Installation 

Effective solutions to reduce noise from power equipment of thermal power stations and boiler houses. How to reduce the noise of the boiler room: at the design stage and with special tools Noise protection in the boiler room

Sound insulation of a boiler room. In this publication, we will consider the causes of increased noise and vibration levels from gas boilers and boiler rooms, as well as ways to eliminate them in order to achieve standard indicators and the level of comfort of residents.

Installation of autonomous modular gas boilers on roofs apartment buildings is gaining popularity among developers. The advantages of such a boiler house are obvious. Among them

    No need to erect a separate building for boiler room equipment

    Reduction of heat losses by 20% due to the small number of heating mains in comparison with heating from the central heating network

    Savings on the installation of communications from the coolant to the consumer

    No need for forced ventilation

    The possibility of full automation of the system with a minimum of staff

One of the disadvantages of a rooftop boiler is vibrations from the boiler and pumps. As a rule, they are the result of shortcomings in the design, construction and installation of boiler room equipment. Therefore, the responsibility for eliminating the increased noise level and soundproofing the boiler room lies with the developer or housing management company.

The noise from the boiler house is low-frequency and is transmitted through the structural elements of the building directly from the source and through communications. Its intensity in a room equipped for a boiler room is 85-90dB. Noise insulation of a rooftop boiler room is justified if it is produced from the source side, and not in the apartment. Soundproofing the ceiling and walls in an apartment with such noise is expensive and ineffective.

Causes of increased noise level in the rooftop boiler room.

    Insufficient thickness and massiveness of the base on which the boiler room equipment stands. This leads to penetration airborne noise to the apartments through the floor slab and the technical floor.

    Lack of proper vibration isolation of the boiler. At the same time, vibrations are transmitted to ceilings and walls, which radiate sound into apartments.

    Rigid fastening of pipelines, communications and their supports is also a source of structural noise. Normally, pipes should pass through building envelopes in an elastic sleeve, surrounded by a layer of sound-absorbing material.

    Insufficient thickness of the pipeline, as a design error, leading to high water velocity and the creation of an increased level of hydrodynamic noise.

Soundproofing of the rooftop boiler room. List of events.

    Installation of vibration isolating supports under the equipment of the boiler room. The calculation of materials for vibration isolation is made taking into account the area of ​​\u200b\u200bthe support and the weight of the equipment;

    Elimination of "hard links" in the places of fastening of pipeline supports with the help of material silomer, thermosound insulation or installation of vibration fasteners on studs fixing communications;

    In the absence of elastic sleeves, expansion of the pipeline passage through the supporting structures, wrapping with elastic material (k-flex, vibrostack, etc.) and a heat-resistant layer (basalt cardboard);

    Wrapping the pipeline with a material that reduces heat loss and has sound insulation properties: , Texound 2ft AL;

    Additional sound insulation of enclosing structures of the roof boiler room;

    Installation of rubber compensators to reduce the transmission of vibrations through the pipeline;

    Installation of silencers in the exhaust gas duct;

    Installation of noise-absorbing materials based on basalt (Stopsound BP) or fiberglass (Acustiline fiber) allows you to reduce background noise in the boiler room by 3-5dB.

SOUND INSULATION OF A BOILER IN A WOODEN HOUSE.

Building codes and fire safety regulations dictate the installation of the boiler in a special room equipped with a separate entrance. As a rule, it is located in the basement or basement. With this arrangement, complaints about an increased noise level from the boiler are rare.

A boiler installed on the same floor with living rooms, which has high noise levels with complete silence in country house may cause inconvenience to residents. Therefore, the soundproofing of the boiler may be relevant.

The reasons for the increased noise level can be similar to those of a rooftop boiler, but on a smaller scale. They also include

    Features of the design of the outer box of the boiler. In most models of boilers, the burner and fan are closed with a separate damper, which reduces the noise produced by the burner. If the only soundproofing protection is the plastic box of the boiler, the noise from the burner can be noticeable.

    Noisy fan from the manufacturer.

    Unbalance of the fan, dirt sticking due to dust from outside and neglect of maintenance measures.

