JP3075625B2 - Method and apparatus for negative pressure suction blast of pipe inner surface - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for blasting the inner surface of a pipe, and more particularly, to a method of sucking a material to be blasted into a pipe to be blasted by negative pressure suction air and floating the inside of the blast pipe in negative pressure suction air. The present invention relates to a method and an apparatus for negative pressure suction blasting of the inner surface of a pipe for polishing, polishing or grinding the inner surface of a pipe to be blasted by a material to be blasted.

[0002]

2. Description of the Related Art Conventionally, there are a high-pressure injection blast method and a negative-pressure suction blast method as a blast method for polishing, polishing or grinding the inner surface of a pipe such as a drawn steel pipe.

A high-pressure injection blasting apparatus using the first conventional high-pressure injection blasting method will be described with reference to FIG.

As shown in FIG. 12, in a high-pressure injection blast apparatus of a first conventional example, a compressor 1 for injecting a polishing material and supplying high-pressure air to be conveyed, and a high-pressure air in the high-pressure air during high-pressure air conversion. Air / air that removes moisture from liquefied air
An abrasive material having a dryer 2, an abrasive material tank 3 for dropping and mixing an abrasive material into a high-pressure air flow, and a nozzle 4 for jetting the abrasive material and high-pressure air for floating and transporting the abrasive material. And the air injection unit 5 is connected to one end of the blast pipe 6,
At the other end of the blast pipe 6, a collection tank 7 that receives the polished material that has been cleaned, polished, or grounded on the inner surface of the blast pipe 6 and collects a part of the polished material, A cyclone 8 for separating granular abrasive material that has not been completely crushed after blasting, polishing, or grinding from the blast air, and a dust collector for separating blasted abrasive material or blast dust from the blast air. 9 and the abrasive material that has been cleaned, polished or ground, and the high-pressure air that floats and transports the abrasive material.
And a blower 10 for sucking air from the recovery tank 7 through the dust collector 9 and sending air from which the abrasive material and abrasive dust have been removed to a silencer 11 for discharge.
An air outlet 12 is connected.

Prior to the description of the operation, general common basic items will be described.

[0006] First, blasting means removing scale from the inner surface of general steel pipes, oil country tubular goods, and other special pipes. Various abrasives are used as blasting materials.

Polishing refers to polishing of the inner surface of a stainless steel tube, aluminum tube, copper tube or the like, and various types of bead materials are used as a polishing material.

[0008] Grinding is to grind the inner surface of a thick steel pipe, special pipe, or the like, and uses a hard abrasive as a polishing material.

[0009] The wind speed of the air flow for transporting the blasting material in the blasted pipe is at least about 60 m / sec to at most 250 m / sec. The speed of the conveyed abrasive differs depending on conditions, but its maximum speed reaches the same speed as the wind speed.

[0010] The unit volume air flow mixed with the abrasive material is
The upper limit of the amount that the abrasive can be suspended and transported in the blasted pipe is mainly determined by the wind speed of the air flow, and although there are some fluctuations due to the specific gravity of the abrasive and the size of the granules, the volume ratio (solid Gas ratio), abrasive material / air (solid-gas ratio) = 1 /
About 1,000 is the upper limit.

The mixing amount (solid-gas ratio) of the abrasive to the air flow is
Depending on the purpose (whether polishing, polishing or grinding), it depends on the manufacturing method, material, inner diameter and length of the blasted tube, about 1/1000
About 1/20000 is used, but the upper limit
The closer to 1000, that is, the greater the solid-gas ratio, the better the efficiency of polishing, polishing or grinding.

When the solid-gas ratio is small, the abrasive material is uniformly dispersed or floated in the air stream, becomes a uniform stream, and is easily suspended and conveyed. When the cleaning material easily flows into the bottom of the pipe flowing near the bottom of the pipe (it is also called a linear flow because the trace of polishing, polishing or grinding becomes linear), and when the solid-gas ratio increases, the bottom flow of the pipe causes a pulsation phenomenon. This causes a sparse / dense change in the flow direction in the pipe bottom flow, resulting in a sparse / dense flow.

In the case of a uniform flow, the inner surface of the pipe is uniformly cleaned,
Polishing or grinding occurs only when the amount of the polishing material is very small, and it takes a long time for polishing, polishing or grinding.

In the case of the pipe bottom flow, as a general phenomenon of the air flow in the pipe, when the velocity becomes higher than the turbulence critical velocity, the laminar flow becomes turbulent through the turbulence advance section, and the spiral swirling flow As the abrasive material progresses, the abrasive material spirals on the inner surface of the pipe by centrifugal force, moves while scavenging, polishing or grinding due to the synergistic effect of speed and centrifugal force, and turbulent flow is stable in turbulent state When the material flows, the trajectory of the blast material becomes constant, and the trace of lapping, polishing or grinding becomes a helical linear shape (thus, in order to uniformly blast, polish or grind the entire inner surface of the pipe) Requires rotating the blasted tube about its axis, as described below.)

In the case of the sparse / dense flow, the speed is slow in the dense portion, and a clogged state is apt to occur, so that it is difficult to use for lapping, polishing or grinding.

Next, the operation of the first conventional high-pressure injection blasting apparatus will be described with reference to FIG.

First, based on the manufacturing method, material, inner diameter and length of the blasted tube 6 and the specifications of the polishing, polishing or grinding,
The air flow of the air flow (determined from the required wind speed and the inside diameter of the pipe, and if the air flow is at least equal to this value, the object can be achieved.)
Working conditions such as the type and amount of the abrasive material are determined. Normally, small-diameter pipes have a small air volume and high pressure, medium-diameter pipes have a medium air volume and medium pressure,
The large-diameter pipe has a large air volume and low pressure, and the static pressure is within 10 kg / cm2 for high-pressure injection (-1 kg / cm2 for negative pressure suction).
Within 2), set the static pressure to secure the air volume.

The type and amount of the abrasive material are determined by the above-mentioned general common basic matter, and a granular abrasive material having a diameter of about 1 mm to 3 mm such as garnet, alumina, sand or the like is used.
Usually, the working conditions are determined empirically, test blasting is performed under the working conditions, the working conditions are modified,
Determine the working conditions that will actually be used.

