JPH0124465Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a valve device that prevents the packing from loosening and improves the sealing effect.

[Technical background of the invention and its problems]

General valves such as globe valves, gate valves, and butterfly valves are widely used in various industries including thermal power plants and oil refinery plants.

FIG. 1 is a longitudinal cross-sectional view of a globe valve as a typical example of these general valves. A valve stem 2 is inserted into a valve body 1 so as to be movable up and down. The valve body 3 is fixed. Then, when the valve stem 2 descends, the valve body 3 comes into contact with the valve seat 4 and closes the flow path 5, and when the valve body 3 rises, it separates from the valve seat 4 and closes the flow path 5.
to open. The amount of fluid can be adjusted by the amount of movement of the valve stem 4 when it moves up and down.

The upper half of the valve box 1 is composed of a packing box 1a, and this packing box 1a and a valve stem 2 are connected to each other.
A lip packing and a gland packing 6 are interposed in the gap between the two. And Grand Patskin 6
A packing presser 7 is disposed above so as to come into contact with the upper surface of the gland packing 6, and the packing presser 7 is fixed by nuts 9 screwed into a plurality of bolts 8 attached to the upper surface of the packing box 1a. . By tightening this nut 9, the packing presser foot 7 descends and presses the packing box 6. 10 indicates a handle for operating the valve.

In such a valve device, the nut 9 is tightened to press the seal holder 7 against the gland seal 6,
The sealing function is maintained by increasing the adhesion between the sliding surface of the valve stem 2 and the packing surface. However, when such a valve device is used for a long period of time, the packing surface gradually wears out, deforms, and is damaged due to friction when the valve stem 2 slides, which causes problems such as a decrease in adhesion and an increase in leakage. In order to solve this problem, it is necessary to make adjustments such as removing the seal holder 7 and increasing the number of shims, or tightening the nut 9 more.

However, the number of valve devices of this type used in thermal power plants, oil refining plants, etc. is enormous, and it takes a lot of time and effort to maintain and inspect the seals of all valve devices. It becomes necessary.

In particular, valve devices used for process control are frequently opened and closed, resulting in severe wear and tear on the gaskets, which further increases the frequency of the above-mentioned retightening adjustments. Additionally, valve devices used in systems that handle hazardous gases are constantly monitored for leaks.
Monitoring all of a large number of valve devices is a difficult task, and leaks may be overlooked.
There has been a need for a valve device that does not deteriorate in sealing performance even after long-term use.

As a valve device to solve such problems and obtain a more reliable sealing effect, as shown in FIG. A valve device is also known in which the gasket 6 is constantly compressed by the expansion force of the gasket 6 to maintain the sealing function for a long period of time. There is a problem that the length of 1a has to be made longer, making the device larger. Also, since the spring 11 and spring receivers 12a and 12b are inserted into a narrow space, inspection of these parts is required when replacing the gaskets. There were also problems such as the amount of time it took.

[Purpose of invention]

The present invention was made to solve the above-mentioned problems, and it improves long-term sealing performance by applying constant tightening force to the seal, and also provides a valve device with a simple structure and easy maintenance and safety. The purpose is to provide.

[Summary of the idea]

The valve device of the present invention includes a packing that is filled in a packing box and makes frictional contact with the sliding surface of the valve shaft, a packing holder that applies a pressing force to the packing, and a presser bolt that attaches the packing holder. In a valve device equipped with a disc spring mechanism consisting of a plurality of disc spring washers for applying a compressive force to a seal, the disc spring mechanism is composed of a plurality of disc spring washers stacked coaxially and in the same direction. A disc spring washer formed of a first disc spring washer group and a second disc spring washer group consisting of a plurality of disc spring washers stacked coaxially and in the same direction so that the disc open portion faces each other. A plurality of disc spring washers are stacked coaxially, and a sliding plate is inserted between adjacent disc spring washers.

More preferably, the sliding plate is made of a Teflon sheet.

[Example of idea]

Hereinafter, one embodiment of the present invention and its operation will be described with reference to FIGS. 3 to 6.

In FIG. 3, numeral 1 indicates the valve box,
A packing box 1a that accommodates a gland packing 6 is formed on the sliding surface between the valve box 1 and the valve stem 2, and a cylindrical box having a flange portion at the upper end is formed in the upper half of the packing box 1a. A gasket presser 7 of the shape is inserted.

A presser bolt 1 is attached to the upper surface of the flange portion of the seal presser 7 for attaching the seal presser 7 to the valve box 1.
A disc spring mechanism 14 is fitted between the lower surface of the head of each presser bolt 13 and the upper surface of the flange portion of the packing presser 7, respectively. By tightening this presser bolt 13, the packing presser 7 descends and presses the gland packing 6.

The detailed structure of this disc spring mechanism will be explained below with reference to FIG.

The disc spring mechanism consists of a plurality of disc spring washers 14a, 14b... stacked coaxially and in the same direction.
A second plate spring washer group consisting of a plurality of plate spring washers 14a, 14a... stacked coaxially and in the same direction as the plate spring washer group of
The flat washer 14 is connected to the flat washer 14 between the disc spring washer group and the disc opening part.
Constructing a group of disc spring washers arranged to face each other through b, the disc spring washers are stacked coaxially in multiple stages, and sliding plates 14c and 14d are provided between adjacent disc spring washers 14a and flat washers 14b. It is said that the configuration consists of inserting the.

The sliding plates 14c and 14d are made of a material that has good sliding properties against the washers, and in this example, Teflon molded into a sheet shape is used.