    Air entering the heating system.

    Incorrect gas burner setting.

    Rigid system for fastening the boiler and outlet pipes.

The soundproofing of the boiler begins with identifying the causes of the increased noise level and is associated with the work of the gas service employees serving it or the company involved in soundproofing the premises.

If the operation of the boiler and the system is adjusted, then

    We mount the boiler on a vibration-isolated platform on mounts with a force meter

    We install rubber compensators in the places where the pipes exit from the boiler body

    We purchase a noise-protective casing for the boiler

    We make additional soundproofing of the walls of the boiler room

    To reduce background noise in the boiler room

Welcome to the Comfort Zone!

Russian Ministry of Health

Moscow

1. Developed by the Research Institute of Occupational Medicine of the Russian Academy of Sciences (Suvorov G.A., Shkarinov L.N., Prokopenko L.V., Kravchenko O.K.), Moscow Research Institute of Hygiene. F.F. Erisman (Karagodina I.L., Smirnova T.G.).

2. Approved and put into effect by the Decree of the State Committee for Sanitary and Epidemiological Supervision of Russia dated October 31, 1996 N 36.

3. Introduced instead of "Sanitary norms for permissible noise levels at workplaces" N 3223-85, "Sanitary norms for permissible noise in residential and public buildings and on the territory of residential development" N 3077-84, "Hygienic recommendations for establishing noise levels at workers places, taking into account the intensity and severity of labor "N 2411-81.

APPROVED
Decree of the State Committee for Sanitary and Epidemiological Supervision
Russia dated October 31, 1996 N 36
Date of introduction since approval

1. Scope and general provisions

1.1. These sanitary norms establish the classification of noise; normalized parameters and limit acceptable levels noise at workplaces, permissible noise levels in the premises of residential, public buildings and in residential areas.

1.2. Sanitary standards are mandatory for all organizations and legal entities in the territory Russian Federation regardless of the form of ownership, subordination and affiliation and individuals regardless of citizenship.

1.3. References and requirements of sanitary standards should be taken into account in the State standards and in all regulatory and technical documents regulating planning, design, technological, certification, operational requirements for production facilities, residential, public buildings, technological, engineering, sanitary equipment and machines, vehicles, household appliances.

1.4. Responsibility for compliance with the requirements of the Sanitary Norms lies with statutory order on heads and officials of enterprises, institutions and organizations, as well as citizens.

1.5. Control over the implementation of the Sanitary Standards is carried out by the bodies and institutions of the State Sanitary and Epidemiological Supervision of Russia in accordance with the Law of the RSFSR "On the Sanitary and Epidemiological Welfare of the Population" dated April 19, 1991 and taking into account the requirements of the current sanitary regulations and norms.

1.6. Measurement and hygienic assessment of noise, as well as preventive measures should be carried out in accordance with the guideline 2.2.4 / 2.1.8-96 "Hygienic assessment of physical factors of production and environment» (under approval).

1.7. With the approval of these sanitary standards, the “Sanitary standards for permissible noise levels at workplaces” N 3223-85, “Sanitary standards for permissible noise in the premises of residential and public buildings and on the territory of residential development” N 3077-84, “Hygienic recommendations for setting levels noise at workplaces, taking into account the intensity and severity of labor "N 2411-81.

2.1. Law of the RSFSR "On the sanitary and epidemiological well-being of the population" dated 19.04.91.

2.2. Law of the Russian Federation "On Environmental Protection" dated 12/19/91.

2.3. Law of the Russian Federation "On Protection of Consumer Rights" dated 07.02.92.

2.4. Law of the Russian Federation "On certification of products and services" dated 10.06.93.

2.5. "Regulations on the procedure for the development, approval, publication, implementation of federal, republican and local sanitary rules, as well as on the procedure for the operation of all-Union sanitary rules on the territory of the RSFSR", approved by Resolution of the Council of Ministers of the RSFSR of 01.07.91 N 375.