When the working conditions are determined, the compressor 1 is operated in accordance with the working conditions, and the generated water in the high-pressure air is removed by the air dryer 2 (to prevent the inner surface of the pipe from being corroded by the water). A predetermined abrasive material is dropped and supplied from the abrasive material tank 3 into the high-pressure air, and a predetermined amount of the high-pressure air is blown from the nozzle 4 through the nozzle 4 while floating and transporting the predetermined amount of the abrasive material per unit volume. It is injected into the tube 6. Abrasive materials suspended and transported in high-pressure air are:
While the inner surface of the pipe is being polished, polished or ground, it reaches the other end of the blasted pipe 6 and squirts into the recovery tank 7 together with high-pressure air. Is collected here. The air containing the crushed abrasive material and the abrasive dust is sucked into the blower 10, and the relatively large crushed abrasive material and the abrasive dust are separated by the cyclone 8, and the small crushed abrasive material and the abrasive dust are removed. Debris is separated by a dust collector 9 and discharged to the atmosphere via a blower 10 and a silencer 11.
However, as described above, since the inside of the blasted tube 6 is polished, polished, or ground only linearly, the blasted tube 6 is rotated about its axis to uniformly blast, polish, or grind the inner surface of the tube. Need to grind.

The change in the static pressure of the high-pressure air in the case of the high-pressure injection blast device is shown in the lower part of FIG.

[0021]

However, in the configuration of the first conventional high-pressure injection blast device, the high-pressure air is
The nozzle 4 is blown into the blast pipe 6 at a speed higher than the turbulent flow critical velocity. However, as shown in FIG. After passing the laminar basin, turbulence occurs. For this reason, in this laminar flow region, the abrasive cannot polish, polish, or grind the inner surface of the blast pipe 6, and the polish, polish, or grind effect becomes zero. The turbulent flow approach zone passes and becomes a turbulent flow area, and after the synergistic effect of the speed and the centrifugal force is generated, the polishing, polishing or grinding effect is generated. Therefore, the high-pressure injection blast apparatus has a first problem that the end of the blast pipe 6 cannot be ground, polished or ground.

Further, in the turbulent flow region, since the wind speed of the high pressure air is not uniform in each section of the blast pipe 6, the abrasive material is drawn to the position where the wind speed of the high pressure air is highest in the cross section of the blast pipe 6. Move fast. As a result, the abrasive material gathers at one location in the cross section and proceeds as a spiral swirling flow, and advances along the inner surface of the blast pipe 6 by the action of the centrifugal force. Therefore, as described above, the inner surface of the blasted tube 6 becomes a tube bottom flow (linear flow) in which the inner surface of the blasted tube is polished, polished, or ground in a spiral linear shape in the longitudinal direction. Therefore, there is a second problem that it is necessary to rotate the blast pipe 6 about its axis in order to clean, polish or grind the entire inner surface of the blast pipe 6.

In particular, in the high-pressure injection blasting apparatus, when the inner diameter of the blasted pipe 6 is large, the wind speed at the end side of the blasted pipe is reduced to a value lower than the wind velocity at which blasting, polishing or grinding can be performed. There is a third problem that polishing or grinding becomes impossible and uniform polishing, polishing or grinding cannot be performed only by rotating the blast pipe 6.

As a countermeasure, in the high pressure injection blast device of the second conventional example, as shown in FIG.
Is connected from one end to the other end of the large-diameter blasted tube 6 ′, and the abrasive is floated from the multiple injection hole nozzles 14. The high pressure air to be conveyed is ejected while being ejected, and the inside of the large-diameter blasted tube 6 'is cleaned, polished or ground.
However, even in this case, since only a plurality of linear blasting, polishing, or grinding can be performed, the large-diameter blasted pipe 6 'is rotated to uniformly clean, polish, or grind the inner surface of the large-diameter blasted pipe 6'. A complicated and inefficient way of doing so. In this case, the high-pressure injection blasting device becomes complicated and expensive, and the working efficiency is poor. In order to insert and withdraw the small-diameter tube 13 for insertion, the length of the large-diameter blasted tube 6 ′ is 2 mm.
There is a fourth problem that double space is required.

Further, the high-pressure injection blast device has a basic problem concerning the solid-gas ratio of the next abrasive material. That is, when the abrasive is mixed with the high-pressure air, the upper limit amount of the high-pressure air that allows the abrasive to be suspended and conveyed is, as described above, about the abrasive / air = 1/1000 in volume ratio. Even if the upper limit amount of the abrasive material is mixed into the high-pressure air, the high-pressure air is injected into the blast pipe 6 after being mixed, and the high-pressure air expands and decompresses there and increases in volume. The amount of abrasive material per unit volume of air in the interior (solid-gas ratio) becomes very small in inverse proportion to the expansion, and accordingly, the effect of the abrasive, polishing or grinding decreases, Alternatively, there is a fifth problem that grinding requires a long time.

Further, the high-pressure injection blast apparatus has a basic problem concerning the following turbulence. That is, since the high-pressure air is injected from the nozzle 4 into the blast pipe 6, it is difficult to make the flow of the high-pressure air carrying the abrasive material turbulent on the injection side. Blast tube 6
Has a sixth problem in that it is jetted as a laminar flow, and the jet-side end cannot be cleaned, polished, or ground.

Next, a negative pressure suction blast apparatus using the negative pressure suction blast method of the third conventional example will be described with reference to FIG.

As shown in FIG. 14, a conventional negative pressure suction blasting method (a method for blasting the inner surface of a pipe: Japanese Unexamined Patent Publication No.
In the third prior art negative pressure suction blasting device using the air suction device 29 incorporating a filter 32, the blasted material after the blasting is separated from the carrier air and accumulated in the accumulation tank 36. The blast pipe A is connected to one end of the blast pipe A by a pipe mounting part 33 via an air suction pipe 30 and an air suction pipe 30, and the abrasive material transport pipe 21 is connected to the other end of the blast pipe A through a nozzle 23. Pipe fitting 28
The air supply pipe 27 for supplying the negative pressure suction air sucked by the air suction device 29 for transporting the abrasive material to the blast pipe A is connected to the abrasive material transport pipe 21. ing. Further, above the air supply pipe 27, a hopper 24, an abrasive cleaning material outlet 25, and a regulating valve 26
Is provided.

Next, the operation of the negative pressure suction blast device of the third conventional example will be described with reference to FIG.

