JPH0432541Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The present invention relates to a support flange leak prevention device for a butterfly valve suitable for low-temperature liquefied gases such as LNG and LPG.

(Prior art) Butterfly valves are often used when transporting low-temperature liquefied gases such as LNG and LPG via pipelines, and the opening and closing of these valves depends mainly on an actuator, and normally the valve stem of the actuator is The valve shaft is fixed via bolts to, for example, a support flange located above a gland packing part provided in a part that penetrates the box, and the valve shaft is configured to rotate smoothly without leaking gas.

If low-temperature liquefied gases such as LNG and LPG leak, there is a risk of explosion, so leakage from the valve body and valve seat surface, as well as from the gland packing parts such as the valve stem, must be avoided.

(Problem that the invention attempts to solve) Regarding the prevention of leakage from the valve stem, for example,
The gland packing described in Publication No. 34028 has a structure in which a porous metal body is impregnated with fluorine resin and is tightened with a cap nut through a gland bushing, so that the tightening effect of the packing is uniform in the depth direction. However, since the tightening effect deteriorates during use, it is necessary to further tighten the cap nut, and deterioration of the packing material over time is unavoidable, and there are concerns about long-term leakage prevention with this method. Ta.

Furthermore, leak prevention using an O-ring as disclosed in Japanese Patent Application Laid-open No. 61-153081, which is another prior art, not only requires selecting a material suitable for extremely low temperatures, but also requires the use of O-rings, which are susceptible to wear and tear. There was a problem.

In addition, butterfly valves that handle LNG at approximately -162℃ and LPG at approximately -45℃ usually use Teflon (registered trademark) gaskets, which are suitable for ultra-low temperatures, but if the surface is damaged, This method had the disadvantage that leakage was difficult to stop no matter how much tightening was done, and insertion into narrow grooves was extremely troublesome.

(Means for Solving the Problems) In view of the above, the present invention utilizes a support flange with a wide area to fit the seal into the annular notches provided on the outer and inner walls of the seal holder in advance, and then insert the seal into the recess. The seal is press-fitted into the groove formed between the recess and the seal holder and between the seal holder and the main valve shaft. Therefore, the packing can be easily inserted into the groove. The gasket used here is a downward V-shaped or U-shaped non-metallic gasket with a built-in stainless steel spring inside, such as a Teflon (registered trademark) gasket. Maintain pressure contact with. This gasket insertion work can be carried out in a wide area outside and can be carried out safely without damaging the surface.

Moreover, the valve shaft inside the support flange is coated for an appropriate length with a bronze bearing bush coated with a material such as lead or Teflon (registered trademark), which has low friction properties even at extremely low temperatures. Keep it rotatable.

(Function and Effect) In the present invention, the upper part of the shaft hole of the support flange welded to the torque tube is expanded to form a gland packing recess having a large diameter part at the upper part and a small diameter part at the lower part, and the packing presser is fitted into the recess. The fitting of the V- or U-shaped packing with a downward spring into the annular notch provided in the fitting can be carried out in a wide area outside, so that the packing will not be damaged. Therefore, when fitting this into the recess, the groove formed by the annular notch between the side wall of the recess can be made narrow, and by press-fitting into this narrow groove, leakage of low-pressure gas can be prevented. Not only is it effective, but the higher the pressure of the gas, the more the legs of the gasket open and press into the groove, and even when using LNG at approximately -162°C, it provides a seal that is equivalent to a complete seal from low to high pressures. Demonstrate.

In addition, the upper part of the packing holder is locked to prevent it from coming off with a snap spring, so the structure is simpler than the prior art system using a cap nut.
Since the gasket has a self-tightening effect, there is no need for additional tightening once it is set, and since there is no gland bolt, the actuator can be attached directly to the valve body, resulting in a short and simple form. Furthermore, since no O-ring is used, it has excellent durability, and can be achieved by making slight changes to the conventional structure, which is highly effective.

