of the seal surfaces. Seepage rates obtained from the lubricated specimen during load cycles under high pressures and from the dry specimen, were very low. Friction loads associated with axial compression or expansion of the assembly under pressure were small, confirming that metal-to-metal sealing in combination with the further tendency of the largely axial fluid pressure load between the pressured surfaces and the unpressured notch cavity to constrict the interfacial region and control the sealing contact stress distributionwas achieved with minimized contact stress yielding acceptably low overall friction sliding loads for full scale applications.
A seal geometry incorporating notch 30 but otherwise similar to that used for the physical tests, as shown in FIGURE 2, was analyzed using the finite element analysis (FEA) method. The mesh for the model constructed provided an initial notch of 0.00025 inches. The analysis considered the tendency of pressure to penetrate the contact region so that pressure 20was applied to all inside surfaces up to the seal location.
FIGURE 5, shows the deformed mesh in the seal region after seal contact has been activated by flow or stress gradients in the grease along the interfacial region. The deformations are exaggerated to better visualize the ability of the gap to control the contact region geometry and hence contact stress distribution under pressure loading.
FIGURES 6 and 7, provide evaluation of the contact pressure. As shown, a wide seal contact width is achieved so that the low contact stress condition required for sliding is w.I(.~~7 a C'V C'Cl , i~ l ~C) ~1:.~ ;-ul:l~;~l l . C1 ~" ~ E~,~.J~'s:~S ~ , f sW':c.ll;;it !' i(l 1)1 1.. 1..: 7. i"r J
lIlt.('I~f HrC:I'iCi.: 4lc~;i )a.'S(:'C~ < 7: : 1.1 V~zL..7.C~~I'1 ~:~ i't:
~;:1t~ C):~ i...'SFW ~Wa1~, requliz~EJd. Used w:i trl ilnv i l.~~w ~. cl).mrt ic~~Il.';, leil~_s va~.ue aJ.~..c;.»r.>
applwp?: iat:e sel or..t-iol: i ~i ~-io;; icln~ ~m ,)cicec_e ~,. __~
c~ovE.rn_ilmt ei.t:lle.r '_~ thG ~>ec.eparr,e i'.l.cw ~>)~ E~c>)nt>c~ ~a:l .>c;,a l z ~~clu.l l c:rni:W
:~.
S~dlZi ~_o FIGLIRF ~' ~.1 1 i,;t:.~:.~ < <; c.~I~~'. 1 :arum ~.:1 >ea.1 ~ In:;
assce:):)L;1 y,;
there cil~f'_ 8 ',TC3I l E.'t:y' 1:71.: c:.1 j a"I I r°:t.:L VE.
:~E.r.t_l.:LIl~ <),'a:eIllt).11'.'', t:~lat CaI1 be constructed using the t=E:a~i~7l~.m.~., ~>,L~ t.~l_E_~ ~r_e;>elzt:
r;uet::hod. I'n each case high PrEy ssux~Er~ct_,~ zzpcorl ~;3 e:evtv ~'Cj . In each case fluid a.t:tempt.:s to migz otc,v r:r_~In <zn 1 a~rA ot_ ruighi pressm:e ~)t..
:second ~-~rld 2~ of sl.<aevr:: a'Ci I cv~.~zr.c_~ t i r .~, E I~~i :''? . F.W
errillo FIGURE 8, there is 1. Lu ;t:.z°~t ~,:? a:~ Ir~ara-i~:z :Lr~ G,~2i.i~:i1 sleeve 20 c:~I:
he adapi_ed to seal ol~l ,HIV ),x1 Ekz..tclr s~zc°irc.c:. c~y:t: a tul:~ular member with pressure cami_nc~ frroln t~~~~ ~~3i1-eca~ia:aa:u~. Re:lei~ri.ng to FIGLTR.'~
9r there is i. 11.u stratcd ~ Inarlrzcx yII ~~rilieii t:wo o.f seal assemblies 10 can be ci:~mb~~rmad . tc~ Izuc:e L t:.he needs of an application in which prc~.:~.~ur~cv a,~ oil Laothl ~ _de.~;. Axis csi_ symne.tzy 51 earl be on e~_ther icicle of. ~;.'eevi:;a 2(7~ a:~ a.i..l_>nz-~tx~<~ted in Figure 1.