In FIG. 14, first, based on the manufacturing method, material, inner diameter and length of the blast pipe A, and the specifications of the blasting, polishing or grinding, the air flow rate of the negative pressure suction air (from the required wind speed and the inner diameter of the pipe). It is possible to achieve the purpose if the air flow rate is equal to or more than this value.), The negative static pressure (within -1 kg / cm2), and the working conditions such as the type and amount of the abrasive material. Normally, small-diameter pipes have a low air volume and high pressure, medium-diameter pipes have a medium air volume and medium pressure, and large-diameter pipes have a large air volume and low pressure. I can decide.

When the working conditions are determined, the air suction device 29 is operated according to the working conditions, and the generated negative pressure suction force is applied to the separator 31, the air suction pipe 30, the blast pipe A, the nozzle 23, the abrasive material, and the like. A predetermined amount of negative pressure suction air for transporting the abrasive material is sucked from the air supply pipe 27 via the transport pipe 21. In this state, a predetermined polishing material from the cleaning material supply unit 22 falls in front of the air supply pipe 27, where it mixes with negative pressure suction air, and from there, the air suction device 29.
The air is conveyed by being floated by negative pressure suction air toward.

The maximum speed of the abrasive material suspended and transported by the negative pressure suction air is the same as the wind speed of the negative pressure suction air in the blast pipe A (minimum 60 m / sec to maximum 250 m / sec). And the inner surface of the blast pipe A is polished, polished or ground.

The abrasive material suspended and transported by the negative pressure suction air reaches the other end of the blast pipe A while cleaning, polishing or grinding the inner surface of the pipe, and finishes the cleaning, polishing or grinding. Most of the blasted, polished or ground blasted material is separated from the negative pressure suction air by a separator 31 through an air suction pipe 30 and the blasted material after the polishing, polishing or grinding is filtered by a filter 32 in an air suction device 29 under a negative pressure. Removed from suction air. The negative-pressure suction air from which the abrasive material and the abrasive dust after the blasting, polishing or grinding are removed is discharged from the air suction device 29 into the atmosphere.

In the negative pressure suction blast device of the third conventional example, since the air velocity in the blast pipe is formed by suction of the air suction device 29, even if the blast pipe is a large-diameter pipe, the wind velocity in the pipe decreases. And the polishing, polishing or grinding effect can be maintained over the entire length from the ejection end to the suction end. Therefore, the third and fourth problems of the high-pressure injection blast device can be solved. Further, when a predetermined abrasive material from the abrasive material supply unit 22 is mixed with the negative pressure suction air in front of the air supply pipe 27 to a maximum amount at which the negative pressure suction air can float and transport the cleaning material. As a feature of the negative pressure suction blast device,
The negative pressure suction air sucked by the air suction device 29 changes the wind speed at the mixing position of the abrasive material to the blast pipe A.
(The inner diameter of the device at the mixing position of the blasting material is made closer to the inner diameter of the blasted tube.) Therefore, the static pressure during mixing of the blasting material and passing through the blasted tube A is reduced. The change is very small compared to the case of the high-pressure injection blasting device, and the negative pressure suction air is suspended and transported as it is in the blasted pipe A, and the abrasive material mixed to the upper limit amount that can be transported while floating is transported. Can be well ground, polished or ground. Therefore, in the case of the high-pressure injection blasting device, the fifth problem that the polishing, polishing or grinding takes a long time due to the decrease in the solid-gas ratio can be solved.

However, the negative pressure suction blast device of the third conventional example cannot solve the sixth problem in the case of the high pressure injection blast device.

The present invention solves the sixth problem of the high-pressure injection blast device described above, thereby solving all the problems of the conventional high-pressure injection blast device and the conventional negative pressure suction blast device. An object of the present invention is to provide a pressure suction blast method and an apparatus therefor.

[0037]

In order to solve the above-mentioned problems, a negative pressure suction blasting method according to the present invention comprises connecting a negative pressure suction part to one end of a blast pipe and connecting the other end of the blast pipe to the other end. The lower part has a horizontally extending cylindrical space that communicates with the atmosphere.
The air supply section is connected to form a downwardly directed negative pressure suction airflow in the air supply section, and the downwardly-pumped negative pressure suction airflow is cleaned in a direction deviated from the axis of the air supply section. By dropping the material, a downwardly directed suction air flow with the abrasive is formed, and a small amount of the suction air flow with the abrasive is entrained.
At least partly along the cylindrical inner wall of the air supply
The negative of the abrasive material-assisted negative pressure suction air flow is guided in an upward direction and connected to a horizontally extending connection portion of the air supply portion connected to the blast pipe arranged in the horizontal direction of the air supply portion. A suction suction swirl flow is formed, and the negative pressure suction unit sucks the polishing material-assisted negative pressure suction air flow into the blasted tube under a negative pressure, and the negative pressure suctioned abrasive material entrained air flow causes the inside of the blasted tube to flow. Vacuuming the inner surface of the pipe, comprising the steps of: cleaning the surface and sucking out the air flow after the polishing from the blast pipe that accompanies the polished material after the polishing and the blast waste generated from the blast pipe. A blast method is provided.

Preferably, the method further comprises a step of turbulating the air flow with the turbulent flow means before introducing the abrasive material entrained negative pressure suction air flow into the blast pipe. The turbulence generating means may be constituted by means for moving a supply position of the cleaning material to the air flow when forming the cleaning material entrained negative pressure suction air flow. Further, it may be constituted by means for moving the position of the air supply unit when forming the abrasive material entrained negative pressure suction air flow. Alternatively, a plurality of openable and closable air inlets provided in the air supply unit and located on the side of the downwardly-moving air flow accompanying the abrasive may be selectively opened and closed. Further, the air supply section may be formed by forming a bulging portion for guiding a part of the downwardly directed suction air flow accompanied by the abrasive material in a direction opposite to the blast pipe.

Further, it can be constituted by a baffle provided in an air supply section connected to the blast pipe arranged horizontally. In this case, it is preferable that the length of insertion of the baffle projection into the abrasive material entrained negative pressure suction airflow is adjustable. Preferably, the baffle is provided so as to obstruct the upward flow of the abrasive material entrained negative pressure suction air in the air supply section. Further, it is also possible to provide such that the obstructing projection obstructs the horizontal flow of the abrasive material entrained negative pressure suction airflow toward the blast pipe.

