JP7345414B2 - Local exhaust ventilation - Google Patents

Description

The present invention relates to a local exhaust system equipped with a chamber having an air intake opening on one side surface, which performs side suction at a predetermined controlled wind speed, and particularly to a side suction type local exhaust system installed in a painting booth. Regarding.

From the perspective of preventing organic solvent poisoning of workers, the performance requirements for local exhaust systems in processes where toxic chemicals and pollutants are generated, such as the painting process, are such that work points are arranged on a flat surface to prevent the scattering of pollutants ( The point between the source of contamination and the worker (the work point closest to the worker) is considered the capture point. To control contamination, air must be drawn in with a local exhaust system to create a controlled airflow at the point of capture.
To define this trapping point, for example, in the case of an external hood, when controlling the wind speed determined by the organic law, a side suction type is used to uniformly distribute the airflow on the vertical plane that forms the trapping point at a wind speed of 0.5 m/s. needs to occur. In other words, with an external hood, when the capture point is set at a surface a predetermined distance from the intake hood opening, and the area is divided into a grid pattern, the air velocity is set so that the predetermined intake air speed (control wind speed) is satisfied in each section. It is necessary to measure and verify performance satisfaction. The suction wind speed, which is the control wind speed, is deeply related to the wind speed distribution at the facing hood opening, and the wind speed distribution at the hood opening is greatly affected by the distance to the exhaust duct. ) is uniform and close to the target wind speed, and in order to economically satisfy the fan capacity, it is necessary to make the negative dynamic pressure generated by the suction in the exhaust ducts in each compartment as uniform as possible. It is preferable to keep it. Therefore, by connecting the exhaust duct near the center of the position facing the intake opening (or the rear side if the opening is provided on the front of the chamber), the central axis of the opening of the external hood The distance between the opening edge and the four corners of the opening edge is often shortened. However, due to the installation location of the local exhaust system and the layout of the exhaust duct, the external hood is a side suction type, so even though the opening is provided at the front of the chamber, the exhaust duct is connected to the top of the chamber. (For example, see Patent Documents 1 and 2). In this case, there is a large difference in the distance from the exhaust duct between each position of the opening surface of the external hood, and the suction air velocity in each section forming the capture point becomes uneven accordingly. It is not possible to obtain sufficient suction wind speed, that is, control wind speed, in a section corresponding to the location of Problems may arise such as:

Therefore, in Patent Documents 1 and 2, a partition plate is provided between the generation source and the exhaust duct, and the partition plate is provided with a suction port whose opening becomes larger toward the bottom, or a plurality of holes are opened at equal intervals. The aim is to equalize the suction wind speed across the opening of the enclosed hood and, ultimately, between compartments.

Japanese Unexamined Patent Publication No. 62-266345 Utility Model Publication No. 3-20686

In Patent Document 1, since the suction port is provided in a part of the center of the flat partition plate, only the center portion of the front compartment faces the suction port, and the suction port is deviated laterally from the center of the front compartment. There is still room for improvement in increasing the suction wind speed in the compartment. Furthermore, it is very time-consuming to measure and verify the wind speed each time an opening is made in a flat partition plate and examine the degree of opening.

In Patent Document 2, since a plurality of holes are provided at equal intervals on the partition plate, the suction wind speed of the trapping point section, which is far from the exhaust duct and corresponds to the lower side of the enclosed hood opening, is higher than that of the upper side. It is slower than partitioning, and ultimately it is difficult to achieve uniformity.

Therefore, an object of the present invention is to provide a local exhaust system that can average the suction wind speed in each section.

The local exhaust device of the present invention is a local exhaust device 1 that performs side suction at a predetermined controlled wind speed, and includes a chamber 2 having an intake opening 22a on one side surface, and a chamber 2 disposed within the chamber 2 and having one end. is provided with a substantially cylindrical and straight inner duct 3 connected to an exhaust duct 10, and the inner duct 3 has a suction port 3a whose size gradually decreases from the other end of the inner duct 3 toward one end. , is provided integrally with the side surface of the inner duct 3 and the other end, and is characterized in that the suction port 3a faces the opening 22a side of the chamber 2.

In the above-mentioned local exhaust device, it is preferable that the suction port 3a is provided at the other end of the inner duct 3 by cutting out approximately half of the inner duct 3 in the circumferential direction.

Further, it is preferable that one end side of the side surface of the inner duct 3 is provided with a non-provided area 3c in which the suction port 3a is not provided.

Furthermore, it is preferable that the other end of the inner duct 3 is open and separated from the inner surface of the chamber 2.

In the local exhaust system of the present invention, since the inner duct has a substantially cylindrical shape, the suction port faces not only the front but also other directions. Therefore, compared to the case where the suction port is provided on a flat plate, there are more sections facing the suction port. In addition, the size of the suction port gradually decreases from the other end that is not connected to the exhaust duct to the one end that is connected to the exhaust duct, so the amount of suction from the section close to the exhaust duct is moderately suppressed. This makes it possible to average the suction wind speed in each section.

When the suction port is provided by cutting out approximately half of the circumferential direction, the number of sections facing the suction port increases. When a non-installation area is provided, the amount of suction from the section near the exhaust duct can be appropriately suppressed, and the suction wind speed in each section can be further averaged. If the other end of the inner duct is open and is away from the inner surface of the unit chamber, the amount of suction from the compartments away from the exhaust duct can be increased, and the suction wind speed in each compartment can be further averaged. be able to.

FIG. 1 is a side sectional view of a local exhaust system according to an embodiment of the present invention. FIG. 2 is a front view of the local exhaust system of FIG. 1; FIG. 2 is a plan view of the local exhaust system of FIG. 1; FIG. 4a is a front view of the inner duct, and FIG. 4b is a sectional view of the inner duct. FIG. 5A is a diagram showing measurement results of suction wind speed, with FIG. 5a showing an example and FIG. 5b showing a comparative example.

Next, one embodiment of the local exhaust system 1 of the present invention will be described in detail based on the drawings. The local exhaust system 1 of the present invention includes a chamber 2 and an inner duct 3 disposed within the chamber 2, as shown in FIGS. 1 to 3.

The chamber 2 is a hollow rectangular parallelepiped, and has a bottom portion 21 that is rectangular in plan view, side wall portions 22 rising from the four sides of the bottom portion 21, and an upper portion 23 that closes the upper end of the side wall portion 22. Among the two side wall portions 22 rising from the long sides of the bottom portion 21, one side wall portion 22 (one side surface) is provided with an intake opening 22a. This opening 22a is provided over almost the entire surface of one side wall portion 22. The upper portion 23 is provided with a connection portion (connection hole+nipple) 23a for connecting the exhaust duct 10. This connecting portion 23a is provided at the centroid of the upper portion 23 in plan view. However, it is not limited to this, and can be changed to multiple locations as appropriate, for example, as long as the location is 0.5D (D: outer diameter of the inner duct 3) or more from the inner surface of the side wall portion 22 rising from the short side of the bottom portion 21. . However, when the surface on which the opening 22a is provided is taken as the front, it is preferable to provide the opening 22a at a symmetrical position when viewed from the front. Although the explanation uses an example in which the connecting portion 23a is provided on the upper portion 23, the connecting portion may be provided on a side wall portion rising from the short side of the bottom portion 21, or the connecting portion may be provided on the bottom portion 21.

The inner duct 3 has a substantially cylindrical and straight pipe shape, and both ends are open. An example of a spiral duct made of galvanized steel is ideal for this purpose. The axis of the inner duct 3 is directed in the vertical direction, and one upper end is connected to the connecting portion 23a of the chamber 2. If the inner height of the chamber 2 is L, then the axial length is 0.8 to 0.9L. Therefore, a gap of 0.1 to 0.2 L is formed between the other end (lower end) of the inner duct 3 and the inner surface of the bottom 21 of the chamber 2. In the explanation, an example will be used in which the connection part 23a is in the upper part 23 and the axis of the inner duct 3 is vertical, but if the connection part is in the side wall rising from the short side of the bottom part 21, the axis of the inner duct 3 is in the left-right direction. It may be in

The inner duct 3 is provided with a suction port 3a whose size gradually decreases from the other end to one end of the inner duct 3, as shown in FIGS. 4a and 4b. Specifically, a notch 3b is provided whose width gradually narrows from the other end toward one end. More specifically, there is an apex that passes through the two centers of the other end of the inner duct 3 (two points on the front and back) when the inner duct 3 is viewed from the side, and at the center when the inner duct 3 is viewed from the front. A notch 3b is provided so that the notch 3b is located. That is, the notch 3b cuts out approximately half of the inner duct 3 in the circumferential direction at the other end of the inner duct 3. Therefore, the suction port 3a is integrally provided on the side surface and the other end of the inner duct 3. Further, the notch 3b is not provided over the entire length of the inner duct 3, and there is a non-provided area 3c on one end side where the intake port 3a is not provided. The axial length of this non-provided area 3c is preferably 0.1 to 0.3L, more preferably 0.2L.

The inner duct 3 having the above structure is a spiral duct whose diameter (inner diameter) is selected so that the flow resistance of air flowing inside is 0.1 mmAq/m. The suction port 3a formed by the notch 3b is connected to the connecting portion 23a so that it directly faces the opening 22a of the chamber 2, and the axial direction of the inner duct 3 is approximately parallel to the opening surface. There is.

