Stem Seals with Triangular Rings

Abstract

A pressure-tight stem cylinder seal and a self-energizing stem shoulder seal matching the stem cylinder seal that both use an equilaterally triangular soft ring as their sealing element, wherein their designing rules are first, by means of wedging function of a hard gland coaxial with the stem cylinder, to convert their original axial tightening force 2f respectively into a radial compression force 4f/√3 of their soft ring 04 on the stem 02 cylinder and another radial compression force 2f of their soft ring 06 on the stem 02 shoulder and ensure that the two soft rings are so compressed from a great room to a small room as to be able to pass a pressure or stress exactly to each different direction, then to cut off their off-stem corners to give their cavities an opening or give each soft ring an axial compressing allowance, and last, by means of anti-extrusion metallic C-rings without axial resistance, to close each opening to provide a full support for the sealing deformation of their soft rings compressed in their cavities.

Claims

1. An equilaterally triangular ring seal for moving rod or shaft cylinders (or called stem cylinder seals with triangular rings), including a single turn anti-extrusion ring (05b), a triangular soft ring (04) truncated at its off-stem corner and a hard metallic gland (03a) that are successively fitted over the cylindrical stem or shaft (02) and, as the triangular soft ring is compressed on the stem cylinder and in a 120° conical seat of stem housings (01) at the same time by a 120° inner conical surface of the hard metallic gland, form a triangular ring-containing cavity consisting of the inner conical surface of the hard metallic gland, the stem cylinder and the conical surface of the seat and having an opening caused by cutting off the cavity's off-stem corner to enable the triangular soft ring therein to be fully compressed, wherein the single turn anti-extrusion ring made of either a bent turn of soft metallic wire with enough length and cross-sectional diameter or a molded turn of nonmetallic material with enough strength is used to resist the extrusion of the triangular soft ring through the gap between the stem and the stem housing, a sliding fit with a small enough clearance is used to resist the extrusion of the triangular soft ring through the gap between the gland and the stem, and an arc-shaped anti-extrusion metallic C-ring (05a) attached to the truncated corner of the triangular soft ring is used to resist the extrusion of the triangular soft ring through the opening of the cavity.

2. A stem cylinder seal with triangular rings as set forth in claim 1, wherein a metallic inverse-J-shaped ring with an arc-shaped hook is substituted for the arc-shaped anti-extrusion metallic C-ring, and the inverse-J-shaped ring is such a variant C-ring formed by extending the C of the C-ring only along the non-sealing surface of the triangular soft ring that the inverse-J-shaped ring has the same arc as the C-ring.

3. A stem cylinder seal with triangular rings as set forth in claim 1 or claim 2, wherein dimensions of the seal are designed and computed to meet the requirement of its maximum allowable working pressure p.sub.mc=0.5R.sub.mrr.sub.uc/r.sub.c+R.sub.mcδ.sub.c/r.sub.c, where 0.5R.sub.mrr.sub.uc/r.sub.c is the maximum withstandable pressure of a triangular soft ring without the anti-extrusion metallic C-ring or inverse-J-shaped ring, R.sub.mcδ.sub.c/r.sub.c is the maximum withstandable pressure of the anti-extrusion metallic C-ring or inverse-J-shaped ring, R.sub.mr is the material's tensile strength of the triangular soft ring, R.sub.mc is the material's tensile strength of the anti-extrusion metallic C-ring or inverse-J-shaped ring, δ.sub.c is the wall thickness of the anti-extrusion metallic C-ring or inverse-J-shaped ring, r.sub.c is the arc radius of the anti-extrusion metallic C-ring or inverse-J-shaped ring, and r.sub.uc is the incircle radius of the fundamental equilateral triangle.