In a preferred embodiment, a reusable abrasive is recovered. It is preferable that a gradient pipe is connected to the blast pipe connection part of the air supply unit to increase the flow rate of the abrasive material negative pressure suction airflow introduced into the blast pipe. Preferably, the speed of the negative pressure air flow accompanied by the abrasive in the blast pipe is 60 m / sec to 250 m / sec.
The abrasive material of the negative pressure air flow accompanied by the abrasive material in the blasted pipe /
Preferably, the volume ratio of air is about 1/1000 or less.

According to another feature of the present invention, a negative pressure suction unit connected to one end of the blast pipe arranged in a horizontal state, and air released to the atmosphere connected to the other end of the blast pipe. The supply section and the negative pressure suction action of the negative pressure suction section supply a polishing material to the air flow flowing downward in the air supply section to form a polishing material accompanying negative pressure suction air flow. A polishing material supply means and a cylindrical space which is open to the atmosphere and is horizontally extended and connected to the other end of the blasted pipe are provided below.
The air supply unit provided in the air supply unit, and the negative pressure suction action of the negative pressure suction unit supplies the abrasive material to the airflow flowing downward in the air supply unit to supply the abrasive material-assisted negative pressure suction air. Abrasive supply means for forming a flow, and a negative pressure suction accompanying the abrasive
At least a part of the drawing air flow is cylindrical in the air supply section.
And guide means for guiding upward along the inner wall, the bottom of the cylindrical space of the air supply provided continuously, and abrasive cleaning agent entrained negative pressure suction air flow toward the downwardly in the horizontal direction A connecting portion for connecting the blast pipe and the air supply section so as to be introduced into the blast pipe with a negative pressure suction swirling flow, and by a negative pressure suction action by the negative pressure suction section, A negative pressure suction blasting device is provided, in which a negative pressure suction air flow accompanied by a cleaning material is introduced into the blast pipe from the air supply section in a turbulent state, and the inner surface of the blast pipe is blasted by the cleaning material.

[0042]

According to the negative pressure suction blast method of the present invention, in the flow of the abrasive material supplied from above in the air supply section and supplied in the downward air flow, the negative pressure suction blast flows into the blast pipe from the air supply section. By making the flow of the cleaning material before pressure suction and the negative pressure suction air accompanying or floating the conveyed material into a flow including a negative pressure suction swirling flow or a turbulent state, the cleaning material and the The negative-pressure suction air to be conveyed in a floating state is transmitted from the air supply unit to the blast target with a negative-pressure suction swirling flow or in a turbulent state, regardless of the number of Reynolds nozzles (or turbulent flow critical velocity). Since the negative pressure suction is introduced into the pipe, the inside of the pipe to be blasted can be uniformly and efficiently polished, polished, or ground throughout the polished material.

Further, the negative pressure suction blast device of the present invention comprises:
By providing turbulence means in the air supply unit for disturbing the downwardly directed abrasive material entrained negative pressure suction airflow, the abrasive material before the negative pressure suction from the air supply unit into the blasted tube and the entrained material, The flow with the negative pressure suction air to be floated and conveyed can be in a state having a negative pressure suction swirl flow or a turbulent state, and the negative pressure suction air flow accompanying the abrasive material is formed into a negative pressure suction swirl flow. Negative pressure suction from the air supply unit into the blast pipe in a turbulent state or in a turbulent state, so that the inside of the blast pipe is uniformly and efficiently cleaned from the ejection end to the suction end of the abrasive material,
It becomes possible to polish or grind.

Further, if turbulence generating means comprising a baffle protrusion is provided, the turbulence is promoted by obstructing the flow of the negative pressure suction air and the abrasive material.

Further, when turbulence means including a plurality of air inlets are provided, a plurality of negative pressure suction air flows which have flowed in interfere with each other to promote turbulence.

If a turbulence generating means comprising an air inlet which moves with time is provided, the negative pressure suction air flow becomes turbulent.

Further, if turbulent flow means comprising an abrasive material drop supply port which moves with time are provided, the position at which the abrasive material is entrained, that is, floated and conveyed by the negative pressure suction air changes, and Becomes turbulent.

Further, if turbulence generating means comprising an eccentric abrasive material dropper for dropping the abrasive material in a direction deviated from the axis of the air supply part is provided, the dropped abrasive material is coated on the inner wall of the air supply part. Turbulence while rotating along.

Further, when turbulence generating means comprising an inflated portion is provided in a direction opposite to a connecting direction of the blast pipe of the air supply portion,
After drawing the negative pressure suction air and a part of the abrasive material flowing into the air supply unit at negative static pressure into the negative static pressure of this bulging part, make it face the connection direction of the blast pipe. Turbulent.

When a gradient pipe whose inner diameter is reduced in the direction of the blast pipe is provided at a connection portion of the air supply section with the blast pipe, the flow of the negative pressure suction air and the abrasive material is increased in the gradient pipe. However, when the critical velocity causing turbulence is exceeded, the abrasive material and the negative-pressure suction air that floats and conveys the abrasive material in the blast pipe are likely to become turbulent.

[0051]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a negative pressure suction blast apparatus using the negative pressure suction blast method of the present invention will be described with reference to FIGS.

In FIG. 1, the negative pressure suction blasting apparatus of the present embodiment comprises, at one end of a blast pipe A, a blasting material which has been polished, polished or ground on the inner surface of the blast pipe A, and the blasting material. A receiver box X that receives the negative pressure suction air for floating and transporting the material, and separates the blasted air from the blasted air that has not been completely crushed after the polishing, polishing, or grinding, and
A receiver for removing the abrasive material separated by the receiver box X (returns the abrasive material to the abrasive material tank 50, not shown) for carrying out the abrasive material separated from the abrasive material; 51, a cyclone 51 and a dust collector 52 for separating air and negative pressure suction air, an abrasive material after polishing, polishing or grinding, and negative pressure suction air for floating and transporting the abrasive material. From the receiver box X, the cyclone 51, and the dust collector 52, and air suction means 53 for sending air from which abrasive material and abrasive dust have been removed to a silencer 54 for discharge. The suction section C is connected, and the other end of the blast pipe A is connected to the air supply section B for supplying the abrasive material and the negative pressure suction air for floating and transporting the same into the blast pipe A. In this air supply part B, D, the air suction by the negative pressure suction section C and the turbulence of the turbulence generating means D cause the air supply section B to remove the abrasive material and the negative pressure suction air for floating and transporting the same. Is blown into the blast pipe A in a turbulent state, and the blasted pipe A is blasted, polished or ground by the blast material conveyed while being suspended in the negative pressure suction air. The part C sucks and discharges the blasted material, the negative pressure suction air, and the blasted, polished or ground debris after the blasting, polishing or grinding from the blast tube A. In this case, the turbulence generation means D controls the air flow supplied into the air supply section B and / or
Alternatively, by disturbing the flow of the cleaning material, the flow of the cleaning material immediately before being ejected into the blast pipe A and the flow of the negative pressure suction air that floats and conveys the material are turbulent in the cleaning material / air supply unit B. The blasting material and the negative pressure suction air for carrying the material in a suspended state are ejected from the air supply unit B into the blast pipe A in a turbulent state.

