JPH1123605A - Flow velocity measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure flow velocity at a large number of measuring points in a short time with small number of measuring persons by measuring the flow velocity of a fluid flowing through each part in a cross-section based on the fluid pressure acting on a pressure hole made in a circular tube being inserted. SOLUTION: When a connecting rod 9 is moved, a second circular tube 4 is moved up and down and pressure holes 02, 03 made at the lower end thereof are set at specified measuring points in the cross-section of a duct 06 in order to measure the flow velocity at that positions. When the number of third circular tubes 3 constituting a Pitot tube 1, the flow velocity can be measured over a longer distance even if the length of individual circular tubes, including the first and second circular tubes 2, 4, is shortened. When the length of individual circular tubes constituting the Pitot tube 1 is shortened, the Pitot tube 1a can be held without requiring a large scale structure, e.g. a crane or a scaffold, and the cost is reduced. Furthermore, the flow velocity can be measured over the entire cross-section of the duct 06 in a short time with a small number of measuring persons.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the flow rate of a fluid such as a gas or a liquid flowing in a large-diameter pipe duct having a large cross-sectional area laid in various plants. A circular pipe with a pressure hole is inserted from the side of the pipe duct into the inside, and by adjusting the position of this circular pipe, the pressure hole is placed at the position where the flow velocity in the pipe duct is measured, and the total pressure at that position is measured. TECHNICAL FIELD The present invention relates to a flow velocity measuring device capable of measuring a pressure and a static pressure so as to measure a flow velocity of a fluid flowing in each part in a cross section of a pipe duct.

[0002]

2. Description of the Related Art In a plant such as a power plant, in order to perform an intended operation of a plant, a large-diameter laid in the plant such as an amount of air required for combustion in a boiler and an amount of exhaust gas discharged from a chimney. It is necessary to accurately grasp the flow rate of the fluid flowing in the various pipe ducts. Normally, the flow of the fluid flowing in the pipe duct is not uniform in the cross section of the pipe duct, and the flow velocity differs at each position in the cross section. It is necessary to measure the flow velocity at as many positions as possible in the cross section.

For this reason, a traverse measurement of the flow velocity in the pipe duct is usually performed, and the average value of the flow velocity at a number of positions obtained by the traverse measurement is regarded as the average value of the fluid flowing in the pipe duct. The flow rate of the fluid flowing in the pipe duct is calculated from the flow velocity.

FIG. 3 is a sectional view showing a flow velocity measuring apparatus conventionally used for traverse measurement of the flow velocity in such a large-diameter pipe duct. As shown in the figure, a circular pipe 01 (hereinafter referred to as a pitot pipe) having pressure holes 02 and 03 at its tip is manufactured, and this is inserted into a large-diameter pipe duct 06 as shown in FIG. As shown in FIG. 3B, one of the pressure holes 02 is arranged so as to face the direction of the flow F at a location where the flow velocity of the flow F flowing in the duct 06 is measured. The pressure and the static pressure acting on the pressure hole 03 are applied to the pitot tube 0 by pressure conduits 04 and 05, respectively.
1, and the pressure difference is measured and calculated to obtain the flow velocity at the installation position of the pressure holes 02 and 03.

[0005] Some of the pipe ducts 06 that need to measure the flow velocity have a height of about 10 m, such as a pipe duct 06 that allows exhaust gas discharged from a chimney to flow. When measuring the flow velocity of exhaust gas or the like flowing through such a large piping duct 06, as shown in FIG. 4, the pitot tube 01 is manufactured to be long according to the size of the piping duct 06, and such a pitot tube 01 is manufactured. The pressure holes 02 and 03 provided at the tip of the tube 01 need to be installed at the flow velocity measurement position to perform measurement.

