HG/T 20570.10-1995 Professional noise control design for process systems
Some standard content:
Professional noise control design for process system
HG/T20570.10-95
Compiled by: Shanghai Chemical Engineering Design Institute
Approved by: Ministry of Chemical Industry
Effective date: September 1, 1996 Prepared by:
Xia Liangzu, Shanghai Chemical Engineering Design Institute
Auditor:
Jiang Xia, Chen Delin, Shanghai Chemical Engineering Design Institute
Gong Renwei, Process System Design Technology Center, Ministry of Chemical Industry
1.0.1 Noise control standards
GB 3096-82
GB3222-82
GBJ 8785
HGJ6-86
GBJ122—88
Noise standards
“Urban area environmental noise standards”
“Urban environmental noise measurement methods”
“Industrial enterprise noise control design specifications” “Chemical construction project environmental protection design regulations” “Industrial enterprise noise measurement specifications”
GB10070-88 “Urban area environmental vibration standards” GB10071-88 “Urban area environmental vibration measurement methods” GB12348-90 “Industrial enterprise factory boundary noise standards” GB12349-90 “Industrial enterprise factory boundary noise measurement methods” HG20503-92 “Chemical construction project noise control design regulations” 1.0.2 Noise limit values
The noise limit values in the working area are shown in Table 1.0.2. Noise limit values in working areasbzxZ.net
Location category
Production workshops and workplaces (workers are exposed to noise for 8 hours continuously every day)Duty rooms, observation rooms, lounges set up in high-noise workshops (indoor background noise level)
No telephone communication requirements
With telephone communication requirements
Workplaces of precision assembly lines and precision processing workshopsComputer rooms (normal work)Offices, laboratories, and design rooms belonging to workshops (indoor background noise level)Main control room, centralized control room, communication room, telephone switchboard room, fire duty room (indoor background noise level)
Offices, conference rooms, design rooms, and central laboratories belonging to factories (including test, analysis, and measurement rooms) (indoor background noise level)
Infirmary, classrooms, nursing rooms, nurseries, and worker duty rooms (indoor background noise level)The noise limit values listed in the above table are extracted from the national standard GBJ87-85. Table 1.0.2
·2 Principles and contents of noise control design for process systems 2.0.1 Principles of noise control design
2.0.1.1 For all new, expanded and renovated engineering projects, the allowable noise of each production device and workplace should be specified and controlled according to the relevant national, industrial or regional standards based on the requirements for noise control in the design contract. 2.0.1.2 The noise generated in the production device should first be controlled from the sound source, that is, low-noise devices and equipment should be used, and low-noise processes should be used to replace high-noise processes. If the above measures still fail to meet the specified requirements and standards, then noise elimination, sound absorption, sound insulation, vibration isolation and comprehensive management measures should be adopted in the engineering design. 2.0.1.3 When the noise level of production workshops and positions still exceeds the relevant national, industrial and local standards after adopting noise control measures, or some high-noise equipment does not require operators to stay near the equipment frequently, operators working in these occasions can wear ear protectors for personal protection. 2.0.1.4 The noise control design of the process system specialty is to cooperate with the design manager and the environmental protection specialty to understand the noise distribution as a whole, complete the noise control design specified by this specialty, and provide the noise control design conditions and data to the relevant specialty. The work of the process system specialty does not replace the noise control design tasks and responsibilities of the environmental protection specialty and other related specialties.
2.0.2 Noise control design content
The noise control design of the chemical plant should be explained in the environmental protection section and the labor safety and industrial hygiene section respectively and form an independent chapter. The environmental protection specialty is the leading specialty and the affiliated specialty to complete the noise control design. The process system specialty participates in the noise control design of the chemical plant, focusing on the noise control and silencing design of the pipe system in the production device during the engineering design stage. Its main contents are: 2.0.2.1 Consult with relevant specialties (process, equipment, pump, environmental protection, pipeline, building, structure, automatic control, heating, water supply and drainage, thermal engineering, industrial furnace, etc.) to select low-noise processes that meet the specified requirements, such as the process and equipment for the generation of public materials in the chemical plant.
