JP3022845B2 - Suction sand pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suction sand pump, and more particularly to a suction sand pump which is most suitable for use in a small-diameter sewer pipe propulsion method.

[0002]

2. Description of the Related Art In the burial work of sewer pipes, a shield method for excavating a small-diameter tunnel with a shield diameter of 300 mm to 500 mm has recently been used. Sand pump used to shield method of this small diameter is set to vertical downhole, by the rotational centrifugal force of the exhaust mud impeller of pump casing, the sludge water discharged from the drilling head, the rotation of the impeller Suction is performed from a suction port formed at the axial end of the shaft, and the pump is lifted to the ground from a discharge port on the outer peripheral portion of the pump casing.

[0003]

The above-mentioned sand pump is small in size and small in diameter (3
0-150 mm), and its suction capacity is also limited. Therefore, vertical shafts must be excavated at intervals of 30-50 m with respect to the horizontal shaft where the sewer pipes are laid. Laying work was prolonged and costs were high.

In order to increase the distance of the horizontal shaft by reducing the number of shafts, it is necessary to increase the pump suction capacity. If this is to be achieved, the suction resistance is increased due to the small diameter of the suction port. , Often caused cavitation.

The only way to prevent cavitation is to reduce the amount of suction water or reduce the excavation speed.
Then, it will take more construction days. for that reason,
Even with a small-diameter sand pump, there has been a demand for a small-sized pump having a high suction capacity and capable of preventing cavitation.

[0006]

The inventor of the present invention has conducted extensive research on a small and high capacity sand pump capable of preventing cavitation. As a result, first, in order to prevent cavitation, a suction impeller is provided adjacent to a pump casing. While providing the suction casing that was made, while forming a bleed water hole in the rear shroud of the impeller for drainage,
It is known that the cavitation phenomenon that occurs in the pump casing due to the air sucked into the sludge water and the like can be prevented by adopting a configuration that actively sucks the air-filled sludge water into the suction casing through the bleed water holes. was gotten.

In this case, a small-diameter hole (10 mm or less), such as a balance hole formed in a rear shroud, is formed in a scattered point shape to prevent axial thrust in a submersible pump or the like. However, in a sand pump that pumps up and discharges sludge water containing sand and gravel, sand and gravel close the holes in small holes such as balance holes.
The function of sucking air and the like is lost.

Therefore, the bleed water passage is set to be less likely to be clogged with gravel, that is, set to have a larger diameter than the gravel. Specifically, a size of 12 mm or more and about 1/3 of the area between the blades of the rear shroud is acceptable.
If it is smaller than 12 mm, there is a possibility of clogging with gravel, and if it exceeds 1/3 of the area between the blades of the rear shroud, it is expected that the lifting power will be extremely reduced. The shape of the bleed water hole is a circular hole (hole diameter 20).
-30 mm), a form in which a plurality of these are formed, a long form, and a form in which a part of the outer periphery of the rear shroud is cut out. In particular, when the bleed water passage was formed in a long hole shape, good results were obtained, which was preferable.

Although it is conceivable that the location of the bleed water passage hole is formed at an arbitrary position on the rear shroud, the portion where the fluid flows most in the sludge water suction / drain passage in the impeller, that is, It is preferable to form the blade (main wing) along the front surface on the flow path side, that is, along the back side in the rotation direction of the blade.

The length of the bleed water passage hole is preferably formed from the root side of the main wing in order to increase the air suction capacity. On the outer peripheral side, the length of the main wing is reduced in order to minimize the reduction in drainage capacity. It is preferable to limit the pressure loss to a position where the pressure loss on the outer peripheral side (radially outer side) can be suppressed as much as possible. It is preferable to keep the position of the main wing at about 1/6 of the main wing length. As described above, the width of the bleed water passage is preferably set to such a size that the drainage capacity is not reduced, and that the bleeding is allowed to pass and the clogging is not caused by sand and gravel.
A width of about 15 mm can be exemplified.

The impeller for mud sewage may be provided with at least a rear shroud and a plurality of blades formed on the front surface thereof, regardless of the presence or absence of the front shroud. The blades are arranged between the front and rear shrouds. In addition, it is preferable to adopt a so-called closed blade type because the suction capacity is increased.

