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For heavy industrial facilities, the impact of noise is an important issue and a significant source is often piping-radiated noise. Whether it’s a problem of occupational noise exposure risk or compliance with environmental noise regulations, noise must be reduced or controlled. The causes of these noise issues are frequently attributed to rotating equipment, exhaust stack exits, or the process pipework that carries the product. In fact, industrial pipework can represent up to half of the facility noise output. Noise reduction from process pipework is inherently beneficial for people, the environment, and facility owners.

Historically, mineral wool-based acoustic insulation systems have been used to reduce noise. Yet, these systems are typically thick (up to 4” for purely acoustic systems), heavy, and the water-absorbent nature of this fibrous material can lead to Corrosion Under Insulation (CUI). Developments in advanced material systems are challenging these traditional systems and alleviating the problems they may cause. While various insulation materials are available to help with noise reduction, the ability of companies to make recommendations, perform acoustic assessments, and provide practical solutions, is not as easy or well understood.

Armacell is a leading global manufacturer of acoustic and thermal insulation products, creating system solutions to meet the demanding design criteria for industrial applications. Armacell’s advanced ArmaFlex, ArmaSound, and ArmaGel materials are specifically designed to meet both the acoustic and thermal requirements for pipework, while providing significant advantages over the traditional mineral wool systems.

Armacell Acoustic Technical Services has developed an acoustic project methodology that focuses on collaboration with facility owners and engineers to ensure that, when determining the best insulation solutions to a noise problem, there is continual engagement in the design and implementation – a “beyond better” approach. This strategic and proven process helps minimize mistakes that can arise from a lack of understanding noise problems and potential solutions.

Pipework noise requires mitigation to meet plant noise requirements. However, use of insulation systems can lead to site operators hesitating in using materials for noise control, primarily due to CUI risks. CUI describes all types of corrosion occurring beneath insulation and is consistently recognized as a key challenge for industrial facilities. CUI is estimated to represent between 40-60% of pipe maintenance costs and 10% of annual maintenance costs are attributed to repairing damage from CUIi,ii.

To mitigate CUI, it is necessary to prevent/reduce the ingress and passage of liquid water or water vapor from external sources to the pipe surface. Unfortunately, moisture can get into the traditional mineral wool systems easily when there is damage to the jacketing, breaks in seals, or punctures in vapor barriers. The fibrous nature of traditional materials, such as mineral wool, ensures that water is readily transferred to the pipe wall via a wicking effect.

In addition to the passage of water/moisture promoting CUI, the presence of water in the mineral wool fibers may reduce the acoustic performance of the construction. This results in a reduction of material performance, even after the removal of any moisture.

During the operation of a facility, it is necessary to routinely inspect the level of corrosion of the pipework to ensure system integrity. This is often a full-time procedure and even though various technology has the capability to investigate without penetrating the insulation, many operators require sections or entire pipe runs to be stripped of insulation for visual inspection and/or repair. This process has been known to occur every three to five years, often at significant cost and effort.

Aside from the risk of CUI, the effect of traditional systems on the design and construction of industrial plant is significant. With the thickness and weight of traditional systems, the amount of additional/increased steelwork required to support the insulated pipework can be high. Weight issues are also a significant factor when designing offshore facilities, as a strict overall weight limit for the whole facility must be followed.

These additional requirements for materials can also influence the environmental footprint of facilities, as more natural resources may be required. Space issues are a considerable factor in the design. With limited spacing and pipe runs being condensed into small areas, there is often no room to install thick traditional insulation systems. This can have a detrimental effect on the ability of a facility to reduce its noise levels to meet health and safety and/or environmental limits.

Traditional Pipework Acoustic Insulation Systems

Acoustic pipework insulation has historically included a combination of open-cell, porous, fibrous materials such as mineral wool and mass layers. The fibrous layer in such systems provide both vibration isolation of the vibrating pipe wall from the external jacketing, and acoustic absorption of the acoustic wave generated by the pipe wall. Mass layer(s) commonly consist of mass-loaded vinyl (MLV) and metal, usually as a jacketing, providing a physical barrier that prevents/reduces the transmission of the acoustic wave. In these systems, the jacketing also acts as the primary barrier for water and moisture ingress. Such traditional acoustic insulation systems have formed an industry standard for decades. 