2.6. Decree of the State Committee for Sanitary and Epidemiological Supervision of Russia "Regulations on the procedure for issuing hygienic certificates for products" dated 05.01.93 N 1.

3. Terms and definitions

3.1. Sound pressure is a variable component of air or gas pressure resulting from sound vibrations, Pa.

3.2. Equivalent / energy / sound level, LA.eq., dBA, intermittent noise - the sound level of constant broadband noise, which has the same RMS sound pressure as this intermittent noise for a certain period of time.

3.3. The maximum permissible level (MPL) of noise is the level of a factor that, during daily (except weekends) work, but not more than 40 hours a week during the entire working experience, should not cause diseases or deviations in the state of health detected by modern research methods in in the process of work or in the remote periods of life of the present and subsequent generations. Compliance with the noise limit does not exclude health problems in hypersensitive individuals.

3.4. The permissible noise level is the level that does not cause significant concern to a person and significant changes in the indicators of the functional state of noise-sensitive systems and analyzers.

3.5. Maximum sound level, LА.max., dBA - the sound level corresponding to the maximum indicator of a measuring, direct-reading instrument (sound level meter) during visual reading, or the sound level value exceeded for 1% of the measurement time during registration by an automatic device.

4. Classification of noise affecting a person

4.1. According to the nature of the noise spectrum, there are:

  • broadband noise with a continuous spectrum more than 1 octave wide;
  • tonal noise, in the spectrum of which there are pronounced tones. The tonal nature of the noise for practical purposes is established by measuring in 1/3 octave frequency bands by exceeding the level in one band over the neighboring ones by at least 10 dB.

4.2. According to the temporal characteristics of noise, there are:

  • constant noise, the sound level of which during an 8-hour working day or during the measurement time in the premises of residential and public buildings, on the territory of residential development changes in time by no more than 5 dBA when measured on the time characteristic of the sound level meter “slowly”;
  • intermittent noise, the level of which during an 8-hour working day, work shift or during measurements in the premises of residential and public buildings, on the territory of residential development changes over time by more than 5 dBA when measured on the time characteristic of the sound level meter "slowly".

4.3. Intermittent noises are divided into:

  • time-varying noise, the sound level of which changes continuously over time;
  • intermittent noise, the sound level of which changes stepwise (by 5 dBA or more), and the duration of the intervals during which the level remains constant is 1 s or more;
  • impulse noise consisting of one or more sound signals, each with a duration of less than 1 s, while the sound levels in dBAI and dBA, measured respectively on the time characteristics "impulse" and "slow", differ by at least 7 dB.

5. Normalized parameters and maximum permissible noise levels at workplaces

5.1. Characteristics of constant noise at workplaces are sound pressure levels in dB in octave bands with geometric mean frequencies of 31.5; 63; 125; 250; 500; 1000; 2000; 4000; 8000 Hz, determined by the formula:

Where P is the root mean square value of sound pressure, Pa;
P0 is the initial value of the sound pressure in the air equal to 2 10-5Pa.

5.1.1. It is allowed to take as a characteristic of constant broadband noise at workplaces the sound level in dBA, measured on the “slow” time characteristic of the sound level meter, determined by the formula:

Where RA is the root mean square value of the sound pressure, taking into account the correction "A" of the sound level meter, Pa.

5.2. A characteristic of intermittent noise at workplaces is the equivalent (in terms of energy) sound level in dBA.

5.3. Maximum permissible sound levels and equivalent sound levels at workplaces, taking into account the intensity and severity of labor activity.

A quantitative assessment of the severity and intensity of the labor process should be carried out in accordance with Guideline 2.2.013-94 "Hygienic criteria for assessing working conditions in terms of harmfulness and danger of factors in the working environment, severity, intensity of the labor process."

6. Rated parameters and permissible noise levels in the premises of residential, public buildings and residential areas

6.1. Normalized constant noise parameters are sound pressure levels L, dB, in octave bands with geometric mean frequencies: 31.5; 63; 125; 250; 500; 1000; 2000; 4000; 8000 Hz. For an approximate assessment, it is allowed to use sound levels LA, dBA.

