Air spray installations. Ventilation shower unit for working inside hot production equipment

An air shower is a local air flow directed at a person. In the area of ​​action of the air shower, conditions are created that are different from the conditions in the entire volume of the room. With the help of an air shower, the following air parameters at the location of a person can be changed: mobility, temperature, humidity and concentration of one or another harmful agent. Typically, the area of ​​action of the air shower is: fixed workplaces, places of the longest stay of workers and places of rest. On fig. 3.19 schematically depicts an air shower used to create the necessary conditions in the workplace.

Most often, air showers are used in hot shops at workplaces subject to the influence of thermal radiation.

Rice. 3.18. Onboard suction: a - simple; b - overturned; in - front blower

Rice. 3.19. Air shower: a - vertical; b - inclined; in - group

3.0 m/s, temperature can vary from 16 to 24 °C. If the air shower is used for dust control, the air speed should not be higher than 0.5-1.5 m/s to prevent dust deposited on the floor from rising.

The design of the air outlet (supply nozzle) has a great influence on the efficiency of the air shower. It is advisable to have this device rotatable and at the same time provide for the possibility of changing the angle of inclination of the flow axis by introducing rotary vanes. On fig. 3.20 shows the supply nozzles designed by V.V. Baturin, made taking into account these two requirements.

Classification of ventilation and air conditioning systems

Rice. 3.20. Supply nozzles designed by V. V. Baturin: a - with an upper supply; b - with lower air supply

The air shower can use outdoor air or indoor air. The latter, as a rule, undergoes appropriate processing (most often cooling). Outside air can also be processed to give it the required parameters.

Shower installations can be stationary or mobile.

Mobile units use indoor air, often treated by spraying water into the exhaust air stream.

The adiabatically evaporating water reduces the air temperature. On fig. Figures 3.21 and 3.22 show water-air showers of this type designed by the Moscow and Sverdlovsk Institutes of Occupational Safety and Health.

In air curtains, as well as in air showers, the main property of the supply torch is used - its relative range. Air curtains are arranged to prevent air from entering through technological openings or gates from one part of the building to another or outside air into production facilities. On fig. 3.23 shows air curtain schemes designed to prevent or drastically reduce the penetration of cold outside air into the workshop through the gate. The air supplied for the curtain can be preheated, and then the curtains are called air-thermal.

Air curtains designed to prevent the penetration of cold air should be provided at gates that are opened more than five times or for at least 40 minutes per shift, as well as at technological openings of heated buildings located located in areas with an estimated outdoor temperature for designing a heating system- 15 °С and below, when the possibility of arranging gateways is excluded. If the decrease in indoor air temperature(technological or sanitary- hygienic reasons) is invalid, curtains can be designed for any duration of opening and any calculated outdoor air temperature. This requires technical- economic rationale for this decision.

Rice. 3.21. Water-air shower type MIOT small model:

Rice. 3.22. Mobile fan unit SIOT-3:

Rice . 3.23. Air curtains: a - operating principle; b - various ways of air supply:

I- air supply from below; II - lateral air supply on one side; III - same on both sides

1 - pipeline for water supply

from the water supply; 2 - casing; 3 - electric motor; 4 - axial fan; 5 - drain pipe; 6 - stand; 1 - axial fan; 2 - electric motor; 3 - nozzles; 4 - metal fairing; 5 - stand on wheels; 6 - pipeline for supplying water from the water supply

In the case of a short-term (up to 10 minutes) opening of the gate, as a rule, a decrease in air temperature is allowed at workplaces protected from blowing by air rushing through the gate, screens or partitions. The degree of reduction depends on the nature of the work performed: with light physical work - up to 14 ° C, moderate work - up to 12 °, hard work - up to 8 °. If there are no permanent jobs in the area of ​​the gate, the temperature in the working area of ​​this area may drop to +5°.

Very close to air-thermal curtains in their purpose are the so-called air buffers, created by supplying warm air to the vestibules of public buildings (shops, clubs, theaters, etc.).

At present, the necessary conditions of the air environment in the workplace are quite often created with the help of special ventilated cabins. In such cabins, conditions are maintained that are different from the conditions in the entire volume of the production facility. This is achieved most often by supplying specially prepared air to the cabins: in hot shops - cooled, in cold, unheated rooms - heated. Ventilated cabins can be classified as local ventilation systems. Naturally, their use is possible when the workplace is strictly fixed, for example, at the control panel. On fig. 3.24 shows a ventilated cabin for a crane control post, developed by the Leningrad Institute of Labor Protection.