~?0 It will be appazent: t:o tzlnc:a :>i;i.~..:l.t-c'3than, art that in t:he present method teaches~.Iiufit~c_t-~r~~ Iz~Evt:'~wc'~afo:r~m~_ng a meta7-<:,}i to-metal seal in hicth far~~::ut.~, , ~y~~l ~,ai.t h l_o~
c:) ~ a:;"f ~ i>.)~:;contaca..
stress. It w~.l~. alsoh~e~)r>n u_1~)t to ,~rl~~~ .>ka.l:Led iIn tile ar:t tizat Inod:ifications i~-c~Inaua:~ t~.a t:llE:t~rat.ed.
enrl:zodiment:.
I.Iay il'u-a withoutdepart:inEl ' e~ ~>}i r i t: c~i t:he illvent.i.om from t~~zlz~a ,7c~o7~e a~~ herei_naft:er detilm~di t~iu :-.mn:, .
n
Claims (45)
1. A sealing apparatus comprising:
a first tubular pressure containment member having an interior surface of revolution;
a second tubular pressure containment member having an exterior surface, an interior surface, a remote end, and a thin walled extension sleeve having a thickness, a first end and a second end defining a length and the first end of the thin walled extension sleeve being conjoined with the remote end; and the second tubular pressure containment member being telescopically engaged with the first tubular pressure containment member with the thin walled extension sleeve positioned wholly within the first tubular pressure containment member in close relation to the interior surface of revolution and with a continuous gap, between the thin walled extension sleeve and the interior surface of revolution of the first tubular pressure containment member over the length of the thin walled extension sleeve.
a first tubular pressure containment member having an interior surface of revolution;
a second tubular pressure containment member having an exterior surface, an interior surface, a remote end, and a thin walled extension sleeve having a thickness, a first end and a second end defining a length and the first end of the thin walled extension sleeve being conjoined with the remote end; and the second tubular pressure containment member being telescopically engaged with the first tubular pressure containment member with the thin walled extension sleeve positioned wholly within the first tubular pressure containment member in close relation to the interior surface of revolution and with a continuous gap, between the thin walled extension sleeve and the interior surface of revolution of the first tubular pressure containment member over the length of the thin walled extension sleeve.
2. The sealing apparatus of claim 1 further comprising a narrow axially extending circumferential notch in the exterior surface of the second tubular pressure containment member, near the thin walled extension sleeve, so that axial fluid pressure on the second tubular pressure containment member inner surfaces will deform the notch and cause the thin walled extension sleeve to move towards contact with the first tubular pressure containment member interior surface of revolution.
3. The sealing apparatus of claim 1 in which, at operating fluid pressure, there is a continuous gap between the thin walled extension sleeve and the first tubular pressure containment member interior surface of revolution over the length of the thin walled extension sleeve.
4. The sealing apparatus of claim 1 in which the first tubular pressure containment member and the thin walled extension sleeve are disconnected to permit at least one of relative axial and relative rotational movement.
5. The sealing apparatus of claim 1 in which the thin walled extension sleeve is integrally formed as part of the second tubular pressure containment member.
6. The sealing apparatus of claim 1 having the remote end of the second elongate pressure containment member of substantially uniform thickness, the extension sleeve of substantially uniform thickness, and the first end of the extension sleeve connected to the remote end of the second elongate pressure containment member over an interval of length not greater than one thickness of the remote end of the second elongate pressure containment member.
7. The sealing apparatus of claim 1 in which the thickness and length of the extension sleeve are determined in accordance with the following formulae:
L>L1 Where L1 >= 0.2.lambda., without notch and L1 >= 0.05.lambda..
with notch, where L = thin walled extension sleeve length L1 = length of the thin walled extension sleeve between the first end and the portion in close relation to the first tubular pressure containment member interior surface of revolution.
r = average extension sleeve radius t = thin walled extension sleeve thickness, and v = Poisson's ratio
L>L1 Where L1 >= 0.2.lambda., without notch and L1 >= 0.05.lambda..
with notch, where L = thin walled extension sleeve length L1 = length of the thin walled extension sleeve between the first end and the portion in close relation to the first tubular pressure containment member interior surface of revolution.
r = average extension sleeve radius t = thin walled extension sleeve thickness, and v = Poisson's ratio
8. The sealing apparatus of claim 1 in which the thickness and length of the extension sleeve are determined in accordance with the following formula:
L2 - length of the thin walled extension sleeve in close relation to the first tubular pressure containment member interior surface of revolution g = gap size, dependent on pressure induced deformations µ= viscosity P = annular pressure Q max = minimum allowable seepage flow rate, and P o= applied differential pressure for maximum flow within operating pressure range.
