Carol Brzozowski 2017-11-16 11:21:54
Contemporary enclosures are not only serving to help businesses meet today’s noise regulations, but also to provide optimal insulation, equipment protection, vibrational dampening, and protection in extreme environments. “We’ve entered a new era in this world’s economy,” points out Frank Kovacs, CEO of Shannon Enterprises. “The concept of going green seems to mean something to everyone. Going green in the early years was all about trapping and saving energy, conserving the BTU count or the energy count of a system, and most of that was thermal insulation. “This current situation has evolved into other aspects of energy, and sound is energy. In many cases, the customer is looking to reduce the energy profile, and sound falls into that category.” Another driver is the building and property line ordinances, he adds. In many cases, that which is insulated is directly related to a machine or following compliance to a law, notes Kovacs. “For instance, if there is a 60-dBA property line ordinance and there are problematic machines within that property line that do not get the customer to that 60-dBA requirement, we can take a look at what is causing the problem and solve it through multiple solutions. “In some cases, enclosures work. And in some cases, direct surface-wrap acoustic blanketing works. Energy is not just derived from thermal insulation efficiencies, it’s also derived from vibration, and sound energy is vibration,” he says. Shannon Enterprises manufactures insulation blanket technology based on the concept of removability for conducting service, inspection, and repair. End-users can remove the system, do the work, and then reinstall it, says Kovacs. Josh Crichton, director of sales for SEMCO duct and acoustical products, points out that environmental concerns have taken on new importance over the last decade. “With the population density as it is in much of the country, noise attenuation has become a larger concern,” he says. “There are a variety of options in terms of cost and appearance with enclosures.” SEMCO provides modular panel systems used to design or build noise abatement solutions tailored to a variety of applications. The system is customizable for both appearance and noise abatement levels, says Crichton. Choosing the right enclosure starts with working with the right team of people as well as a sound consultant, as noise is the primary concern, says Crichton. Additionally, there are visual concerns and thermal requirements that need to be addressed. Factors to consider include whether the application is inside of a building or on its rooftop. “Working with the correct individual from the design standpoint is essential to be able to take into account the array of needs on a given project,” says Crichton. Given the ease of how SEMCO’s panel systems fit together, it can be tempting to take a shortcut and complete installations through a maintenance department or not hire competent installers, “but I would recommend seriously looking at the installation needs and working with someone along those lines,” says Crichton, adding that the company has a list of referrals for acoustical consultants. “Many people recognize that there’s a noise problem. They may even understand that there are panel products out there that would be an option. But understanding the differences between a standard metal panel option and an engineered system solution for their problem is key,” says Crichton. Robinson Custom Enclosures, a division of Robinson Metal, designs and installs custom solutions to fit end-users’ needs for a particular site, taking into account code compliance in various regions, and meeting or exceeding acoustical codes as well as structural integrity, notes Jeremy Off, engineering manager for the company’s enclosures division. Sound attenuation through the Acoustic Shield Insulation and Acoustic Blanket Insulation products is one application of Shannon Enterprises’ blankets. The company has developed acoustic application products primarily to accommodate complex surface geometry as well as custom-designed enclosures on “complicated surfaces,” notes Kovacs. Its Acoustic Shield Insulation solution is used for scroll compressors, pumps, and liquid chiller discharge piping. The Acoustic Blanket Insulation is used to treat radiant noise on complex surfaces generating 4-15 dBA reduction, such as liquid chillers, compressors, and pumps. Sound reduction can occur through two approaches, adds Kovacs. “There is a source, a path, and a receiver,” he says. “The source is the energy traveling through the air through its path, and then the experience being the receiver on the opposite end.” A barrier wall is one approach: “You create a house around the source energy and thereby remove the sound exposure from the perspective of the receiver,” says Kovacs. The other option is a direct surface treatment through applying an acoustic blanket system to the direct surface to address the source noise. Kovacs says sometimes both