The plurality of blades may be any of two to five blades, but the drainage of the gravel of an equivalent diameter contained in the sludge water discharged at the head (the width of the flow path capable of discharging the gravel) and ,
Considering the improvement of the suction capacity, the three-blade type is preferable. As the shape of each blade, a spiral shape protruding in the direction of rotation of the impeller is employed, and various shapes can be employed according to the target to be pumped and drained. For example, a blade shape in which a short auxiliary wing on the front side in the rotation direction and a long main wing on the rear side intersect at a root portion and are formed in a substantially V shape can be exemplified. In this case, the bleed water holes may be formed in a long hole shape or the like along the concave curved surface on the flow path side on the back side in the rotation direction of the main wing.

[0013] The pneumatic sludge water passing through the bleed water passage hole is guided to the adjacent suction casing side through the gap between the rotary boss portion of the drainage impeller and the rear wall of the pump casing, and is guided to the suction impeller. It is sucked by the negative pressure generated on the shaft center side by the rotation, thereby preventing the occurrence of cavitation caused by a local pressure drop on the pump casing side. At this time, simultaneously with the rotation of the suction impeller, a centrifugal force acts from the rotation center side to the outer peripheral side, so that the sludge water is sucked in this portion as well, and it becomes a suction type with a two-stage impeller, and the sludge water is formed. The suction capacity can be increased.

The suction casing also has a front wall and a rear wall formed before and after (in the axial direction of the rotating shaft) the spiral casing main body.
A shroud in which a plurality of blades are formed in a spiral shape on the front wall may be employed. The number of blades of this suction impeller can be set as appropriate.However, since large-diameter gravel in the incoming sludge water is blocked by the bleed water passage of the impeller for discharging sludge, the flow path interval between the blades is There is no need to set it so large, and the suction capacity can be improved by increasing the number of blades. Specifically, an impeller having eight blades can be exemplified.

The blades are formed at positions outside the outer periphery of the boss portion of the impeller for drainage in order to efficiently suction the pneumatic sludge water introduced from around the rotary boss portion of the impeller for drainage. Is desirable. Each of the blades can be employed irrespective of a linear shape or a curved shape, but as is well known, the suction capability is improved by forming a curved shape with a convex ridge on the front side in the rotation direction.

Furthermore, the three-dimensional blades are arranged such that the root side of each blade of the suction impeller is inclined forward (inclination angle with the shroud at 45 to 85 °) and the outer peripheral side is vertical (intersection angle with the shroud is 90 °). It has been found that the suction capacity can be further increased by adopting the configuration.
Of course, each blade and the front wall of the suction casing allow rotation of the impeller, and are arranged with a minute gap through which the sludge can be sucked by the blade.

A mechanical seal device is provided at the outside of the rotary shaft of the suction casing. In order to reduce the fluid pressure applied to the mechanical seal device, it is desirable to employ a configuration in which a pressure reducing blade is provided. The vacuum vane is susceptible adopted configuration provided separately from the suction impeller, better to adopt a structure in which by using a back surface of the shroud of Sakusho burn-Pella providing vacuum vanes, it is possible to reduce the axial width of the suction casing This is advantageous. The pressure reducing blade may be configured so that a plurality of spiral blades are provided on the shroud, and a negative pressure is applied to the rotation center side.

The use of such a suction sand pump is used for sludge discharge and lifting work in various works, and it is particularly preferable to use the suction sand pump in the shield method, which is a small-diameter sewer pipe propulsion method. That is, 30 to 150
When used in a sand pump having a suction port with a small diameter of mm, it is possible to improve the suction capacity without causing cavitation, and it is suitable for use in a small-diameter sewer pipe propulsion method requiring a small and high capacity. It is. Also,
The sand pump may be either a horizontal type or a vertical type, and may be appropriately selected depending on the installation location.

However, when used in the shield method, the sludge water discharged contains bentonite and cement milk, and if left behind after using the pump, these will solidify before the next construction. As a result, the pump may not be used. Therefore, it is necessary to discharge the sludge water in the pump casing and the suction casing after the construction is completed.

In order to discharge the sludge water to the outside of the pump, a bypass pipe communicating the suction casing with the suction port is provided, and after the construction is completed, the supernatant liquid of the sludge water is suctioned by the pump and sucked from the suction casing. It is preferable to form a circulation path returning to the mouth, because the sludge water accumulated in the casing can be diluted and discharged. As a configuration of the bypass pipe, it is also possible to adopt a configuration in which a bypass valve or the like is provided at an intermediate portion thereof, and the bypass pipe is closed during the sludge discharge processing, and is opened only at the time of cleaning.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall side sectional view showing an embodiment of a suction sand pump of the present invention, and FIG. 2 is a front view of the same.

