JPH08128551A - Air valve for countermeasure against water hammer - Google Patents

Abstract

PURPOSE: To provide an inexpensive air valve provided with a simple structure by which generation of an impact pressure accompanying recollision of a water column is prevented. CONSTITUTION: A piston 6 stored in a casing 1 is energized by means of a spring 7 so as to close an intake passage 4 with a large diameter in an intake cover 5, and a float 10 is arranged in the inside of the piston 6 so as to be guided to an air discharge hole 8 with a small diameter on the top of the piston 6 by means of a float case 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a large negative pressure due to a water hammer effect in a water supply pipe due to a power failure or the like, which causes water column separation, and the separated water column re-collides due to reverse flow of water on the discharge side. However, the present invention relates to a water hammer air valve for preventing the risk of damaging the water pipe by generating extremely large impact noise and vibration.

[0002]

2. Description of the Related Art In a water supply facility having a long pipeline, a negative pressure is generated in the water pipeline when the output of an electric motor for driving a pump is suddenly cut off due to an unexpected power failure or the like. Water column separation occurs when the saturated vapor pressure of water in the pipe becomes lower than that.

When the level of the water pipe ahead of the place where the water column separation occurs is higher, the water before the water column separation place causes a backflow due to the static head at the end of the water pipe, causing re-collision near the water column separation place. It is well known that the pipes are broken up and the pipeline is destroyed, and measures are taken to prevent this.

In other words, a relatively small pump is provided with a flywheel so that even if a power failure occurs, the inertia of the flywheel causes the rotation of the pump to gradually decrease so that the negative pressure generated in the pipeline is reduced. Try not to grow. However, this method has restrictions on the size and size of the flywheel in terms of manufacturing and operation. If the negative pressure is very large or if the pump becomes large, the flywheel becomes large, which makes implementation difficult.

There is also a method of installing a pressure regulating water tank (one-way surge tank) at a place where a negative pressure is generated in the water pipe, but when the water pipe is long and there are two or more places where water column separation occurs A pressure regulating water tank must be installed at each location, and it is necessary to secure a site for the installation site, which increases equipment costs.

Further, there is a method of installing a pressure air tank in the pump station, and if it is installed in the pump station, it will be effective for all water supply pipelines, so there will be no problem of securing the site, but the actual head will be small, It is difficult to use for the water supply equipment where most of the total pump head is the loss of the water supply pipe, and the equipment cost is more expensive than the pressure control water tank.

As described above, these conventional techniques have a problem of effectiveness and a problem of price in any of the above measures, which is the second best measure, but as a measure of low equipment cost, water column separation is required at a place where water column separation occurs. By installing an air valve (JIS B 2063) or an air valve with a structure similar to this, by positively sucking in air, the water column is separated under atmospheric pressure, and the pressure rises when the water column re-collides. A method of reducing the impact is also performed (for example, Japanese Utility Model Laid-Open No. 3-60690 by the present applicant).

However, the air valve currently used sucks a large amount of air into the pipe when a negative pressure is generated in the water pipe,
When the reverse flow of water separated from the water column starts, the air sucked and introduced into the pipe is rapidly discharged, so that the water column that has flowed backward in the pipe line will collide again under atmospheric pressure. In this case, when the pressure rise value at the time of re-collision of the water column is increased by several times as compared with the case where the air valve is not installed due to the influence of the air in the pipe when the air valve is installed, in certain cases Other than that, conventional air valves cannot be used as a countermeasure against water hammer.

[0009]

[Problems to be Solved by the Invention] If an air valve is provided at a location where water column separation occurs due to a water hammer effect, and air is sucked and introduced when a negative pressure is reached, almost atmospheric pressure air enters, so The water column is easily separated under atmospheric pressure. Due to the actual head of the water pipe end, the water separated in the water column flows backward and re-collides, but the air valve currently used discharges a large amount of sucked air, so the air discharge resistance is small, therefore,
The water column collides in a state almost like a natural fall, resulting in a large impact and a large pressure rise.

An object of the present invention is to provide an air valve for countermeasure against water hammer which is simple in structure, inexpensive and effective.

[0011]

According to the present invention, a piston for closing a large-diameter intake passage of an intake cover, which is housed in a casing provided upright in a water supply pipe, and a spring for urging the piston toward the closing side. And a small-diameter air discharge hole provided at the top of the piston, and a float facing the air discharge hole.

[0012]

The present invention is configured as described above.
When the pump is operating and sending water, the pump stops due to a power outage, etc., and if negative pressure due to a water hammer occurs in the water supply pipeline, negative pressure is applied to the inside of the piston and the piston moves to create an intake passage. Open and suck a large amount of air into the water pipe,
Water at the location where the air valve is installed causes water column separation in the water pipe near the atmospheric pressure.

Next, the separated water column causes a backflow due to the water level on the discharge side. However, since the air is discharged from the air valve only gradually, most of the sucked air remains even if the backflow starts. This air remains in the water pipe, and this air dissipates the collision caused by the backflow of the water column, so the air in the pipe is compressed by the amount equivalent to the energy of the water column that flows backward, and the pressure rises. In the case of a conventional air valve that discharges at the same speed as the time, air is discharged with almost no resistance to match the backflow velocity of the water column, so the water column will re-collide under atmospheric pressure, and The pressure rise also has a large value, which may cause inconvenience such as breakage of the pipe.

