VALVE SYSTEM WITH IMPROVED SEALING

Abstract

A method for assembling a valve body and a stuffing box of a valve system is provided. The stuffing box has a collar in contact with a top surface of the valve body. The method includes deforming the stuffing box during assembly thereof to the valve body, so that the height by which the collar protrudes is decreased after assembly.

Claims

1. A method for assembling a valve body and a stuffing box of a valve system, the stuffing box comprising a collar in contact with a top surface of the valve body, the method comprising deforming the stuffing box during assembly thereof to the valve body, so that the height by which the collar protrudes is decreased after assembly.

2. The method of claim 1, the stuffing box being assembled to the valve body by screwing.

3. The method of claim 2, the valve body having an internal surface defining an annular groove, the annular groove comprising an upper side, a lower side and a bottom extending axially between the upper and lower sides, the annular groove forming with the stuffing box an annular cavity for receiving a sealing element.

4. The method of claim 3, comprising a first step of placing the stuffing box in contact with the top surface of valve body, while keeping a gap between the lower side of the annular groove and the stuffing box.

5. The method of claim 4, comprising a second step of mechanically deforming the collar of the stuffing box so that the lower side of the annular groove comes into contact with the stuffing box.

6. The method of claim 5, the second step mechanically deforming the collar of the stuffing box due to screwing torque during the assembly.

7. The method of claim 4, the stuffing box comprising a first and a second shoulder, the gap being formed axially between the lower side of the annular groove and the second shoulder.

8. The method of claim 7, the second step comprising mechanically deforming the collar of the stuffing box so that a shoulder of the valve body defining the lower side of the annular groove comes into contact with second shoulder.

9. A valve system, comprising a valve body and a stuffing box assembled to the valve body by screwing, the stuffing box comprising a collar in contact with a top surface of the valve body, the collar of the stuffing box being deformed during assembly thereof to the valve body so that a height of the collar is decreased after assembly.

10. The valve system of claim 9, the valve body having an internal surface defining an annular groove, the annular groove comprising an upper side, a lower side and a bottom extending axially between the upper and lower sides, the annular groove forming with the stuffing box an annular cavity for receiving a sealing element.

11. The valve system of claim 10, the annular groove having a depth of at least 1 mm.

12. The valve system of claim 10, a shoulder of the valve body defining the lower side of the annular groove coming in axial abutment with the stuffing box.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG. 1A, already described, is a schematic longitudinal cross section of a known valve system;

[0035] FIG. 1B, already described, is an enlarged view of an open-groove sealing structure;

[0036] FIG. 2 is a schematic view of a valve system of the invention;

[0037] FIG. 3 is a partial view of a valve system of the invention;

[0038] FIGS. 4 and 5 are enlarged views of circled areas IV and V of FIG. 3;

[0039] FIGS. 5A and 5B are isolated views respectively of the valve body and the stuffing box of FIG. 5;

[0040] FIG. 6 is a partial view of the valve system of FIG. 3, at the beginning of the assembly;

[0041] FIGS. 7 and 8 are enlarged views of circled areas VII and VIII of FIG. 6.

DETAILED DESCRIPTION

[0042] A valve system 1 of the invention, as shown in FIG. 2, comprises a valve body 20 and a top box 10. The valve body 20 houses a plunger 40 fixed to a reciprocating stem 50 at one end. The opposite end of the reciprocating stem 50 extends into the top box 10, which comprises an actuator for controlling the up and down movement of the stem 50 along the longitudinal axis X of the system, thus the opening and closing of the valve by the plunger 40.

[0043] As shown in FIG. 3, a stuffing box 30 is screwed to the valve body 20 via cooperating threads 16, situated respectively on an internal surface 29 of the valve body 20 and an external surface 39 of the stuffing box 30. The stuffing box 30 comprises a central bore 51 inside which the stem 50 may slide.

[0044] As can be seen in FIG. 4, a top surface 38 of the collar 37 forms a smooth joint line 8 with an adjacent top surface 28 of the valve body 20, without the presence of any substantial acute- or right-angle external protrusion between the top surfaces 28 and 38. In this way, there is no substantial retention area created at the joint line 8, which helps to avoid accumulation of undesired substances therein.