2.0.2.2 Determine the appropriate flow rate to carry out noise control design of the piping system. Control the high noise caused by the high flow rate end flow of the piping valves (including control valves), special pipe fittings (such as ejectors, etc.) and the pipe system due to the sudden change of material flow direction in the pipeline, as well as the flare pipe system, safety valve vent pipe system, etc. 2.0.2.3 When high noise cannot be avoided for the equipment, pipe fittings, and machinery within the jurisdiction of this profession, sound insulation, vibration isolation, and noise reduction countermeasures should be proposed, such as the installation of soundproof enclosures, soundproof rooms, soundproof wrapping, vibration dampers, elastic connections, silencers, etc. 2.0.2.4 Submit the above-mentioned contents to the relevant professionals and design managers in the form of condition tables and data tables. 2.0.2.5 The basis for the work shall be proposed by the design manager and the environmental protection professional. At the beginning of basic engineering design, the process system professionals put forward the "Noise Control Design Regulations Preparation Requirements" of the above content. After completing the PI Figure A version, 350
If necessary, the process system professionals will put forward the "Noise Control Design Regulations" of their profession for use by this profession and related professions in the deepening of engineering design.
2.0.3 Noise Control Design Procedure
The noise control design procedure diagram specifies the general procedure of noise control design for the process system profession, as shown in Figure 2.0.3.
1. Distance attenuation
2. Barrier attenuation
3. Sound absorption condition
Sound field condition
Noise condition
Noise standard|| tt||GBJ87-85
GB3096-82
GB12348-90
GB10070-88
Requirements for use
1.Technology requirements
(pressure drop, heat dissipation, ventilation)
2.Safety issues
3.Construction issues
4.Maintenance issues
5.Economy
Technology major
Condition table
Determine the noise
Attenuation
Solid sound insulation
Vibration damping
Provide the condition table to the environmental protection major
Architecture major
Environmental protection Protection major
Condition table
Vibration absorber
Flexible pipe
System major
Noise survey
Sound transmission path
Noise elimination and sound insulation design
Transmission area
Inside the structure
Determine the noise reduction required for the component
Single-sex support and hanger
Damp vibration reduction
Selection and structural design
Determine the type of noise elimination and sound insulation structure
Silencer structure
Configuration type
System major related plan and elevation drawings
Sound insulation and sound elimination design
Construction instructions
Sound insulation layer material
Material specifications, quantity|| |tt||Construction and use precautions
Design indicators of sound volume and sound attenuation
Figure 2.0.3 System professional noise control design procedure diagram Sound insulation layer
Configuration
Sound insulation wing
Configuration
3 Pipeline system
3.0.1 Main noise sources in the pipeline system and their spectrum characteristics3.0.1.1 Main noise sources in the pipeline system
(1) Valve throttling noise
When the valve is throttled, noise is generated downstream with medium and high frequency characteristics. When the air flow velocity is equal to the speed of sound, strong shock wave noise will be generated. Therefore, when throttling, it is necessary to control the pressure drop ratio (pressure ratio before and after the throttling point) so that it is less than the critical pressure ratio 1.89. When the pressure drop ratio exceeds the critical pressure ratio, the shock wave noise increases rapidly until the pressure drop ratio is equal to 3, at which point the increase gradually slows down.
(2) Cavitation noise
Cavitation noise is also called cavitation noise or cavitation noise. When there is an obstacle in a part of the pipeline, cavitation noise is generated due to the local high speed and low pressure. At a certain speed, the pressure of the liquid is lower than its vapor pressure, thus generating bubbles, which suddenly burst and generate noise.
(3) Water hammer sound
Due to the sudden opening and closing of valves or water pumps, the liquid pressure in the pipeline changes suddenly, and the pressure wave (impulse) is reflected back and forth along the pipeline, generating a noise like a collision, as high as 110-115dB, and causing severe vibration of the pipeline system. (4) Mechanical vibration noise
Due to pressure changes and fluid pulses, valve components, pipeline systems, and hangers vibrate, and the noise frequency is below 1000Hz. The second source of mechanical vibration noise is the resonance of valve components at their natural frequency, which is a monotonous noise with a frequency usually between 2000 and 7000 Hz. (5) Solid-borne sound
The mechanical noise, airflow noise and vibration generated by various power equipment connected to the pipe system radiate noise to the air through the pipe system.