For this reason, a crane hook 09 suspended from a crane truck or the like (not shown) moved to the vicinity of a piping duct 06 for which the flow velocity needs to be measured, and a pitot tube 01 suspended from a suspended wire 010 is suspended. Is suspended through one of the mounting holes 07 selected from a plurality of mounting holes 07 provided in the width direction of the pipe duct 06, and the height of the pressure hole 02 is measured to measure the flow velocity. After the adjustment, the measurement seat 0 provided around the opening of the mounting hole 07
At 8, the pitot tube 01 is fixed, and the exhaust gas flow velocity at one point in the cross section of the piping duct 06 in which the pressure holes 02 and 03 are installed is measured.

After this measurement, using a crane truck again,
The pitot tube 01 is lifted and fixed so that the pressure holes 02 and 03 are installed at the measurement positions of different heights in the cross section of the pipe duct 06 at the position of the mounting hole 07, and the measurement is performed. By repeating such an operation, the mounting hole 0
The exhaust gas flow velocity at each height where vertical measurement of 7 is required is measured. Further, when the measurement of the mounting hole 07 in the vertical direction is completed, then, for example, an adjacent mounting hole 0
7, the pitot tube 01 is suspended, and similarly, the exhaust gas flow velocity at each height of the adjacent mounting hole 07 is measured, so that the exhaust gas flow velocity in the entire cross section of the pipe duct 06 is sequentially measured. By the traverse measurement, the flow velocity in the entire cross section of the pipe duct 06 is measured.

As is clear from the above description, in the flow velocity measurement of the piping duct 06 using the conventional flow velocity measuring device, if the diameter of the piping duct 06 becomes large, in other words, the flow velocity is measured. When the length of the pitot tube 01 to be measured becomes long, it is difficult to stably support the pitot tube 01 only with the measuring seat 08, and the pitot tube 01 generates a large load due to the pressure of the exhaust gas passing when measuring the exhaust gas flow velocity.
A large supporting device is required above the pipe duct 06, and it is extremely difficult to lift and suspend the pitot tube 01 by human power. Lifting and suspending of the pipe 01 becomes indispensable, and in conjunction with the installation of the support device described above, a scaffold must be erected in the piping duct 06. Further, a predetermined position for measuring the pressure hole 02 It takes a long time to measure the flow velocity including the preparation work, such as the necessity of a small operation of lifting and hanging the pitot tube 01 for installation in the pitot tube 01.

That is, if the size of the piping duct 06 for measuring the flow velocity of the internal fluid becomes large, the measurement by the flow velocity measuring device which has been conventionally used increases costs for erection of a scaffold, arrangement and operation of a crane truck, and the like. A problem arises that the measurement is bulky, requires a large number of measurement personnel, and requires a long time for measurement.

[0010]

SUMMARY OF THE INVENTION According to the present invention, a pitot tube is constituted by a plurality of short circular tubes, and at the tip of these circular tubes, in order to solve the above-mentioned problems of the conventional flow velocity measuring device. A circular pipe provided with a pressure hole for measuring the flow velocity is inserted inward from the mounting hole opened on the wall surface of the piping duct for measuring the flow velocity, and is temporarily fixed around the mounting hole. The inside of the larger diameter pipe is slid to extend from the tip of the pipe, and the pressure hole is set at a predetermined position in the cross section of the pipe duct for measuring the flow velocity. Therefore, even when measuring the flow velocity in a larger pipe duct, it is possible to easily install the pressure hole at a predetermined position without requiring heavy equipment such as a crane truck, and furthermore, a circle receiving the fluid pressure during the measurement. At least easy installation of scaffolds for holding pipes Reduction can, and in a short time with less measurement personnel, even for larger cable duct, and to provide a flow rate measuring apparatus that can flow velocity measurement at a number of measurement points inside.

[0011]

Therefore, the flow velocity measuring device of the present invention has the following means.

(1) An opening in a wall surface of a large-diameter pipe duct, in which the flow velocity of a fluid flowing through each part in a cross section is measured by a fluid pressure acting on a pressure hole formed in an inserted circular pipe. There was provided a first circular pipe which was inserted inward from the mounting hole and was temporarily fixed to the wall surface of the piping duct to constitute a part of the pitot tube.