As shown in the figure, a sand pump 1 according to the present embodiment is used in a small-diameter sewer pipe propulsion method and drains sludge mixed with gravel. The sand pump 1 is mainly provided at the bottom of a shaft. It is installed through. In the sand pump 1, a mechanical seal device 6, a suction casing 7, and a pump casing 8 are sequentially arranged along a rotating shaft 5 provided on a motor shaft 4 of a motor 3.

The pump casing 8 is a spiral casting, and has a small diameter (having a diameter of 30 to 150 m) via a suction pipe 9 at the axial end of the rotary shaft 5 located at the center thereof.
m), and a discharge pipe 12 with a discharge port 11 is connected to an upper outer peripheral portion of the rotating shaft 5 in a direction perpendicular to the axis (radial direction).

Inside the pump casing 8 is a front wall 8a.
A sludge exhaust impeller 13 is bolted to the tip of the rotary shaft 5 between the rear wall 8b and the rear wall 8b. A suction impeller 14 for sucking the sucked air-containing sludge and preventing cavitation is fixed to the rotary shaft 5 in the suction casing 7 adjacent to the rear side of the pump casing. Further, the suction casing 7
A bypass pipe 15 is provided between the pump casing 8 and the suction pipe 9.

FIG. 3 is a front view of the drainage impeller, and FIG. 4 is a side sectional view of the same. As shown in the figure, the sludge exhaust impeller 13 includes a boss portion 17 fitted to the rotating shaft 5 and a disk-shaped rear shroud 18 extending radially at the end thereof.
A donut-shaped front shroud 20 having a suction port 19 opening at the suction port side at the center, and three blades 21 arranged and fixed in a space sandwiched by these front and rear shrouds 18, 20. Closed blades are used to increase the suction capacity by the front and rear shrouds 18 and 20.

As shown in FIG. 3, the three blades 21 are arranged in a spiral shape protruding in the direction of rotation of the impeller, with a flow passage width capable of discharging gravel of an equivalent diameter contained in the sludge water discharged from the head. ing. Each blade 21 is formed in a substantially V-shape, with a short auxiliary wing 23 on the front side in the rotation direction (the direction of the arrow in FIG. 3) and a long main wing 24 on the rear side intersecting at a root portion. Note that the width (length in the axial direction) of the auxiliary wing 23 and the main wing 24 is set to the same width on both the root side and the outer peripheral side.

The rear shroud 18 is formed with a bleed water hole 25 for guiding air sucked together with the sludge water to the suction casing side along the flow path side of the main wing 24. The bleed water hole 25 is formed at a central portion of the main wing 24 by 2/3 of the length of the main wing (specifically, 135 mm).
It is formed long to the extent (specifically 90 mm),
Its width is 12 to 15 mm so that the drainage capacity does not decrease and allow the passage of gravel so as not to be clogged with gravel.
Set to about.

The suction casing 7 is a spiral cast product disposed adjacent to the rear side of the pump casing 8, and a space defined by front and rear walls 7a and 7b is a suction chamber, as shown in FIG. The gap (1 to 2 mm) between the central hole 27 of the front wall 7a and the outer peripheral portion of the boss 17 of the impeller 13 is used as a suction passage for pneumatic sludge water. Accordingly, the air-filled sludge water having passed through the bleed water passage 25 passes through the front wall 7a of the suction casing 7 from the gap between the periphery of the boss portion 17 of the drainage impeller 13 and the rear wall 8b of the pump casing 8. The suction is performed by the negative pressure generated on the shaft center side by the rotation of the impeller 14. This prevents the occurrence of cavitation caused by a local pressure drop on the pump casing side. Also, the suction casing 7
The mechanical seal device 6 is disposed in contact with the rear wall 7b.

FIG. 5 is a front view of the suction impeller, FIG. 6 is a perspective view of the blade, FIG. 7 is a sectional view of the same, and FIG. 8 is a rear view of the pressure reducing blade on the rear side.

As shown in FIG. 7, the suction impeller 14
In the front wall recess 29 of the shroud 28, a plurality of (eight) blades 30 are formed in a spiral shape. The root of the blade 30 is provided with a boss 1 in order to efficiently suck the pneumatic sludge water guided from around the boss 17 of the impeller 13 for drainage.
7 is disposed at a position outside the outer diameter.