General exchange ventilation systems can be supply and exhaust (Fig. 3.5, 3.6, 3.9). When using general exchange systems, the task is to create the necessary conditions for the air environment in the entire volume of the room or in the volume of the working area. Unlike local systems, in this case, all the hazards released in the room are distributed throughout the entire volume. Consequently, the main task that must be solved when designing the systems under consideration is to ensure that the content of one or another hazard in the indoor air does not exceed the maximum allowable concentration, and the values ​​of meteorological parameters meet the relevant requirements.

Often the room is equipped with supply and exhaust general ventilation systems (Fig. 3.10).

The general exchange method of creating the specified conditions of the air environment is also widely used in combination with air conditioning systems.

Rice. 3.24. ventilated cabin

In this course, this method is given a lot of attention, since it is the main one for MO objects.

Air showering is the most effective measure for creating the required meteorological conditions (temperature, humidity and air velocity) at permanent workplaces. The use of air showers is especially effective in case of significant thermal radiation or in open production processes, if the technological equipment that emits harmful substances does not have shelters or local exhaust ventilation. Air showering is a jet of air directed to a limited workplace or directly to the worker.

The mobility of air in the workplace during air showering reaches from 1 to 3.5 m/s. Showering is carried out with special pipes, while the jet is directed to the irradiated areas of the body: head, chest. The size of the blown area is m. Showering can be carried out with external untreated air, adiabatically cooled air or isohumidity cooling. In some cases, it is allowed to use recirculated air, while there should be little thermal radiation and no harmful emissions.

The cooling effect of air showering depends on the temperature difference between the body of the worker and the air flow, as well as on the speed of air flow around the cooled body. When the jet coming out of the hole is mixed with the surrounding air, the velocity, temperature difference, and concentration of impurities in the cross section of the free jet change. The jet must be directed in such a way as to prevent, as far as possible, hot or fume-laden air from being sucked in. For example, when a fixed workplace is located near an open furnace opening, a showering device should not be placed near the opening with the direction of the jet towards the worker, since in this case it is impossible to avoid the suction of hot gases, as a result of which superheated air will flow to the worker. When calculating air showering systems, design parameters A for warm and design parameters B for cold periods of the year should be taken. To calculate year-round air showering, the warm period is taken as the calculation period, and only the supply air temperature is determined for the cold period.

Systems supplying air to the air shower nozzles are designed separately from systems for other purposes. The distance from the place of air outlet to the workplace should be taken at least 1 m. Calculation procedure

1. They are set by the air parameters at the workplace, they indicate the installation location of the nozzle, the distance from the nozzle to the workplace, and are also set by the type of shower nozzle. 2. We determine the air velocity at the outlet of the nozzle depending on the normalized air mobility in the room , where is the normalized air mobility, is the distance from the nozzle to the workplace, m, is the coefficient of change in speed, is the section of the selected nozzle. 3. We determine the minimum temperature at the outlet of the branch pipe , where is the normalized temperature, is the coefficient of temperature change. 4. We determine the air flow required for supply to the nozzle.

Calculation of the air showering system at the workplace of the metal pourer

Air showering is one of the most effective measures to combat radiant heat, as well as toxic gases and vapors released during the work of forging hammers and presses. Supplied from above through special devices, heated (in winter) and cooled (in summer) air supplies the worker with fresh humidified air, and by adjusting the air speed, it is possible to achieve a partial decrease in air temperature at the workplace. Sometimes air is supplied to the workplace through flexible rubberized hoses from a mobile air shower unit. The appearance of the shower installation is shown in Fig. 3.4.

Figure 3.4 - Shower installation

We will calculate the air shower according to the method of Zlobinsky B.M.

The calculation of air showers is reduced to determining the diameter of the shower pipe and the parameters of the air leaving it.

The jet cross-sectional diameter is calculated by formula 2:

where is the turbulence coefficient, depending on the shape of the outlet section (0.06 - 0.12). Let's take =0.12.

x is the distance from the jet outlet from the nozzle to the workplace. Let's take x = 2 m.

d 0 - diameter of the outlet section of the pipe. Let's take d 0 \u003d 0.7.