The first circular pipe has such a length and weight that the measuring member can be inserted into the mounting hole of the pipe duct and can be temporarily connected and fixed to the pipe duct without requiring a large-scale device. It is preferable that the first circular pipe is inserted into the mounting hole of the pipe duct by using a horizontally installed pipe duct so that the pipe can be inserted from above the pipe duct using gravity. In this case, it is more preferable to provide a mounting hole in the wall surface at the upper end. Further, the cross-sectional shape of the pipe duct to which the first circular pipe is attached may be any shape such as a circle, a square, and a polygon.

(2) The diameter of the first circular tube is made smaller than that of the first circular tube so that it can be inserted into the first circular tube, and a pressure hole is provided at the distal end, so that the inside of the first circular tube slides. Then, the pressure hole is extended from the tip of the first circular pipe, and the pressure hole is set at a predetermined position on the cross section of the piping duct for measuring the flow velocity. Two circular tubes were provided.

[0015] In addition, between the first circular pipe and the second circular pipe,
Allowing each of the first and second circular tubes to slide with respect to each other, together with the first and second circular tubes;
It is preferable to provide one or more third circular tubes which constitute a part of the pitot tube. Further, when the sliding portion between the first circular tube and the second circular tube and the third circular tube are provided, in addition to this, each of the first circular tube and the second circular tube It is preferable to provide grooves respectively for restricting rotation of the sliding portion about the mutual axis in the sliding portion between the first and third circular tubes. In addition, at the rear end of the second circular tube, from the distal end of the first circular tube, or from the distal end of the third circular tube when the third circular tube is provided, the second circular tube is formed. It is preferable to provide a stopper for preventing the slipping out.

(3) In the case where the first circular pipe and the second circular pipe and the third circular pipe are provided, in addition to the above, they are disposed inside the third circular pipe and these are disposed. A pressure conduit is provided that expands and contracts freely in response to expansion and contraction due to sliding of the circular tube, and that transmits fluid pressure acting on the pressure hole to the outside of the mounting hole. Note that the pressure conduit is not configured such that the pressure conduit itself expands and contracts when the first circular tube and the second circular tube expand and contract, and that a load is generated in the pressure conduit itself. It is preferable that the shape of the swivel-formed conduit be deformed so that it can expand and contract in accordance with expansion and contraction of the circular tube.

(4) The second circular pipe is extended from the tip of the first circular pipe, and the pressure hole provided at the tip of the second circular pipe is positioned at the flow velocity measuring position on the cross section of the pipe duct for measuring the flow velocity. Telescopic means to be installed are provided. The expansion and contraction means uses the gravity acting on the second circular pipe to extend the second circular pipe from the first circular pipe so that the pressure hole can be accurately set at the flow velocity measuring position. Is preferred.

The flow velocity measuring device according to the present invention has the above (1) to
By means of (4), (a) even when measuring the flow velocity in a large-diameter pipe duct, the length can be reduced to at least half the length of the conventional pitot tube, and the weight is significantly reduced. The first circular pipe is preferably inserted into a mounting hole drilled at the upper end of the pipe duct, and the upper end of the first circular pipe is connected and fixed to the pipe duct. Insert the second circular tube inside from the upper end of the tube,
The second circular pipe is slid inside the first circular pipe by the expansion and contraction means and lowered, so that the pressure hole provided at the tip of the second circular pipe measures the flow velocity in the cross section of the pipe duct. Will be set to the position.

A pressure conduit for transmitting the fluid pressure acting on the pressure hole to a measuring device provided outside the pipe duct is also a first pressure conduit.
Inside and outside of the first and second circular pipes, the fluid pressure acting on the pressure holes at the time of the flow velocity measurement continues. Even when the flow velocity measurement position on the cross section of the pipe duct is the position farthest from the mounting hole, accurate measurement can be performed.