The change in the negative static pressure of the negative pressure suction air of the negative pressure suction blast device is shown in the lower part of FIG.

FIG. 2 is a detailed view of the air suction means 53 of FIG.

Using one negative pressure suction blast device of this embodiment, one blast tube A from a small diameter tube (small air amount high pressure) to a large diameter tube (large air amount low pressure) or In order to blast the plurality of tubes at the same time, it is necessary to arbitrarily set the range of the air volume and the negative static pressure of the negative pressure suction air of the air suction means 53 over a wide range. For that purpose, it is effective to use a turbo blower for large air volume and low pressure and a vacuum blower or vacuum pump for small air volume and high pressure as the air suction means 53 alone or in various combinations.

In FIG. 2, two turbo blowers 55,
The on / off valves 59, 60, 61, 62 can be used or stopped one by one, two in parallel, and two in series. FIG. 3 shows the operating characteristics in this case.

FIG. 3 shows one turbo blower alone,
Air volume (m3 / mi) when two units are used in parallel and two units are used in series
n) and the relationship between negative static pressure (-mmHg). In FIG. 3, the air flow from 0 to the maximum value cannot be used in a surging area because surging occurs when used in a negative pressure suction blast device. In the case of using two units in parallel, the surging area is eliminated, and in the case of using two units in series, the surging area becomes narrow. In addition to these effects, in this embodiment in which one unit is used alone, two units are arranged in parallel, and two units are used in series, the range of the negative air suction air volume and the negative static pressure of the air suction means 53 is set very wide. it can. Accordingly, one or many of the large-diameter pipes and the medium-diameter pipes can be blasted under appropriate conditions.

In this case, the turbo blowers 55, 5
No. 6 must be capable of operating at the same pressure.

In FIG. 2, the two vacuum blowers or vacuum pumps can be used or stopped one by one or two in parallel by the on-off valves 63 and 64. Since vacuum blowers and vacuum pumps have a negative static pressure limit of -760 mmHg, it is not necessary to use them in series.

FIG. 4 shows the operating characteristics in this case.

FIG. 4 shows a vacuum blower or a vacuum pump,
Air volume when using one unit alone and two units in parallel (m3 /
min) and the negative static pressure (-mmHg). In the case of a vacuum blower or a vacuum pump, since there is no surging region, it is possible to cope with a considerably high pressure and a small air volume. Therefore, one or many of the small-diameter pipes and the medium-diameter pipes can be blasted under appropriate conditions.

In this case, the vacuum blowers or the vacuum pumps 57 and 58 need not be capable of operating at the same pressure.

In the parallel operation, the turbo blower 55 or 56 and the vacuum blower or vacuum pump 57 or 58,
There are combinations of the turbo blowers 55 and 56 and the vacuum blowers or vacuum pumps 57 and 58, the series of the turbo blowers 55 and 56, and the vacuum blowers or the vacuum pumps 57 and 58 alone or in parallel. Becomes wider. In this case, it is not necessary that the turbo blower and the vacuum blower or the vacuum pump can operate at the same pressure.

The on-off valves 59 and 60 can have a damper function in addition to the function of the on-off valves.

The air in each circuit is silencer 56,
It is discharged to the atmosphere via 57, 58, 59.

FIGS. 6 to 8 are detailed views of the turbulence generating means D of FIG. Next, the details of the abrasive material / air turbulence generator D will be described.

In FIG. 6, at one end of the blasted tube A,
A gradient pipe F whose inner diameter is reduced in the direction of the blast pipe A is attached, and an inner diameter d '(about 1.5 times the inner diameter d of the blast pipe A) is attached to the gradient pipe F. In order to reduce the change in wind speed in the supply section B and in the blast pipe A, the inner diameter d 'is better as close to d.) And the length S is about 6 times the inner diameter d. An air supply section B is connected, and an expansion section H is provided at the rear end of the air supply section B in a direction opposite to the connection direction of the blasted tube A. An eccentric material dropping port P for dropping the blast material K in a direction deviated from the axis of the portion B is provided. An opening J leading to the inside of B is provided as a rectangular opening long in the axial direction of the air supply unit B, and the cleaning material K received in the opening J is supplied with air. Falls along the inner wall of the B, and is conveyed suspended in the negative pressure suction air rises to the upper along its inner wall.

The baffle protrusion I is provided at this raised position. The combination of the eccentric falling port P and the opening J has a clockwise rotation and a counterclockwise rotation. Further, a baffle projection E is provided inside the front end of the opening J so that the eccentric material dropping port P reciprocates back and forth along the opening J. Further, the insertion length of the baffle protrusions I and E is made variable.

In FIG. 7, at least one opening / closing air inlet N which repeats opening / closing with time is provided on the side surface of the air supply section B. In the case of a plurality of such cases, it is the same as providing a negative pressure air inlet which moves with time.

In FIG. 8, an air inlet M is provided at the rear end of the air supply section B.

Next, the operation of the turbulence generating means D shown in FIGS. 6 to 8 will be described.

In FIG. 6, since the inner diameter of the gradient pipe F is reduced in the direction of the blast pipe A, the speed of the negative pressure suction air sucked by the negative pressure suction section C increases in the gradient pipe F. Then, exceeding the critical velocity causing turbulence, the abrasive material K and the negative pressure suction air that floats and conveys the abrasive material K in the blast pipe A easily become turbulent.

The bulging portion H provided at the rear end of the air supply portion B in the direction opposite to the connection direction of the blast pipe A flows into the inside of the air supply portion B under negative pressure. A part of the flow of the negative pressure suction air and the cleaning material K is once drawn into the negative pressure of the bulging portion, and then turbulently flows toward the connection direction of the blast pipe A to form the blast material K. And the negative pressure suction air carrying the same are brought into a turbulent state. In addition, the polishing material K may accumulate below the bulging portion H. To prevent this, the inclined plate G
Should be provided.