4. An equilaterally triangular ring seal for moving rod or shaft shoulders (or called stem shoulder seals with triangular rings), including a triangular soft ring (06) truncated at its off-stem corner and a hard metallic gland (07) that are fitted together over the spherical stem shoulder (02) by their 60° conical surfaces and, as the triangular soft ring is compressed on the stem housing (01) by the spherical stem shoulder and the hard metallic gland, form a triangular ring-containing cavity consisting of the inner conical surface of the hard metallic gland, the spherical surface of the stem shoulder and the flat surface of the stem housing and having an opening caused by cutting off the cavity's off-stem corner to enable the triangular soft ring therein to be fully compressed, wherein a contact fit without clearance between the stem shoulder and the stem housing as well as the hard metallic gland is used to resist the extrusion of the triangular soft ring at two non-truncated corners, and an arc-shaped anti-extrusion metallic C-ring (05a) attached to the truncated corner of the triangular soft ring is used to resist the extrusion of the triangular soft ring through the opening of the cavity.

5. A stem shoulder seal with triangular rings as set forth in claim 4, wherein a metallic J-shaped ring with an arc-shaped hook is substituted for the arc-shaped anti-extrusion metallic C-ring, and the J-shaped ring is such a variant C-ring formed by extending the C of the C-ring only along the non-sealing surface of the triangular soft ring that the J-shaped ring has the same arc as the C-ring.

6. A stem shoulder seal with triangular rings as set forth in claim 4 or claim 5, wherein dimensions of the seal are designed and computed to meet the requirement of its maximum allowable working pressure p.sub.mc=0.5R.sub.mrr.sub.us/r.sub.s+R.sub.msδ.sub.s/r.sub.s, where 0.5R.sub.mrr.sub.us/r.sub.s is the maximum withstandable pressure of a triangular soft ring without the anti-extrusion metallic C-ring or J-shaped ring, R.sub.msδ.sub.s/r.sub.s is the maximum withstandable pressure of the anti-extrusion metallic C-ring or J-shaped ring, R.sub.mr is the material's tensile strength of the triangular soft ring, R.sub.ms is the material's tensile strength of the anti-extrusion metallic C-ring or J-shaped ring, δ.sub.s is the wall thickness of the anti-extrusion metallic C-ring or J-shaped ring, r.sub.s is the arc radius of the anti-extrusion metallic C-ring or J-shaped ring, and r.sub.us is the incircle radius of the fundamental equilateral triangle.

7. An equilaterally triangular ring seal for moving rod or shaft cylinders (or called stem cylinder seals with triangular rings), including a single turn anti-extrusion ring (05b), a triangular soft ring (04) truncated at its off-stem corner and a hard metallic gland (03a) that are successively fitted over the cylindrical stem or shaft (02) and, as the triangular soft ring is compressed on the stem cylinder and in a 120° conical seat of stem housings (01) at the same time by a 120° inner conical surface of the hard metallic gland, form a triangular ring-containing cavity consisting of the inner conical surface of the hard metallic gland, the stem cylinder and the conical surface of the seat and having an opening caused by cutting off the cavity's off-stem corner to enable the triangular soft ring therein to be fully compressed, wherein the single turn anti-extrusion ring made of either a bent turn of soft metallic wire with enough length and cross-sectional diameter or a molded turn of nonmetallic material with enough strength is used to resist the extrusion of the triangular soft ring through the gap between the stem and the stem housing, a sliding fit with a small enough clearance is used to resist the extrusion of the triangular soft ring through the gap between the gland and the stem, and an anti-extrusion metallic coiled ring (FIG. 6) or an anti-extrusion close wound coil spring ring (FIG. 7) attached to the truncated corner of the triangular soft ring is used to resist the extrusion of the triangular soft ring through the opening of the cavity.

8. An equilaterally triangular ring seal for moving rod or shaft shoulders (or called stem shoulder seals with triangular rings), including a triangular soft ring (06) truncated at its off-stem corner and a hard metallic gland (07) that are fitted together over the spherical stem shoulder (02) by their 60° conical surfaces and, as the triangular soft ring is compressed on the stem housing (01) by the spherical stem shoulder and the hard metallic gland, form a triangular ring-containing cavity consisting of the inner conical surface of the hard metallic gland, the spherical surface of the stem shoulder and the flat surface of the stem housing and having an opening caused by cutting off the cavity's off-stem corner to enable the triangular soft ring therein to be fully compressed, wherein a contact fit without clearance between the stem shoulder and the stem housing as well as the hard metallic gland is used to resist the extrusion of the triangular soft ring at two non-truncated corners, and an anti-extrusion metallic coiled ring (FIG. 6) or an anti-extrusion close wound coil spring ring (FIG. 7) attached to the truncated corner of the triangular soft ring is used to resist the extrusion of the triangular soft ring through the opening of the cavity.