6.2. The normalized parameters of intermittent noise are equivalent (in terms of energy) sound levels LAeq, dBA, and maximum sound levels LAmax, dBA.

Evaluation of non-permanent noise for compliance with permissible levels should be carried out simultaneously on the equivalent and maximum sound levels. Exceeding one of the indicators should be considered as non-compliance with these sanitary standards.

6.3. Permissible values ​​of sound pressure levels in octave frequency bands, equivalent and maximum sound levels of penetrating noise in the premises of residential and public buildings and noise in residential areas.

Bibliography

  • Guideline 2.2.4 / 2.1.8.000-95 "Hygienic assessment of the physical factors of the production and environment."
  • Guideline 2.2.013-94 "Hygienic criteria for assessing working conditions in terms of harmfulness and danger of factors in the working environment, severity, intensity of the labor process."
  • Suvorov G. A., Denisov E. I., Shkarinov L. N. Hygienic regulation of industrial noise and vibrations. — M.: Medicine, 1984. — 240 p.
  • Suvorov G. A., Prokopenko L. V., Yakimova L. D. Noise and health (environmental and hygienic problems). - M: Soyuz, 1996. - 150 p.
  • Permissible levels of noise, vibration and sound insulation requirements in residential and public buildings. MGSN 2.04.97 (Moscow city building codes). - M., 1997. - 37 p.

To eliminate each of these noises, various ways. In addition, each type of noise has its own properties and parameters, and they must be taken into account when manufacturing low-noise refrigeration chillers.

Can apply a large number of different insulation and not achieve the desired result, but on the contrary, using the minimum amount of the “right” material in the right place, using insulation according to the technology, to achieve excellent low noise.

To understand the essence of the soundproofing process, let's turn to the main methods for achieving low-noise industrial water coolers.

First you need to define the basic terms.

Noise — undesirable, unfavorable for the target human activity within the radius of its propagation sound.

Sound — wave propagation of particles oscillating due to external influence in some medium - solid, liquid or gaseous.

There are other less common and significantly more expensive and cumbersome solutions to achieve near-absolute silence, if required by the chiller installation site. For example, soundproofing technical room, where the compressor-evaporative unit of the chiller is located, the use of water condensers or wet cooling towers without the use of fans, and some others are more exotic, but they are extremely rarely used in practice.

Page 7 of 21

Due to the fact that noise at modern power plants, as a rule, exceeds permissible levels, in last years noise suppression works were widely developed.
There are three main methods for reducing industrial noise: noise reduction at the source itself; reduction of noise on the ways of its propagation; architectural, construction and planning solutions.
The method of reducing noise at the source of its occurrence is to improve the design of the source, to change technological process. The most effective application of this method in the development of new power equipment. Recommendations for reducing noise at the source are given in § 2-2.
For sound insulation of various rooms of the power plant (especially the engine and boiler rooms), as the most noisy, building solutions are used: thickening the outer walls of buildings, the use of double-glazed windows, hollow glass blocks, double doors, multilayer acoustic panels, sealing windows, doors, openings, right choice places of air intake and exhaust of ventilation installations. It is also necessary to ensure good sound insulation between the machine room and the basement, careful sealing of all openings and openings.
When designing a machine room, small rooms with smooth, sound-absorbing walls, ceilings, and floors are avoided. Wall cladding with sound-absorbing materials (SAM) can give a noise reduction of approximately 6-7 dB in medium-sized rooms (3000-5000 m3). For large rooms, the cost-effectiveness of this method becomes controversial.
Some authors, such as G. Koch and H. Schmidt (Germany), as well as R. French (USA), believe that the acoustic treatment of the walls and ceilings of the station premises is not very effective (1-2 dB). The data published by the French Energy Authority (EDF) indicate the promise of this noise suppression method. The treatment of ceilings and walls in boiler rooms at the power plants of Saint-Depy and Chenevier made it possible to obtain a sound reduction of 7-10 dB A.
At the stations, separate soundproof control rooms are often built, the sound level in which does not exceed 50-60 dB A, which meets the requirements of GOST 12.1.003-76. Service personnel spend 80-90% of their working time in them.
Sometimes acoustic cabins are installed in machine rooms to accommodate service personnel (duty electricians, etc.). These soundproof booths are independent frame on supports, to which the floor, ceiling, walls are attached. Cabin windows and doors must have increased sound insulation (double doors, double glazing). Provided for ventilation ventilation unit with silencers at the air inlet and outlet.
If it is necessary to have a quick exit from the cabin, it is performed semi-closed, i.e. one of the walls is missing. In this case, the acoustic efficiency of the cabin is reduced, but there is no need for a ventilation device. According to the data, the limit value of the average sound insulation for semi-enclosed cabins is 12-14 dB.
The use of separate cabins of a closed or semi-closed type in the premises of stations can be attributed to personal means protection of operating personnel from noise. Personal protective equipment also includes Various types earbuds and headphones. The acoustic efficiency of earbuds and, especially, headphones in the high-frequency region is quite high and is at least 20 dB. The disadvantages of these tools is that, along with the noise, the level of useful signals, commands, etc. decreases, and skin irritation is also possible, mainly at elevated ambient temperatures. However, it is recommended that you use earbuds and headphones when operating in environments with noise that exceeds acceptable levels, especially in the high frequency region. Of course, it is advisable to use them for short-term exits from soundproof booths or control panels to areas of increased noise.