In addition, the eccentric falling port P for the abrasive material is
The abrasive material K is dropped on the air supply unit B in a direction deviated from the axis of the air supply unit B, and the dropped abrasive material K rotates along the inner wall of the air supply unit B. Then, the negative pressure suction air to be conveyed is easily turbulent.

Further, an eccentric material dropping port P for dropping the abrasive material K in a direction deviated from the axis of the air supply section B, and an abrasive material falling from the eccentric material dropping port P The rectangular opening J that is long in the axial direction of the air supply unit B that receives the K, the dropped abrasive material K rotates along the inner wall of the air supply unit B and becomes turbulent. The negative pressure suction air to be conveyed while floating is brought into a turbulent state.

Further, the baffle protrusions I and E obstruct the flow of the abrasive material K and the negative-pressure suction air for suspending and transporting the abrasive material K to form a turbulent flow. The transported negative pressure suction air is brought into a turbulent state. The baffle may be provided anywhere in the air supply unit B. For example, it may be provided in the gradient tube F or at an end thereof.

In addition, reciprocating the eccentric falling port P of the abrasive material back and forth along the opening J means that the abrasive material K always moves along the trajectory in which it is suspended and transported in the negative pressure suction air. -It is effective to uniformly clean, polish or grind the entire surface of the blast tube A because it is changed.

The provision of at least one open / close air inlet N which repeats opening and closing with time on the side surface of the air supply unit B and the provision of an air inlet M at the rear end of the air supply unit B are as follows. Creating a negative pressure suction air flow in various directions in the air supply unit B to turbulence the entire negative pressure suction air flow, or
The plurality of negative pressure suction air flows interfere with each other and turbulence the entire negative pressure suction air flow.

The turbulence generating means D of the present invention is not limited to the structure of the above-described embodiment, and various forms are possible as long as the blasting material K and the negative pressure suction air carrying it can be turbulent. And can be designed freely.

FIGS. 9 to 11 are detailed views of the receiver box X of FIG.

Using one negative pressure suction blasting apparatus of this embodiment, one blast pipe A from a small diameter pipe (small air volume and high pressure) to a large diameter pipe (large air volume and low pressure) is used. In order to simultaneously blast the plurality of tubes, it is necessary to be able to arbitrarily set the range of the air volume and the negative static pressure of the negative pressure suction air of the air suction means 53 as described above, The negative pressure suction force is simultaneously applied to one or more of the blast pipes A from the small diameter pipe (small air amount high pressure) to the large diameter pipe (large air amount low pressure), and the abrasive material is also cleaned. And a negative pressure suction air for transporting the same, a polishing material is collected, and a receiver box X for discharging the negative pressure suction air to the atmosphere is required.

FIG. 9 shows that the negative pressure suction force of the air suction means 53 is simultaneously applied to each of the blast pipes A from the small diameter pipe (small air amount high pressure) to the large diameter pipe (large air amount low pressure). Or a receiver box X acting on a plurality of them,
FIG. 4 is a detailed view of an abrasive-cleaning material discharging means Y for discharging the separated abrasive material from a receiver box X;

In FIG. 9, the receiver box X is
The receiver box X is connected to the blast pipe A, and transmits the abrasive material K and the negative pressure suction air for floating and transporting the material.
A plurality of dummy pipes 70 having discharge holes 69 for discharging downwards (the inner diameter of the dummy pipes 70 is 1.5 to 2 times the inner diameter d of the blast pipe A) and a first-stage box. 71, a skirt 74 of the first-stage box 71,
It has a second-stage box 72, a skirt 75 of the second-stage box 72, and a connection pipe 73 that connects the upper end of the first-stage box 71 to the dust collector 52.
Is the abrasive material K separated and accumulated in the second-stage box 72.
A screw conveyor 76 for unloading from the lower end of the second-stage box 72, a hopper tank 77 for storing the abrasive material K unloaded by the screw conveyor 76, a bypass tank 79 connected to the hopper tank 77 via an on-off valve 78, It has a bypass tank 79 and an on-off valve 80 provided between the atmosphere.

The above-mentioned plurality of dummy pipes 70 correspond to FIG.
As shown at 0, they are arranged horizontally side by side.

The operation of the receiver box X is shown in FIG.
It will be described based on. The abrasive material K, which has been cleaned, polished or ground in the blast pipe A, and the negative pressure suction air for floating and transporting the same, are provided with the discharge holes 69 of the plurality of dummy pipes 70.
At the same time, the speed is suddenly reduced, the power for transporting the abrasive material of the negative pressure suction air is lost, and the abrasive material K which is still in a granular form and can be reused is removed. Partly,
It falls to the lower part of the second stage box 72. Since the negative pressure suction air is discharged downward from the discharge hole 69 in the vertical center axis of the first stage box 71 and the second stage box 72, the negative pressure suction which has lost most of the cleaning material K is described. The air rises along the side surfaces of the second box 72 and the first box 71. A skirt 75 of the second-stage box 72 is provided on the upper side surface of the second-stage box 72, and most of the abrasive material K remaining and conveyed in the negative-pressure suction air is supplied to the skirt of the second-stage box 72. 75 second stage box 7
Fall to the bottom of 2. Next, the negative-pressure suction air from which the cleaning material K has been separated twice rises along the side surface of the first-stage box 71. A skirt 74 of the first-stage box 71 is provided on the upper side surface of the first-stage box 71, and most of the abrasive material K remaining and conveyed in the negative-pressure suction air is removed from the first-stage box 71. It is blocked by the skirt 74 and falls to the lower part of the second step box 72. When the negative-pressure suction air reaches this position, almost all of the cleaning material K in the negative-pressure suction air falls to the lower part of the second-stage box 72, and the cleaning material K, which has been finely divided into dust, and the cleaning material K Only the debris is conveyed to the negative pressure suction air and sent to the cyclone 51.

In this case, as shown in FIG. 10, when the number of dummy pipes 70 arranged horizontally and horizontally is increased and the first-stage box 71 is widened, the dummy pipes arranged at both ends are increased. There is a difference between the negative pressure suction force acting on the blast pipe A connected to 70 and the negative pressure suction force acting on the blast pipe A connected to the dummy pipe 70 arranged at the center. . To prevent this,
As shown in FIG. 11, a separate plate 81 is provided in the first-stage box 71 to form a separate first-stage box 71 '. At the top of each of the separated first-stage boxes 71 ',
A connection tube 73 to the cyclone 51 is connected.