Each of the blades 30 has a shape that is convexly curved forward in the rotational direction (the direction of the arrow in FIG. 5), and the inclination angle of the root side 30a with the shroud 28 is 45 as shown in FIG.
Is inclined in the rotational direction front side in the range of to 85 °, the inclined progressively is loosened by the outer peripheral end 30b increases toward the outer peripheral side sheet
By setting the angle of intersection with the louds 28 to be vertical (90 °), the suction capacity is enhanced. Further, each blade 30 and the front and rear walls 7a and 7b are arranged with a small gap that allows rotation of the impeller 14 and allows sludge water to be sucked by the blade 30.

Shroud 28 of suction impeller 14
On the rear surface, a pressure reducing blade 31 is formed to reduce the fluid pressure applied to the mechanical seal device 6 side. The decompression blades 31 are spirally arranged on the shroud 28 (8 pieces).
The blades are provided so as to be curved so that the rotation center side becomes a negative pressure (the rotation direction is the direction of the arrow in FIG. 8).

The bypass pipe 15 uses the supernatant liquid of the sludge water after completion of the construction, pumps it, returns it from the suction casing 7 to the suction pipe 9 side, circulates it, and puts it in the casings 7 and 8. The accumulated sludge is diluted and discharged, and an opening / closing valve (not shown) is provided at an intermediate portion of the diluted sludge. The bypass pipe 15 is closed during the discharge of the sludge and is opened only at the time of cleaning. Is adopted.

The mechanical seal device 6 has a well-known structure in which a lubricant 36 is housed in a cylindrical box 35 and a rotary shaft 5 is surrounded by a cylindrical mechanical seal 37. The structure prevents water from entering the motor side.

The sand pump 1 having the above-described structure is moved from 300 mm to
When the present invention is applied to a shield construction for burying a sewer pipe having a small diameter of 500 mm, the sand pump 1 is installed at the bottom of the shaft and excavation is promoted. At this time, the sludge water sent from the excavation head side (not shown) is sucked from the small-diameter pump suction port 10 by the rotational centrifugal force of the sludge impeller 13, and the front shroud 20 of the sludge impeller 13 is moved. Through the flow path between the blades 21 from the suction opening 19 to the outer peripheral side, and is lifted from the discharge port 11 on the outer peripheral side of the pump casing 8.

In the pump casing 8, since the suction port 10 has a small diameter, if the suction force is increased, cavitation may occur. Since the water hole 25 is formed through the suction casing 7 and the suction impeller 14 located on the rear side, a part of the pneumatic sludge water is sucked, so that cavitation due to a local pressure drop can be prevented. Moreover, suction impeller 1
4 also sucks the sludge water, so that the impeller 13
The two-stage impeller of the suction impeller 14 and the suction impeller 14 make a system for sucking the sludge water, so that the suction capacity can be greatly improved. Therefore, a propulsion method without a shaft of 100 to 150 m, which could not be achieved by a conventional sand pump, is enabled.

Furthermore, since the bleed water passage 25 is formed in a long hole shape along the main wing 24 of the impeller 13 for drainage, it is continuously closed without being clogged by the gravel contained in the sludge water. Cavitation can be prevented from occurring.

On the other hand, on the suction impeller 14 side, the blade 30 has a shape in which the root side is inclined forward in the rotation direction, so that the sludge water suction capacity can be increased. Further, the pressure reducing blades 31 are provided on the back surface of the suction impeller 14 to reduce the load on the mechanical seal device, so that the durability of the mechanical seal 37 is also improved.

FIG. 9 is a rear view showing another embodiment of an impeller for drainage, and FIG. 10 is a side sectional view of the same. The drainage impeller 13 of this example includes front and rear shrouds 18 and 2.
0, and two S-shaped blades 21 interposed therebetween, each blade 21 having a short auxiliary wing 23 on the front side in the rotation direction,
And a long main wing 24 on the rear side. And
Of the rear shroud 18, a part of the drainage flow path between the main wing 24 and the auxiliary wing 23 and a part located on the back side in the rotation direction of the auxiliary wing 23 are cut out in a substantially V shape from the outer peripheral side to extract air. A hole 25 is provided. The area of the bleed water passage 25 occupies about １ ／ of the area of the flow passage through which the sludge water is drained. Other configurations are the same as those of the above embodiment.

In the above-described configuration, similarly to the above-described embodiment, the suction casing 7 and the suction impeller 14 located on the rear side pass through the bleed water hole 25 of the rear shroud 18 of the muddy impeller 13 to supply air. Since a part of the sludge water is sucked, the occurrence of cavitation due to a local pressure drop can be prevented. Moreover, since the sludge water is sucked also by the suction impeller 14, the sludge water is sucked by the two-stage impeller 13 of the sludge exhaust impeller 13 and the suction impeller 14, so that the suction capacity can be greatly improved.