approaches are applied by using an acoustic enclosure and also treating various equipment components to address sound. Through sound testing and surveys, key components requiring a direct wrap are identified. “Take a machine like a liquid chiller, which is comprised of a number of different components,” he says. “The compressor is typically the primary source of noise, but the motor also could be a sound source problem. There could be an issue with discharge piping coming from the compressor. If the compressor was a screw compressor, the screw compressor has an oil separator which could also contribute. These individual components on a machine have to be defined and addressed individually.” Case in point, the sound level on a liquid chiller could be lowered in three ways: by three decibels, by three to five decibels, or by six to 10 decibels. If an end-user is seeking to shave a peak frequency harmonic because of one or two problematic frequencies, it can be done by merely insulating a discharge pipe, says Kovacs. “The scenarios are different in that the customer may have different expectations for what kind of performance they want to generate,” he adds. Noise codes can vary from reductions that need to be applied at a property line to more broad-based ones indicating that no piece of equipment can radiate noise at a certain level, says Off. “The thing about these acoustical codes is that most of them are decades old, drafted in the 1930s, 40s, and 50s,” points out Off. “It’s just that the authorities of jurisdiction are really cracking down on them.” Noise attenuation is predicated on the amount needed to be addressed, as well as thermal and fire protection requirements, says Sam Smullin, spokesperson for Soundown. Acoustic foam materials serve as sound absorption treatments, whereas acoustic barrier composites include a mass layer that serves as a sound-blocking component, he says. “You’re limited in how much reduction you can get from absorption,” notes Smullin. “You can take the reverberant noise out of what’s happening in the cabinet, but you’re not significantly stopping the noise from coming out when you add the barrier in there—you’re increasing the ability of the enclosure to stop the noise transmitting through the panel.” The weight and position of the mass layer in the composite and the thickness of the composite “will determine what you can stop for noise in any given frequency, and how much better of a job you can do at low frequencies,” he adds. Case in point: putting a quarter-inch of foam or fiberglass behind a one-pound barrier starts blocking noise at 380 Hz. With a thicker decoupler, the same one-pound of mass layer and half-inch foam behind it starts blocking noise at 250 Hz. One inch gets it down to 163 Hz. “It’s important in looking at the insulation not only the thickness and weight, but how it’s constructed and where the barriers are placed in it to make sure it’s optimal for blocking low-frequency noise, which is mainly what we’re talking about out of these generators,” says Smullin. There are two parts to address vibrational dampening, notes Smullin. The first is the dampening of the actual panels of the enclosure itself. “You want to make sure the panels aren’t radiating noise from vibrational energy coming in through the attachment of the enclosure of the generator,” he says. The second issue is the reduction of the vibration going into the structure, such as in the equipment room, where the “big concern is that you have this vibration going into the structure which will flank the enclosure and travel the structure-born noise instead of airborne noise,” points out Smullin. “If it’s an enclosure that includes the base frame that the generator attaches to, it’s important to use good isolation mounts that are correct for the application,” he adds. Smullin suggests either rubber springs or pad mounts underneath the entire enclosure. That is a common approach in high-end construction applications such as medical facilities where addressing noise and vibrations is critical, he points out. Another consideration with respect to vibration dampening is looking at how the exhaust is attached and making sure the exhaust piping is vibration-isolated between it and the structure of the enclosure, says Smullin. In some regions in which his company does work, end-users will often hire acoustical consultants that write the specifications around the noise ordinances and work in concert with Robinson Enclosures to create the optimal product, says Off. Smullin notes that the insulation is “really what’s going to optimize the sound attenuation of the enclosure overall. At the same time, the enclosure needs to be well-designed with regard to air flow, how the exhaust is handled, baffling of any openings, and sealing of openings. “Think of it like trying to stop water,” he points out. “If you leave openings, it’s going to come out wherever the openings are. So you have to design the enclosure first to handle any of those openings so doors are