JPH075022U - Orifice flow detection end - Google Patents

Abstract

(57) [Summary] [Purpose] Prevents blockage due to scaling or particle adhesion when measuring the flow rate of fluids containing minute particles or fluids that easily scale, and also performs maintenance such as cleaning and inspection. It provides an orifice flow detection end that is extremely easy to perform. [Structure] A structure in which a pressure transmission hole for transmitting pressure before and after the orifice plate to the outside has a slit shape parallel to the orifice plate, and while maintaining this shape, is connected to a pressure transmission conduit to a differential pressure gauge. Orifice flow rate detection end.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to the detection end of an orifice flow meter in a differential pressure type flow meter used for flow rate detection.

[0002]

[Prior art]

 Plants and equipment consisting of multiple devices are equipped with various measuring devices for flow, pressure, temperature, etc. in order to manage and operate them. Of these, flow rate detection is one of the most essential and indispensable. Is.

A differential pressure type flow meter is a general and widely used method for detecting the flow rate. This is to reduce a part of the inside of a conduit through which gas or liquid flows, measure the pressure deviation before and after that, and calculate and measure the flow velocity from this value, and the structure is simple. However, it has a feature of relatively high accuracy.

In this differential pressure type flow meter, the structure for reducing the flow path of the conduit uses a so-called disc-shaped plate (hereinafter referred to as an orifice plate) in which a hole smaller than the inner diameter of the conduit is used. Orifice flow meters are most commonly implemented.

Regardless of whether the fluid flowing in the conduit is a gas or a liquid, when the property is relatively stable and the state does not change, the orifice flow meter has a relatively high accuracy and its flow velocity (hereinafter, flow velocity and Can be measured.

The detection end (hereinafter referred to as the orifice flow detection end) of this orifice flow meter is roughly classified into an orifice plate and a front pressure transmission hole (the pressure on the front side of the orifice plate when viewed from the flow direction is outside the conduit). It has a relatively simple structure consisting of three parts: a hole provided for transmitting) and a rear pressure transmitting hole (a hole for taking out the pressure on the rear side of the orifice plate to the outside of the conduit).

On the other hand, in the case where particles having a minute diameter are mixed in the fluid, or when the fluid itself is changed to be heterogeneous and adheres to the inside of the conduit (hereinafter, referred to as scaling), the orifice is particularly used. There is a problem that the two pressure transmission holes provided at the front and rear of the plate cannot be used because they are blocked by this scaling.

[0008]

[Problems to be solved by the device]

 In order to solve this problem, it has been proposed to increase the diameter of the pressure transmission hole.However, increasing the diameter of the pressure transmission hole causes the orifice flow meter to reduce the slight pressure difference before and after the orifice plate. Since it is a method of detecting and using it, it is easily affected by unnecessary pressure fluctuations caused by turbulence of eddy currents, etc., which makes the most important accuracy of the instrument worse, and is practically difficult.

For this reason, a so-called ring orifice flow rate detection end, which is a shape in which a minute gap is provided all around the inner surface of the conduit before and after the orifice plate, is also proposed. Not only is it a complicated structure due to the fact that it has to be manufactured by dividing the uniform gap across it, the front-rear pressure transmission hole, the orifice plate, etc., but also the hole that finally transmits to the outside of the conduit. Has a small diameter, and blockage in this area cannot be avoided, so it is not a fundamental solution.

For these reasons, although the orifice flow meter is simple and highly accurate, it is difficult to apply it to a place where a scale trouble is expected, and it is difficult to apply it to other ultrasonic flow meters and vortex flow meters. However, there is no choice but to use a high-level method, and there are significant restrictions on where it can be used.

The present invention has been made in view of the above problems, and an object thereof is to detect the flow rate of a fluid in which a problem due to scaling is expected, and to use the advantages and performances of the conventional orifice flow meter. It is possible to adapt while maintaining the above, and more specifically, it is extremely difficult to cause blockage due to scale in the front and rear pressure transmission holes that are part of the structure of the orifice flow rate detection end.