L2 - length of the thin walled extension sleeve in close relation to the first tubular pressure containment member interior surface of revolution g = gap size, dependent on pressure induced deformations µ= viscosity P = annular pressure Q max = minimum allowable seepage flow rate, and P o= applied differential pressure for maximum flow within operating pressure range.
9. The apparatus according to claim 1 further comprising a weak solid interfacial compound disposed in the region between the thin walled extension sleeve and the interior surface of revolution of the first tubular pressure containment member, and in which the width and length of the thin walled extension sleeve are determined in accordance with the following formula:
L2 = length of the thin walled extension sleeve in close relation to the first tubular pressure containment member interior surface of revolution, g = gap size dependent on pressure induced deformation, .tau. = allowable static shear strength of interfacial material, P = annular pressure, and P o = maximum applied differential pressure.
L2 = length of the thin walled extension sleeve in close relation to the first tubular pressure containment member interior surface of revolution, g = gap size dependent on pressure induced deformation, .tau. = allowable static shear strength of interfacial material, P = annular pressure, and P o = maximum applied differential pressure.
10. A method of forming a seal comprising the steps of:
providing a first tubular pressure containment member having an interior surface of revolution;
providing a second tubular pressure containment member having an exterior surface, an interior surface, a remote end, and a thin walled extension sleeve having a thickness, a first end and a second end defining a length and the first end of the thin walled extension sleeve being conjoined with the remote end; and telescopically engaging the second tubular pressure containment member with the first tubular pressure containment member with the thin walled extension sleeve positioned wholly within the first tubular pressure containment member in close relation to the interior surface of revolution, and with a continuous gap between the thin walled extension sleeve and the interior surface of revolution of the first tubular pressure containment member over the length of the thin walled extension sleeve
providing a first tubular pressure containment member having an interior surface of revolution;
providing a second tubular pressure containment member having an exterior surface, an interior surface, a remote end, and a thin walled extension sleeve having a thickness, a first end and a second end defining a length and the first end of the thin walled extension sleeve being conjoined with the remote end; and telescopically engaging the second tubular pressure containment member with the first tubular pressure containment member with the thin walled extension sleeve positioned wholly within the first tubular pressure containment member in close relation to the interior surface of revolution, and with a continuous gap between the thin walled extension sleeve and the interior surface of revolution of the first tubular pressure containment member over the length of the thin walled extension sleeve
11. The method of claim 10, further comprising placing a narrow axially extending circumferential notch in the exterior surface of the second tubular pressure containment member, near the thin walled extension sleeve, so that axial fluid pressure on the second tubular pressure containment member inner surfaces will deform the notch and cause the thin walled extension sleeve to move towards contact with the first tubular pressure containment member interior surface of revolution.
12. The method of claim 10 in which, at operating fluid pressure, there is a continuous gap between the thin walled extension sleeve and the first tubular pressure containment member interior surface of revolution over the length of the thin walled extension sleeve.
13. The method of claim 7.0 in which the first tubular pressure containment member and the thin walled extension sleeve are disconnected to permit at least one of relative axial and relative rotational movement.
14. The method of claim 10 in which the thin walled extension sleeve is integrally formed as part of the second tubular pressure containment member.
15. The method of claim 10 in which the remote end of the second elongate pressure containment member is of substantially uniform thickness, tree extension sleeve is of substantially uniform thickness, and the first end of the extension sleeve is connected to the remote end of the second elongate pressure containment member over an interval of length not greater than one thickness of the remote end of the second elongate pressure containment member.
16. The method of claim 10 in which the thickness and length of the extension sleeve are determined according to the following formulae:
L>L1 Where L1 >= 0.2.lambda., without notch and L1 >= 0.05.lambda. with notch, where L = thin walled extension sleeve length L1 = length of the thin walled extension sleeve between the first end and the portion in close relation to the first tubular pressure containment member interior surface of revolution r = average thin walled extension sleeve radius t = than walled extension sleeve thickness, and v = Poisson's ratio
L>L1 Where L1 >= 0.2.lambda., without notch and L1 >= 0.05.lambda. with notch, where L = thin walled extension sleeve length L1 = length of the thin walled extension sleeve between the first end and the portion in close relation to the first tubular pressure containment member interior surface of revolution r = average thin walled extension sleeve radius t = than walled extension sleeve thickness, and v = Poisson's ratio
17. The method of claim 20 in which the thickness and length of the thin walled extension sleeve are determined in accordance with the following formula:
L2 = length of the thin walled extension sleeve in close relation to the first tubular- pressure containment member interior surface of revolution g = gap size, dependent on pressure induced deformations µ= viscosity P = annular pressure Q max = minimum allowable seepage flow rate, and P o= applied differential pressure for maximum flow within operating pressure range.