One of the ways to reduce noise on the paths of its propagation in the premises of stations are acoustic screens. Acoustic screens are made from thin sheet metal or other dense material, which may have a sound-absorbing lining on one or both sides. Acoustic baffles usually have small size and provide local reductions in direct sound from the noise source without significantly affecting the level of reflected sound in the room. At the same time, the acoustic efficiency is not very high and depends mainly on the ratio of direct and reflected sound in calculated point. Increasing the acoustic efficiency of screens can be achieved by increasing their area, which should be at least 25-30% of the sectional area of ​​the room fences in the plane of the screen. At the same time, the efficiency of the screen increases by reducing the energy density of the reflected sound in the screened part of the room. Screen Applications large sizes It also makes it possible to significantly increase the number of workplaces where noise reduction is ensured.

The most effective use of screens is in conjunction with the installation of sound-absorbing linings on the enclosing surfaces of the premises. A detailed presentation of the methods for calculating acoustic efficiency and screen design issues is given in and
To reduce noise throughout the engine room, installations that emit intense sound are covered with casings. Sound-insulating casings are usually made of sheet metal lined on the inside of the PDU. It is possible to completely or partially sheathe the surfaces of the installations with soundproofing material.
According to the data given by American experts in noise attenuation at the International Energy Conference in 1969, the complete equipping of high power turbine units (500-1000 MW) with soundproof casings makes it possible to reduce the level of emitted sound by 23-28 dB A. When turbine units are placed in special isolated boxes efficiency increases to 28-34 dB A.
The range of materials used for sound insulation is very wide and, for example, for the insulation of 143 steam units that were introduced into the USA after 1971, it is distributed as follows: aluminum -30%, sheet steel - 27%, gelbest - 18%, asbestos cement - 11%, brick - 10%, porcelain with an external coating - 9%, concrete - 4%.
In national teams acoustic panels the following materials are used: soundproofing - steel, aluminum, lead; sound-absorbing foams, mineral wool, fiberglass; damping - bituminous compounds; sealing - rubber, putty, plastics.
Wide application received polyurethane foam, fiberglass, sheet lead, vinyl reinforced with lead powder.
The Swiss company Air Force, to reduce the noise of the brush apparatus and exciters of high-power turbine units, covers them with a continuous protective casing with a thick layer of sound-absorbing material, in the walls of which silencers are built into the inlet and outlet of the cooling air.

The design of the casing provides free access to these nodes for carrying out current repair. As studies by this company have shown, the soundproofing effect of the casing of the front part of the turbine is most pronounced at high frequencies (6-10 kHz), where it is 13-20 dB, at low frequencies (50-100 Hz) it is insignificant - up to 2-3 dB .