In the valve device having such a configuration, the presser bolt 13
By tightening, the seal retainer 7 presses the gland seal 6 and maintains the sealing function, but at this time, each disc spring washer 14a is compressed and distorted, so each disc spring washer 14a has this distortion. A reaction force is generated that tries to recover the . This reaction force presses the seal presser 7 downward, and a compressive force is constantly applied to the seal 6. Therefore, by adjusting the tightening force of the presser bolt 13, the compressive force applied to the packing 6 can be adjusted.

Now, in such a valve device, the presser bolt 13
When tightening, a torsional stress is applied to the disc spring washer according to the friction coefficient between each disc spring washer, and this torsional stress causes the strain-load characteristics (hysteresis) when the disc spring washer contracts and expands. ) changes.

For example, if the coefficient of friction between each disc spring is large, the stress in the torsional direction that acts on the disc spring washer will also be large, and the strain vs. load characteristics will deteriorate. This amount of distortion can be reduced by inserting a plate to significantly reduce the friction coefficient between the disc spring washers.
Load characteristics are improved. That is, the sliding plate has the effect of reducing the friction coefficient between the respective disc spring washers and reducing the stress in the torsional direction of the disc spring washers.

If this strain-load characteristic deteriorates, the amount of strain when the disc spring washer contracts and expands will be greatly different, so if the sealing surface gradually wears out and the disc spring washer gradually expands, the seal 6 will always be stable. A problem arises in that it is no longer possible to apply a compressive force.

An experiment was conducted to investigate the effect of this sliding plate, and the results will be explained with reference to FIGS. 5 and 6. Figure 5 shows the strain-load characteristics obtained through experiments for the valve device of this example described above, the valve device that does not use a sliding plate, and the valve device that has lubricant applied to the contact surface of each disc spring washer. In the figure showing the results, the chain line A in the figure indicates the disc spring washer 14a when a Teflon sheet is used as the sliding plate 15.
The strain amount-load characteristics are shown in which the solid line B shows the case where no sliding plate is inserted, and the dashed line C shows the case where lubricant is applied to the contact surface of the disc spring washer.

As is clear from the figure, when no sliding plate is inserted, the amount of strain in response to the load differs greatly between contraction and extension, and hysteresis is large; however, when a sliding plate is inserted, the amount of strain during contraction and extension is large. The difference between the load and the amount of strain at is small, and the hysteresis is small.

Furthermore, when a lubricant was applied between the disc spring washers, the hysteresis was between the two.

The reason why the hysteria is improved by using the Teflon sheet as shown in the above experimental results is due to the difference in the friction coefficient of the contact surface of each disc spring.The friction coefficient of the Teflon sheet in this example is 0.05~
This is because the friction coefficient of the contact surface between the disc spring washers is approximately 0.15 or more, whereas the friction coefficient is approximately 0.10.

By improving the hysteresis in this way, the seal retainer always receives a stable pressing force from the disc spring washer, and therefore the compressive force of the gland seal is also stabilized, improving sealing performance.

In addition, when lubricant is applied to the contact surface of the disc spring washer, the hysteria is improved, although not as much as when a Teflon sheet is inserted, but when used for a long time, regular application of lubricant is recommended. Alternatively, injection work is required, which poses a problem from a maintenance perspective.

Figure 6 shows the results of actual measurements of changes in the amount of seal leakage with respect to the number of reciprocations of the valve stem, where the chain line A represents the case of the valve device of the present invention, and the solid line B represents the case of the conventional structure shown in Figure 1. The case of a valve device is shown.
As is clear from the figure, according to the present invention, the time point at which seal leakage starts is about 10 times longer than in the conventional valve device, and the increase in the amount of leakage after the start of leakage is also small.

In the above description, an example in which the present invention is applied to a globe valve has been described, but the present invention can be widely applied to various valve devices equipped with a shaft sealing mechanism.

[Effect of idea]

As explained above, according to the valve device of the present invention, the friction coefficient between the disc spring washers is reduced by the sliding plate inserted between the disc spring washers, and the hysteresis of the disc spring washers is improved. It maintains a certain level of sealing function during use, and its simple structure makes it easy to apply to existing equipment, greatly improving workability during maintenance and inspection.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view illustrating a conventional valve device, FIG. 2 is a vertical cross-sectional view showing an example of an improved seal portion in a conventional valve device, and FIG. 3 is an implementation of the seal portion in the valve device of the present invention. A longitudinal sectional view showing an example; FIG. 4 is an enlarged longitudinal sectional view showing the disc spring mechanism shown in FIG. 3;
Figure 5 is a graph showing the load-strain characteristics with and without a sliding plate inserted between the disc spring washers and when a lubricant is applied to the contact surface of the disc spring washer. 2 is a graph illustrating the relationship between the amount of packing leakage and the number of valve shaft reciprocations in the conventional valve device and the conventional valve device. 6... Gland packing, 7... Packing holder, 13... Holding bolt, 14... Belleville spring mechanism,
14a...Disc spring washer, 14b...Flat washer, 14
c, 14d...Sliding board.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A packing that is filled in a packing box and makes frictional contact with the sliding surface of the valve stem, a packing holder that applies a pressing force to the packing, and a holding bolt that attaches the packing holder. and a disc spring mechanism including a plurality of disc spring washers for applying a compressive force to the packing, wherein the disc spring mechanism includes a plurality of discs laminated coaxially and in the same direction. A first disc spring washer group consisting of spring washers and a second disc spring washer group consisting of a plurality of disc spring washers stacked coaxially and in the same direction are arranged so that the open plate parts face each other. The valve is characterized in that it has a configuration in which a plurality of disc spring washers are stacked coaxially in multiple stages, and a sliding plate is inserted between adjacent disc spring washers. Device. (2) The valve device according to claim 1, wherein the sliding plate is made of a Teflon sheet.