The speed at which air exits the nozzle is calculated by the formula:

where area is the average air speed at the working site. This speed should not exceed 0.3 m/s. Let's take the area \u003d 0.3 m / s;

b is a coefficient varying from 0.05 to 1 depending on the ratio. Let's take d r.pl. =2 m, then:

We substitute the obtained values ​​into (3) and obtain that

The required temperature at the outlet of the branch pipe is determined by the formula:

where t o.c. - ambient temperature, it is 20-25 0 С. Let's take 22.5 0 С.

t cp - the average desired air temperature at the melting site. According to SanPiN 2.2.4.548-96, the allowable temperature at the site is 19-21 0 С, let's take 20 0 С.

C is a coefficient that, like the coefficient b, depends on the ratio and varies from 0.345 to 0.22. Let's take C \u003d 0.25.

Thus, in order for the temperature at the melting site to be equal to 20 0 C, an air jet d=2.05 m is provided at t patr = 19.3 0 C, which is supplied to the melting site by a fan with a speed of 0.15 m/s and with a productivity of 1800 m 3 / h.

The calculation of the economic efficiency of installing an air showering system of the VD-1800 type at the workplace of a metal pourer will be made in the organizational and economic section of the graduation project.

Diseases caused by exposure to the heating microclimate of foundry (hot) shops and their prevention

Heating microclimate is a combination of parameters in which there is a change in heat exchange between a person and the environment, manifested in the accumulation of heat in the body (> 2 W) and / or in an increase in the proportion of heat loss by evaporation of moisture (> 30%). The impact of the heating microclimate also causes a violation of the state of health, a decrease in working capacity and labor productivity.

Working in such conditions can lead to uncomfortable heat sensations, significant stress on the processes of thermoregulation, and with a large thermal load - to health problems (overheating).

This kind of microclimate is created in rooms where the technology is associated with significant heat releases into the environment, that is, when production processes take place at high temperatures (roasting, calcining, sintering, melting, boiling, drying). The sources of heat are the surfaces of equipment, fences heated to a high temperature, processed materials, cooling products, hot vapors and gases escaping through equipment leaks. The release of heat is also determined by the operation of machines, machine tools, as a result of which mechanical and electrical energy is converted into heat.

Class 36d, 1a, USSR

Iatenaa-teiaeeekav

P. V. Uchastkin

VENTILATION SHOWER UNIT FOR WORK

INSIDE HOT PRODUCTION EQUIPMENT

In some cases, it becomes necessary to carry out work inside hot production equipment. These include repair work in the furnaces of powerful electric steam boilers.

: stations, hot open-hearth furnaces, as well as work on production operations inside furnaces for heating and firing various products, etc.

These works are carried out under conditions of high temperature (up to 100), which is caused by the need to reduce the downtime of the specified production equipment. These works are very heavy and do not allow their long-term maintenance.

L7H Lightening of the dust During such works, a mobile ventilation shower unit is offered. The principle of operation of the installation is aimed at creating a zone of low temperature in the hot space by supplying air with a lower temperature than the temperature inside the hot equipment.

A distinctive feature of the proposed installation is the method of protecting the air shower torch from excessive new! singing temperature while mixing in the surrounding grief: .ci o Air.

Known designs of such installations do not provide protection for the suffocating 1ra kel a From on Grs VYA1. For the indicated shortcoming, it was proposed to install water-spray nozzles on the shower head. which create a curtain of finely sprayed water on the periphery of the air torch. Sucking from the surrounding space to the main jet, hot air meets atomized water on its way. An intense IIcoapeHIIe of water occurs, resulting in a decrease in the ambient air temperature, which leads to a significant decrease! !o temperature in the suffocating flame.

To move the torch, it is proposed to use a flexible air duct, at the end of which is a 11PIHI Pe11.7PH d31INRU1oshi1 pump. H!OH:Ioå can be mounted on a stand so that it can be rotated as needed! direction. No. 84128

Figure 1 (Fig. 1) shows a diagram of a ventilation shower installation in operation, in Fig. 2 - installation without hose, side view; in fig. 3 - "the same, front view.