[0012]

[Means for Solving the Problems]

 The inventors of the present invention have conducted diligent studies to prevent problems due to scaling of the orifice flow rate detection end. It was found that the above problems can be solved if the structure is connected to the pressure transmission conduit (hereinafter referred to as the pressure transmission conduit) to the differential pressure gauge while maintaining this shape, and the present invention was achieved. Is. That is, according to the present invention, the pressure transmission hole for transmitting the pressure before and after the orifice plate to the outside has a slit shape parallel to the orifice plate, and the pressure transmission conduit to the differential pressure gauge is maintained while maintaining this shape. It is an orifice flow rate detection end characterized by a structure connected to the.

Hereinafter, the present invention will be described in more detail.

In the orifice flow rate detecting end of the present invention, the pressure transmitting hole for transmitting the pressure before and after the orifice plate to the outside has a slit shape parallel to the orifice plate, and while maintaining this shape. It is a structure connected to a pressure transmission conduit to a differential pressure gauge.

If the long side of the slit in the pressure transmission hole is as long as possible, it is suitable as a measure against clogging (foreign matter). The length that enters the body may become shorter, weakening the strength and possibly damaging the pressure transmission pipe. For this reason, it is preferable that the long side of the slit and the insertion length of the pressure transmission tube are about half each of the width of the orifice flange surface. In addition, the short side has the same length as the conventional pressure transmission hole diameter (generally about 2 to 5 mm) to prevent unnecessary pressure fluctuations caused by turbulence and vortices of the fluid flowing in the conduit. Is preferred. The length of the short side is determined by the inner diameter of the conduit.

The long side of the slit may have the same length as the pressure transmission hole (inner diameter), but by gradually expanding toward the central portion of the conduit through which the fluid flows, it is effective in preventing clogging due to scale. When the pressure transmission hole is enlarged (long side), it may be determined in consideration of machining or strength of the orifice.

The two slit-shaped pressure transmission holes may be processed separately and then combined, but by using a structure that is an integral block type, the mounting is easy and the number of gasket packings is half. This is preferable because it has the effect of reducing leak points and further reduces manufacturing costs.

The two slits for transmitting the pre-pressure and the post-pressure of the orifice plate have an angle such that the center line of the long side of the orifice plate is not in contact with each other when viewed from the flow direction in the conduit, and the pressure transmission pipes connected thereafter are in contact with each other. It is necessary to shift them, but as a standard, a range of 90 ° (right angle) to 180 ° (facing) is preferable from the viewpoint of manufacturing and construction.

The orifice plate is provided with a hole that is concentric with the conduit and has a diameter smaller than the inner diameter of the conduit. This hole can be calculated from the fluid physical properties and the operating conditions like the normal orifice design. It may be determined appropriately.

The present invention will be described below with reference to FIG. 1, but the present invention is not limited thereto.

In the conduit 1, an orifice plate 2 and an orifice flow rate detecting end 5 in which a front pressure transmitting hole 3 and a rear pressure transmitting hole 4 for extracting the pressure before and after the orifice plate are integrated are inserted. Has been done.

The orifice plate 2 has a hole that is concentric with the conduit 1 and has a diameter smaller than the inner diameter of the conduit 1 (hereinafter referred to as an opening diameter), where the fluid flow is once narrowed and passed. After that, the flow returns to the original flow along the inner diameter of the conduit 1 again, but due to the behavior of this flow, a differential pressure across the orifice plate 2 depending on the flow velocity is generated.

The pressure transmission holes 3 and 4 are slit-shaped parallel to the orifice plate 2 at positions closest to the orifice plate 2, and are connected to the pressure transmission pipe 6 while maintaining this shape. There is.

The long side of the slit is at a position where it is joined to the pressure transmission pipe 6 and has a length equal to or longer than the inner diameter of the pressure transmission pipe 6, and the short side is turbulence or vortex of the flow line of the fluid flowing in the conduit 1. The width should be such that it does not cause unnecessary pressure fluctuations due to factors such as

The long side of the slit is in a shape in which it gradually expands toward the central portion of the conduit through which the fluid flows, and the maximum long side of the slit is maximum at the inner wall of the conduit 1.

