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Fundamentals of noise control in Power Generation plant

The science behind the sound mitigation solution applied to power plants.

Soundproofing refers to the processes involved in checking the sound from entering or leaving a specified area by absorbing and/ or mitigating the sound. Soundproofing mechanisms can be employed in several situations, especially industries notorious for sound pollution mostly attributed to the use of heavy-duty machinery, Power Generation plants are part of these.

 

Noise pollution source in power generation plants

There are numerous main sources of noise within a power plant and only a few of the major causes are taken in the exam here.

The sound power level from equipment can spread from about 120 dB to over 155 dB depending on the size and type of machine. There is no easy method to generally categorize one unit as being noisier than another, in fact, the amount of MWs turbine produce does not directly affect the noise they produce. However, diesel engines are more predictable, and generally, the higher the horsepower or kilowatt rating, the higher the noise level because more cylinders and fuel are needed.

Here is a list of some of the common noise source in power plants:

  • Combustion turbine (CT)
  • Heat recovery steam generator
  • Diesel engine
  • Superchargers on diesel engines
  • Steam generators, regulators, by-pass and control valves and piping
  • Air-cooled condensers (ACC)
  • Cooling towers, produce fan and gearbox noises
  • Fuel gas pressure regulating, metering and valve stations
  • Main step-up transformers
  • Condensate pumps, condenser units, and associated piping
  • Piping and pipe hangers not acoustically isolated from structures
  • Blow-off and venting processes
  • Remote water-pumping stations.

The sound emissions from power generation equipment can be reduced by applying noise control devices.

 

Sound Field Definition

To analyze noise from equipment, we need to define the sound field – that is, how the sound will propagate from the equipment or the sources of noise. Near field, far field, free field, and reverberant field are frequently mentioned. These are regions that describe certain characteristics of sound propagation as illustrated in the Figure.

Descriptions according to ISO 12001:2009

  • Near field
    • The near field of a source is the region close to a source where the sound pressure and acoustic particle velocity are not in phase.
  • Far field
    • The far field of a source begins where the near field ends and extends to infinity. Note that the transition from near to far field is gradual in the transition region. In the far field, the direct field radiated by most machinery sources will decay at the rate of about 6 dB each time the distance from the source is doubled.
  • Free field
    • The free field is a region in space where sound may propagate free from any form of obstruction.
  • Reverberant field
    • The reverberant field of a source is defined as that part of the sound field radiated by a source that has experienced at least one reflection from a boundary of the room or enclosure containing the source.

Fundamentals of Noise Control

Noise control or mitigation involves several steps, and the amount of noise reduction is driven by having to meet an environmental noise limit or some regulatory limit, not to mention workers’ safety. A simple model using the classical approach to noise control (shown below) allows the examination of the options for effective and economical noise control:

source of noise → path of noise →received noise

Solutions

Applying noise control involves affecting one of these three elements. Most often it is the ‘path of noise’ that is controlled by the use of acoustic enclosures, barrier walls, silencers, and other similar noise control treatments. This method is the most widely used as the degree of noise control can be tailored depending upon the noise requirements and generally it is the more economical approach. The control on the ‘source of noise’ can be expensive because it may require a complete redesign and retooling process which takes time and money.

For new plants, examine the structure arrangement and locate the noisiest equipment or operations away from noise-sensitive areas. Grouping smaller sources together can be beneficial in that a common noise barrier or enclosure can solve a lot of small problems.

 

Stopson Italiana Soundproofing Solutions

Enclosures and Barriers

Shaped around noisy equipment, indoor or outdoor, on-base or off-base, designed to provide optimum noise attenuation in any critical environment. Made of modular acoustic panels and linings for sound isolation while ensuring equipment maintenance, ventilation, weather protection, and fire safety.

  • Noise abatement by 15dB(A) to 50dB(A)+
  • Vibration absorbers, anti-shock systems with noise control settings
  • Combustion air intake Unit with optional air filtration
  • Exhaust gas removal for combustion engines
  • Indoor/Outdoor Applications

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Silencer and other solutions are available at Stopson Italiana, Check-out all the soundproofing products.

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10 Steps to choose the right Soundproofing Materials

Soundproofing Materials: 10 Steps to choose the right one and how to test their effectiveness in the Industrial context.

 

Soundproofing refers to the processes involved in checking the sound from entering or leaving a specified area by absorbing and/ or mitigating the sound. Soundproofing mechanisms can be employed in a number of situations, some of which may include private homes, religious centers, offices, studios, and most especially industries notorious for sound pollution mostly attributed to the use of heavy-duty machinery.

Over the years, it has been discovered that noise pollution has the potential of causing damage to our health than we initially conceived. And as a result of these findings, employers of labor owe their employees good working conditions and a safe working environment, which typically involves a working area that dissipates noise levels below standardized noise thresholds. 

What’s more, it’s common knowledge that a noisy environment negatively affects concentration and attentiveness, and would drastically reduce productivity and the quality of service.

More negative effects

Noise pollution doesn’t stop there, it also targets the psychological health of its victims and can trigger health issues such as high blood pressure, hearing impairments, stress, and insomnia. In truth, the list is inexhaustible. 