L2 = length of the thin walled extension sleeve in close relation to the first tubular- pressure containment member interior surface of revolution g = gap size, dependent on pressure induced deformations µ= viscosity P = annular pressure Q max = minimum allowable seepage flow rate, and P o= applied differential pressure for maximum flow within operating pressure range.
18. The method of claim 10 further comprising disposing a weak solid interfacial compound in the region between the thin walled extension sleeve and the interior surface of revolution of the first tubular pressure containment member, and in which the width and length of the thin walled extension sleeve are determined in accordance with the following formula:
L2 = length of the thin walled extension sleeve in close relation to the first tubular pressure containment member interior surface of revolution g = gap size dependent on pressure induced deformation, .tau. = allowable static shear strength of interfacial material, P = annular pressure, and P o = maximum applied differential pressure.
L2 = length of the thin walled extension sleeve in close relation to the first tubular pressure containment member interior surface of revolution g = gap size dependent on pressure induced deformation, .tau. = allowable static shear strength of interfacial material, P = annular pressure, and P o = maximum applied differential pressure.
19. A sealing apparatus comprising:
a first tubular pressure containment member having an exterior surface of revolution;
a second tubular pressure containment member having an exterior surface, an interior surface, a remote end, and a thin walled extension sleeve having a thickness and a first end and a second end defining a length, the first end of the thin walled extension sleeve being conjoined with the remote end; and the second tubular pressure containment member being telescopically engaged with the first tubular pressure containment member with the exterior surface of revolution positioned wholly within the thin walled extension sleeve in close relation to the thin walled extension sleeve and with a continuous gap between the thin walled extension sleeve and the first tubular pressure containment member exterior surface of revolution over the length of the thin walled extension sleeve.
a first tubular pressure containment member having an exterior surface of revolution;
a second tubular pressure containment member having an exterior surface, an interior surface, a remote end, and a thin walled extension sleeve having a thickness and a first end and a second end defining a length, the first end of the thin walled extension sleeve being conjoined with the remote end; and the second tubular pressure containment member being telescopically engaged with the first tubular pressure containment member with the exterior surface of revolution positioned wholly within the thin walled extension sleeve in close relation to the thin walled extension sleeve and with a continuous gap between the thin walled extension sleeve and the first tubular pressure containment member exterior surface of revolution over the length of the thin walled extension sleeve.
20. The sealing apparatus of claim 19, further comprising a narrow axially extending circumferential notch in the interior surface of the second tubular pressure containment member, near the thin walled extension sleeve so that axial fluid pressure on the second tubular pressure containment member surfaces will deform the notch and tend to deflect the thin walled extension sleeve towards contact with the first tubular pressure containment member exterior surface of revolution.
21. The sealing apparatus of claim 19 in which, at operating fluid pressure, there is a continuous gap between the thin walled extension sleeve and firsts tubular pressure containment member exterior surface of revolution over the length of the thin walled extension sleeve.
22. The sealing apparatus of claim 19 in which the first tubular pressure containment member and the thin walled extension sleeve are disconnected to permit at least one of relative axial and relative rotational movement.
23. The sealing apparatus of claim 19 in which the thin walled extension sleeve is integrally formed as part of the second tubular pressure containment member.
24. The sealing apparatus of claim 19 having the remote end of the second elongate pressure containment member of substantially uniform thickness, the extension sleeve of substantially uniform thickness, and the first end of the extension sleeve connected to the remote end of the second elongate pressure containment member over an interval of length not greater than one thickness of the remote end of the second elongate pressure containment member.
