GB2311835A

GB2311835A - Lubricating valve stems

Info

Publication number: GB2311835A
Application number: GB9705457A
Authority: GB
Inventors: Taylor L Jones
Original assignee: FMC Corp
Current assignee: FMC Corp
Priority date: 1996-04-03
Filing date: 1997-03-17
Publication date: 1997-10-08
Anticipated expiration: 2017-03-17
Also published as: SG102523A1; GB2311835B; GB9705457D0; NO971497L; CA2200131A1; NO971497D0

Abstract

A valve comprises a stem 10 having threads 11. Lubricant can be introduced into the valve via an injection fitting 22 and can be directed to the threads 11 via holes 8, 13, 14. A reservoir in the form of a coil-shaped washer 12 may be provided. The stem is used to operate a gate in which a nut 18 is attached to the gate. The nut 18 is engaged with the threads 11 such that rotation of the stem causes translation of the nut and gate to open/close the valve. A stem relief hole 19 is provided in the gate and this may contain some of the lubricant. Hole 14 may be located down the outside of the valve casing.

Description

LUBRICANT INJECTION SYSTEM FOR A GATE VALVE STEM This invention relates to gate or similar valves employing a threaded stem. More particularly, the invention relates to a system for lubricating the threaded stem.

Frequently, manually operated large bore and high pressure gate valves experience high friction between the stem threads and lift nut threads. Lubrication serves to reduce this friction, thereby reducing the operating torque by as much as 50%. After a few cycles of opening and closing the valve, the grease or other lubricant becomes displaced. As the friction increases between the stem threads and the gate lift nut threads due to the displacement of lubricant, the operating torque likewise increases. When this elevated operating torque becomes too great, the operator needs a method for lubricating between the stem and gate lift nut threads.

Presently, several methods exist for lubricating the threads, including: (1) disassembling the valve, and (2) filling the valve body cavity with lubricant in order to infuse lubricant into the stem relief hole where the stem threads are located. Disassembly of the valve enables lubricant to be placed directly on the stem and lift nut threads, but requires a breach of the valve pressure system which renders the valve inoperable while disassembled.

Additionally, disassembly is a labor intensive, time consuming procedure. The method of filling the body cavity with lubricant is also ineffective. This method is neither labor intensive nor does it render the valve inoperable; however, even with a great deal of lubricant being placed into the valve body cavity, very little lubricant actually works its way into the stem relief hole. Therefore, very little lubricant contacts the stem threads. Another disadvantage of this method is the potential for lubricant to leak into the valve body cavity and mix with the fluid flowing in the valve flow path.

Therefore, there is a need for a gate valve wherein lubricant may be applied directly to the valve stem and gate lift nut threads without (1) disassembling the gate valve body, or (2) filling the valve body cavity.

According to the invention, there is provided a valve comprising: a stem having threads; a lubricant reservoir; a hole for distributing lubricant to the threads of said stem; and a channel that connects said reservoir to said hole.

Correspondingly, the invention provides an improved valve stem with lubricating means for use in a gate valve of the type comprising a threaded valve stem and gate lift nut assembly, said improved valve stem comprising: a valve stem shaft having a first end adapted to receive torque to effect rotation of the shaft and a second end having a threaded surface adapted to mate with and co-operate with a threaded opening through the gate lift nut such that rotation of said valve stem relative to said gate lift nut causes said lift nut to translate along said stem; a lubricant distribution hole; and a channel means axially extending through said valve stem shaft and in communication with said lubricant distribution hole and a lubricant reservoir.

Further preferred features of the invention are in the dependent claims. The present invention will be better understood by a reading of the following description of illustrative embodiments, with reference to the attached drawings, wherein : Fig. 1A is a cross-sectional schematic drawing of one embodiment of the invention; Fig. 1B is an enlarged detail of a portion of Fig. 1; Fig. 2 is a cross-sectional schematic drawing of another embodiment of the invention; Fig. 3 is a cross-sectional schematic drawing of a further embodiment of the invention; and Fig. 4 is a cross-sectional schematic drawing of a still further embodiment of the invention.