(6) The end flow of liquid in the pipeline, the vortex of gas, the sudden change of fluid flow rate and flow direction will all produce strong noise.
3.0.1.2 Spectral characteristics of pipe system noise
The spectral characteristics of pipe system noise are mainly determined by the structural size, pipe arrangement and natural attenuation. The typical spectrum curve is shown in Figures 3.0.1-1 to 3.0.1-3. Comprehensive analysis shows that its peak frequency is between 1000Hz and 2000Hz, and the main sound level is above 500Hz.
Figure 3.0.1-2
Figure 3.0.1-1
Noise spectrum of outlet pipe of DH-80 air compressor
Noise spectrum of pipe of air supply system of a certain blower 31.5
Radiated noise spectrum of a certain vent valve
3.0.2 Estimation of pipe sound insulation
3.0.2.1 Calculation of minimum resonance frequency of pipe
The pipe itself is a single-layer sound insulation wall. From its shape, it can be regarded as an infinitely long cylinder. Therefore, the calculation of its sound insulation should take into account the minimum resonance frequency on the pipe cross section, also known as the self-ringing frequency of the pipe. Its calculation is shown in formula (3.0.2-1).
fB—minimum resonance frequency of the pipe, Hz;
Longitudinal wave propagation speed in the pipe, m/s, 5100m/s for steel pipe; d--pipeline diameter, m.
3.0.2.2 Estimation of pipe sound insulation
Given the pipe diameter and wall thickness, the limit value of pipe sound insulation can be obtained from Figure 3.0.2. 50
2468246810-1
Pipe thickness/pipe diameter
Figure 3.0.2 Pipe sound insulation estimation chart
(3.0.2-1)
3.0.2.3 Below the lowest resonance frequency, the sound insulation of a circular pipe can still be estimated according to Figure 3.0.2, but it needs to be corrected using Table 3.0.2.
Correction value of sound insulation of circular pipe below self-sounding frequency fifr
Correction value dB
3.0.2.4 Above the lowest resonance frequency, the sound insulation of the pipe is almost the same as that of a single-layer flat plate. The calculation formula of the average sound insulation of a single-layer flat plate can be used to estimate its sound insulation, see formula (3.0.2-2). 355
When m≤200kg/m
R-13.5lgm+14
R—average sound insulation, dB;
mSurface density of a single-layer flat plate, kg/m.
3.0.3 Countermeasures for pipe system noise control
3.0.3.1 Selection of low-noise valves
Common low-noise valves include the following: (1) Multi-stage pressure reduction type
The valve core and valve seat are matched in multiple stages, that is, a vertical series throttling layer is set in the valve seat to reduce the pressure drop ratio of each stage, thereby reducing the impact noise and cavitation noise. This type of valve is suitable for occasions with large pressure drops, and its noise can be reduced by 20 to 25 dB (A) compared with general control valves. However, due to the small flow capacity of the valve, which is only 1/3 to 1/4 of that of general ball control valves, the noise reduction effect is not obvious under low pressure drop and large flow. (2) Dispersed flow channel type
It uses a channel composed of many small holes or slender gaps to replace the large channel of general valves, thereby reducing valve noise.