Common examples of potential systems are presented in ISO 15665:2003 “Acoustics - Acoustic insulation for pipes, valves and flanges” and are supplemented by Shell DEP 31.46.00.31-Gen “Acoustic Insulation for Piping (Amendments/Supplements to ISO 15665)”. These documents summarize an acoustic insertion loss across 4 classifications (A to D) for 3 pipe diameters, up to a diameter of 1 m.  ISO 15665 and ASTM E1222 also define protocols to be followed for testing any acoustic insulation system and determining the system Acoustic Insertion Loss.

Although these standards present other possible material systems and requirements that may be expected to meet the required acoustic insertion loss performance curves, the overriding requirement should always be independent acoustic testing of any insulation system, regardless of component materials used. Therefore, selection of new materials that can reduce or remove the negative elements of traditional materials, but that can be configured to meet the acoustic performance is clearly advantageous. Armacell has developed such insulation systems.

ArmaSound Industrial Systems – ArmaFlex (AF)

Armacell’s secret is in the engineered, multi-layer designs. A deep understanding of different insulation materials and how they behave when used together, led to the development of ArmaSound Industrial Systems.

ArmaFlex insulation is a flexible elastomeric foam (a rubber-based material). Since ArmaFlex is closed-cell in nature, it is highly impervious to water and moisture ingress. The use of correct adhesive between layers further increases the resistance to passage of water in either liquid or vapor form. This ensures that ArmaFlex based ArmaSound Industrial Systems can be an excellent mitigator of CUI risk, by providing superior protection against moisture ingress.

The characteristics of ArmaFlex also ensure that should inspection of the pipework be required, it is only necessary to remove small sections, or plugs of material. This can be completed with a simple knife. Following inspection, a replacement plug can be easily inserted and adhered to the surrounding material. Upon curing, the seal is as good as the original insulation material. This ensures peace of mind regarding pipe integrity and significantly reduces inspection and maintenance costs.

Acoustically, specific material layers perform an acoustic task. The use of a closed-cell, flexible, low-density foam of low dynamic stiffness comprises the base layer to provide important vibration isolation (ArmaFlex). The addition of a high-density, open-cell layer such as ArmaSound RD240, provides the needed acoustic absorption and damping that is also often used. Mass layers such as ArmaSound Barrier E/H/D deliver the necessary mass barriers. External jacketing can then be elastomeric, metallic, or a composite. 

ArmaSound Industrial Systems AF Class D

Compared to traditional mineral wool systems, the thickness and weight of the ArmaSound Industrial Systems AF is significantly less for ISO 15665 Class A to Class C, with the comparison of Shell DEP 31 Class D being roughly equivalent. The main limitation on the use of the ArmaFlex is the temperature range. ArmaSound Industrial Systems AF can be used in the -40oF to 250oF range without the use of additional sacrificial thermal insulation. To resolve this constraint, Armacell developed the ArmaGel based ArmaSound Industrial System AG.

ArmaSound Industrial Systems – ArmaGel (AG)

ArmaSound Industrial Systems ArmaGel (AG) comprises silica-based aerogel particles that are embedded into a fibrous blanket. The blanket provides the essential support of the mass layer and excellent vibration isolation between the pipe wall from the jacketing.

The addition of aerogel into the blanket provides the necessary hydrophobicity needed to repel liquid water

(to prevent wicking as seen in mineral wool), damping of the fibers, and acoustic absorption. This combination allows for a significant reduction in thickness and weight and excellent acoustic insertion loss. Such effectiveness subsequently provides increased acoustic performance and also, CUI protection.

Performance Met with Minimal Thickness and Weight

*Weight and thickness based on typical values and application conditions.

The ArmaGel systems are significantly thinner than other acoustic insulation systems. Their ability to operate over a wider temperature range ensure that acoustic insulation can be provided between -321oF and 1200oF.

The range of ArmaSound Industrial Systems for noise control of pipework, valves, and flanges is clearly able to meet the necessary acoustic insertion loss requirements identified in international standards. The range does so with a high degree of efficiency and helps operators minimize lifetime costs, maintenance, inspection, and CUI risk. In addition to these significant improvements, Armacell can offer further advantages in the delivery of world-class noise control.

Beyond Better – The Armacell Solution Philosophy

Many insulation manufacturers provide materials for noise control. Armacell have a mission to take the next step. While Armacell produces superior performing insulation materials, only by using these materials in the correct context and location and advising customers how to achieve the solutions to their problems using our materials is such a venture worthwhile. Material solutions and service should be “beyond better”.