The abrasive material K accumulated in the lower part of the second-stage box 72 is carried out by the next abrasive material carrying means Y.

In the abrasive material discharging means Y, the abrasive material K stored in the receiver box X is transferred to the screw conveyor 7.
At 6, it is carried out to the hopper tank 77. When the polishing material K is accumulated in the hopper tank 77 by a certain amount or more, the on-off valve 80
Is closed, the on-off valve 78 is opened, the abrasive material K in the hopper tank 77 is transferred to the bypass tank 79, and the on-off valve 78 is closed. During this time, the hopper tank 77 continuously receives the abrasive material K carried out by the screw conveyor 76. The cleaning material K that has moved to the bypass tank 79 is opened into the atmosphere by opening the on-off valve 80. In this way, the polishing material K can be continuously collected while the negative pressure suction blast device is continuously operated. Although this collected abrasive material K is not shown,
It is sent to the abrasive material tank 50 and reused.

As described above, the negative pressure suction blast device of this embodiment is one unit and is one of the blast pipes A from the small diameter pipe (small air amount high pressure) to the large diameter pipe (large air amount low pressure). Not only can one or a plurality thereof be simultaneously and continuously blasted, but also the entire surface from end to end in the blasted tube A can be rapidly and uniformly blasted.

[0090]

According to the present invention, in the flow of the blast material supplied from above in the air supply section and supplied in the downward air flow, negative pressure suction is performed from the air supply section into the blast pipe. The blasting material and the abrasive are transported in a turbulent state including the negative pressure suction swirl flow by bringing the flow of the blasting material and the negative pressure suction air that accompanies or floats the blasting material before the cleaning. the negative pressure suction air, regardless of the Reynolds number (or turbulence critical speed), including a negative pressure suction swirling flow
In the turbulent flow state, the air is supplied from the air supply unit into the blast pipe by suctioning under a negative pressure, so that the inside of the blast pipe can be uniformly and efficiently cleaned, polished or ground over the entire blasting material. become. Further, by providing a means for turbulently moving the downwardly swirling material entrained negative pressure suction swirling air flow in the air supply unit, the abrasive material before the negative pressure suction from the air supply unit into the blast pipe and entrained that can be a turbulent state with a negative pressure suction swirling flow flows between the negative pressure suction air for conveying suspended, the abrasive cleaning agent entrained negative pressure suction air flow, comprising a negative pressure suction swirling flow Since negative pressure suction is performed from the air supply unit into the blast pipe in a turbulent state, the inside of the blast pipe can be uniformly and efficiently cleaned, polished, or ground from the ejection end to the suction end of the abrasive material. Become. This solves all of the above-mentioned first to sixth problems of the prior art, and the end in the blasted pipe from the small diameter pipe (small air amount high pressure) to the large diameter pipe (large air amount low pressure). If the entire surface from the end to the end is swiftly cleaned (for example, a 14-m-long oil well pipe is polished, the conventional high-pressure injection blasting device required 40 to 120 minutes per line in each operation. In the present invention, four pieces are simultaneously worked, and four pieces are completed in 15 to 20 minutes.) In addition, there is an effect that blasting can be performed uniformly.

Further, in the vacuum suction blasting device for the inner surface of the pipe according to the present invention, the speed of the negative pressure suction air is increased and the negative pressure suction air is disturbed in the gradient pipe whose inner diameter is reduced toward the blast pipe. Exceeding the critical velocity at which the flow occurs, turbulence is likely to occur in the blast pipe, and the entire surface from end to end in the blast pipe can be blasted quickly and uniformly.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a detailed view of the air suction means of FIG.

FIG. 3 is an operation diagram of FIG. 2;

FIG. 4 is an operation diagram of FIG. 2;

FIG. 5 is an operation diagram of a conventional example.

FIG. 6 is a detailed view of an air supply unit and a turbulence generation unit of FIG. 1;

FIG. 7 is a detailed view of an air supply unit and a turbulence generation unit of FIG. 1;

FIG. 8 is a detailed view of an air supply unit and a turbulence generation unit of FIG. 1;

FIG. 9 is a detailed side view of the receiver box and the abrasive material discharging means of FIG. 1;

FIG. 10 is a partially detailed plan view of the receiver box of FIG. 1;

FIG. 11 is a partial detailed side view of the receiver box of FIG. 1;

FIG. 12 is a configuration diagram of a first conventional example.

FIG. 13 is a configuration diagram of a second conventional example.

FIG. 14 is a configuration diagram of a third conventional example.

[Explanation of symbols]

A Blasted pipe B Air supply section C Negative pressure suction section D Turbulent flow means E Baffle projection F Gradient tube H Bulging section I Baffle projection J Opening K Polishing material N At least one open / close air that repeats opening and closing with time Inlet (moving negative pressure air inlet) M Negative pressure air inlet P Moving eccentric eccentric falling port X Receiver box Y Abrasive discharging means d Inner diameter of blast pipe d 'Inner diameter of air supply section 50 Cleaning material tank 51 Cyclone 52 Dust collector 53 Air suction means 54 Silencer

Claims (27)