Referring to Figs. 1A and 1B, an embodiment of a gate valve 1 according to the present invention is shown. The valve 1 comprises a stem 10 having threads 11, a layered coil-shaped washer 12, several lubricant distribution channels or holes 13 for distributing lubricant to threads 11 of stem 10, and a channel or hole 14 that connects the washer 12 to the distribution holes 13 via a transverse hole 8 that is positioned transverse to the longitudinal central axis of the stem 10. Thus, lubricant flows from the washer 12 through the transverse hole 8, through the longitudinal hole 14 and finally to the distribution holes 13. In this embodiment, each distribution hole 13 is a hole that runs from the threaded surface 11 of the stem 10 to the longitudinal hole 14. The layered coil-shaped washer 12 preferably has a number of approximately 0.0625 inch (0.159 mm) thick coils which stretch around the outside diameter of the stem backseat 20. In the embodiment shown, the top four coils are notched to allow lubrication to travel into the transverse hole 8 and into the hole 14. With the gate 17 in the closed position, lubricant is forced into the threads of the lift nut 18. With the gate 17 in the open position, which is depicted in Fig. lA, the lubricant fills the stem relief hole 19 of gate 17, thereby forcing lubricant onto the stem threads 11. The lower coils 15 of washer 12 restrict lubricant in washer 12 from entering the valve body cavity 16. Coils 15 force the lubricant into the transverse hole 8 in the stem, instead of letting it pass into the valve body cavity 16. The valve 1 also comprises an injection fitting 22 on the outside diameter of the bonnet flange 21. Lubricant may be injected through the injection fitting 22 to infuse the washer 12 with lubricant.

Referring to Fig. 2, another embodiment of the present invention is shown. The valve 2 of this embodiment comprises a stem 10 having threads (not shown), a receptacle for lubricant, such as injection fitting 22, a hole 13 in the stem 10 for filling the stem relief hole 19 of the gate 17 with lubricant, and a channel or hole 14 that connects the receptacle 22 to the hole 13. The injection fitting 22 is connected anteriorly to the stem 10. The hole 14 runs the length of the stem 10 between the injection fitting 22 and the hole 13 in the bottom of the stem 10. With the gate 17 in the open position, which is depicted in Fig. 2, the lubricant fills the stem relief hole 19 of gate 17, thereby forcing lubricant onto the stem threads. As the gate 17 is closed, lubricant is forced onto the threads of the lift nut 18.

Referring to Fig. 3, a further embodiment of the present invention is shown. The valve 3 of this embodiment comprises a stem 10 having threads 11, a receptacle for lubricant, such as injection fitting 22, holes 13 for distributing lubricant to the threads 11 of the stem 10, and a channel or hole 14 that connects the receptacle 22 to the holes 13. The injection fitting 22 is disposed anteriorly to the stem 10. The valve 3 comprises a check valve 23 between the hole 13 and the hole 14 that restricts lubricant flow from the holes 13 back up the hole 14. The check valve 23 is a spring loaded valve preferably located in the lower portion of hole 14. A pipe plug 24 blocks the end of hole 14 and retains the spring loaded ball check valve 23 in position.

Referring to Fig. 4, a further embodiment of the present invention is shown. The valve 4 of this embodiment comprises a stem 10 having threads (not shown), an injection fitting 22 for supplying lubricant, a hole 13 for distributing lubricant to the threads of the stem 10, and a channel or hole 14 that connects the injection fitting 22 to the hole 13. The stem 10 may be set to force the lubricant to pass through a transverse hole 8 that connects with the longitudinal hole 14. The lubricant injection fitting 22 is located on a bonnet flange 21. The lubricant hole 14 comprises the distribution hole 13 at the lower end of the stem 10, and continues up through the center of the stem 10, through the transverse hole 8 in the backseat shoulder 20, and through a channel or hole 7 in the bonnet flange 21. This embodiment allows for lubrication when the gate 17 is first closed. The lubricant is injected through the bonnet flange lubricant fitting 22. The lubricant passes through the hole 7 in the bonnet flange 21, through the hole 8 in the stem back seat shoulder 20, down the hole 14 in the center of the stem 10, and out hole 13. The lubricant then fills the stem relief hole 19 in the gate 17. As the gate 17 is opened, lubricant is forced onto the stem threads (not shown in Fig. 4). After the lubrication process has been completed, the gate 17 is returned to its normal operating position. The valve 4 also comprises a vent hole 25 through the side of the gate 17 located near the lift nut 18.

