Aspiration unit (general view)

Contents

Introduction

1. Design Part

1.1. Identification of equipment to be aspirated

1.2. Calculation of air exchange multiplicity and justification of selection

type of network to be designed

1.3. Technological features of aspirated equipment calculation

1.4. Aspiration Network Layout

1.5. Calculation and selection of dust collector

1.6. Determination of dust collector resistance

1.7. Pre-fitting the fan to the mains

1.8. Dust collector and fan arrangement

1.9. Designing a Duct Route

1.10. Calculation of aspiration plant

1.10.1. Source data, objectives and calculation tasks

1.10.2. Network Design Diagram

1.10.3. Network Calculation

1.10.4. Determining Overall Network Resistance

and selection of fan

2. Aspiration network wiring diagram

2.1. Duct Connection Materials and Views

2.2. Design of confusers, diffusers, tees

and taps

2.2.1. Design of confusers and diffusers

2.2.2. Design of taps

2.2.3. Tee Design

3. Calculation of purified air emission into atmosphere of aspiration networks

4. Explosion safety of aspiration unit

Conclusion

List of literature used

Appendix No.

Appendix No.

Appendix No.

Introduction

Modern technological processes are associated with the movement and mechanical treatment of bulk products, which are accompanied by a large release of dust into the environment. Therefore, the most important task of ventilation plants is to maintain air cleanliness and create comfortable working conditions in working rooms. The dust content of air in them according to sanitary standards should not exceed 2-6 mg/m3. This task can be accomplished if you eliminate the division of dust into the air of working rooms by aspiring equipment, that is, using the suction of air from the equipment housings, sealing casings, where dust is formed.

Ventilation equipment has an important role to play in the implementation of decisions to improve the well-being of workers through improved working conditions. Its perfection depends on the health of people, improving their working conditions, improving productivity and production efficiency, as well as protecting the air basin from pollution, preventing dust explosions.

Reducing dust emissions into the atmosphere through the use of high-efficiency dust collectors in aspiration plants not only protects the environment, but also saves valuable food and fodder products, of which dust consists.

During aspiration, a vacuum is created inside the sealing casings and equipment, which makes it possible to eliminate dust release into the room. Comfortable working conditions can be created using air conditioning.

Ventilation plants are very important for maintaining the cleanliness of the ambient air. According to the new sanitary standards, permissible concentrations of dust when released into the atmosphere are not established, but the concentration of dust in the air in the territory adjacent to the enterprise of the settlement should not exceed 0.5 mg/m3.

Ventilation and aspiration plants are widely used in modern industrial enterprises of various industries. High technical level of these plants has been achieved.

The degree of perfection of aspiration plants depends greatly on the level of their design. This is a creative process based on the theoretical knowledge, experience, technical maturity and creative ability of a design engineer.

In this course project, aspiration of the equipment of the peeling compartment of the cereal mill is considered. Formulas (1) - (18), [1] are used in calculations.

1.3 Technological features of aspirated equipment calculation

This equipment separates the same dust in size or similar in quality.

We take into account the technological requirements for the air parameters in the workshops. Air temperature 16... 23 0С, relative humidity 60... 70%, speed - no more than 0.5 m/s. These process air parameters do not contradict the sanitary and hygienic requirements for the air of the working rooms, but coincide with them and can be implemented by designing ventilation plants with air recirculation .

1.4 Aspiration Network Layout

Aspiration networks are arranged according to spatial, technological, temperature principles, the principle of operational reliability and the principle of simultaneous operation.

According to the principle of simultaneous operation, we combine equipment operating at the same time into one network.

Considering the temperature principle, it is impossible to combine equipment having different air temperatures into one network, since when mixing warm and cold air, condensation of water vapors and sticking of dust to the walls of the duct are possible.

We take into account the principle of operational reliability, which is that machines with a controlled mode of air flow, as well as with their own fan (for example, grain sieve-air separators) are designed into independent local installations; the number of suction points in one network is not more than ten.

According to the technological principle, which takes into account the uniformity of equipment and the equivalence of dust, we combine equipment in one network in which the dust is the same or close in quality. These are BKG grits.

According to the spatial principle, we combine closely located equipment into one network and prefer vertical ducts when combining equipment, since this makes the networks more economical and operationally reliable.

1.8 Dust collector and fan arrangement

Knowing the dimensions of the selected dust collectors and fans and following the installation recommendations, [1, p. 137138] arrange them as follows. We install on free seats, while mounting the fan and dust collector as close as possible to each other. The fan is installed on the floor (since installation on the ceiling entails inconvenience in its maintenance and repair). When installing fans and dust collectors, simplify the duct as much as possible.

After selecting the installation location, draw fans and dust collectors on the general view drawings of the workshop at a scale of 1:50 in sections and plan.

1.9 Duct Route Design

Before starting the design of the duct route, draw aspirated equipment with the dimensions of aspiration holes and their reference to the main axes on the general drawings of the workshop.

At the beginning of the design of the duct route, draw confusers (suction pipes) of aspirated equipment.

After drawing confusers on the drawings of the general view of the workshop, we draw the duct route in axes, and after choosing the optimal option, we finally draw it at a scale of 1:50.

When drawing air ducts, their diameters (mm) are calculated preliminary by the formula:

; (7)

where - air flow rate, m3/h, we find it by adding the flow rates of aspirated machines combined with tees;

- air speed, m/s.

When drawing the duct route, follow the instructions for its design [1, p. 138139].

Ducts are conducted along the shortest path with the smallest number of taps, parallel and perpendicular to walls and beams, avoiding oblique long ducts that violate symmetry and worsen industrial aesthetics;

First, we combine the air ducts of the most distant machines with low air flow rates and resistances with tees, and then connect them to machines with increased flow rate and resistance: with the same flow rates and resistances, we use symmetrical tees that simplify the route.

Horizontal air ducts are conducted above the windows under the ceiling at the same level so as not to obscure the premises and not worsen the industrial aesthetics; minimum height from the floor to protruding parts of air ducts is taken not less than 2.2 m;

When designing a route, if possible, we apply the minimum number of types of installation elements taking into account typical structures manufactured in factories or in special workshops.

We take standard diameters of air ducts; we take the radius of the taps equal to, the angles of the tees are taken equal to 30 °, the optimal angle

narrowing confusers of aspirated machines.

1.10 Calculation of aspiration unit

1.10.1 Initial data, purposes and tasks of calculation

Purpose and tasks of calculation.

The purpose of the calculation is to determine all the parameters of the aspiration plant for the final selection of the fan, which ensures its reliable and economical operation.

The calculation tasks consist in determining the diameters of the air ducts of all sections of the plant, pressure losses in each section and total plant pressure losses along the main main line; equalizing pressure losses in tees in parallel sections, as well as in final selection of fan in the network, finding power for fan drive and in selection of electric motor.

Data for calculation.

To calculate the aspiration plant, it is necessary to know the locations of aspirated equipment, fans, dust collectors and the location of the duct route, that is, you need to have a design of a general type of aspiration plant (sheet 1) at a scale of 1:50.

In addition, the following data are required:

o air flow rate and pressure loss in aspirated equipment;

o the length of the straight sections and the characteristics of the shaped parts of the ducts, that is, the dimensions of the confusers of the machines, the radii and angles of the taps, the angles of the tees, etc.;

o resistance, suction and air leakage in the dust collector;

o presence of vacuum in working rooms.

2. Aspiration network wiring diagram

The wiring diagrams of the training projects are drawn on a scale of 1:20, with the exception of straight sections of ducts, which are drawn without observing the scale with breaks, based on uniform filling of the sheet. Wiring diagrams draw planar ones .

On the wiring diagrams we depict on a scale all parts of the ducts: straights, confusers, taps, tees, diffusers, etc. The diameters of the ducts are drawn based on the results of the network calculation. Fans and dust collectors on wiring diagrams can be drawn without detailed

images, i.e. schematically. Flange joints and transverse folds are drawn with main lines, and longitudinal folds of air ducts are not drawn.

2.1 Materials and types of duct connections

Air ducts are made of galvanized thin-sheet steel with a sheet size of 1,000x2,000 mm. The thickness of sheet steel is assumed depending on the diameter of the duct. For diameters up to 450 mm, we take thickness = 0.55 mm. Dimensions and mass of round air ducts are selected from Table 37 [1, p. 159].

Straight sections of air ducts are made with links 2... 4 m long.

Longitudinal and transverse seams of air ducts are made non-detachable folding. For greater tightness, we use double folds. Transverse joints for increasing stiffness are made using standing folds

The width of the folds depends on the thickness of the steel sheet. With a thickness of 0.55 mm, the width is 8 mm.

Split connections of air duct links are made on flanges: for diameters up to 315 mm from strip steel with a diameter of 25 × 4 mm, for diameters from 355 to 560 mm from angular steel with a size of 25 × 25 × 3 mm. To attach the flanges on the ends of the air duct links, edge flanges are made on the 8... 10 mm.

We connect flanges with diameters of up to 560 mm with M6 × 20 bolts using gaskets made of sheet rubber with a thickness of 3... 5 mm or cardboard on surik.

The number of bolts is assumed depending on the diameters of the round ducts in accordance with Table 38. [1, p. 160]

For ease of installation, the holes for bolts in the flanges are made oval with dimensions along the axes of 7 × 10 mm or round diameters of 7 mm.

Round flanges of angular and strip steel are bent on the flange bending mechanism. Rectangular-shaped flanges are manufactured on a flange bending mechanism or by welding.

2.2 Design of confusers, diffusers, tees and taps

2.2.1 Design of confusers and diffusers

The shapes and dimensions of the confuser of aspirated equipment are designed taking into account the design of this equipment.

The most common shape of the confuser and diffuser is a truncated cone or a transition from a rectangular section to a round one.

The optimal constriction angle of the confuser is 45 °. The confuser to the aspirated equipment is fixed on flanges made of strip steel with a size of 25x4 mm, which are fixed to the confuser on the flanges. Gasket is installed between flange and equipment housing.

On round and a confusor in the form of the truncated cone we design the diffuser with transition of rectangular section on sheet 3 - KP .AC04 .

2.2.2 Design of taps

The taps are designed from links, the number of which depends on the angle α of the taps, for taps with an angle α = 90 ° seven links are taken, of which five average 15 ° and two extreme 7.5 °, which are called cups (half-links). During design we specify dimensions for references D = 140 mm and α = 90 °.

The assembly drawing of branch is carried out on sheet 3 - KP .AC04.SB.

2.2.3 Tee Design

Tees are designed with angle α = 30 °. Dimensions of asymmetrical tees and crosses during design are taken from Table 39 [1, p. 165] by diameter of duct = 250 mm.

We make tees using racks or falcons.

We draw development of the T-connector on sheet 3 - KP .AC04.