How to reduce water meter error

Abstract

To solve the problem that instrumental error of a water meter exceeds an acceptance tolerance because of turbulence in water flow caused by a rear end of a check valve shaft hindering the water flow when a packing-integrated check valve is installed immediately upstream of a water meter and a check valve body of the packing-integrated check valve is slightly open.SOLUTION: A given length of a rear end potion of a valve shaft of a check valve body is gradually tapered down into a tapered shape, R-shape or the like, or is machined to have groove-like recesses formed on an outer surface thereof such that a portion to be inserted to a hole of a packing mounting member has a plus-shaped cross-section and is tapered down toward a secondary side.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a check valve with an integrated packing and a valve stem for reducing the influence on flow measurement of check valves and other devices installed in metering equipment, which has come under scrutiny following the revision of the certification and inspection regulations for specified measuring instruments (water meters, hot water meters, etc.) in March 2005. [Background technology]

[0002] The measurement requirements for water meters are described in JIS B 8570-2, and the rated maximum flow rate Q3 [m 3 / h], and then select the rated minimum flow rate Q1 [m 3 / h], select the ratio of Q3 / Q1, and from this, calculate the transfer flow rate Q2 [m 3 / h] is calculated using Q2 / Q1 = 1.6.

[0003] Water meter instrument error testing is performed by measuring the flow rate at the following three points. 1) Between Q1 and 1.1 x Q1 (Test tolerance ±5%) 2) Between Q2 and 1.1 x Q2 (Test tolerance ±2%) 3) Between 0.9 x Q3 and Q3 (Test tolerance ±2%) For example, if the nominal diameter is 13, Q3 = 2.5 [m 3 / h] and Q3 / Q1 = 100, then Q1 = 0.025 [m 3 / h], Q2 = 0.04 [m 3 / h]. These flow rate values ​​are checked in 1), 2), and 3), and the water meter is shipped once it has been confirmed that the instrument error is within the inspection tolerance. Tests in which a check valve with an integrated gasket was installed immediately upstream of a water meter revealed that the instrument error became large, particularly at flow rates near 1) and 2), and that this sometimes exceeded the calibration tolerance (standard).

[0004] The flow rates of Q1 and Q2 above can be converted into units as follows: Q1 = 0.025 [m 3 / h] ≒ 0.417 [L / min] Q2 = 0.04 [m 3 / h] ≒ 0.667 [L / min] and the flow rates of Q1 and Q2 are less than 1 [L / min]. Compared to the standard flow rate of 16 [L / min] for a nominal diameter of 13 in the Japan Water Works Association standard JWWA B 129 "Water supply backflow prevention valve," this was a very small flow rate, and the check valve body of the check valve with integrated gasket was slightly open.In this slightly open state, the rear end of the valve stem obstructed the flow of water, causing the water flow to become turbulent, and it was discovered that this could cause the water meter's instrument error to exceed the calibration tolerance.

[0005] Regarding the measurement of flow rate and adjustment of instrument error in water meters, for example, Patent Document 1 proposes measuring the flow rate by the number of rotations of a resistor plate rotatably supported on an adjustment panel, and adjusting the support position of the resistor plate to adjust the instrument error, while Patent Document 2 proposes grasping the amount of water used in finer units by obtaining a digital (pulse) signal corresponding to the amount of water flowing through the flow path inside the water meter. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 7-270201 [Patent Document 2] Patent Publication No. 2021-76390 Summary of the Invention [Problem to be solved by the invention]

[0007] However, with the revision of the inspection and certification rules for the above-mentioned specified measuring instruments (water meters, hot water meters, etc.), the pressure loss standard based on the JIS standard will be adopted, which will raise concerns about the impact on water flow of check valves installed in water meters like the above-mentioned to prevent backflow, especially check valves installed immediately upstream of the water meter.

[0008] When a check valve is installed immediately downstream of a conventional water meter, there are no factors that affect the water flowing into the water meter, so there is no instrument error exceeding the standard (the difference between the amount of water that actually passes through the meter and the amount indicated by the meter).

[0009] However, tests have shown that instrument error increases at flow rates near the above mentioned ranges of 1) between Q1 and 1.1 x Q1 (test tolerance ±5%) and 2) between Q2 and 1.1 x Q2 (test tolerance ±2%), and may exceed the test tolerance (standard). The flow rates of Q1 and Q2 are calculated by unit conversion: Q1 is 0.025 m 3 / h]≒0.417[L / min], Q2 is 0.04[m 3 / h] ≒ 0.667 [L / min], both of which are less than 1 [L / min].