Most industries the world over understand the importance of the health of employees, yet cannot afford to get rid of such heavy-duty machinery due to a lack of quieter alternatives. To solve this problem, it is best to lock in the noise that these machines produce by the installation of quality soundproofing materials.

 

Soundproofing Materials and How They Work

As was earlier stated, soundproofing simply refers to mitigating the noise within a certain area. This is achievable by installing certain materials (insulators) that trap sound and absorb them. 

There exist different types of soundproofing materials and you’d need to consider a lot of factors like the kind of building to be soundproofed and the intensity of noise to be absorbed among many other factors.

Here are a few soundproofing materials used in for industrial soundproofing applications:

 

  • Mineral Wool (Rockwool Rockboard)
  • Soundproof Fiberglass (Owens Corning 703)
  • Acoustic Fiberglass.
  • Acoustic Foam Panels.
  • Echo Absorber™ Acoustic Cotton.
  • Fabric Wrapped Acoustic Panels.
  • Fire Rated Foam. 

 

Ten Steps towards choosing the right soundproofing material

 

There are no wrong materials when it comes to soundproofing, it really just depends on what you aim to achieve. We have, however, come up with 10 guidelines to be followed when choosing soundproofing materials in order to get the best out of soundproofing.

 

 

 

  • The level/Source of Noise: The level of noise that is to be locked out or in, goes a long way in deciding the kind of materials to use. For minimal noise, soft, specially designed foams can help to absorb the noise, but for noise emanating from heavy-duty machinery, more advanced noise insulators may be adopted.

 

  • Propagation of Noise: Noise can either be airborne or structure-borne. To get the best materials for soundproofing, you would need to first determine how the noise travels from the original source to the receiver. This is because some insulators are suited for airborne noise transmission and may be quite ineffective for noise that is structured-based and vice versa.

 

  • What are these materials are made of: Some soundproofing materials are more eco-friendly than others, and should generally influence the choice of materials. Some others may include flammable agents which may not be suitable for certain applications.

 

  • Thermal Insulation: Some soundproofing materials carry with them some thermal insulation features, which helps to reduce heat also. It is advisable to get these types of soundproofing materials for cost-effectiveness and the added advantage, especially in an industrial setting.

 

  • Ease of Installation and Maintenance: When choosing soundproofing materials, it’s advisable that opt for the ones that are easier to install for time maximization. For example, when decoupling walls and ceilings to keep sound front traveling through them, it is best to make use of the resilient sound clips instead of resilient channels because they are easier to install.

 

  • Why are you soundproofing? In choosing the right materials, you must understand the purpose for which you are soundproofing in the first place. If the aim is to lock sound in, you should not consider soundproofing materials like the mass loaded vinyl which is specifically designed to keep sound out.

 

  • Additional soundproofing: If you are looking to cover the loopholes that may remain after general soundproofing, you should consider getting additional soundproofing such as the under door draft stopper as it seals the small gap between the bottom of the door and the floor, and ensures that there are no under-door spaces that could let noise penetrate or escape.

 

  • What parts of the area are most important? You should also determine what parts of the noise prone workspace you want to focus on when soundproofing, as this will help to decide the kind of materials to look out for. For example, the weather stripping can only be used to seal gaps around doors and windows, hence it should not be considered for soundproofing walls.

 

  • The best material wins: It is of paramount importance to purchase the best quality materials affordable. You can seek expert opinion in deciding what materials are of the best quality based on your proposed applications. Low-quality materials will only bring you discomfort in the long run and in some cases a potential industrial hazard.

 

  • Soundproofing windows: When soundproofing windows, the use of double-glazed windows may fail miserably to effectively mitigate noise pollution, hence, you may opt for thick glass as a more functional alternative. The thicker the glass, the better the results. 

 

How to Test the Effectiveness of Your Soundproofing Materials 

To ensure that you are purchasing the best and most effective soundproofing materials for your industry, it is best to run a series of tests. Here are some methods to employ in testing the effectiveness of soundproofing materials:

  • Making use of Impedance tools: The impedance tube is pretty much a tube with circular ends. There are different types based on size, shape, and material used in making it. This tube can be used in free field situations to test the transfer of sound in a bid to understand the specific soundproofing needs.

 

  • The impact insulation class: This is used to test sound-blocking floor soundproofing products. There are other products such as the impact insulation class that test other soundproofing efficiency of other parts of a workspace. 

 

  • If your industry related noise challenges require that you test how effective sound-blocking materials are for ceilings and walls, you may use the CAC and STC respectively.

 

  • For sound absorption material testing, the NRC is your best method. NRC is the comparing of different sound absorption levels through the use of speakers and microphones.

Stopson Italiana produces customized solutions according to the client’s needs. The main soundproofing solutions can be collected in 2 categories:

Silencers

Absorptive for cold and hot gases, reactive for engines or small boilers exhaust, combined absorptive and reactive for venting systems. Circular or rectangular shape, atmospheric or pressurized for any gas, temperature range 
, and applications providing sound attenuation up to 70 dB and reduce residual noise to a sustainable level.

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Enclosures and Barriers

Shaped around noisy equipment, indoor or outdoor, on-base or off-base, designed to provide optimum noise attenuation in any critical environment. Made of modular acoustic panels and linings for sound isolation while ensuring equipment maintenance, ventilation, weather protection, and fire safety.

→Read more