As described above, even when the pipe duct has a larger diameter and the flow velocity measurement position is located far away from the mounting hole for inserting the pitot tube, the flow velocity can be reduced by a plurality of lightweight and short circular pipes. The pressure hole can be installed at the measurement position, and the measurement can be prepared only by the operation of the measurer or simple auxiliary equipment without the need for heavy equipment such as a crane truck and without the need for an erecting scaffold. Become like

Further, since the diameter of the second circular pipe can be reduced, the first circular pipe and the second circular pipe of the fluid at the time of measuring the flow velocity can be obtained.
The fluid pressure acting on the circular pipe can be reduced, and the supporting device or the supporting scaffold for holding the first circular pipe and the second circular pipe at the time of measurement can be simplified or eliminated. Furthermore, the installation work of the pressure hole at the flow velocity measurement position becomes easy,
Since the measurement can be performed in a short time, the number of measurement personnel can be reduced, and the measurement time can be significantly reduced.

Further, by providing the pitot tube with a third circular tube in addition to the first circular tube and the second circular tube, shortening and weight reduction of the pitot tube are further promoted. In addition, measurement work including measurement preparation work becomes easier. In addition, by providing a groove in a sliding portion or the like between the first circular pipe and the second circular pipe, sliding becomes smoother, expansion and contraction becomes smoother, and the first The relative twist between the circular pipe and the second circular pipe is eliminated, and the pressure hole provided in the second circular pipe can always be accurately faced with the flow direction, improving the accuracy of flow velocity measurement. Can be done.

Further, by providing the stopper, it is possible to reliably prevent the second circular tube from coming off from the tip of the first circular tube or the third circular tube, thereby improving the operational reliability. be able to. In addition, the first circular tube and the second circular tube
The expansion and contraction of the pressure conduit corresponding to the expansion and contraction of the circular pipe etc. is performed by deforming the shape formed in a spiral etc. The transmitted fluid pressure can be reliably and accurately transmitted to the outside of the pipe duct. further,
By using the gravity acting on the second circular pipe as the expansion and contraction means, the structure can be simplified, and the accuracy of setting the pressure hole at the flow velocity measurement position can be improved.

A second flow velocity measuring apparatus according to the present invention employs the following means in addition to the above-mentioned means (1) to (4).

(5) A first type, which is installed around the opening of the mounting hole opened in the wall surface of the pipe duct and is temporarily fixed to the wall surface of the pipe duct to constitute a part of the pitot tube. The circular pipe is rotated about the axis, and the second circular pipe that slides in the first circular pipe and expands and contracts is rotated about the axial center, and the pressure applied to the tip of the second circular pipe. Rotating means for setting the direction of the hole so as to face the direction of flow of the fluid is provided. The pressure holes are generally provided with a total pressure hole and a static pressure hole. In this rotating means, the direction of the pressure hole for measuring the total pressure is directly opposed to the flow direction of the fluid. It will be set.

According to the flow rate measuring device of the present invention, in addition to the above (a), the flow direction in the pipe duct is changed or the first circular pipe or the second circular pipe is twisted by the means (5). Even if the direction of the pressure hole deviates from the direction of flow due to, for example, it is possible to immediately correct the direction of the pressure hole so as to directly face the direction of flow, and always measure the accurate flow velocity at the flow velocity measurement position This makes it possible to improve the measurement data, thereby contributing to the improvement of the operation efficiency of a plant or the like.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a flow velocity measuring device according to the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a first embodiment of a flow velocity measuring device according to the present invention.
FIG. 1A is a diagram showing a contraction time, and FIG. 1B is a diagram showing a stretching time. In the drawings, the same members as the conventional members are denoted by the same reference numerals, and description thereof will be omitted as much as possible.