Further, in the two slit-shaped pressure transmission holes 3 and 4, the center lines of the long sides are displaced at an angle of 90 ° when viewed from the flow direction in the guide tube, so that the pressure transmission tube 6 is I try not to touch each other.

A pressure transmission pipe 6 is attached to each of the two pressure transmission holes 3 and 4, and is connected to a differential pressure gauge through the pressure transmission pipes 6. The differential pressure before and after the orifice plate 2 measured here is The square root of the value is calculated as the fluid flow rate using a relationship proportional to the flow velocity.

[0028]

【Example】

 Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

Example An orifice flow rate detecting end as shown in FIG. 1 was used. That is, the orifice plate 2 and the pressure transmission holes 3 and 4 were manufactured by grinding from a single metal block. The long side of the slit was 60.0 mm wide, the short side of the slit was 3 mm wide, and the size of the opening diameter was 65.67 mm.

Using this orifice flow rate detection end, a fluid containing a fine scale having a sticking property was circulated in a conduit 1 having a circular cross section and a constant diameter to measure the flow rate.

As a result, the measurement accuracy was maintained, and the pressure transmission holes 3 and 4 were not clogged with scale or the like.

Comparative Example Using the conventional ring orifice flow rate detection end shown in FIG. 2, flow rate measurement was performed by the same method as in the example.

As a result, the scale having a minute diameter blocked the pressure transmission hole, and the measurement was impossible.

[0034]

[Effect of device]

 By using the orifice flow rate detection end of the present invention, it is possible to perform highly accurate flow rate measurement without causing trouble such as blockage of the pressure transmission hole even for fluid mixed with fine scale. .

Even when used for a long period of time, there is an effect that cleaning and maintenance from the pressure transmission pipe side can be facilitated without disassembling the conduit and the detection end.

Since the structure of the detection end is simple and the orifice plate, the two pressure transmission holes and the like can be integrated, there are a plurality of attachments to the guide tube as compared with the conventional ring orifice flow rate detection end and the like. This has the effect of reducing the number of joints and greatly reducing the possibility of leakage of the contents (fluid) from this portion to the outside.

Even if the conventional orifice flow meter is used and frequent maintenance is required due to scaling, it is possible to switch to the orifice flow rate detection end of the present invention without changing the differential pressure type flow rate detection method. And, a big improvement can be achieved.

As described in detail above, the orifice flow rate detection end of the present invention can measure the orifice flow rate even if the target fluid is a fluid that is easily scaled, and the series of configurations is extremely simple. Therefore, it is a very meaningful device that can be used in a wide range of industrial fields, such as low cost and extremely easy maintenance and management.

[Brief description of drawings]

FIG. 1 is a view showing the structure of an orifice flow rate detecting end of the present invention.

FIG. 2 is a view showing a structure of a conventional ring orifice flow rate detecting end.

[Explanation of symbols]

 1 ... Conduit 2 ... Orifice plate 3 ... Front pressure transmission hole 4 ... Rear pressure transmission hole 5 ... Orifice flow rate detection end 6 ... Pressure transmission pipe

Claims (3)

[Scope of utility model registration request] 1. The detection of the flow rate of gas or liquid by a differential pressure type,
Also, at the orifice flow rate detection end used when performing with the orifice system, the pressure transmission hole for transmitting the pressure before and after the orifice plate to the outside is a slit shape parallel to the orifice plate, and while maintaining this shape An orifice flow rate detecting end, which is structured to be connected to a pressure transmission conduit to a differential pressure gauge. 2. The orifice flow rate detection end according to claim 1, wherein the two pressure transmission holes each having a slit shape have an integrated block type structure. 3. The long side of each of the two slit-shaped pressure transmission holes is gradually enlarged toward the center of the conduit through which the fluid flows, and becomes maximum at the inner wall surface which is in contact with the main stream of the fluid. The orifice flow rate detection end according to claim 1.