It should be noted that while the invention has been described in terms of the preferred embodiments wherein the hole 14 is located down the longitudinal central axis of the stem 10, it need not necessarily be so located; for example, the hole 14 may be located down the outside of the valve casing around the stem. In such an embodiment, a distribution hole or holes would be located through the casing to allow for lubricant communication to the threads, etc.

While the particular embodiments for lubricating threads of a valve as herein shown and disclosed in detail are fully capable of obtaining the objects and advantages herein before stated, it is to be understood that they are merely illustrative of the presently preferred embodiments of the invention and that no limitations to the scope of the invention as defined in the claims are intended by the details of construction or design herein shown.

Claims

CLAIMS:

1. A valve comprising: a stem having threads; a lubricant reservoir; a hole for distributing lubricant to the threads of said stem; and a channel that connects said reservoir to said hole.

2. A valve according to claim 1, wherein said lubricant reservoir is a coil-shaped washer.

3. A valve according to claim 1 or 2, wherein said lubricant reservoir is positioned about said stem.

4. A valve according to any preceding claim, comprising a plurality of said distribution holes for distributing lubricant to the threaded surface of the stem.

5. A valve according to any of claims 19 wherein the distribution hole communicates with a stem relief hole formed in a valve gate.

6. A valve according to any preceding claim, comprising: a valve housing having a flow passage therethrough and adapted to mate between two open conduits in a flow line thereby forming a continuous closed flow path therewith; a valve gate movably mounted in said valve housing and adapted to move into and out of the flow path causing a stop flow and an open flow position, respectively; a gate lift nut having a threaded internal through hole and mounted to said valve gate; a first end of the stem extending outside the housing being adapted to receive torque to effect rotation of the stem and a second end of the stem having the threads and being received within said lift nut through hole, whereby rotation of the valve stem causes the lift nut and the valve gate to translate along the stem moving the gate selectively into the stop flow or open flow positions.

7. A valve according to claim 6 further comprising: a valve cavity formed inside the valve housing containing the flow passage, said valve gate and said second end of said valve stem; and a valve bonnet assembly positioned adjacent to said valve housing and having a bonnet opening through which said first end of said valve stem extends, wherein said lubricant reservoir is located within said bonnet assembly.

8. A valve according to claim 7 further comprising a lubricant sealing means for preventing lubricant from leaking into said valve cavity.

9. A valve according to claim 8 wherein said lubricant sealing means is a ring seal located in said bonnet assembly about said stem.

10. A valve according to any preceding claim, further comprising a check valve between said distribution hole and said channel that restricts lubricant back flow from said distribution hole to said channel.

11. An improved valve stem with lubricating means for use in a gate valve of the type comprising a threaded valve stem and gate lift nut assembly, said improved valve stem comprising: a valve stem shaft having a first end adapted to receive torque to effect rotation of the shaft and a second end having a threaded surface adapted to mate with and co-operate with a threaded opening through the gate lift nut such that rotation of said valve stem relative to said gate lift nut causes said lift nut to translate along said stem; a lubricant distribution hole; and a channel means axially extending through said valve stem shaft and in communication with said lubricant distribution hole and a lubricant reservoir.

12. An improved valve stem according to claim 11, wherein said lubricant distribution hole extends from the threaded surface of said valve stem shaft to the interior of said valve stem shaft for distributing lubricant to said threaded surface.

13. An improved valve stem according to claim 11, wherein said lubricant distribution hole extends from a surface of said second end of said shaft to the interior of said valve stem shaft for filling a stem relief hole of a valve gate with lubricant.

14. An improved valve stem according to any of claims 11 - 13, wherein said reservoir is a coil-shaped washer.

15. An improved valve stem according to any of claims 11-14, wherein said reservoir is positioned about said stem.

16. An improved valve stem according to any of claims 11-15, comprising a plurality of said holes for distributing lubricant to the threads.

17. An improved valve stem according to any of claims 11-16, wherein said channel is within said stem.

18. An improved valve stem according to any of claims 11-17, comprising means located about said stem for restricting lubricant from entering a valve body cavity.

19. An improved valve stem according to any of claims 11-18, comprising a check valve between said hole and said channel means that restricts lubricant flow from said hole to said channel means.

20. A valve or improved valve stem according to any preceding claim, comprising a lubricant receptacle for infusing said reservoir with lubricant.

21. A valve substantially as described with reference to or as shown in the drawings.

22. An improved valve stem with lubricating means for use in a gate valve substantially as described with reference to or as shown in the drawings.