Rice. 2-10. Sound pressure levels at a distance of 1 m from the gas turbine body type GTK-10-Z
1 - with a decorative casing; 2- with housing removed

Particular attention should be paid to sound insulation in power plants with gas turbine drives. Calculations indicate that at gas turbine power plants, the placement of gas turbine engines (GTE) and compressors is most economical in individual boxes (if the number of GTEs is less than five). When placing four gas turbine engines in a common building, the construction cost of the building is 5% higher than when using individual boxes, and with two gas turbine engines, the difference in cost is 28% Therefore, when there are more than five units, it is more economical to place them in a common building. For example, Westinghouse installs five Type 501-AA gas turbines in one acoustically insulated building.

Usually for individual boxes, sheet metal panels are used, on the inside of which there is a sound-absorbing lining. The sound-absorbing cladding can be made of mineral wool or mineral wool semi-rigid slabs in a fiberglass sheath and covered on the side of the noise source with a perforated sheet or metal mesh. The panels are interconnected by bolts, at the joints - elastic gaskets.
Very effective are multilayer panels used abroad, made of inner perforated steel and outer lead sheets, between which a porous sound-absorbing material is placed. Also used are panels with a multi-layered inner cladding made of a layer of vinyl reinforced with lead powder and located between two layers of fiberglass - inner, 50 mm thick, and outer, 25 mm thick.
However, even the simplest decorative and soundproofing skins provide a significant reduction in background noise in machine rooms. On fig. Figures 2-10 show the sound pressure levels in octave frequency bands, measured at a distance of 1 m from the surface of the decorative casing of a gas compressor unit of the GTK-10-3 type. For comparison, there is also a noise spectrum measured with the cover removed at the same points. It can be seen that the effect of a casing made of a steel sheet 1 mm thick, lined inside with glass fiber 10 mm thick, is 10–15 dB in the high-frequency region of the spectrum. Measurements were made in a workshop built according to standard project, where 6 GTK-10-3 units are installed, covered with decorative cladding.
A common and very important problem for energy enterprises of any type is the sound insulation of pipelines. The pipelines of modern installations form a complex extended system with a huge surface of heat and sound radiation.

Rice. 2-11. Sound insulation of the gas pipeline at the Kirchleigeri TPP: a - insulation scheme; b - components of a multilayer panel
1- metal sheathing from sheet steel; 2 - stone wool mats 20 mm thick; 3- aluminum foil; 4 - multilayer panel 20 mm thick (weight I m2 is 10.5 kg); 5 - bituminous felt; 6 layers of thermal insulation; 7- layer foam

This is especially true for combined cycle power plants, which sometimes have a complex branched network of pipelines and a system of gates.

To reduce the noise of pipelines transporting strongly disturbed flows (for example, in areas behind pressure reducing valves), reinforced sound insulation, shown in Fig. 2-11.
The soundproofing effect of such a coating is about 30 dB A (reduction of the sound level compared to a "bare" pipeline).
For cladding large diameter pipelines, multilayer thermal and sound insulation is used, which is reinforced with ribs and hooks welded to the insulated surface.
The insulation consists of a layer of mastic covelite insulation 40-60 mm thick, on top of which a 15-25 mm thick armored wire mesh is laid. The mesh serves to strengthen the covelite layer and create an air gap. The outer layer is formed mineral wool mats 40-50 mm thick, on top of which a layer of asbestos-cement plaster 15-20 mm thick is applied (80% asbestos grade 6-7 and 20% grade 300 cement). This layer is closed (pasted) with some technical fabric. If necessary, the surface is painted. A similar method of sound insulation using previously existing thermal insulation elements can significantly reduce noise. Additional costs associated with the introduction of new sound insulation elements are negligible compared to conventional thermal insulation.
As already noted, the most intense aerodynamic noise occurs during the operation of fans, smoke exhausters, gas turbine and combined-cycle plants, waste devices (blowing lines, safety lines, lines of anti-surge valves of gas turbine compressors). ROU can also be included here.