The 4th unit of the installation consists of a centrifugal fan 1 medium pressure and an electric motor 2. The fan impeller is mounted on the motor shaft. The fan and the electric motor are mounted on a trolley 3, which has three wheels: two of them are mounted on a common axis, the third is swivel. Turning the wheel 1 II cT c H Il P H Il o M o IH H P g H o B T II H . T Ya kos o f O R vI;1 0 H H e x o I O B o l l I B c T H telekkn provides it with good maneuverability. The fan inlet is protected with mesh. For winding the rubber plya11GYA 4, a coil b is used.

On the frame of the trolley, a starting device 6 of the electric motor is mounted, consisting of two package switches. One of the switches is used to turn the motor on or off, the other to switch phases, so that with any connection to the electric current network, the direction of rotation of the electric motor necessary for the fan is ensured.

The air duct 7 is made in: 1de of a flexible metal sleeve and has a length of 6 liters. For more convenient use, it consists of two links connected “into us” with the help of cuffs and locks. At one end of the air duct there is a square flange for connection to the fan outlet, and at the other end there is a transition pipe with a round flange and tightening locks for connection with a shower head 8. The latter is a transition outlet, inside which 10 guide vanes are installed. The nozzle is articulated with a tripod 9, there is a round flange around which o "can freely rotate 360. On the upper part of the nozzle, a tap 10 pipes for supplying water and water sprayers 11 with a diameter of 0.6 l1m are fixed.

To prevent clogging of water sprayers, a l2 mesh filter is placed on the rubber hose. The hose has an inner diameter of 10 mm, at one end it has a union nut for connection with a tube of water sprayers, and on the other - a nut for connecting to a faucet on the water supply.

The worker must be in the area of ​​the airflow coming out of the nozzle, so that the head and upper body are in the flow.

When moving the worker, the choking flow is directed to a new location by turning the nozzle around the axis.

The unit allows you to reduce the temperature at the workplace by

30 - 50C. If usually after 5 - 10 l1in stay inside the furnace of a boiler or an open-hearth furnace, the body temperature of a worker reached 39, then when working with the proposed installation and for from 30 11k to one hour, the body temperature was 37. ,1", invention

1. Ventilation shower installation for work inside hot production equipment, characterized in that, in order to prevent the temperature increase of the showering air torch from mixing ambient air with it, water spray nozzles are installed on the periphery of the shower nozzle ycxaHoBle, creating a water curtain around the air torch, providing a decrease in the temperature of the sucked air. No. 84128

2. Installation according to claim 1, characterized by the use of a flexible air duct, at the end of which a shower nozzle is attached, in order to bring the shower torch closer to the place of work.

3. Installation according to paragraphs. 1 and 2, characterized in that the showerhead is mounted on a stand with the possibility of turning it to direct the showering torch. No. 84128

11dp. to the stove 30j. (II – 61)

oum format. 70 108)i;

CBTI at 1 (office for Ivobrstspii and discoveries of the prp Council of Ministers of the USSR

Moscow, Center, M. Cherkassky lane, 216.

Volume It, 35 ed. l.

Price 7 kop.

Printing house, Sapunova Ave., 2, Editor N.I. Mosin Tskred A.A.

Air showering is used to create the required meteorological conditions at permanent workplaces during thermal radiation and in open production processes, if the technological equipment that emits harmful substances does not have shelters or local exhaust ventilation. When showering, either outside air can be supplied with its processing in supply chambers (cleaning, cooling and heating in the cold season, if necessary), or internal air. When designing air showers, measures must be taken to prevent the blowing off of industrial harmful emissions to nearby permanent jobs. The air jet should be directed so that, if possible,

it excluded the suction of hot or gas-polluted air. Systems supplying air to air showers are designed separately from systems

other destination. Air distributors are usually installed at a height of at least 1.8 m from the floor (up to their lower edge). The distance from the place of air outlet to the workplace should be at least 1 m, and the air flow should be directed: - to the chest of a person horizontally or from above at an angle of up to 45 ° to ensure normalized temperatures and air speed at the workplace; - in the face (breathing zone) horizontally or from above at an angle of up to 45 ° to ensure acceptable concentrations of gas and dust at the workplace; at the same time, normalized temperature and air velocity must be ensured. Depending on the air supplied and treatment, air shower systems are divided into: 1. supplying outdoor air with treatment, 2. supplying outdoor air without treatment, 3. supplying indoor air with cooling, 4. supplying indoor air without treatment. Downdraft airflow is a type of air shower. It is carried out by applying from a close distance to fixed workplaces or to a resting place for workers. The falling flow makes it possible to provide at the workplace, where the conditions do not meet sanitary standards, favorable environmental conditions at low costs of cold, heat and electricity. Air oases- a certain volume of the room in which meteorological conditions are maintained that are different from the entire volume of the room. Arrange in rooms with excess heat and high altitude. A small area of ​​the workshop, which is the place of permanent residence of the attendants, is fenced off from the entire workshop with partitions 2-2.2 m high and flooded with cold air.