9. A stem cylinder seal as set forth in claim 7 or a stem shoulder seal as set forth in claim 8, wherein the seal with its triangular soft ring having the anti-extrusion metallic coiled ring can withstand a maximum pressure pmc or p.sub.mr=0.5R.sub.mrr.sub.u/r+R.sub.m ln [1/(1−√k)], where 0.5R.sub.mrr.sub.u/r is the maximum withstandable pressure of a triangular soft ring without the anti-extrusion ring, R.sub.m ln [1/(1−√k)] is the maximum withstandable pressure of the anti-extrusion metallic coiled ring, R.sub.mr is the material's tensile strength of the triangular soft ring, R.sub.m is the material's tensile strength of the anti-extrusion metallic coiled ring, r.sub.u is the incircle radius of the fundamental equilateral triangle, r is the cross-sectional outline radius of the metallic coiled ring and about equal to the extrusion arc radius of the triangular soft ring without the anti-extrusion ring at the opening of the cavity, and k is the ratio of total cross-sectional area of wires to cross-sectional-outline area of the anti-extrusion metallic coiled ring.

10. A stem cylinder seal or stem shoulder seal as set forth in any claim of claims 1 to 9, wherein the anti-extrusion ring used to resist the extrusion of the triangular soft ring through the opening of the cavity is made of high strength non-metallic materials.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0051] In FIGS. 1 to 6 showing the triangular ring seals of the invention, 01 is valve bodies or bonnets collectively called stem housings; 02, stems; 03a, hard metallic glands of soft sealing rings for stem cylinders; 03b, bonnets of glands for stem cylinders; 04, soft sealing rings for stem cylinders; 05a, anti-extrusion metallic rings attached to the truncated corner of soft sealing rings; 05b, single turn anti-extrusion rings between stems and their housings; 06, soft sealing rings for stem shoulders; 07, hard metallic glands of soft sealing rings for stem shoulders; 08a, spherical washers; 08b, Belleville washers; 08c, hexagonal screws; 09, hexagonal nuts; 10, valve handles; 11, valve locks; and 12, spaced tying turns for anti-extrusion metallic coiled rings.

[0052] FIG. 1 shows a small size of rising stem cylinder seals for valves, where FIG. 1b is the partial enlarged view of the stem cylinder seal in FIG. 1a.

[0053] FIG. 2 shows a large size of rising stem cylinder seals for valves, where FIG. 2b is the partial enlarged view of the stem cylinder seal in FIG. 2a.

[0054] FIG. 3 shows non-rising stem cylinder and shoulder seals for ball valves, where FIG. 3b is the partial enlarged view of the stem shoulder seal in FIG. 3a. The partial enlarged view of the stem cylinder seal in FIG. 3a is as shown in FIG. 2b.

[0055] FIGS. 4a and 4b show triangular soft rings for stem cylinder seals respectively with an anti-extrusion metallic C-ring and an anti-extrusion metallic inverse-J-ring, where the circular ring with thickness δ=kr.sub.uc is the wall's cross-section of the simulating O-ring of metallic thin wall tubing of incircle rings of the triangular soft ring.

[0056] FIGS. 5a and 5b show triangular soft rings for stem shoulder seals respectively with an anti-extrusion metallic C-ring and an anti-extrusion metallic J-ring, where the circular ring with thickness δ=kr.sub.us is the wall's cross-section of the simulating O-ring of metallic thin wall tubing of incircle rings of the triangular soft ring.

[0057] FIGS. 6b and 6c are respectively the real cross-sectional view and its simulating cross-sectional view of FIG. 6a-shown anti-extrusion metallic coiled rings substituted for anti-extrusion metallic C-shaped, inverse-J-shaped or J-shaped rings.

[0058] FIG. 7 shows anti-extrusion close wound coil spring rings substituted for anti-extrusion metallic C-shaped, inverse-J-shaped or J-shaped rings.