25. The sealing apparatus of claim 19 in which the thickness and length of the extension sleeve are determined in accordance with the following formulae:
L>L1 Where L1 >= 0.2.lambda. without notch and L1 >=0Ø5.lambda. with notch, where L = thin walled extension sleeve length L1 = length of the thin walled extension sleeve between the first end and the portion in close relation to the first tubular pressure containment member exterior surface of revolution.
r = average thin walled extension sleeve radius t = thin walled extension sleeve thickness, and v = Poisson's ratio
L>L1 Where L1 >= 0.2.lambda. without notch and L1 >=0Ø5.lambda. with notch, where L = thin walled extension sleeve length L1 = length of the thin walled extension sleeve between the first end and the portion in close relation to the first tubular pressure containment member exterior surface of revolution.
r = average thin walled extension sleeve radius t = thin walled extension sleeve thickness, and v = Poisson's ratio
26. The sealing apparatus of claim 19 in which the thickness and length of the thin walled extension sleeve are determined in accordance with the following formula:
L2 - length of the thin wailed extension sleeve in close relation to the first tubular pressure containment member exterior surface of revolution g = gap size, dependent on pressure induced deformations µ = viscosity P = annular pressure Q max = minimum allowable seepage flow rate, and P0 = applied differential pressure for maximum flow within operating pressure range.
L2 - length of the thin wailed extension sleeve in close relation to the first tubular pressure containment member exterior surface of revolution g = gap size, dependent on pressure induced deformations µ = viscosity P = annular pressure Q max = minimum allowable seepage flow rate, and P0 = applied differential pressure for maximum flow within operating pressure range.
27. The sealing apparatus of claim 19 further comprising a weak solid interfacial compound disposed in the region between the thin walled extension sleeve and the exterior surface of revolution of the first tubular pressure containment member, and in which the width and length of the thin walled extension sleeve are determined in accordance with the following formula:
where L2 - length of the thin walled extension sleeve in close relation to the first tubular pressure containment member exterior surface of revolution g = gap size dependent on pressure reduced deformation, ~ = allowable static shear strength of interfacial material, P = annular pressure, and P0 = maximum applied differential pressure.
where L2 - length of the thin walled extension sleeve in close relation to the first tubular pressure containment member exterior surface of revolution g = gap size dependent on pressure reduced deformation, ~ = allowable static shear strength of interfacial material, P = annular pressure, and P0 = maximum applied differential pressure.
28. A method of forming a seal comprising the steps of:
providing a first tubular pressure containment member having an exterior surface of revolution;
providing a second tubular pressure containment member having an exterior surface, an interior surface, a remote end, and a thin walled extension sleeve having a thickness and a first end and a second end defining a length, the first end of the thin walled extension sleeve being conjoined with the remote end; and telescopically engaging the second tubular pressure containment member with the first tubular pressure containment member with the exterior surface of revolution positioned wholly within the thin walled extension sleeve in close relation to the thin walled extension sleeve and with a continuous gap between the thin walled extension sleeve and the first tubular pressure containment member exterior surface of revolution over the length of the thin walled extension sleeve.
providing a first tubular pressure containment member having an exterior surface of revolution;
providing a second tubular pressure containment member having an exterior surface, an interior surface, a remote end, and a thin walled extension sleeve having a thickness and a first end and a second end defining a length, the first end of the thin walled extension sleeve being conjoined with the remote end; and telescopically engaging the second tubular pressure containment member with the first tubular pressure containment member with the exterior surface of revolution positioned wholly within the thin walled extension sleeve in close relation to the thin walled extension sleeve and with a continuous gap between the thin walled extension sleeve and the first tubular pressure containment member exterior surface of revolution over the length of the thin walled extension sleeve.
29. The method of claim 28, further comprising placing a narrow axially extending circumferential notch in the interior surface of the second tubular pressure containment member, near the thin walled extension sleeve so that axial fluid pressure on the second tubular pressure containment member surfaces will deform she notch and tend to deflect the thin walled extension sleeve towards contact with the first tubular pressure containment member exterior surface of revolution.
30. The method of claim 28 in which, at operating fluid pressure, there is a continuous gap between the thin walled extension sleeve and first tubular pressure containment member exterior surface of revolution over the length of the thin walled extension sleeve.
31. The method of ca.aim 28 in which the first tubular pressure containment member and the thin walled extension sleeve are disconnected to permit at least one of relative axial and relative rotational movement.
32. The method of claim 28 in which the thin walled extension sleeve is integrally formed as part of the second tubular pressure containment member.
33. The method of claim 28 in which the remote end of the second elongate pressure containment member is of substantially uniform thickness, the thin walled extension sleeve is of substantially uniform thickness, and the first end of the extension sleeve is connected to the remote end of the second elongate pressure containment member over an interval of length not greater than one thickness of the remote end of the second elongate pressure containment member.
34. The method of claim 28 in which the thickness and length of the extension sleeve are determined in accordance with the following formulae:
L>L1 Where L1 >= 0.2.lambda. without notch and L1 >=0.05.lambda. with notch, where L = thin walled extension sleeve length L1 = length of the thin walled extension sleeve between the first end and the portion in close relation to the first tubular pressure containment member exterior surface of revolution.
r = average extension sleeve radius t = thin walled extension sleeve thickness, and v = Poisson'a ratio
L>L1 Where L1 >= 0.2.lambda. without notch and L1 >=0.05.lambda. with notch, where L = thin walled extension sleeve length L1 = length of the thin walled extension sleeve between the first end and the portion in close relation to the first tubular pressure containment member exterior surface of revolution.
r = average extension sleeve radius t = thin walled extension sleeve thickness, and v = Poisson'a ratio
35. The method of claim 28 in which the thickness and length of the extension sleeve are determined in accordance with the following formula:
L2 - length of the thin walled extension sleeve in close relation to the first tubular pressure containment member exterior surface of revolution g = gap size, dependent on pressure induced deformations µ = viscosity P = annular pressure Q max = minimum allowable seepage flow rate, and P0 = applied differential pressure for maximum flow within operating pressure range.
L2 - length of the thin walled extension sleeve in close relation to the first tubular pressure containment member exterior surface of revolution g = gap size, dependent on pressure induced deformations µ = viscosity P = annular pressure Q max = minimum allowable seepage flow rate, and P0 = applied differential pressure for maximum flow within operating pressure range.
36. The method of claim 28 further comprising disposing a weak solid interfacial compound in the region between the thin walled extension sleeve and the exterior surface of revolution of the first tubular pressure containment member, and in which the width and length of the thin walled extension sleeve are determined in accordance with the following formula:
L2 - length of the thin walled extension sleeve in close relation to the first tubular pressure containment member exterior surface of revolution g = gap size dependent on pressure induced deformation, ~ = allowable static shear strength of interfacial material, P = annular pressure, and P0 = maximum applied differential pressure.
L2 - length of the thin walled extension sleeve in close relation to the first tubular pressure containment member exterior surface of revolution g = gap size dependent on pressure induced deformation, ~ = allowable static shear strength of interfacial material, P = annular pressure, and P0 = maximum applied differential pressure.
37. A method of forming a metal-to-metal seal in high pressure applications with low contact stress, comprising the steps of:
firstly, providing a first elongate pressure containment member having a surface of revolution;
secondly, providing an exterior surface, an interior surface, a remote end, and a thin walled extension sleeve having a first end and a second end, the first end of the thin walled extension sleeve being conjoined with the remote end;
thirdly, coupling the first elongate pressure containment member and the second elongate pressure containment member with the sleeve positioned wholly within the first elongate pressure containment member in close relation to the surface of revolution; and fourthly, placing the first elongate pressure containment member and the second elongate pressure containment member in an environment in which fluid pressure exceeds initial contact stress between the sleeve and the surface of revolution at some point of an intended operation pressure range and tends to cause a flow of fluids from the second end to the first end of the sleeve along an interfacial region between the sleeve and the surface of revolution, such fluid pressure and flow producing a pressure gradient along the interfacial region sufficient to deform the sleeve and generate an increasing contact stress that restricts flow along the interfacial region to predefine acceptable limits with such increasing contact stress remaining less than the contained fluid pressure.
firstly, providing a first elongate pressure containment member having a surface of revolution;
secondly, providing an exterior surface, an interior surface, a remote end, and a thin walled extension sleeve having a first end and a second end, the first end of the thin walled extension sleeve being conjoined with the remote end;
thirdly, coupling the first elongate pressure containment member and the second elongate pressure containment member with the sleeve positioned wholly within the first elongate pressure containment member in close relation to the surface of revolution; and fourthly, placing the first elongate pressure containment member and the second elongate pressure containment member in an environment in which fluid pressure exceeds initial contact stress between the sleeve and the surface of revolution at some point of an intended operation pressure range and tends to cause a flow of fluids from the second end to the first end of the sleeve along an interfacial region between the sleeve and the surface of revolution, such fluid pressure and flow producing a pressure gradient along the interfacial region sufficient to deform the sleeve and generate an increasing contact stress that restricts flow along the interfacial region to predefine acceptable limits with such increasing contact stress remaining less than the contained fluid pressure.
38. The method as defined in claim 37, the sleeve being integrally formed as part of the second elongate pressure containment member.
39. The method as defined in claim 37, a narrow radially extending circumferential notch being placed near the remote end of the second elongate pressure containment member on one of the exterior surface and interior surface where the fluid pressure is less than on the other of the first side and the second side, thereby creating a gas that deforms in response to fluid pressure acting in an axial direction and tending to force the sleeve into engagement with the surface of revolution.
40. The method as defined in claim 37, having the remote end of the second elongate pressure containment member of substantially uniform thickness, the sleeve of substantially uniform thickness, and the first end of the sleeve connected to the remote end of the second elongate pressure containment member over an interval of length not greater than one thickness of the remote end of the second elongate pressure containment member.
41. The method as defined in claim 37, leaving the thickness and length of the sleeve determined in accordance with the following formula:
L<L1 Where L1 >= 0.2.lambda. with notch, where ~
r = average extension sleeve radius t = thin walled extension sleeve thickness, and v = Poisson's ratio
L<L1 Where L1 >= 0.2.lambda. with notch, where ~
r = average extension sleeve radius t = thin walled extension sleeve thickness, and v = Poisson's ratio
42. The method as defined in claim 37, having an initial gap between the first pressure containment member and the second pressure containment member, the thickness and length of the sleeve necessary to compensate for such initial gap being determined in accordance with the following formula:
g = gap size, dependent on pressure induced deformations µ = viscosity P = annular pressure Q max = maximum allowable seepage flow rate, and P0 = applied differential pressure for maximum flow within operating pressure range.
g = gap size, dependent on pressure induced deformations µ = viscosity P = annular pressure Q max = maximum allowable seepage flow rate, and P0 = applied differential pressure for maximum flow within operating pressure range.
43. The method as defined in claim 37, having an initial gap between the first pressure containment member and the second pressure containment member with a weak solid interfacial length of the sleeve necessary to compensate to such initial gap being determined in accordance with the following formula:
g = gap size dependent on pressure induced deformation, ~ = allowable static shear strength of interfacial material, P = annular pressure, and P0 = maximum applied differential pressure.
g = gap size dependent on pressure induced deformation, ~ = allowable static shear strength of interfacial material, P = annular pressure, and P0 = maximum applied differential pressure.
44. A method of forming a metal-to-metal seal in high pressure applications with low contact stress, comprising the steps of firstly, providing a first elongate tubular member having a surface of revolution;
secondly, providing a second elongate tubular member having an exterior surface, an interior surface, a remote end of substantially uniform thickness, and a thin walled extension sleeve of substantially uniform thickness having a first end and second end, the first end of the thin walled extension sleeve being conjoined with the remote end, over an interval of length not greater than one thickness of the remote end of the second elongate pressure containment member, the second elongate tubular member having a narrow radially extending circumferential notch in the exterior surface adjacent the remote end;
thirdly, coupling the first elongate tubular member and the second elongate tubular member by telescopically inserting the second elongate tubular member within the first elongate tubular member with the sleeve positioned wholly within the first elongate pressure containment member in close relation to the surface of revolution; and fourthly, placing the first elongate tubular member and the second elongate tubular member in an environment in which fluid pressure exceeds initial contact stress between the sleeve and the surface of revolution at some point of an intended operating pressure range and acts against the internal surface of the second elongate tubular member and tends to cause a flow of fluids from the second end to the first end of the sleeve along an interfacial region between the sleeve and the surface of revolution, such fluid pressure and flow producing a pressure gradient along the interfacial region sufficient to deform the sleeve and generate an increasing contact stress that restricts flow along the interfacial region to predefined acceptable limits with such increasing contact stress remaining less than the contained fluid pressure.
secondly, providing a second elongate tubular member having an exterior surface, an interior surface, a remote end of substantially uniform thickness, and a thin walled extension sleeve of substantially uniform thickness having a first end and second end, the first end of the thin walled extension sleeve being conjoined with the remote end, over an interval of length not greater than one thickness of the remote end of the second elongate pressure containment member, the second elongate tubular member having a narrow radially extending circumferential notch in the exterior surface adjacent the remote end;
thirdly, coupling the first elongate tubular member and the second elongate tubular member by telescopically inserting the second elongate tubular member within the first elongate tubular member with the sleeve positioned wholly within the first elongate pressure containment member in close relation to the surface of revolution; and fourthly, placing the first elongate tubular member and the second elongate tubular member in an environment in which fluid pressure exceeds initial contact stress between the sleeve and the surface of revolution at some point of an intended operating pressure range and acts against the internal surface of the second elongate tubular member and tends to cause a flow of fluids from the second end to the first end of the sleeve along an interfacial region between the sleeve and the surface of revolution, such fluid pressure and flow producing a pressure gradient along the interfacial region sufficient to deform the sleeve and generate an increasing contact stress that restricts flow along the interfacial region to predefined acceptable limits with such increasing contact stress remaining less than the contained fluid pressure.