14. Measures to combat mechanical and aerodynamic noise generated by ventilation units.

If a complex sound does not contain clearly expressed frequency

posing, they call him noise. Noises are estimated using spec-

Trograms in which the sound energy of a complex sound is distributed over frequencies or frequency bands.

Vibration isolation of ventilation units by means of spring dampers,

The use of soundproofing walls in the ventilation chamber,

False ceiling installation.

Arrangement of floating floors and reduction of air velocity.

To reduce the level of mechanical noise, it is necessary to connect the air ducts to the fan through flexible connectors.

To reduce the level of aerodynamic noise on the main sections of the air ducts, silencers (plate and tubular) should be provided

Noise reduction measures in ventilation and air conditioning systems are based on two types of operations, applied simultaneously or sequentially:

Measures related to the noise source itself;

Measures related to channels, noise transmission.

Sound waves appear as a result of non-stationary processes

owls, which always accompany the steady-state average operation of the fan.

Velocity pulsations and pressure fluctuations in the air stream, pro-

flowing through the fan are the cause of aerodynamic noise. (vortex noise, noise from local flow inhomogeneities, rotational noise)

fluctuations of structural elements of the ventilation

installations cause mechanical noise. The excitation of mechanical noise in fans usually has an impact character - in ball bearings, a drive, knocks in the gaps.

The noise generated by the ventilation unit is transmitted to the following

ways:

a) through the air inside the air ducts to the room through

supply and exhaust grilles or into the atmosphere through the air intake grilles of the supply systems or through the exhaust system shafts; b) through the walls of transit air ducts to the room through which they are laid;

c) according to the air environment surrounding the ventilation unit, to

enclosing structures of the chamber and through them into adjacent rooms

scheniya. Each of the listed noise transmission paths determines the appropriate measures that must be taken to reduce noise in rooms with a rated sound level.

NOISE REGULATION

Noises are normalized based on their permissible impact on the organization

human nism, i.e., impacts in which noise either does not affect a person’s well-being at all or this effect is insignificant. (63-8000 Hz)

ACOUSTIC CALCULATION OF THE VENTILATION SYSTEM The task of acoustic calculation of ventilation systems is to determine the sound pressure level created at the design point by the operating ventilation unit.

MEASURES TO REDUCE LEVELS

SOUND PRESSURE Reduced sound pressure levels at constant

workplaces or at the design points of the premises can be carried out

application of a complex of the following measures: 1) installation of fans, the most advanced in terms of acoustic characteristics; 2) selection of optimal fan operation modes: a) at maximum efficiency; b) with the minimum possible pressure developed by the fan 3) a decrease in the air velocity in the branches, elbows, tees and other elements of the ventilation network: a) up to 5-6 m/s in the main air ducts and up to 2-4 m/s in the branches for public buildings and auxiliary buildings of industrial enterprises; b) up to 10-12 m/s in main air ducts and up to 4-8 m/s in branches for industrial buildings. 4) a change in the acoustic qualities of the room, a decrease in the sound power level of noise sources along the sound propagation path by installing silencers or lining the internal surfaces of air ducts with sound-absorbing materials.

SILENCER DESIGNS

Used to dampen noise in ventilation systems.

silencers of dissipative action, i.e. those in which

scattering of sound energy.

By design, silencers are divided into tubular, honeycomb

high, lamellar and chamber

VIBRATION ISOLATION OF VENTILATION UNIT

Vibrations that occur during the operation of the ventilation unit,

are transmitted to the air ducts and the base on which the unit is mounted. Vibrations cause structural sound *. When the fan is installed on the foundation, ground vibrations are transmitted to the foundations, walls and ceilings of the building. When installing a fan on a floor, structural sound is directly transmitted to the underlying room. Reduction of structural sound transmitted to the base can be achieved by installing fans on vibration isolators.