[0045] As shown in FIGS. 5 and 5A, the valve body 20 comprises an annular groove 21 on its internal surface 29. The annular groove 21 comprises a bottom 24, an upper side 22 and a lower side 23. The bottom 24 of the annular groove 21 extends axially between the upper and lower sides 22, 23. The lower side 23 is defined by a shoulder 98 of the valve body.

[0046] The annular groove 21 preferably has a depth d, measured in a direction parallel to a radial direction of the valve system, which is at least of 1 mm.

[0047] The annular groove 21 has a height h, measured in a direction parallel to the longitudinal axis X of the valve system, that is preferably of between 2 and 5 mm.

[0048] The shoulder 98 has a width w.sub.1 preferably of between 2 mm and 10 mm when measured radially.

[0049] The stuffing box 30, as shown in FIGS. 5 and 5B, comprises on its external surface 39 a first shoulder 45 and a second shoulder 46. The first shoulder 45 is configured for coming in axial contact with the sealing element 15. The second shoulder 46 is in axial abutment with the shoulder 98 defining lower side 23 of the groove 21.

[0050] The first and second shoulders are separated by a cylindrical surface 34 extending axially.

[0051] The first shoulder 45 may have a width w.sub.2 of between 2 mm and 10 mm.

[0052] The second shoulder 46 may have a width w.sub.3 of between 2 mm and 10 mm.

[0053] In the illustrated embodiment, the annular cavity 80 is located closer to the plunger 40 than the threads 16, when observed in the longitudinal direction X of the valve system.

[0054] The valve system comprises a first interface 84 between the stuffing box 30 and the valve body 20 that is situated farther to the plunger 40 than the annular cavity 80. As can be seen in FIG. 5, the first interface 84 is radially inner to the bottom 24 of the groove 21.

[0055] The valve system comprises a second interface 83 between the stuffing box 30 and the valve body 20 that is situated axially closer to the plunger 40 than the annular cavity 80. The second interface 83 is radially inner to the surface 34.

[0056] For assembly the valve system, the stuffing box 30 is screwed into the valve body until the collar 27 comes into abutment with the top surface 28 of valve body 20, as shown in FIG. 6 and FIG. 7. As shown in detail in FIG. 8, an axial gap 99 of a height h is then existing between the lower side 23 of the groove 21 and the shoulder 46.

[0057] Then, by screwing further the stuffing box 30 into the valve body 20, the collar 37 is mechanically deformed, leading to the configuration shown in FIG. 4.

[0058] During this plastic deformation of the collar, the height h by which the collar 37 protrudes from the top surface 28 is decreased, substantially to a value of less than 1 mm. In this way, there is no pronounced discontinuity between the top surface 28 of the valve body 20 and the top surface 38 of the collar 37, which helps avoid accumulation of undesired material in the zone around the joint line 8.

[0059] At the end of the screwing, the shoulder 98 of the valve body comes into abutment with the second shoulder 46 of the stuffing box 20, so that the sealing element 15 is axially compressed by the first shoulder 45 and the shoulder 98 and expands radially.

[0060] Four sealing interfaces are thus formed, respectively between the sealing element 15 and the bottom 24, between the sealing element 15 and the lower side 23, between the sealing element 15 and the cylindrical surface 34, and between the sealing element 15 and the first shoulder 45.

[0061] The stuffing box 30 does not axially compress the sealing element 15 on its portion which is received in the annular groove 21.

[0062] As shown in FIG. 5, after assembly, the first shoulder 45 is axially closer to the lower side 23 than is the upper side 22 of the annular groove 21.

[0063] A ratio l/h between the distance l from the first shoulder 45 to the lower side 23 and the height h of the annular groove 21, is preferably between 0.5 and 0.9.

[0064] The ratio between the depth d of the groove 21 and the width w.sub.2 of the first shoulder 45, i.e. d/w.sub.2 is preferably at least 2.

[0065] The invention is not limited to any particular top box, and various changes may be brought to the top box without departing from the scope of the invention.