As shown in the figure, in the present embodiment, the pitot tube 20 is composed of a first circular tube 2, a third circular tube 3, and a second circular tube 4.
The pressure holes 02 and 03 are provided at the tip of the second circular tube 4 disposed at the forefront, similarly to the conventional pitot tube 01. Although only one third circular tube 3 is provided, two or more third circular tubes 3 may be provided. Further, one ends of pressure conduits 04 and 05 are connected to the pressure holes 02 and 03, respectively. The pressure conduits 04 and 05 are wound in a coil shape, and the second circular pipe 4 and the third Is inserted through the inside of the circular pipe 3 and the first circular pipe 2 from the mounting hole 07 formed in the piping duct 06 to the outside, and the other end is connected to a pressure measuring instrument not shown. .

The second circular tube 4 can slide inside the third circular tube 3, and the inner periphery of the third circular tube 3 has a movement of the second circular tube 4. Guide groove 5 for guiding
Is provided. Also, on the outer periphery of the base end of the second circular tube 4,
A projection 6 provided on the third circular tube and sliding on the guide groove 5 described above is provided. The projection 6 restrains the rotation of the second circular tube 4 with respect to the third circular tube 3, and when the second circular tube 4 extends from the tip of the third circular tube 3,
The rear end (base end) of the circular tube 4 is prevented from falling out of the distal end of the third circular tube 3 so as not to come off.

The third circular tube 3 can slide inside the first circular tube 2, and the inner periphery of the first circular tube 2 has the above-mentioned third circular tube 3. And a groove 7 for guiding the movement of the third circular tube 3 is provided. Also, a projection 8 that slides on the guide groove 7 provided in the first circular tube 2 is provided at the base end of the third circular tube 3. 1
When the third circular tube 4 extends from the distal end of the first circular tube 1, the base end of the third circular tube 3 is connected to the first circular tube 2. The tip is prevented from slipping out and not falling off.

A second circular tube 4 having a projection 6 provided on the outer peripheral side
In order to extend and move the second circular tube 4 from the distal end of the third circular tube 3 on the inner peripheral surface of the base end portion of the first circular tube 2, the first circular tube 2, The lower end of a connecting rod 9 as an expansion / contraction means, which is inserted through the inside of the third circular tube 3, is connected. The connecting rod 9 is provided with a hinge 10 at an arbitrary length, and as shown in FIG. 1A, is configured to be bent when the pitot tube 1 is retracted.

Further, as shown in FIG. 4, the first circular pipe 2 is a measurement pipe provided at the upper end of the pipe duct 06 at the periphery of mounting holes 07 provided at equal pitches in the width direction of the pipe duct 06. The outside is fixed to the seat 08 and connected and fixed to the piping duct 06.

Since the flow velocity measuring device 11 of the present embodiment is configured as described above, by moving the connecting rod 9, the second circular tube 4 moves up and down, and the second circular tube 4 moves. The pressure holes 02 and 03 provided at the lower end of 4 and a predetermined measurement position in the cross section of the piping duct 06 are set, and the flow velocity at the measurement position is measured.

First, the pressure holes 02 and 03 are set by moving the connecting rod 9 to a predetermined measurement position set at the uppermost stage below the mounting hole 07 of the pipe duct 06, and the flow velocity is measured.
Move the connecting rod 9 again to move the second circular tube 4 downward,
The pressure holes 02 and 03 move to the next lower measurement positions to perform measurement. In this manner, the flow velocity is measured from the measurement position above the pipe duct 06 to the measurement position below the second duct, and the second flow rate is measured.
When the protrusion 6 provided at the base end of the circular tube 4 hits the lower end of the guide groove 5 of the third circular tube 3, the third circular tube 3 moves downward and is located further below. The flow velocity at the measurement position can be measured.