(57) [Claims] 1. A horizontally extending cylinder having a negative pressure suction unit connected to one end of a blast pipe, and an air communication with the other end of the blast pipe.
An air supply unit having a lower part of the air supply unit connected thereto to form a downwardly directed negative pressure suction air flow in the air supply unit, and from the axis of the air supply unit in the downwardly directed negative pressure suction air flow. Dropping the abrasive material in a shifted direction to form a downwardly-sweeping material-assisted negative pressure suction airflow, and forming at least a part of the abrasive material-assisted negative pressure suction airflow into a cylindrical shape of the air supply unit. The abrasive material-assisted negative pressure is introduced into a horizontally extending connection portion of the air supply portion , which is guided upward along the inner wall of the air supply portion and is connected to the blast pipe arranged in the horizontal direction of the air supply portion. A negative pressure suction swirling flow of the suction air flow is formed, and the negative pressure suction unit sucks the polishing material-assisted negative pressure suction air flow into the blast pipe, and the negative pressure suctioned abrasive material entrained air flow The inner surface of the blasted pipe is cleaned by the Negative pressure suction blasting method tube surface, characterized in that it consists of a suction to step a Ken 掃後 airflow entrains the research 掃屑 generated from the last tube from the object blast pipe. 2. The method according to claim 1, further comprising a step of turbulating the air flow with a turbulent flow means before introducing the abrasive material entrained negative pressure suction air flow into the blast pipe. 2. The negative pressure suction blast method according to 1. 3. The turbulent flow means is constituted by a means for moving a supply position of an abrasive material to an air flow when forming an abrasive material entrained negative pressure suction air flow. Item 3. The negative pressure suction blast method according to Item 2 . 4. The turbulent flow means is constituted by selectively opening and closing a plurality of openable and closable air inlets provided in an air supply unit and located on a side of the downwardly-moving air entrainment material. The negative pressure suction blast method according to claim 2 , wherein 5. The turbulence generating means forms a bulging portion in the air supply portion for guiding a part of the downwardly directed suction air flow accompanied by the abrasive material in a direction opposite to the blast pipe. The negative pressure suction blast method according to claim 2 , wherein: 6. The negative pressure suction according to claim 2 , wherein the turbulence generating means is a baffle provided in an air supply unit connected to the horizontally disposed blast pipe. Blasting method. 7. The negative pressure suction blasting method according to claim 6 , wherein the length of insertion of the baffle protrusion into the abrasive material entrained negative pressure suction airflow is adjustable. 8. The negative pressure suction blast method according to claim 7 , wherein the obstruction projections are provided so as to obstruct the upwardly directed abrasive material entrained negative pressure suction air flow in the air supply unit. . 9. The negative pressure suction according to claim 8 , wherein the obstruction is provided so as to obstruct the horizontal flow of the negative pressure suction air flow accompanying the abrasive material toward the blast pipe. Blasting method. 10. A negative pressure suction blasting method inner surface according to claim 1 to 9, further comprising a step of recovering a reusable abrasive cleaning agent. 11. The method according to claim 11, further comprising a step of connecting a gradient pipe to a connection section of the blast pipe of the air supply section to increase a flow rate of the negative pressure suction air flow of the abrasive to be introduced into the blast pipe. negative pressure suction blasting method according to claim 1 to 10, wherein. 12. The negative pressure suction blasting method according to claims 1 to 11 the speed of the Institute cleaning agent entrained negative air flow of the blast pipe is characterized in that to free 60 m / sec is 250 meters / sec. 13. The negative pressure according to claims 1, wherein the Labs cleaning agent entrained volume ratio of abrasive cleaning agent / air negative pressure air stream of the blast pipe is about 1/1000 or less 12 Suction blast method. 14. A negative-pressure suction unit connected to one end of the blast pipe which is arranged in a horizontal state, the horizontal being exposed to the atmosphere is connected the other end of the blast pipe
An air supply unit provided with a cylindrical space extending below the air supply unit, and a negative pressure suction effect of the negative pressure suction unit to supply an abrasive material to an air flow flowing downward in the air supply unit to perform polishing. A blasting material supply means for forming a blasting material entrained negative pressure suction air flow;
Guide upward along the cylindrical inner wall of the air supply
A guiding means, provided continuously in a cylindrical space below the air supply unit;
The blast pipe and the air supply unit are communicated so that the downwardly directed abrasive-assisted negative pressure suction air flow is introduced into the blast pipe with a horizontal and negative pressure suction swirl flow. A negative pressure suction air flow introduced from the air supply unit into the blast pipe in a turbulent state by the negative pressure suction action of the negative pressure suction unit. A negative pressure suction blasting device that blasts the inner surface of the pipe to be blasted with a material. 15. The turbulent flow means is constituted by selectively opening and closing a plurality of openable and closable air inlets provided in an air supply unit and located on a side of the downwardly-moving air entrainment material. The negative pressure suction blast device according to claim 14, wherein 16. The air supply unit according to claim 16, wherein the turbulence generating means forms a bulge in the air supply unit for guiding a part of the downwardly directed suction air flow accompanied by the abrasive material in a direction opposite to the blast pipe. 2. The method according to claim 1, wherein
4 negative pressure suction blasting device according to. 17. The negative pressure suction according to claim 14 , wherein the turbulence generating means is a baffle provided in an air supply unit connected to the blast pipe disposed horizontally. Blast equipment. 18. The negative pressure suction according to claim 14 , wherein the turbulent flow means is a baffle provided in an air supply unit connected to the horizontally disposed blast pipe. Blast equipment. 19. The negative pressure suction blasting device according to claim 18 , wherein the length of insertion of the baffle protrusion into the abrasive material accompanying negative pressure suction airflow is adjustable. 20. The negative pressure suction blast device according to claim 19 , wherein the obstruction projection is provided so as to obstruct the upward flow of the abrasive material accompanying negative pressure suction air flowing upward in the air supply unit. . 21. The method of claim, wherein the baffle projection is provided so as to interfere with the horizontal direction of flow directed to the blast tube of the Institute cleaning agent entrained negative pressure suction air stream 18
Negative pressure suction blast device. 22. The apparatus according to claim 14 , further comprising a collecting means for collecting a reusable abrasive material.
2. A negative pressure suction blast device for the inner surface of a pipe according to 1 . 23. A discharge port, wherein the recovery means discharges a downward flow of an abrasive-entrained negative pressure suction air flow including abrasive chips discharged from the blast pipe while decreasing the flow velocity from the flow passage. 23. The negative pressure suction blasting device according to claim 22 , further comprising means for directing the air flow upward at a relatively low speed thereafter. 24. The negative pressure suction blast device according to claim 23 , wherein means for collecting and carrying out a reusable abrasive material below the discharge port is provided. 25. The apparatus according to claim 25, further comprising a gradient pipe for increasing the flow rate of the negative air suction airflow of the polishing material introduced into the blast pipe connected to the blast pipe connection part of the air supply unit. 25. The negative pressure suction blast device according to claim 14, wherein: 26. The negative pressure suction blasting device according to to the speed of the Institute cleaning agent entrained negative air flow of the blast tube is not claim 14, characterized in that to free 60 m / sec is 250 meters / sec 25. 27. The negative pressure according to 26 to claims 14, wherein the volume ratio of abrasive cleaning agent / air in the lab cleaning agent entrained negative air flow of the blast pipe is about 1/1000 or less Suction blast device.