45. A method of forming a metal-to-metal seal in high pressure applications with low contact stress, comprising the steps of:
firstly, providing a first elongate pressure containment member having a surface of revolution;
secondly, providing a second elongate pressure containment member of having an exterior surface, an interior surface, a remote end, and a thin walled extension sleeve having a first end and a second end, the first end of the thin walled extension sleeve being conjoined with the remote end;
thirdly, coupling the first elongate pressure containment member and the second elongate pressure containment member with the sleeve positioned wholly within the first elongate pressure containment member in close relation to the surface of revolution; and fourthly placing the first elongate pressure containment member in an environment in which fluid pressure exceeds initial contact stress between the sleeve and the surface of revolution at some point of an intended operating pressure range and tends to cause a flow of fluids from the second end to the first e:nd c;>f t.hE; sleeve a~.ong an ~.nterfacial region between the sleeve and the sur:T:ace of revolution, such fluid pressure and flow ~:~roc~~,a.c;~.:cug =1 pr~essl.~re grad::i.ent along the interfacial :reg.ion suff:~c;::~.er~t; tta deform the :sleeve and generate an increasing contact strews that restricts flow along the interfacia:L reg:i.c>rp t:.a p:r~~c~e:,~i.'i.ra.ed acceptable limits while permitting relatives movement of the f.irst:: elongate pressure containment member crud 1: he ~:ecc~nd elongate pressure containment member wik~h ~~~~c~.h :izucz:~:a~~asi.ng co:ntac:t stress remaining less than t he contained flu.~_c:;~ pressure.
firstly, providing a first elongate pressure containment member having a surface of revolution;
secondly, providing a second elongate pressure containment member of having an exterior surface, an interior surface, a remote end, and a thin walled extension sleeve having a first end and a second end, the first end of the thin walled extension sleeve being conjoined with the remote end;
thirdly, coupling the first elongate pressure containment member and the second elongate pressure containment member with the sleeve positioned wholly within the first elongate pressure containment member in close relation to the surface of revolution; and fourthly placing the first elongate pressure containment member in an environment in which fluid pressure exceeds initial contact stress between the sleeve and the surface of revolution at some point of an intended operating pressure range and tends to cause a flow of fluids from the second end to the first e:nd c;>f t.hE; sleeve a~.ong an ~.nterfacial region between the sleeve and the sur:T:ace of revolution, such fluid pressure and flow ~:~roc~~,a.c;~.:cug =1 pr~essl.~re grad::i.ent along the interfacial :reg.ion suff:~c;::~.er~t; tta deform the :sleeve and generate an increasing contact strews that restricts flow along the interfacia:L reg:i.c>rp t:.a p:r~~c~e:,~i.'i.ra.ed acceptable limits while permitting relatives movement of the f.irst:: elongate pressure containment member crud 1: he ~:ecc~nd elongate pressure containment member wik~h ~~~~c~.h :izucz:~:a~~asi.ng co:ntac:t stress remaining less than t he contained flu.~_c:;~ pressure.
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002184864A CA2184864C (en) | 1996-09-05 | 1996-09-05 | Method of forming a metal-to-metal seal in high pressure applications with low contact stress |
| AU41954/97A AU4195497A (en) | 1996-09-05 | 1997-09-05 | Method of forming a metal-to-metal seal |
| PCT/CA1997/000652 WO1998010213A1 (en) | 1996-09-05 | 1997-09-05 | Method of forming a metal-to-metal seal |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002184864A CA2184864C (en) | 1996-09-05 | 1996-09-05 | Method of forming a metal-to-metal seal in high pressure applications with low contact stress |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2184864A1 CA2184864A1 (en) | 1998-03-06 |
| CA2184864C true CA2184864C (en) | 2004-05-11 |
Family
ID=4158847
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002184864A Expired - Fee Related CA2184864C (en) | 1996-09-05 | 1996-09-05 | Method of forming a metal-to-metal seal in high pressure applications with low contact stress |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2184864C (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116753385B (en) * | 2023-08-16 | 2023-11-07 | 江苏五星波纹管有限公司 | Chemical anti-corrosion sleeve compensator |
-
1996
- 1996-09-05 CA CA002184864A patent/CA2184864C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2184864A1 (en) | 1998-03-06 |
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