Therefore, by increasing the number of the third circular tubes 3 constituting the pitot tube 1, the first circular tube 2 and the second circular tube 4 are increased.
Even if the length of each of the circular tubes including the pitot tube is shortened, measurement can be performed up to a longer distance, and the individual circular tubes constituting the pitot tube 1 can be shortened to hold the pitot tube 1; Eliminating the need for a large-scale device such as an erecting scaffold eliminates the cost, and allows a small number of measurement personnel to measure the flow velocity in the entire cross section inside the piping duct 06 in a short time.

FIG. 2 is a sectional view showing a second embodiment of the flow velocity measuring device according to the present invention. FIG.
FIG. 2B is a diagram showing the state at the time of stretching.

As shown in the figure, in the present embodiment, the connecting rod 9 as the expansion and contraction means in the first embodiment is used.
In place of, the second circular pipe 4 and the third circular pipe 3 are suspended,
The wire 12 for setting the pressure holes 02 and 03 provided at the distal end of the second circular tube 4 at a predetermined measurement position is provided. This wire 12 is connected to a winding portion 13
And a winding device 13 of a winding device including a motor 14 for driving the motor.

Further, the end face of the measuring seat 08 erected on the peripheral edge of the mounting hole 07 is connected to the gear 1 via a thrust bearing 15.
6 and 17 are provided, and further, a motor 18 for driving these is provided, so as to constitute a rotating means 19 for rotating the first circular tube 2 around the axis and rotating the pitot tube 1. I have to.

The flow velocity measuring device 20 according to the present embodiment is configured as described above,
When the 3 is moved, the wire 12 as the expansion / contraction means unwinds,
The operation and effect that the second circular pipe 4 is moved up and down by being unwound and the pressure holes 02 and 03 can be set at predetermined measurement positions as in the first embodiment can be obtained. In addition, wire 1
No. 2 cannot generate a force for lowering the second circular tube 4 like the connecting rod 9, so the unwinding of the wire 12 causes the second
Is moved downward by its own weight.

That is, the piping duct 06 for measuring the flow velocity
The pitot tube 1 is set on the measuring seat 08 provided at the position, and the second circular tube 4 is moved up and down by the wire 12, so that the pressure hole is set at a predetermined measurement position, and the flow velocity can be measured. Then, the pressure hole 0 can be
As a result, 2,03 positions can be set, the number of measurement personnel is small, and automatic measurement is also possible.

Further, the thrust bearing 15, the gears 16, 1
The pitot tube 1 is rotated by a rotating means composed of the motor 7 and the motor 18, and even if the flow direction in the piping duct 06 changes, or the pitot tube 1 is twisted, etc. Even when the directions of the pressure holes 02 and 03 provided at the tip of the nozzle do not match the flow direction, the pressure holes 02 can be accurately aligned so as to directly face the flow direction. . Therefore, the pressure holes 02 and 03 can be changed only by driving the motor 18, and from this point also, automatic measurement can be performed and the number of measurement personnel can be reduced.

[0042]

As described above, according to the flow velocity measuring apparatus of the present invention, the flow rate measuring device is inserted inward from the mounting hole opened in the side wall of the large-diameter pipe duct, and temporarily inserted into the side wall of the pipe duct. And a first circular tube, which is configured to constitute a part of the pitot tube, has a smaller diameter than the first circular tube,
A pressure hole is provided at the distal end, and slides inside the first circular pipe to extend from the distal end of the first circular pipe, and the pressure hole is set at a predetermined position in a cross section of a pipe duct for measuring flow velocity. , Together with the first circular tube, are disposed inside the second circular tube, the first circular tube, and the second circular tube constituting the pitot tube, and correspond to expansion and contraction caused by sliding of these circular tubes. A pressure conduit that expands and contracts freely and transmits fluid pressure acting on the pressure hole to the outside of the mounting hole, and a pressure that is provided at the distal end by extending and retracting the second circular tube from the distal end of the first circular tube. The hole is provided with expansion and contraction means which is installed at a fluid measurement position on the cross section of the piping duct for measuring the flow velocity.