Determination of the appropriate noise control method depends on the physical, regulatory, operational, and financial restraints placed by project owner. It is imperative first to understand the physical problem and to frame any solution within those limitations. Failure to do so will likely result in a poor/failed project. Engaging with the project stakeholders at an early stage, educating all parties, and using an ALARP (As Low As Reasonably Practicable) approach, provides the most effective project solution.

The ALARP approach allows a project to consider benefits against aspects of implementing and working with the solution. Such aspects can be cost, operability, inspection, maintenance, etc.  A range of solutions can be implemented over time to allow the plant operator to practicably implement the solution over a short, medium, and long term, according to the lifetime of their asset.

Armacell has the capability to present solutions with tangible benefits, in a simplistic manner that is straightforward to understand. Thus, allowing the project team to feel empowered and develop confidence that their issues are being dealt with in a technical and professional manner. This is part of the “beyond better” approach.

Noise control studies may be undertaken by noise consultants, but this is often limited to the identification and quantification of the noise issue. Acoustic solution providers such as Armacell, now offer a holistic service. This includes the capability to recommend, supply, and qualify the adopted mitigation measures, thereby delivering a total engineering approach to the project.

To understand what the solutions need to be, it is necessary to fully understand the problem at hand and the issues framing the problem. Within a project, such understanding can take many forms. Initially, it is common for the plant to have a ‘Noise Problem’ but to not fully comprehend the details surrounding this problem. Similarly, the cause and effect of this noise problem is often not fully understood in the wider context of the project. Noise can be a symptom of wider problems or be caused by the actions of other parties. 

As an example, routine maintenance may remove existing acoustic insulation from pipework to reduce the CUI risk. Noise levels are then unwittingly increased, and noise risk is raised. In a complex pipe run, this situation may not be immediately obvious. By looking at the noise issue and reason it arose in the first place, it is possible to find a solution that reduced the noise and reduced the CUI risk – solving both problems at once.

The role of the noise control engineer is to understand the whole nature of the problem, the physical cause, financial restrictions imposed by the client, and deliverables for the project. If any of these aspects are not fully understood, it is nearly impossible to achieve a successful solution.

When operators are aware of noise problems, they may have investigated the issue themselves or brought in a third party to consult. Both approaches are perfectly valid and may identify the source of the problem, but not necessarily the solution. Armacell is however, able to undertake these investigations or utilize the existing studies/data and demonstrate how our advanced material systems may work to resolve these issues. 

The process often requires site acoustic measurements and/or acoustic modelling. By developing a calibrated noise simulation, it is possible to predict possible solutions and understand the impact of those solutions on the noise problem. Such an approach can be undertaken with existing or new measurements, on-site or remotely.

Using the ALARP approach, a series of potential, solutions to the problem can be assessed. All solutions should be defined as a source, transmission or receiver solution, or a combination of these, as well as elimination or low noise equipment replacement options. As the physical noise problem should have been defined at the start of the project, solutions should be presented within an ALARP framework to determine a workable solution. Depending on the project, it may be prudent to provide a short, medium, and long-term noise control strategy as well.

Regardless of the nature of the problem, be it simple or complex, the solutions should be defined simply in a cost-benefit-operability format to allow an informed decision to be made.

ArmaSound Industrial Systems deliver high-performing noise control for pipework while minimizing thickness, weight, and providing superior protection against the risk of CUI when compared to traditional mineral wool insulation systems.

Armacell’s Acoustic Technical Services works with facility owners to define, understand, and recommend feasible noise control as a whole project solution. By following a proven approach, Armacell can help identify the cause of noise problems, provide advice, solutions, and demonstrate how those solutions will resolve the issue.

If the answer to the question, “Do You Have a Noise Problem?” is YES, Armacell’s Acoustic Technical Services team can help solve your noise problem. World-leading noise control systems and knowing where to apply them – Beyond Better.

For more information, please visit www.armacell.com/energy

i: NACE Impact Study, 2016, Annex D pg D-10

ii: European Federation of Corrosion (EFC), Minutes of meeting, presentation Exxon Mobil Chemical Company, “Piping Systems CUI: Old problem: different approaches”; Brian J. Fitzgerald, Charles Droz, Stefan Winnik, 2003

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