DETAILED DESCRIPTION OF THE INVENTION

[0059] As shown in FIGS. 1-3, the final orientation of a valve stem 02 is determined by the installing of its cylinder-sealing soft-ring 04 into a 120° conical seat of its housing 01. Hence, in order to ensure that a hard gland 03a can cause the soft ring 04 to have a uniform circumferential compression in its conical seat and on the stem 02, it shall be required first that three basic surfaces of the soft ring are coaxial, second that the inner conical surface of the hard gland is always coaxial with the stem during installation, third that there is an enough gap between the gland and the stem housing to ensure that the gland and the stem can swing with the soft ring during installation, and then that the soft ring is loaded by the mating of conical and spherical surfaces, for example, the soft ring in FIG. 1 shall be loaded by the mating of the bonnet's (03b's) inner conical surface coaxial with its fastening threads and the gland's (03a's) outer spherical surface coaxial with its inner conical surface, the soft ring in FIG. 2 shall be loaded either by the mating of the clamp's (03b's) inner conical surface and the gland's (03a's) outer spherical surface coaxial with its inner conical surface or by the mating of the spherical washer's (08a's) outer spherical surface and the conical port of the screw's through-holes, and the soft ring in FIG. 3 shall be loaded by the mating of the Belleville washer's (08b's) outer spherical surface and the relevant chamfered port, in order to ensure that gland's loading resultant force coincides with the stem axis.

[0060] In order to ensure that non-rising stems have a stem shoulder seal (see FIG. 3) formed by a spherical and spherical mating pair and coaxial with its stem cylinder seal and thus ensure that both of the two seals have a fully uniform circumferential compression of their soft rings at the same time, first have the spherical sealing surface Sr of shoulder sealing soft rings 06 pre-made into a conical surface coaxial with the other basic surfaces (see FIG. 5), have the stem or the spherical stem shoulder case-hardened and prepare a metallic ring whose dimensions are the same as the cylinder sealing soft ring 04; then, by substituting the metallic ring for soft rings 04, make a heavy installation of the shoulder seal in position to work the pre-made conical surface of soft rings 06 and the housing surface between diameters d and Di (see FIG. 3b) into a spherical surface coinciding with the case-hardened spherical stem shoulder; and last finish the formal installing of the stem by substituting the soft ring 04 for the metallic ring. When the installing causes its shoulder to touch its housing, the installed metallic touch can eliminate both the infinite loading of the stem shoulder seal by tightening force for installation and the unloading of the stem cylinder seal by fluid pressure on the stem end, and also can result in the fluid pressure on the end of gland 07 causing not only an enhanced stem shoulder seal but also such a weakened stem-ejecting-out power as to cause an effect of both lowering the friction between the stem shoulder and the stem housing and enhancing the stem cylinder seal, and thus the spherical and spherical metallic mating pair between the stem shoulder seal and the stem cylinder seal can be called an isolating mating pair therebetween. Because the installing torque will soar when the installing of a stem causes its shoulder to touch its housing, the extent to which the stem is installed can be controlled by feeling. If a stem is installed only to cause its shoulder to just touch its housing, the installing will only cause its shoulder seal as an energizing seal but not its cylinder seal as a pressure-tight seal to function, and so it may not be needed to consider retightening to cause the cylinder seal to function until both the shoulder ring seal and the isolating mating pair as self-energized seals fail, which can avoid shutting down the system beyond the plan. The compressing forces on each surface of the shoulder sealing ring and the cylinder sealing ring are respectively 2f and 4f/√3=2.31f before the isolating mating pair is installed to its tight contact, and hence, if it is desired to make the cylinder sealing ring and the shoulder sealing ring have the same sealing stress at this time, the lengths Cs and Cc of fundamental triangle sides of the shoulder sealing ring and the cylinder sealing ring shall be designed roughly in accordance with Cs=0.5√3Cc=0.87Cc. However, if it is desired only to cause the shoulder sealing ring and the isolating mating pair but not the cylinder sealing ring to function, it is recommended that the shoulder ring and the cylinder ring are designed in accordance with Cs<0.5√3Cc=0.87Cc.