Thus, even if the pipe duct has a larger diameter and the flow velocity measuring position is located at a position far apart from the mounting hole for inserting the pitot tube, it is possible to extend a plurality of lightweight and short circular pipes. The pressure hole can be installed at the flow velocity measurement position, and the measurement can be prepared only by the simple operation of the measuring person without the need for a crane truck or the like, and without the need for an installation scaffold.

Further, since the diameter of the second circular pipe can be reduced, the pressure of the fluid for measuring the flow velocity, which acts on the first circular pipe and the second circular pipe, can be reduced. The erection scaffold holding the first circular pipe and the second circular pipe at the time of measurement can be simplified or eliminated. Furthermore, since the work of installing the pressure hole at the flow velocity measurement position becomes easy and can be performed in a short time, the number of measurement personnel can be reduced, and the measurement time can be significantly reduced, and accurate flow velocity measurement can be performed. Become like

Further, according to the flow velocity measuring device of the present invention,
A first circular pipe, which is installed around the opening of the mounting hole and is temporarily fixed to the side wall of the pipe duct and constitutes a part of the pitot tube, is rotated around an axis, and the first circular pipe is rotated. A rotating means is provided for setting the direction of a pressure hole formed at the tip of a second circular tube which expands and contracts by sliding in the circular tube in the flow direction of the fluid.

As a result, the direction of the flow of the fluid in the pipe duct is changed, or the direction of the pressure hole is deviated from the direction of the flow due to the twisting of the first and second circular pipes. Can also be corrected immediately to face the flow direction, and the accurate flow velocity at the flow velocity measurement position can always be measured, and the measurement data can be improved. Can be contributed to.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of a flow velocity measuring device according to the present invention, FIG. 1 (a) is a diagram showing a contraction time, FIG. 1 (b) is a diagram showing a stretching time,

2A and 2B are cross-sectional views showing a second embodiment of the flow velocity measuring device according to the present invention, wherein FIG. 2A is a view showing a contraction state, FIG. 2B is a view showing a stretching state,

3 (a) is a longitudinal sectional view, FIG. 3 (b) is a transverse sectional view taken along the line AA shown in FIG. 3 (a),

FIG. 4 is a front view showing a conventional flow velocity measuring device when it is installed in a pipe duct.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pitot tube 2 1st circular tube 3 3rd circular tube 4 2nd circular tube 5 Guide groove as expansion / contraction means 6 Projection 7 Guide groove 8 Projection 9 Connecting rod 10 Hinge 11 Flow velocity measuring device 12 Wire as expansion / contraction means DESCRIPTION OF SYMBOLS 13 Winding part 14 Motor 15 Thrust bearing 16 Gear 17 Gear 18 Motor 19 Rotating means 20 Flow velocity measuring device 01 Circular pipe (Pitot tube) 02, 03 Pressure hole 04, 05 Pressure conduit 06 Pipe duct 07 Mounting hole 08 Measurement seat 09 Crane hook 010 Hanging wire

Claims (2)

[Claims] The flow rate of a fluid flowing through each part of a large-diameter pipe duct is measured by a fluid pressure acting on a pressure hole formed in a circular pipe inserted into the pipe duct. In the measuring device, a first circular pipe inserted inward from a mounting hole opened in the pipe duct,
The pressure hole is provided at a distal end portion, a second circular tube that slides inside the first circular tube and extends from the distal end of the first circular tube, the first circular tube, and the second circular tube. A pressure pipe disposed inside the second circular pipe so as to be able to expand and contract, and transmitting fluid pressure acting on the pressure hole to outside of the mounting hole; A flow rate measuring device provided with expansion / contraction means for extending from a pipe and setting the pressure hole at a flow velocity measurement position. 2. A rotating means installed around the opening of the mounting hole for rotating the first circular tube around an axis and setting the direction of the pressure hole to the direction of fluid flow. The flow velocity measuring device according to claim 1, wherein: