Aspiration is the most difficult type of room ventilation. The essence of aspiration is that polluted air with particles harmful substances gathers in one place. The aspiration system prevents polluted air from spreading throughout the room. The main place of use of this kind of ventilation is carpentry workshops, workshops metalworking, brick factories, mining and processing enterprises, grain storages and other places where small particles of various substances are constantly in the air. Setting up an aspiration system is a laborious and delicate process that requires not only sufficient qualifications, but also great professional experience.
Aspiration systems are modular and monoblock. Monoblock systems are more mobile. The monoblock aspiration system consists of a fan, a separator and a container for waste collection. Such systems are usually installed directly at the point of air pollution. In this case, the ventilation system works only in those places where air pollution occurs. In such places, hoods are installed that take in air into which harmful impurities have entered. This is the simplest and most profitable type of ventilation, because the aspiration system is concentrated at one point, and large volumes of air intake are not required to clean it. Immediately absorbing air with harmful impurities, the aspiration unit does not allow dust and small particles to spread throughout the room, preventing them from entering the eyes and lungs. A well-placed local aspiration system can reduce air purification costs and energy costs. However, its effectiveness is insufficient for large volumes of pollution and if the production process is associated with frequent movements.
A modular aspiration system is designed and installed depending on the task assigned to it. It's over a complex system including fans low pressure, separators, air filters, cutting modules and press containers for waste collection. One of the components of the aspiration system is a cyclone - it allows you to separate the air from various small particles that have fallen into it; working like a centrifuge, the cyclone, due to centrifugal force, leaves all the debris on its walls, so all the dust remains in it. In wood processing enterprises, the aspiration system is equipped with special filter sleeves, which are engaged in capturing small chips and microscopic particles that occur during the wood processing process. With the help of roof filters, the air undergoes additional cleaning before returning to the room if the aspiration system is recirculating. In a direct-flow aspiration system, polluted air is cleaned of harmful impurities and released into the atmosphere, rather than being returned back to the room.
Ventilation and suction are closely related to each other, but do not confuse the ventilation system with the aspiration system. The main difference between the aspiration system is the presence of inclined air ducts. The special angle of inclination of such air ducts ensures the prevention of stagnation in the aspiration system. Besides, suction systems are push and pull. Their type depends on how the devices that capture fine particles and dust are located to the devices that cause air movement, that is, fans. It is due to the action of air (in most types of aspiration systems) on the dust contained in the place of air intake that it is cleaned.
There are many types of suction equipment available. Bag filters are most often used to capture dry particles of dust and gases. Depending on the nature of air pollution, silo filters, ash collectors etc. Often, for work at the enterprise, special aspiration tables are installed, which are engaged in the intake of air containing harmful impurities, right on the spot. For production associated with the release of various gases and droplets into the air, special aspiration equipment is used to clean the air from gases and aerosols. At the place of work of grinding machines, where a large amount of metal dust and chips are formed, specialized dust collecting units for collecting abrasive dust. After cleaning from various suspensions, the air returns to the room.
At enterprises associated with the release of dry dust into the air: abrasive, grinding dust, quartz sand, etc., filter-cyclone dust-collecting installations are usually used. Such installations cover a wide range of different contaminants and are able to withstand large temperature and pressure ranges. Units for grinding machines are engaged in air purification from dry, non-sticky dust, they are equipped with special filter cassettes. Unlike small-sized bag filters, such systems are designed for a higher level of contamination.
For correct selection A suitable aspiration system must take into account the layout of the equipment and its specification, as well as how the technological process occurs and which materials are processed. An important factor is the volume of pollution and the operating time of each device.
Production processes are often accompanied by the release of dust-like elements or gases that pollute the indoor air. The problem will be solved by aspiration systems designed and installed in accordance with regulatory requirements.
Let's figure out how they work and where they use such devices, what types of air purifying complexes are. Let's designate the main working units, describe the design standards and the rules for installing aspiration systems.
Air pollution is an inevitable part of many manufacturing processes. In order to comply with the established sanitary norms air purity, use aspiration processes. With their help, dust, dirt, fibers and other similar impurities can be effectively removed.
Aspiration is suction, which is carried out by creating an area of low pressure in the immediate vicinity of the source of pollution.
To create such systems requires serious special knowledge and practical experience. Although the operation of aspiration devices is closely related to the functioning, not every ventilation specialist will be able to design and install this type of equipment.
For achievement maximum efficiency combine ventilation and aspiration methods. The ventilation system in the production room must be equipped to ensure a constant supply of fresh air from outside.
Aspiration is widely used in the following industries:
- crushing production;
- wood processing;
- manufacturing of consumer products;
- other processes that are accompanied by the release a large number substances harmful for inhalation.
It is far from always possible to ensure the safety of employees with standard protective equipment, and aspiration may be the only way to establish a safe production process in the shop.
Aspiration units are designed for efficient and quick removal from the air of various small contaminants that are formed during industrial production
Removal of contaminants using systems of this type is carried out through special air ducts, which have a large angle of inclination. This position prevents the appearance of so-called stagnation zones.
Mobile ventilation and aspiration units are easy to install and operate, they are perfect for small businesses or even for a home workshop
An indicator of the effectiveness of such a system is the degree of non-knocking out, i.e. the ratio of the amount of contaminants that have been removed to the mass of harmful substances that have not entered the system.
There are two types of aspiration systems:
- modular systems– stationary device;
- monoblocks– mobile installations.
In addition, aspiration systems are classified according to the level of pressure:
- low-pressure- less than 7.5 kPa;
- medium pressure- 7.5-30 kPa;
- high-pressure- over 30 kPa.
The complete set of aspiration system of modular and monoblock type differs.
In hot shops, heating of the air coming from outside is not needed, it is enough to make an opening in the wall and close it with a damper.
Conclusions and useful video on the topic
Here is an overview of the unpacking and installation of the RIKON DC3000 mobile suction system for the woodworking industry:
This video demonstrates a stationary aspiration system used in furniture production:
Aspiration systems are a modern and reliable way to clean the air in industrial premises from dangerous contaminants. If the structure is properly designed and installed without errors, it will demonstrate high efficiency at minimal cost.
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90 degree bend.
Pattern of a branch of five links. Marking the line of conjugation of the branch links.
The pattern of the left side of the pattern of the branch link is mirrored to the right, or drawn on the right according to the same pattern and dimensions. Pattern width calculation formula: 3.14D + seam allowances. The width of the seam allowances is taken, for example, 14 + 14 = 28 mm with a folded edge of 7 mm.
Transition from rectangular to round section, confuser, diffuser.
The pattern of a direct symmetrical transition consists of two identical parts.
Cut off the circular section line with a small margin; in the finished transition, clarify and strike it out along the circular section of the connected branch pipe or along the flange; and cut off completely with an edge allowance for the connecting seam or flange.
In some cases, you can take L~h: if the difference in the cross sections of the transition is not very large, or if the accuracy of its height is not significant. Deviation from the given height can be compensated by the length of the next fitting attached to it.
Transition from a round section to a round one of a different diameter.
Construction of a pattern (sweep) of a straight confuser, a circular diffuser.
In some cases, you can take L~h: if the difference in the cross sections of the transition is not very large, or if the accuracy of its height is not significant. The deviation from the specified height of the transition can be compensated by the length of the next fitting to be attached to it.
Transition from one rectangular section to another rectangular.
Transition pattern in two parts:
When calculating the length of the pattern, take into account the material allowances for attaching the lower and upper rectangular flanges.
Tee. Pattern drawing and manufacturing sequence.
The proposed method for constructing a pattern is less accurate than that described in special or educational literature, but is successfully applied in practice in the manufacture of parts for ventilation, aspiration and gravity transport.
The length of the tee can be taken from the dimensions of standard tees with a central angle of 30 degrees. The size table shows the minimum length of a standard tee - depending on the diameter of the straight shaft of the free-flow duct d . For the manufacture of a tee according to the proposed approximate method, it is recommended to take a slightly longer pattern length, for example, depending on the diameter of the base D. If it is necessary to make a tee, the length of which differs from those indicated in the table, then the dimensions "a" and "b" should be clarified by calculation. Calculation formulas for a tee 30 degrees:
a=0.5l tr ; b=0.87l tr.
As you accumulate practical experience the length of the part and its pattern will be determined independently, taking into account the installation location in the duct network and the method of connection with other fittings of the ventilation system.
Dimensions of straight asymmetrical tees with a central angle of 30 degrees:
|
Diameter |
Lengthl tr |
A |
b |
|
1072 |
|||
|
1184 |
1027 |
||
|
1316 |
1142 |
On a separate sheet of iron or thick paper draw a side view of the tee. A full drawing is not necessary - just those lines of the drawing that are needed to determine the "C" dimension are sufficient.
The figure shows a straight asymmetrical tee with an angle of 30 degrees and a drawing of its side view:
Drawing of a pattern of a through shaft and a side branch of a tee:
Tee manufacturing sequence.
Prepare connecting folds on the long sides of both parts of the pattern. Bend edges 7 and 14 mm on the inner line of the junction of the trunks. Align the parts of the pattern, overlapping the smaller one with the larger one. Connect the branch pattern with the straight trunk pattern along the junction line with a one-and-a-half lying fold. The joint connection sequence is shown in the figure:
Bend both stems of the tee into a round shape, fasten the folds, seal the seam seam. Fill the beginning of the internal connecting seam at a length of 3 - 5 cm, sufficient to install a flange or connection with a round section pipe. The base, through passage and side shafts of the tee should be evenly marked and cut along the flange or round nozzle of the appropriate diameter, leaving allowances for the flanging for connection with the next part. The result is a symmetrical pant-shaped tee. It can be made asymmetrical by cutting the base perpendicular to the duct, or left trouser-shaped by cutting the base perpendicular to the "C" line. If a wide cuff (clamp) is used for the connection, then the main section of the tee must be supplemented with a straight branch pipe of the same diameter.
A tee with a different central angle is drawn and made in the same way, but the dimensions "a", "b" and "C" are determined for the corresponding joining angle. In a 45 degree tee, dimensions "a" and "b" are the same.
Many technological processes extraction and processing of raw materials, production of materials in the chemical, textile, woodworking and other industries are accompanied by the release of dust, which is one of the main harmful production factors. Dust not only adversely affects workers and worsens their working conditions, but also disrupts the technological parameters of the equipment and the conditions of the production process, which in turn leads to a decrease in product quality. Efficient air purification (aspiration) has not only sanitary-hygienic, environmental and technological, but also economic importance.
Aspiration systems create a vacuum in the shelters of technological equipment, prevent the release of harmful substances into the premises and ensure the removal of these hazards to the places intended for this. Harmful factors released in production include dust, heat and moisture release, emission of harmful gases. The functions of aspiration systems are reduced to the efficient and reliable removal of these hazards from working areas and industrial premises to the protection of atmospheric air from pollution.
The composition of modern aspiration plants includes:
- fans,
Devices for air purification, as well as for the storage and disposal of accumulated waste.
There are two ways to place the fans: before the waste disposal devices (installations high pressure) and downstream (low pressure or vacuum units). Operating experience has shown that greater efficiency work and more long term operation have systems with low pressure installations. In this case, the fan blades are not worn out by the waste stream, and the air purification efficiency is increased by 25-30%. The increase in energy consumption is offset by a simpler impeller design, reduced maintenance and repair costs, and increased fan life.
The aspiration system can be centralized, when all available equipment is connected to one installation (typical for small enterprises with compactly located machines) or with a group connection, when certain groups of machines have own settings. The performance of the unit and the power of the fan drive is selected in accordance with required power for each of the machines, as well as as a result of calculating the resistance of the air ducts. It depends on the total length, diameter of the ducts, the number of branches, as well as the number and radius (angle) of rotation. With a 10% increase in volume flow, the required fan power increases by approximately 33%.
Unfortunately, our enterprises traditionally use cyclones to clean the air from waste. During the day they are characterized by a low degree of air purification (no more than 95%), i.e. it is impossible to return such air back to the room, and it is released into the atmosphere. From the point of view of energy saving, this is completely unacceptable. Modern installations, as a rule, are equipped with special filters, which, from leading domestic and foreign manufacturers, provide air purification to a concentration of not more than 0.1-0.2 mg/m3 (99.9%). This makes it possible to recover heat during the cold season and significantly reduces the company's costs for space heating.
Bag filters are the most widely used for high-capacity installations. Such models provide fine air purification from dust particles that have minimum size up to several micrometers. The dust accumulated on the filter element is automatically removed by shaking (mechanical action on the filter element) or pulsed action of compressed air. Modern filters have a fairly long service life (up to 10 years).
The suction system is complex engineering system. Therefore, the calculations of aspiration systems should be carried out by a specialist in this field, i.e. a person who knows the principle of operation and the basics of aerodynamic calculation of aspiration systems for technological machines and pneumotransport of dispersed materials, the device, principle of operation and characteristics of such basic elements of systems as dust collectors, fans, shutters, fire and explosion protection systems, etc.
The primary task of a potential buyer when choosing dust-collecting equipment is to determine technical requirements to the aspiration system, consisting of the following data:
Operating time of each machine or group of machines;
Diameter and number of local suctions, air velocity in the suction;
The volume of waste and the size of the removed particles;
The presence of mobile suction and the amount of movement;
The volume of the waste storage bin.