[0010] Compared to the standard flow rate of 16 [L / min] for a nominal diameter of 13 in the Japan Water Works Association standard JWWA B 129 "Water Supply Backflow Prevention Valve," this is a very small flow rate, and the check valve body of the check valve with integrated packing is in a slightly open state. In this slightly open state, the rear end of the valve stem obstructs the flow of water, causing the water flow to become turbulent, causing the water meter's error to exceed the calibration tolerance. When a water meter's error exceeds the standard, water users are charged for water based on the amount of water measured by the water meter, which can lead to major problems such as overcharging or undercharging water users, leading to a loss of fairness and credibility in the water billing system. [Means for solving the problem]

[0011] The present invention is a method for reducing the instrument error of a water meter equipped with a check valve with an integrated packing, the check valve including a check valve body, a check valve seat provided on the primary side of the check valve body, and a packing mounting member provided on the secondary side of the check valve body, supporting a packing that abuts against the water meter and supporting the check valve body. The check valve body has a valve umbrella that is biased toward the check valve seat on the primary side and a valve stem that extends from the valve umbrella toward the secondary side, and is supported by the packing mounting member in a state where the valve stem is slidably inserted into a valve stem sliding support hole that passes through the packing mounting member. The tip portion of the valve stem on the secondary side is gradually tapered toward the secondary side, and the water passage volume of the water passage portion between the tip portion of the valve stem on the secondary side of the check valve and the inner wall of the valve stem sliding support hole is reduced. Gradually towards the secondary side This prevents the rear end of the valve stem from obstructing the flow of water, rectifying the water flow and reducing the instrumental error of the water meter even when the check valve is only slightly open and there is a very small flow rate. That is, in Example 1, the above effect can be obtained by gradually tapering the rear end side of the valve stem of the check valve body of the packing-integrated check valve. According to this means, as another operational effect, when attaching the check valve body during assembly, since the rear end of the valve stem is tapered, it is easier to insert the check valve body into the valve stem sliding support hole of the packing attachment member, improving assembly efficiency.

[0012] Furthermore, in Example 2, by making the cross-sectional shape of the valve stem that passes through the valve stem sliding support hole of the packing attachment member a cross-section rather than a circle, the cross-sectional area of ​​the water passage can be made larger than that of the circle shape (expanding the water passage volume), which also reduces the instrumental error of the water meter. [Effects of the Invention]

[0013] The above configuration is based on the premise that the check valve body is contained and fixed within the cartridge body by a spring, a check valve seat, and a check valve gasket, which ensures a constant distance from the rear end of the check valve body to the inlet of the water meter, thereby achieving the effect of reducing the instrument error of the water meter. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a front cross-sectional view of a check valve with integrated packing, showing an embodiment of the present invention, in which a check valve body having a valve stem according to the present invention is inserted into the cartridge body of the check valve with integrated packing. [Figure 2] 2 is a front cross-sectional view of the check valve with integrated packing of FIG. 1, showing the flow state of water with arrows when the water flow rate is very low. FIG. [Figure 3] 1A and 1B show the structure of a check valve body having a valve stem according to the present invention inserted into a cartridge body, where FIG. 1A is a front cross-sectional view of a check valve with an integrated gasket, and FIG. 1B is a front cross-sectional view of a check valve body. [Figure 4] FIG. 10 is a corresponding view of a front view and a right side view of a check valve body according to another embodiment of the present invention, in which the cross section of the valve stem is in a + shape. [Figure 5] FIG. 1 is an overall front view of a gasket-integrated check valve into which a check valve body having a valve stem according to the present invention is inserted, with the main parts cut away to show the state in which other piping to which a stop valve, an expansion pipe, and a water meter are sequentially connected is omitted. DETAILED DESCRIPTION OF THE INVENTION

[0015] An embodiment of the present invention will now be described with reference to the drawings. Reference numeral 1 denotes a check valve body, which is composed of a valve head 11 and a valve stem 12 installed in the center thereof to support the check valve body. The check valve body is inserted into a cartridge body 2 of a check valve with an integrated packing, which is installed on the primary side of a water meter X via an expandable tube Y, and is pressed against a check valve seat 5 installed on the primary side of the cartridge body 2 via a spring 4 which is tensioned and biased in the expanding direction.

[0016] When water flows in from the primary side of the check valve with integrated packing, the flow pressure applied to the valve head 11 of the check valve body 1 compresses the spring 4 that biases the check valve body 1, moving the check valve body 1 to the secondary side, separating the check valve body 1 from the check valve packing 6 and allowing the water to flow through the gap to the secondary side.

[0017] However, with regard to this water flow, when the check valve body is slightly open as mentioned above, the rear end of the valve stem obstructs the flow of water, causing the water flow to become turbulent and causing the water meter's instrument error to exceed the certification tolerance.As a result of research and experiments conducted by the applicant, it was found that in order to avoid this, the check valve body needs to be inserted into the cartridge body 2 using the following structure.

[0018] That is, as shown in Figure 3, the length of the valve stem sliding support hole of the packing mounting member that supports the valve stem 12 of the check valve body 1, which moves due to the flow pressure of the water flow, is A, and the length from the start point of the outer surface reduced diameter part of the rear end of the valve stem to the rear end of the valve stem sliding support hole (the part where the outer surface reduced diameter part of the valve stem and the valve stem sliding support hole overlap) for expanding the water passage volume of the water flow part of the valve body part is B, and the value of B / A is set in the range of 0.1 to 0.9, and the expansion angle from the rear end of the valve stem in the direction of the opening diameter of the water flow inlet part of the check valve seat is C, and this angle is set to an insertion and fitting setting structure.