[0061] Similarly, a backseat seal matching a stem cylinder seal for rising stems shall be designed and installed the same as the above stem shoulder seal to make the backseat seal be formed by a spherical and spherical mating pair and coaxial with the stem cylinder seal, ensuring that the backseat seal and the cylinder seal can function at the same time when a valve is fully turned on.

[0062] In order to ensure that the compressing stress of sealing soft rings is not affected by their abrasion and thermal expansion, they shall be fully compressed by live loads from elastic deformation of Belleville washers 08b, glands 03a and/or anti-extrusion rings 05a properly designed and installed. Because the maximum allowable working pressure and the providable maximum compressing stress of a triangular soft ring are mainly determined by extrusion resistance of its anti-extrusion ring but not by strength of its material, a size of triangular soft rings can be designed and provided by using the softest ring to meet the requirement of maximum possible working pressure of the size of triangular soft rings, or, except for material, there can be no dimensional difference between all the triangular soft rings for a size whose maximum possible working pressure does not exceed their maximum allowable working pressure. The triangular soft rings for general purposes are made of either pure polytetrafluoroethylene (PTFE) or flexible graphite and, for a particular purpose, made of lead or gold. In order to save raw materials and constructing spaces, their tightening structures shall be designed in accordance with their actual maximum allowable working pressures.

[0063] An equilaterally triangular pressure-tight stem-sealing ring has three basic surfaces that have three equal action forces and three different areas and are respectively used as its dynamic sealing surface, static sealing surface and loading surface. To make the dynamic sealing surface have a sealing stress greater than that of the static sealing surface and provide a dynamic sealing deformation for moving stems in time, the dynamic sealing surface must achieve both supports from the static sealing surface and the loading surface stronger than the dynamic sealing surface at the same time, and hence the truncating of stem-sealing rings at their off-stem corner shall not be so much as to cause either of non-dynamic sealing surfaces to have an area smaller than that of the dynamic sealing surface. For this purpose, the fundamental triangle for stem cylinder seals shall be the equilateral triangle whose altitude hc is the side length of another equilateral triangle whose altitude is the height of the truncated arc top (see FIG. 4), and the fundamental triangle for stem shoulder seals shall be the equilateral triangle whose altitude hs is the side length of another equilateral triangle whose altitude is the center height of the truncated arc (see FIG. 5). To make the isolating mating pair a self-energized seal just installed to its tight contact, it is recommended that the shoulder seal is designed in accordance with its fundamental triangle side length Cs=0.6Cc. Therefore, the fundamental triangle side length Cc=2hc/√3=2(D−d)/3 for stem cylinder seals and the fundamental triangle side length Cs=2hs/√3=0.6Cc=0.4(D−d) for stem shoulder seals, where 0.5(D−d)=the height of the off-stem round corner top of stem cylinder seals or the wall thickness of sealing rings for stem cylinders, hc=(D−d)/√3 and hs=√3Cs/2=0.2√3(D−d).

[0064] The extrusive deformation of an anti-extrusion ring without enough extrusive resistance will cause its extrusion arc radius to decrease and its extrusion resistance to triangular soft rings to increase, and so it is unnecessary to care too much about the manufactured deviation that causes the anti-extrusion ring to have a decreased extrusion resistance. However, it is necessary to care particularly whether the extrusion gap at non-truncated corners in high pressure service is eliminated enough because the maximum allowable working pressure of triangular soft rings is determined in accordance with their extrusion resistance at the truncated corner.

[0065] It is the anti-extrusion metallic coiled ring just tied up to have a circular cross-sectional outline that can have no axial resistance but an enough radial extrusive resistance when compressed in position with its soft ring. Therefore, it shall be necessary to pay attention to the tying of anti-extrusion metallic coiled rings. An anti-extrusion metallic coiled ring can be tied up by its coiling wire in an either spiral coil or spaced turn (12) way (see FIG. 6a). The density of its tying coil or turns determines the circular coherence of its circumferential cross-sectional outline, and the tied power does its axial resistance to compression.

[0066] The anti-extrusion metallic coiled ring shown in FIG. 6 and the anti-extrusion close wound coil spring rings shown in FIG. 7 are the anti-extrusion metallic ring whose manufacture does not need any dedicated tool, but the former's maximum allowable working pressure is computable and the latter's, incomputable but determinable by tests.