well-sealed and gasketed, and that there’s good baffling of intake and exhaust air. You have to make sure you’re getting the most out of the insulation based on the enclosure design, and not over-insulating an enclosure that’s not going to do any better than it already is.” When it comes to insulation, “modern onsite power systems are much more sophisticated than they used to be,” notes Mike Witkowski, chief operating officer for Pritchard Brown. “There are many more electronic controls and devices, like emissions equipment, that require a more controlled environment in order to operate properly,” he adds. “In addition to noise abatement, the insulating materials need to be chosen so they provide a level of thermal protection to keep climate control within the enclosure and also to account for the fact that many of the modern engines are running at higher temperatures due to emissions regulations. The exhaust gas temperatures can exceed 1,300 degrees on smaller engines; so insulation needs to work over a large range of temperatures.” SEMCO’s modular panel product has a tongue-in-groove joint that does not require fasteners, notes Crichton. “That not only helps in appearance if you don’t have a screw head every one or two feet, but in terms of project costs, it reduces installation and labor,” he says. SEMCO has a variety of insulation options from two to more than six inches in an array of project-specific, fill-type offering capabilities on the thermal end, he adds. From an engineering standpoint, noise and vibration control are tied together, notes Witkowski. “They are essentially the same science; but in one, the medium is air, and the other is a solid medium that determines whether it’s vibration or noise,” he says. “Vibration needs to be controlled to extend the life of the equipment. Limiting the vibration between the moving parts on the engine and a base helps ensure you meet the sound requirements. They work together to meet the sound requirements.” Equipment protection comes into play in a lot of areas, such as in the Midwest where enclosures serve to protect from the elements, “or from those who should not be in close proximity to the equipment, either for safety reasons or otherwise, as well as asset security,” says Crichton. “Fencing is a cheap option when it comes to security of the asset, but it doesn’t do much in terms of protection from the elements and longevity of the equipment,” he adds. “Enclosure solutions are a great benefit and they are a great alternative to in-situ construction—which can be a bit costly and unsightly in many cases—if you’re looking to minimize the individual footprint of the equipment in question.” Noting that there are many electronic elements, microprocessors, and programmable logic controllers on a system that need protection from the weather, Witkowski points out that enclosures “have always had to keep the weather out as well as the noise in.” To that end, Pritchard Brown offers IBC seismic certification enclosures to handle areas where there are concerns with earthquakes, as well as systems that protect equipment under other weather conditions. Case in point: the nuclear energy industry developed a ‘diverse and flexible coping capability’ called FLEX, which is intended to establish a safety framework as a result of lessons learned from Fukushima Daiichi. According to the Nuclear Energy Institute, FLEX builds on earlier safety steps by providing an effective and efficient way to make US nuclear energy facilities even safer. It is meant to address critical problems encountered at Fukushima Daiichi: loss of power and reactor cooling capability. FLEX is also designed to provide an additional layer of backup power after extreme events by stationing vital emergency equipment such as generators, battery packs, pumps, air compressors, and battery chargers in multiple locations. The intent is to help maintain cooling if normal systems and other backup systems fail by stationing additional pumps and power sources in multiple locations to provide cooling water to the reactors, according to the Institute. Pritchard Brown has designed a mobile generator set enclosure for the ‘Diverse and Flexible’ Backup Reactor Feedwater Pump Program at an East Coast nuclear facility, designed to survive and function subsequent to any foreseeable natural disaster at a nuclear facility, says Witkowski. That includes tornado-force (360 miles per hour) winds and debris, earthquakes, and flooding. The trailerized units incorporate fire suppression, projectile resistance, pressure equalization, and sound attenuation. The unit is designed to be deployable by one person in under 15 minutes. The system is protected for NEI 12-06 seismic, wind, steel rod projectile requirements and is designed to withstand a steel rod three feet in length and one-inch in diameter, weighing eight pounds and traveling at 292 feet per second—including striking a glancing blow from any angle up to 90 degrees from vertical, says Witkowski. The system also is