[0019] When this insertion setting structure was applied to a check valve with an integrated packing equivalent to JWWA B 129 with a nominal diameter of 13, A was 5.5 mm, B was 2.8 mm, the B / A value was 0.51, and C was 30 degrees. Incidentally, the length from the tip of the rear end of the valve stem to the start position of the outer surface reduced diameter portion was defined as D, and when the applicant applied this in practice, for a nominal diameter of 13 in the pipe, D was 2.9 mm.

[0020] The D dimension corresponding to each nominal diameter is 0.7 to 5.1 mm for nominal diameter 13, 1.4 to 7.0 mm for 20, 1.4 to 8.6 mm for 25, 2.1 to 10.9 mm for 30, and 2.6 to 15.4 mm for 40.

[0021] In Example 1, the outer surface diameter reduction portion of the stem is gradually tapered at the rear end of the stem 12 of the check valve disc. The water flow passing through the inlet opening 51 applies flow pressure to the valve head 11 of the check valve disc 1, compressing the spring 4 that biases the check valve disc 1 and moving the check valve disc 1 to the secondary side, separating the check valve disc from the check valve packing 6 and allowing the water flow to pass through the gap to the secondary side, and part of the water flow passes from the back surface of the valve head 11 along the outer surface of the stem to the secondary side of the check valve with integrated packing.

[0022] At the rear end of the valve shaft, there is an outer surface reduced diameter portion, which gradually expands the water passage volume, allowing water to flow through the outflow opening 32 to the water meter X, thereby reducing the instrument error of the water meter.

[0023] In Example 2, the cross-sectional shape of the valve stem 12 that passes through the valve stem sliding support hole 31 of the packing mounting member 3 is made cross-shaped instead of circle-shaped. As a result, the off-axis surface of the valve stem has a groove-like recess 25 formed on the off-axis surface as shown in Figure 4, and is formed in a shape that tapers toward the secondary side. This makes it possible to further expand the cross-sectional area of ​​the water passage part (water passage volume) compared to the circle-shaped case. [Industrial Applicability]

[0024] The method for reducing the instrumental error of a water meter and the valve stem of the check valve used therein according to the present invention, as described above, prevent the rear end of the valve stem from obstructing the flow of water, gradually expand the water channel volume, straighten the water flow, and reduce the instrumental error of the water meter even when the check valve is slightly open and the flow rate is very low, making it extremely useful in the plumbing equipment industry. [Explanation of symbols]

[0025] 1. Check valve 11. Check valve body valve head 12. Valve stem of check valve body 13 +-shaped groove-like depression in the valve stem 2 Cartridge body 21 Female thread that mates with the male thread of the check valve seat 3 Packing mounting material 31 Valve stem sliding support hole 32 Outlet opening 4 Spring 5 Check valve seat 51 Inflow opening 6. Check valve packing 7. Packing A Length of valve stem sliding support hole in packing mounting member B Length of outer surface reduced diameter part of rear end of check valve shaft C. The angle of expansion in the radial direction of the opening of the water flow inlet of the check valve seat X Water meter Y Water stop valve expansion pipe Z stop valve D: Length from the tip of the rear end of the valve stem to the start position of the outer surface tapered part

Claims

1. A method for reducing instrument error in a water meter equipped with a check valve integrated with a packing, comprising: The packing-integrated check valve is A check valve body; a check valve seat provided on the primary side of the check valve body; a packing mounting member that is provided on the secondary side of the check valve body, supports a packing that abuts against the water meter, and supports the check valve body; The check valve body is a valve head that is biased toward the check valve seat on the primary side and a valve stem that extends from the valve head toward the secondary side, the valve stem being supported by the packing mounting member in a state in which the valve stem is slidably inserted into a valve stem slide support hole that penetrates the packing mounting member, A method for reducing instrumental error in a water meter, characterized in that the tip portion of the secondary side of the valve stem is gradually made thinner as it approaches the secondary side, and the water passage volume of the water passage section between the valve stem and the inner wall of the valve stem sliding support hole is gradually expanded as it approaches the secondary side, thereby reducing the instrumental error of the water meter.

2. 2. A method for reducing instrumental error in a water meter as described in claim 1, wherein the check valve body is inserted into a cylindrical cartridge body that accommodates the check valve body, the check valve seat, and the gasket mounting member, and the ratio of the length of the valve stem sliding support hole to the length of the overlap between the secondary side tip portion of the valve stem and the valve stem sliding support hole is set in the range of 0.1 to 0.9, and the expansion angle from the secondary side tip portion of the valve stem in the radial direction of the opening of the water flow inlet portion of the check valve seat is set to 5 to 150 degrees.

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