Silencers are used to limit the spread of such noise along the flow of the transported medium and its release into the surrounding atmosphere. Silencers occupy an important place in the overall system of measures to reduce noise at power plants, because sound from working cavities can be directly transmitted through intake or discharge devices into the surrounding atmosphere, creating the highest levels of sound pressure (compared to other sources of sound radiation). It is also useful to limit the propagation of noise through the transported medium in order to prevent its excessive penetration through the walls of the pipeline to the outside by installing noise suppressors (for example, a pipeline section behind a pressure reducing valve).
On modern powerful steam turbine units, silencers are placed on the intake of the blower fans. In this case, the pressure drop is strictly limited by the upper limit of the order of 50-f-100 Pa. The required efficiency of these silencers is usually from 15 to 25 dB in the 200-1000 Hz section of the spectrum in terms of installation effect.
So, at the Robinson TPP (USA) with a capacity of 900 MW (two blocks of 450 MW each), to reduce the noise of blower fans, with a capacity of 832,000 m3/h, suction mufflers were installed. The muffler consists of a housing (steel sheets 4.76 mm thick), in which a grid of sound-absorbing plates is located. The body of each plate is made of perforated galvanized steel sheets. Sound-absorbing material - mineral wool, protected by fiberglass.
Koppers manufactures standard sound attenuating blocks used in fan silencers used for drying pulverized coal, air supply to boiler burners, room ventilation.
The noise from smoke exhausters is often a significant hazard, as chimney it can escape into the atmosphere and spread over considerable distances.
For example, at the TPP "Kirchlengern" (Germany), the sound level near the chimney was 107 dB at a frequency of 500-1000 Hz. In this regard, it was decided to install an active silencer in the chimney of the boiler building (Fig. 2-12). The muffler consists of twenty wings 1 with a diameter of 0.32 m and a length of 7.5 m. Taking into account the complexity of transportation and installation, the wings are divided into parts along the length, which are connected to each other and bolted to the supporting structure. The rocker consists of a body made of sheet steel and an absorber (mineral wool) protected by fiberglass. After installing the silencer, the sound level at the chimney was 89 dB A.
The complex task of reducing the noise of gas turbines requires an integrated approach. Below is an example of a set of measures to combat the noise of gas turbines, an essential part of which are silencers in gas-air paths.
To reduce the noise level of a gas turbine unit with a 17.5 MW Olympus 201 turbojet engine, an analysis of the required degree of noise attenuation of the installation was carried out. It was required that the octave noise spectrum, measured at a distance of 90 m from the base of the steel chimney, would not exceed PS-50. The layout shown in fig. 2-13 provides attenuation of GTU suction noise by various elements (dB):


Geometric mean frequency of the octave band, Hz ..............................................

1000 2000 4000 8000

Sound pressure levels at a distance of 90 m from the suction of the gas turbine unit to the sound attenuation .............................................................. .............

Attenuation in an unlined 90° turn (elbow) ..............................................

Attenuation in a lined 90° turn (elbow) ..............................................

Weakening due to the air filter. . . ................................................................. .........

Weakening due to shutters ..............

Attenuation in the high-frequency part of the muffler .............................................. ...

Attenuation in the low-frequency part of the muffler .............................................. ................

Sound pressure levels at a distance of 90 m after noise suppression....

A two-stage plate-type muffler with high and low frequency stages is installed at the air inlet to the gas turbine. The silencer stages are installed after the cycle air cleaning filter.
An annular low-frequency muffler is installed on the GTU exhaust. The results of the analysis of the noise field of the GTU with the turbojet engine on the exhaust before and after the installation of the muffler (dB):


Geometric mean frequency of the octave band, Hz........

Sound pressure level, dB: before silencer installation. . .

after installing the muffler. .

To reduce noise and vibrations, the GTU gas generator was enclosed in a casing, and silencers were installed at the air inlet in the ventilation system. As a result, the noise measured at a distance of 90 m was:

Similar noise suppression systems are used for their gas turbines by the American firms Solar, General Electric, and the Japanese firm Hitachi.
For high-capacity gas turbines, silencers at the air intake are often very bulky and complex engineering structures. An example is the noise suppression system at the Var gas turbine CHPP (Germany), which has two Brown-Boveri GTUs with a capacity of 25 MW each.