The local exhaust device 1 having the above configuration is used by connecting the exhaust duct 10 to the connecting portion 23a and attaching the air filter 11 to the opening 22a as appropriate. The installation location is, for example, inside a paint booth.

Next, the measurement results of the suction wind speed will be explained.

(Example 1)
As Example 1, a chamber 2 having a height of 1500 mm, a width of 1500 mm, and a depth of 850 mm was used. The opening dimensions of chamber 2 are approximately 1500 x 1500 mm. An air filter 11 made of nonwoven fabric was attached to the entire surface of the opening 22a. The inner duct 3 is a spiral duct made of galvanized steel plate, and has an outer diameter of 500 mm (plate thickness 0.6 mm, inner diameter approximately 500 mm), and an axial length of approximately 1350 mm. This inner duct 3 has a notch 3b whose cutting surface is an imaginary plane that passes through the two centers of the other end of the inner duct 3 (the two points in the front and back) when the inner duct 3 is viewed from the side, and goes diagonally upward. has been established. The axial length of the non-installed area 3c was approximately 300 mm. A gap of about 150 mm was provided between the lower end of the inner duct 3 and the inner surface of the bottom 21 of the chamber 2. The exhaust duct 10 had a square cross section of 600×450 mm, and was connected to the connecting portion 23a via a rounded corner elbow 12. A limit load fan (#3 1/2) was connected to the exhaust side of the exhaust duct 10. The displacement is 6600 m ³ /h x 420 Pa.

(Comparative example 1)
It was the same as Example 1 except that the inner duct 3 was not provided.

The suction wind speed was measured in each section at a position 50 cm away from the filter surface by dividing the filter surface into nine sections. The results are shown in Figures 5a,b.

The numbers in parentheses in Figures 5a, b indicate the suction wind speed in each section. In Comparative Example 1 (Fig. 5b), which does not include the inner duct 3, among the sections 1 to 9, sections 1 to 3 and 5 meet the requirements for external hoods (side suction type) stipulated by the organic solvent poisoning prevention regulations. The suction wind speed (controlled wind speed) satisfies 0.5 m/s, but this value is not satisfied in sections 4 and 6 to 9. Additionally, the maximum wind speed was 1.2 m/s, while the minimum wind speed was 0.3 m/s, indicating a large variation in wind speed in each section. On the other hand, in Example 1 (FIG. 5a), which includes the inner duct 3, it can be seen that 0.5 m/s is satisfied in all sections. In addition, the maximum wind speed is 0.65 m/s, the minimum wind speed is 0.53 m/s, and the variation in wind speed in each section is small.

In this way, in the local exhaust system 1 of the present invention, it is possible to average the suction wind speed in each section. This is because the lower end of the inner duct 3 is shaped like a hopper, and as a result, the number of sections facing the suction port 3a increases, and as a result, the airflow flowing through the air filter 11 can be sucked into the inner duct 3 without resistance, and as it goes upward, This is because the airflow sucked in from the narrowed slit-shaped suction port 3a is attracted by the main airflow flowing upward inside the inner duct 3 and smoothly merges with the main airflow, creating a smooth airflow. Conceivable.

Although the embodiments of this invention have been described above, this invention is not limited to the above embodiments, and can be implemented with various changes within the scope of this invention. For example, in the above embodiment, the suction port 3a is provided by the notch 3b, but the suction port 3a may be provided by a plurality of holes. Similar effects can be achieved by gradually reducing the size of the hole (width in the circumferential direction of the inner duct) from the other end toward one end. Furthermore, even if the holes are of the same size, the same effect can be achieved if the number of holes is gradually reduced from the other end toward one end.

1 Local exhaust device 2 Chamber 21 Bottom part 22 Side wall part 22a Opening 23 Top part 23a Connection part 3 Inner duct 3a Suction port 3b Notch 3c Non-installation area 10 Exhaust duct 11 Air filter 12 Rounded elbow L Inner height of chamber D Inner duct outer diameter of

Claims (4)

A local exhaust device that performs side suction at a predetermined controlled wind speed,
a chamber having an intake opening on one side surface;
a substantially cylindrical straight inner duct disposed within the chamber and connected at one end to an exhaust duct;
A suction port whose size gradually decreases from the other end to the one end of the inner duct is integrally provided on the side surface of the inner duct and the other end,
A local exhaust device characterized in that the suction port faces toward the opening side of the chamber. 2. The local exhaust system according to claim 1, wherein the suction port is provided at the other end of the inner duct by cutting out approximately half of the inner duct in the circumferential direction. 3. The local exhaust system according to claim 1, further comprising a non-disposed area in which the suction port is not provided on one end side of a side surface of the inner duct. The local exhaust device according to any one of claims 1 to 3, wherein the other end of the inner duct is open and separated from the inner surface of the chamber.

Images