(Example) In FIG. 1, the valve body 1 is inside the valve box 2,
It is fixed with a pin 5 between the upper main valve shaft 3 and the separated lower sub-valve shaft 4, and is configured to maintain a seal with a sealing part 6 when the valve is closed, and the main valve shaft 3 is attached to the upper part of the valve box. Built into the torque tube 7 welded to the
The torque tube 7 is connected to the upper support flange 8
A valve shaft tip 9 protruding from the support flange 8 by welding to the support flange 8 is connected to an actuator (not shown) by a key 10. The main valve shaft 3 is covered with a bearing bush 11, and the valve body 1 is It can be opened and closed smoothly even at low temperatures.

As shown in Figure 2, the support flange 8
A gland packing recess 16 is formed by connecting the large diameter part 13 at the upper part of the shaft hole 12 and the small diameter part 14 at the lower side by an inclined side wall 15, and forming a gland packing recess 16. Small diameter part 14
Annular notches 17, 17' provided in the outer wall located at
Insert V- or U-shaped Teflon (registered trademark) gaskets 18 and 18' with downward springs into the holes. Therefore, this packing can be handled in a wide area outside without damaging the packing surface.

When fitting the packing holder 19 into which the packings 18 and 18' have been fitted in advance into the recess 16,
The width of the grooves 25, 25' formed by the outer wall and between the annular notch provided on the inner and outer walls of the packing holder and the main valve shaft can be narrow, so that the packing holder can be inserted into these narrow grooves 25, 25'. Not only is this press-fitting effective against low-pressure gas leaks, but the higher the gas pressure becomes, the lower the V-shaped or U-shaped legs open and press into the grooves.
Even with LNG at 162°C, it exhibits sealing performance equivalent to a complete seal from low pressure to high pressure. Moreover, such a configuration can be implemented by slightly modifying the conventional device. The seal retainer 19 has a snap spring 2 fitted into an annular groove 21 carved in the upper wall 20 of the large diameter portion.
2 prevents the head of the seal presser 19 from coming off. The bottom surface of the seal presser 19 is supported by a ring 23. Since the gaskets 18, 18' used here have self-tightening properties, there is no need for additional tightening during use.Therefore, there is no need to expose the gland to the outside, and the size can be reduced. side wall 1
5 is not necessarily limited to an inclined surface, and may be formed with a step. Further, in order to make the seal more effective, a plurality of seals may be installed at a plurality of locations as shown in FIG. 3, and the upper seal holder 24 may be used to prevent them from coming off.

In the above configuration, even if gas leaks and rises along the bearing bush 11, the inside and outside 2
sealed by seals 18, 18' at
Leakage to the vicinity of the actuator is prevented.

As described above, in the present invention, the support flange of the butterfly valve, which conventionally did not have an appropriate device for preventing leakage, can be improved by slightly changing the conventional structure, and the effect is great.

[Brief explanation of the drawing]

The figures show an embodiment of the present invention, in which Figure 1 is a schematic sectional view of a butterfly valve with a support flange, and Figure 2 is a schematic sectional view of a butterfly valve with a support flange.
The figure is an enlarged sectional view of the main part of the part indicated by Y in Fig. 1, which is equipped with a leakage device, and Fig. 3 is an enlarged sectional view of the main part in another embodiment corresponding to Fig. 2. .

Claims (1)

[Scope of utility model registration request] In a low-temperature butterfly valve, the main valve shaft is built in a torque tube that seals and communicates between the valve body and the support flange, and is supported by a bearing bush. A gland packing recess with a small diameter portion formed on the lower side, a packing holder having annular cutouts on the outer and inner walls of the packing holder and fitting into the recess, and a sealing holder that is fitted into the recess to separate the recess and the packing. A non-metallic packing with a downward V-shaped or U-shaped spring press-fitted into a groove formed between the presser and between the packing presser and the main valve shaft, and the larger the pressure, the more self-tightening the seal is pressed against the sealing surface, and the large diameter portion. A support flange leak prevention device for a low-temperature butterfly valve, comprising a snap spring that fits into an annular groove carved in an upper wall to prevent the head of the seal holder from coming off, and a ring that supports the seal holder.