Since the air sucked into the pipe is gradually discharged from the air discharge port, the moving speed of the water column accompanying the discharge of air is small, and the pressure rise due to the discharge of air does not occur. Further, when the location where the air valve of the present invention is installed is in the middle of the uphill or downhill of the water pipe, the air sucked into the pipe rises along the inclination of the water pipe with the passage of time. Is discharged from the pipe end of the water supply pipe, or is collected at the top part in the middle of the water supply pipe, and air is discharged from the air valve installed in this part.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a casing 1 of a water hammer countermeasure air valve, which is generally denoted by reference numeral A, is erected vertically by a flange portion 2 on a water supply conduit (not shown). An intake cover 3 is provided above the casing 1, and an intake passage 4 having a large diameter is formed in the intake cover 3.

On the other hand, inside the casing 1, a piston 6 is vertically movably housed via a cylindrical piston guide 5. A spring 7 is interposed between the piston 6 and the piston guide 5 to urge the piston 6 in a direction to close the intake passage 4.

A valve seat 9 having a small diameter air discharge hole 8 is provided at the top of the piston 6, and a spherical float 10 is provided inside the piston 6. The float 10 is centered in the air discharge hole 8 by a cylindrical float case 11 provided upright on the piston guide 5.

Next, the operation will be described. When the inside of the water supply pipe becomes negative pressure, the force acting on the inner surface of the piston 6 becomes larger than the urging force of the spring 7, and therefore the piston 6 descends to open the intake passage 4 having a large diameter, and a large amount of Air is sucked into the water supply line. At the same time as the air is introduced into the air valve A, the float 10 is separated from the valve seat 9 and, therefore, the air is sucked from the small-diameter air discharge hole 8 although the amount is very small.

When the water column in the water supply pipe is separated under atmospheric pressure and the negative pressure is eliminated by sufficiently sucking and introducing air, the piston 6 rises by the force of the spring 7 and closes the intake passage 4.

When the separated water column starts to flow backward due to the water level on the discharge side, the pressure in the water supply conduit starts to rise, and air is gradually discharged from the small-diameter air discharge hole 8 provided in the valve seat 9.
Since the backflow velocity of the water column is faster than the air discharge amount,
The air in the pipeline is compressed by the amount equivalent to the energy of the backflow and the pressure rises, but since a large amount of air remains in the pipeline, the collision of the water column does not occur, and therefore the shock pressure abnormality No rise will occur.

FIG. 2 shows another embodiment of the present invention, in which the diameter of the float 10A of the air valve A1 is equal to that of the float 10A.
This is an example in which the diameter is formed to be as small as 44 mm with respect to 00 mm, so that the float case 11A is formed to have a small diameter, and the others are configured similarly to FIG.

FIG. 3 also shows another embodiment of the present invention, in which the float case 11B of the air valve A2 is hung from the top of the piston 6 and the others are constructed in the same manner as in FIG.

FIG. 4 also shows another embodiment of the present invention, in which a concave valve seat 12 is formed on the top of the piston 6A of the air valve A3, and a plug 14 having an air discharge hole 13 is provided. Float case 11 loose for 10A
This is an example in which C is provided.

When the air is completely discharged, the float 1
If the 0, 10A has a structure capable of sealing the air discharge holes 8, 13, the float cases 11, 11A, 11B, 11
It is not necessary to provide C.

[0025]

As described above, according to the present invention, the following effects can be obtained. That is, when a negative pressure is generated in the water supply conduit due to the sudden stop of the water supply pump due to a power failure or the like, the piston descends and a large amount of air is sucked and introduced into the water supply conduit. As soon as the negative pressure is released, the piston rises due to the force of the spring and closes the air flow path, so a large amount of air introduced by suction is gradually discharged from the small discharge hole. Even if the water flows backward due to the water level on the discharge side, the energy of the reverse flow is absorbed by the remaining air in the pipe being compressed, so a pressure rise corresponding to the energy of the reverse flow occurs. Since collisions do not occur between them, it is possible to avoid the risk of damage to the water supply line. Further, it can be provided at a low cost with a simple structure such as a piston float.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a first embodiment of the present invention.

FIG. 2 is a side sectional view showing a second embodiment of the present invention.

FIG. 3 is a side sectional view showing a third embodiment of the present invention.

FIG. 4 is a side sectional view showing a fourth embodiment of the present invention.

[Explanation of symbols]

 A, A1 to A3 ... Air valve for water hammer countermeasure 1 ... Casing 2 ... Flange portion 3 ... Intake cover 4 ... Intake passage 5 ... Piston guide 6, 6A ... Piston 7 ... Spring 8, 13 ... Air discharge hole 9, 12 ... Valve seat 10, 10A ... Float 11, 11A-11C ... Float case 14 ... Plug

Front page continuation (72) Inventor Shigeo Takita 11-1 Haneda Asahi-cho, Ota-ku, Tokyo Ebara Corporation (72) Inventor Yoshio Sato 2-13-1, Miyuki-cho, Muroran-shi, Hokkaido Kita Kaido Advanced Information Technology Ebara Environmental Techno Co., Ltd. in Hokkaido

Claims (1)

[Claims] 1. A piston which is housed in a casing provided upright in a water supply line and which closes a large-diameter intake passage of an intake cover,
A water hammer countermeasure air valve, comprising: a spring for urging the piston toward the closing side; a small-diameter air discharge hole provided at the top of the piston; and a float facing the air discharge hole. .