FIG. 11 is an overall side sectional view of a vertical sand pump showing another embodiment of the present invention. In each of the above embodiments, the embodiment of the horizontal type sand pump is shown. However, the present invention is not limited to this, and the present invention can be applied to a vertical type sand pump, and the same operation and effect as the horizontal type sand pump can be obtained. Play. In this case, the sand pump 1 has a form in which a pump casing 8, a suction casing 7, a mechanical seal device 6, and a motor 3 are sequentially arranged from the pedestal 2 side, and the suction pipe 9 has a form curved in an elbow shape. I have. These and other functional components
Since the same operation and effect as those of the above embodiment are provided, the same reference numerals are given and the description thereof will be omitted.

[0042]

As is apparent from the above description, according to the present invention, a two-stage impeller of a drainage impeller and a suction impeller is provided to increase the suction capacity. The suction capacity can be improved, and cavitation can be suppressed by the bleeding water holes of the impeller for drainage.Moreover, since the bleeding water holes are formed in a long hole shape, the sand and gravel are mixed. Even if it is sludge water, there is an excellent effect that the bleed water passage can be prevented from being closed.

[Brief description of the drawings]

FIG. 1 is an overall side sectional view showing an embodiment of a suction sand pump of the present invention.

FIG. 2 is a front view of the same.

FIG. 3 is a front view of an impeller for drainage.

FIG. 4 is a side sectional view of the same.

FIG. 5 is a front view of a suction impeller.

FIG. 6 is a perspective view of the blade.

FIG. 7 is a sectional view of the same.

FIG. 8 is a rear view showing a decompression vane on the rear side of the same.

FIG. 9 is a rear view showing another embodiment of the impeller for drainage.

FIG. 10 is a side sectional view of the same.

FIG. 11 is an overall side cross-sectional view of a vertical sand pump showing another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Suction sand pump 5 Rotating shaft 6 Mechanical seal device 7 Suction casing 8 Pump casing 10 Suction port 11 Discharge port 13 Impeller for mud drain 14 Suction impeller 15 Bypass pipe 18 Rear shroud 20 Front shroud 21 Blade 23 Auxiliary wing 24 Main wing 25 Bleed air Water hole 28 Shroud 37 Mechanical seal

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F04D 7/04 F04D 9/04

Claims (4)

(57) [Claims] 1. A sand pump for draining sludge water mixed with gravel, comprising: a pump casing having a suction port formed at an axial end of a rotating shaft and having a discharge port on an outer peripheral portion; A sludge impeller fixed to a shaft, a suction casing adjacent to the pump casing on a side opposite to the suction port in an axial direction of the rotating shaft, and suctioning air-filled sludge water sucked into the pump casing. And a suction impeller fixed to the rotating shaft in the suction casing to prevent the occurrence of cavitation, and a bleed water passage for guiding a part of the sludge water to the suction casing side is provided. The suction impeller is formed on the rear shroud on the rear side of the impeller for drainage, and the plurality of blades are spirally formed on the front wall of the shroud. Each blade is formed to be curved in a convex shape on the front side in the rotation direction, and the root side is formed with the shroud.
Tilt forward in the direction of rotation in the range of 45-85 °
And the slope is gradually loosened toward the outer peripheral side.
Set so that the angle of intersection with the shroud is vertical on the side
It has been sand pump. 2. The shroud according to claim 2, wherein said impeller for sludge discharge includes front and rear shrouds.
Closed blade type with multiple blades arranged between
The bleed water hole is provided on the rear side of the drainage impeller.
Formed in the loud, and the size of the bleed water
The diameter of the gravel is larger than that of the
A number of blades are formed along the back of the blades in the rotation direction.
The sand pump according to claim 1. 3. The shroud according to claim 1, wherein the drainage impeller has front and rear shrouds.
And two S-shaped blades interposed therebetween.
The root is a short aileron on the front side in the rotation direction and a long main wing on the back side
And a main wing and a supplementary part of the rear shroud.
Part of the drainage channel between the ailerons and the direction of rotation of the aileron
The part located on the back side is cut out in a substantially V shape from the outer peripheral side
The sand pump according to claim 1, wherein the bleed water hole is provided. 4. The sand pump according to claim 1, wherein the inside diameter of the suction port is a small diameter of 30 to 150 mm.