3.0.3.2 Setting the auxiliary control valve
When a certain opening of the main control valve causes resonance in the pipeline, the bypass auxiliary control valve can be opened appropriately and its opening can be adjusted to avoid resonance in the pipeline. Figure 3.0.3-1 lists the setting of the auxiliary control valve. Main control valve
Figure 3.0.31 Auxiliary control valve installation method
When the main control valve generates strong noise due to large pressure drop, the throttling of valves A and B can be used to share the pressure drop of the main control valve. If a certain opening of the main control valve excites the resonance of the pipeline, the bypass valve C can be opened appropriately to change the opening of the main control valve, thereby avoiding resonance in the pipeline. Setting the flow limiting orifice
Adding a flow limiting orifice in the pipeline can reduce the throttling pressure drop of the valve. In addition, the orifice itself also has a resistive silencing effect. Practice has shown that the proper selection of the flow limiting orifice can generally reduce noise by 10 to 15 dB (A). The opening of the flow-limiting orifice is fixed and cannot be adjusted. When the load changes, the effect also changes. Therefore, the flow-limiting orifice should be designed according to the commonly used load parameters. 3.0.3.4 Selecting a suitable muffler
Installing a suitable muffler at the inlet and outlet of the gas power equipment and upstream and downstream of the valve of the air flow pipeline is an effective measure to control the propagation and radiation of equipment noise and valve noise along the pipeline. Mufflers are divided into resistive mufflers, reactive mufflers, impedance composite mufflers, etc., and the noise reduction effect is generally 20~25dB (A).
In liquid transportation pipelines, when the liquid pressure is greater than 1MPa, liquid mufflers can be used, and the general noise reduction is 20dB/0.5m.
A 1/4 wavelength bypass pipe can also be set in the pipeline to change the phase of the pipeline pulsation and play a role in interference noise reduction.
3.0.3.5 Control flow rate
When the flow rate of the fluid in the valve or pipeline is high, the noise is also high. Reducing the flow rate can reduce the noise. In the absence of cavitation, the flow rate doubles and the noise increases by 18dB. For pipelines with strict noise restrictions, the flow rate needs to be limited. Generally, the method of expanding the pipe diameter is used to reduce the flow rate. For pipe sections with sharp changes in cross-section and flow direction, the flow rate should be further reduced. In actual use, different environments have different requirements for pipeline noise, but airflow conveying pipelines are not subject to this restriction because the friction between solid particles in the airflow and the pipe wall will greatly increase the pipeline noise. The pipeline flow rate limit values are shown in Table 3.0.3-1.
Flow velocity limit value in pipe for noise control
Sound pressure level around pipe, dB
3.0.3.6 Reasonable pipe connection
Table 3.0.3-1
Flow velocity limit value for noise prevention
Avoid T-shaped connection of pipe branches as much as possible. It is better to use split-flow pipe split type instead, especially for pipes with diameter greater than 200mm.
The turning radius of the pipe should generally be greater than 5 times the diameter. For the pump pipe, its direction of rotation should be the same as the rotation direction of the pump blades. See Figure 3.0.3-2. 357
Turn immediately after valve
T-shaped connection
The pipe turn is in the same direction as the impeller's rotation direction
T-shaped connection
T-shaped connection
Steam turbine
Injection valve
Centrifugal pump
Compressor
Blower
Qu Yi Ying Hai
Straight section is as long as possible
The turn is in the same direction as the rotation
Pipe diameter>200
Downstream splicing
Splicing with R=5d
Figure 3.0.3-2 Reasonable pipeline connection
3.0.3.7 Use flexible connection
Flexible connecting pipe can isolate noise from transmitting in the pipeline, prevent the vibration of power equipment from being transmitted to the pipeline, and compensate for the deviation of the pipeline centerline. Flexible pipes have standard products, which can generally reduce noise by 1015dB (A). 3.0.3.8 Pipe sound insulation supports and hangers
The use of elastic supports and hangers can prevent pipeline noise from being transmitted from hangers and supports to walls, ceilings, and foundations. Such elastic supports and hangers have standard products.
3.0.3.9 Add sound-absorbing lining to the pipe
In the pipe and elbow, a certain thickness of sound-absorbing material is lined to form a simple resistive silencer element, called a silencer straight pipe or silencer elbow. The thickness of the sound-absorbing layer is between 50mm and 80mm, and it is protected by breathable fabric-glass cloth or metal perforated plate. The protective structure is selected according to the air flow velocity in the pipe. The protective structure will move the sound absorption coefficient and characteristic curve of the sound-absorbing material to the low-frequency direction, which is beneficial for controlling low-frequency noise, but it will reduce the sound absorption effect for controlling high-frequency noise, so it should be paid attention to when using it. Different protective structures are suitable for different air flow velocities, as shown in Figure 3.0.3-3.
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