Rice. 2-12. Installation of a silencer in the chimney of Kirchlengerä TPP

Rice. 2-13. Noise suppression system for an industrial gas turbine with an aircraft gas turbine engine as a gas generator
1- outer sound-absorbing ring; 2- internal sound-absorbing ring; 3- bypass cover; 4 - air filter; 5- turbine exhaust; 6 - plates of a high-frequency silencer on suction; 7- plates of the low-frequency silencer on suction

The station is located in the central part of the populated area. A silencer is installed at the intake of the GTU, consisting of three stages arranged in series. The sound-absorbing material of the first stage, designed to dampen low-frequency noise, is mineral wool covered with synthetic fabric and protected by perforated metal sheets. The second stage is similar to the first, but differs in smaller gaps between the plates. Third step
consists of metal sheets covered with sound-absorbing material and serves to absorb high-frequency noise. After installing the silencer, the noise of the power plant, even at night, did not exceed the norm adopted for this area (45 dB L).
Similar complex two-stage mufflers are installed at a number of powerful domestic installations, for example, at the Krasnodar CHPP (GT-100-750), Nevinnomysskaya State District Power Plant (PGU-200). A description of their construction is given in § 6-2.
The cost of noise suppression measures at these stations amounted to 1.0-2.0% total cost station or about 6% of the cost of the gas turbine itself. In addition, the use of silencers is associated with a certain loss of power and efficiency. The construction of silencers requires the use of large quantities of expensive materials and is quite laborious. Therefore, the issues of optimizing the design of silencers are of particular importance, which is impossible without knowledge of the most advanced calculation methods and the theoretical basis of these methods.

NOISE LEVEL

Sound power is measured in decibels (dB) in the frequency range from 31.5 to 16000 Hz and in the middle of each frequency band, i.e. at frequencies 31.5; 63; 125; 250 Hz etc. A person perceives sound in the range from 63 to 800 Hz.

Sound power in dB is divided into levels A, B, C and D. The permissible norm of the general noise level is considered to be level A, which is closest to the human sensitivity range. To designate this characteristic, we most use the term "Sound pressure level".

NOISE SOURCE

A running engine is a source of mechanical noise originating in
gas distribution mechanism fuel pump etc., as well as appearing in the combustion chambers, as a result of vibration, air intake and fan operation, if installed. Generally, intake air and radiator noise is less than mechanical noise. Noise level data can be found in the Product Information Manual if required. Noise can be reduced by using a sound-absorbing coating. If the mechanical noise is attenuated to the level 5 mentioned in the Noise level section, attention should be paid to the air and fan noise.

An effective and relatively cheap way is to cover the engine with a casing. At a distance of 1 m from the housing, sound attenuation reaches 10 dB(A). Only specially designed housings are effective, so it is advisable to consult with experts regarding its parameters.

If there are certain requirements for noise outside the premises in which the units are located, the following conditions must be observed:

1) Building structure

The outer walls are made of double bricks with

voids.

Windows - double glazing with spacing

between panes 200 mm.

Doors - double doors with tambour or

single, with screen wall opposite

doorway.

2) Ventilation

Fence openings fresh air and exhaust of heated air must be equipped with noise barriers. These issues should be discussed by the Owner with the Manufacturer.

Screens should not reduce the cross section of the ducts, as this will increase the resistance on the fan. For larger engines requiring more air, screens need to be correspondingly larger and the building needs to be able to fit them properly.

3) Vibration isolation mounts

Mounting the units on anti-vibration mounts prevents the transmission of vibration to walls, other parts of the unit, etc. Vibration is often one of the causes of noise. (See anti-vibration mounts).

4) Exhaust damping

It allows you to attenuate the noise by 30...35 dB(A) at a distance of 1 m from outer wall rooms, provided that high-quality sound absorbers and exhaust silencers are used at the inlet and outlet.