JPS61218872A - Low torque ball valve with high air-tightness - Google Patents

Abstract

PURPOSE:To provide high air-tightness and low operating torque by controlling the pressure in a pressure chamber between the seat ring and valve body by means of a selector valve. CONSTITUTION:When a ball valve of trunnion supporting type is in closed position, seals N1, N2 are pressed to a ball L strongly by the piston force of pressure chambers B, D to provide high air-tightness. When the valve is to be opened, inside the pressure chamber becomes negative pressure by operation of a five-way valve V, so that the seals N1, N2 are separated from the ball L, when there is no friction between the seals N1, N2 and ball L with only friction at the ball supporting part remaining. This provides high air-tightness and reduces the operating torque greatly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a trunnion-supported ball valve with high airtightness and low operating torque.

[Conventional technology]

2. Trunnion-supported ball pulp maintains high airtightness by applying the differential pressure between the upstream and downstream pressures of the valve to the seat ring of the ball.

[Problem that the invention seeks to solve]

As mentioned above, the seat ring is pressed against the ball with strong pressure due to the differential pressure. Therefore, when opening the valve, the ball is rotated while the seat ring is pressed, so a large operating torque is required. This also causes a large amount of wear on the seat ring and the like.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention provides a trunnion-supported ball pulp that maintains high airtightness and can be opened with a low operating torque.

In the present invention, pressure chambers B and D are formed between seat rings S, S provided on the upstream side A and downstream side E of the ball valve, respectively, and the valve body M, and these pressure chambers B,
The pressure of D is controlled by a switching valve V.

[For production]

By operating the switching valve V, high airtightness can be maintained when the ball valve is closed, and the ball valve can be operated with low operating torque during operation.

〔Example〕

FIG. 1 is an explanatory diagram of the mechanism and operation of the trunnion supported ball valve of the present invention, and FIGS. 2 and 3 are explanatory diagrams of the operation of the three-way valve used in the five-way switching valve.

Seat rings SI and S2 are provided with a ball L in a flow path in a pulp body M, and sealing materials NI and Nt are respectively attached to the parts that contact the ball L in the wave path on the upstream side A and the downstream side E of the ball L. It is provided so that it can be slid. These seat rings S1 and S2 form pressure chambers B and D between them and the valve body M at their outer intermediate portions.

Furthermore, each of the seat rings S and S has an O-ring insertion groove 1.1 on the outer periphery of both sides of the pressure chambers B and D, respectively.
... is provided, and the airtightness between the seat rings S, , St and the valve body M is maintained by O-rings 2, 2, ....

Further, a cavity C is provided in the pulp body M along a plane passing through the center of the ball L and perpendicular to the flow path. Inside this cavity C, a spring R is applied between the flange portion of each seat ring and the cavity side wall in a direction parallel to the wave path.
are provided so that the sealing materials N, , N2 lightly contact the ball L even when no internal pressure is applied to the valve.

2 and 3 are explanatory diagrams of a three-way valve V, in which the input side is connected to the upstream side A of the valve, the cavity C1 downstream side E, and the output side is connected to the valve V, respectively.

+ Connected to pressure chambers B and D through VD.

3 is an operating lever for the three-way valve V.

Next, the operation will be explained based on these drawings.

b) Pressure PA on upstream side A + Pressure Pc on cavity C
, if the pressure pi on the downstream side E is pa > pc > PI.

When closed, the three-way valve V is moved to the right as shown in the second diagram due to the differential pressure between pA and pA and is centered. At this time, the pressures in pressure chambers B and D are p, , p.

Since PA = PI and PC = pゎ, the upstream seat ring Sl has a circumferential cross-sectional area A inside the pressure chamber outside the circumference where the sealing material N is in contact with the ball L.
, multiplied by the pressure difference pA-p, the piston force A+(Pa-
Pc) to press the ball L. In addition, the seat ring St on the downstream side has a pressure difference p in the circumferential cross-sectional area ^2 in the pressure chamber inside the circumference where the sealing material N2 is in contact with the ball L.
The ball L is pressed by the piston force A2 (pc-Pi) multiplied by c-pi, and a high airtightness is maintained.

In this state, the cavity pressure PC becomes abnormally high and P
When C>PA, the value of the piston force A+(Pa Pc) pushing the upstream seat ring S1 becomes negative, the seat ring S1 is pulled away from the ball L, and the cavity pressure P is increased to the upstream side A. Being let go (self-relieving function).

When performing the opening operation, the state shown in the third figure is achieved by moving the lever 3 of the three-way valve V in the direction of the arrow in FIG. 2 (to the left in the figure). In this case, Pc = P, Pi = PE, so the piston force pushing the upstream seat ring SI is /h < PC-PA), the downstream seat ring S
The piston force pushing t is At (Pt-PC), and both are negative values, so both seat rings S,
, S, is moved away from the ball L. Therefore, the ball L can be operated with a low operating torque.

口）Contrary to the case where the pressure relationship is ①, PA <P(<
In case of pf.

The three-way valve V is set by moving to the left as shown in the third figure due to the pressure difference between Pt and Pa. This is an axial symmetry that is completely opposite to that shown in Fig. 2, and the explanation in (a) is applied in the opposite manner. In other words, this valve is a non-directional valve that performs the same function even if the upstream and downstream directions are reversed. That is, when closed, a high airtightness can be maintained, and by operating the lever 3 of the three-way valve V, the ball L can be operated with a low operating torque.

c) Next, with the line pressurized, valves V and vI.

When closed, the cavity pressure P is separated from the upstream side A and the downstream side E, so it is possible to reduce it to zero while maintaining the piston force of the seat ring.

That is, double block and bleed can be realized.

〔Effect of the invention〕

As described above, when the trunnion supported ball valve of the present invention is in the closed state, the sealing materials N, , Nt are strongly pressed against the ball L by the pistons in the pressure chambers B and D, so that the valve has high airtightness. During the opening operation, the pressure chamber becomes negative pressure due to the operation of the three-way valve V, so the sealing material N, , N
Since t is separated from ball L, sealing material N, ,
Since there is no friction between the ball N and the ball L, and only the friction of the ball support, the operating torque is greatly reduced, and as a result, wear and tear on the ball surface and the sealing material can be minimized.

Furthermore, it has a self-relief function to the upstream side in case of an abnormal increase in cavity pressure, and also has a double block and bleed function.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the mechanism and operation of the trunnion supported ball valve of the present invention, and FIGS. 2 and 3 are explanatory diagrams of the operation of the three-way valve. M...Valve body, L...Ball,
S,,S,...Seat ring,B,D...
...Pressure chamber, ■... Three-way 8 switching valve. 2nd note $3

Claims (1)

[Claims] The ball valve is characterized in that pressure chambers are formed between the seat rings and the valve body provided on the upstream and downstream sides of the valve, respectively, and a five-way switching valve is provided to control the pressure in the pressure chambers. Highly airtight low torque ball valve.