protected for dynamic wind pressure of +266 PSF (windward), -166 PSF (leeward), -166 PSF (roof), and -3 PSI atmosphere pressure. It features sound attenuation of 15-20 dB(A), a 24-hour fuel tank with spill containment, an FM-approved water-mist fire suppression system, and auxiliary power connection for heat, lighting, and fire detection when in standby. It also features a camlock connection box for external entry of generator output leads. “This one is a portable unit designed so the nuclear power plant can start its reactor pumps regardless of what the extreme threat could be,” says Witkowski. “It had to meet wind and seismic and pieces of things being blown around by the wind. It needed to work from a temperature range of -5[°F] to 110 [°F] with a relative humidity of 90%.” Witkowski points out that when the wind is moving fast like a tornado passing over a fixed enclosure on the ground, “there is a severe atmospheric pressure change that takes place that can actually do more damage than the wind itself, so that needed to be accounted for.” Regarding flooding, “the key is to make sure if the enclosure is being installed in a flood-prone area, that the base design needs to be modified so it’s tall enough to keep the anticipated floodwaters from reaching where the equipment will be,” he says. Designing for a 24-inch water height for potential flooding events also was included as one of the natural disasters the nuclear power plant enclosure needed to survive, says Witkowski. With regard to seeing different codes coming out for fire rating and fire protection, many building owners have specific failure criteria where they indicate that they need the generator enclosure to be the last thing standing in a fire, says Off, adding that this goes “hand in hand” with sound attenuation. “That’s one of the most active markets now: the extreme application where they need a really quiet enclosure that also needs to be the last thing standing in a fire or if it’s next to mission critical equipment, when that starts on fire, our enclosure needs to be still standing,” he adds. Kovacs points out there are a number of considerations in outdoor applications as the blanket system is going to be susceptible to ultraviolet rays and possible wind and rain. The goal is a product that has a 15-year service life under any conditions, he adds. Extreme conditions such as hurricanes and earthquakes call for robust enclosures. “They are powering fire pumps, building fire suppression systems, and sprinkler systems,” says Off. “That’s what these enclosures are providing power to, so they need to be the last thing standing when that tropical storm comes through, for instance.” The goal is to create an enclosure that can potentially last longer than the once-in-a-lifetime weather event or withstand severe seismic events, he adds. In addition to placing units in areas prone to hurricanes, Robinson also has installations in California, such as a tight space constraint package where generators are stacked on top of one another to offer a dense footprint in terms of the power requirement, says Off. In order to withstand withstand cold weather environments, Robinson's enclosures are double-walled with sub-base tanks that are not only designed for structural integrity, but to also keep fuel at the right temperature. Fuel polishing systems, heaters, and thermostats are integrated into such systems to ensure that the generators will operate optimally. In terms of equipment protection, Off points out that UL2200 has been written into many specifications lately, which verifies that the enclosure is not negatively affecting the factory rating of the genset within it, such as restricting air flow, causing rain to be pulled into the enclosure, or causing the genset to vibrate out of sync. SEMCO offers panels made from materials designed for flexibility in extreme environments, such as aluminum and stainless steel of various grades, says Crichton. “For example, we’ve put quite a bit of product on oil rigs off of the coast of the Northeast,” he says. “You’ve got not only the salt water environment, but the extreme weather, and temperature fluctuation.” SEMCO offers a variety of coatings for extreme environments, including a significant amount of powder coating, says Crichton. Powders range from a standard bare metal galvanized coating on a base product to series 11000 TCI. Witkowski states with respect to extreme conditions in places like Florida, that, “there’s no need to worry about keeping heat in when the generator set isn’t running, but in colder areas, it’s very important that it be kept warm in the enclosure so that the diesel will start properly.” Pritchard Brown also has been involved in providing three 2MW onsite generators in sound attenuating enclosures for the town of Seaside Heights, NJ, that demonstrate their design capacity to withstand extreme weather situations. “The systems were installed on elevated pads to raise them above the floodplain,” notes Witkowski. “During Superstorm Sandy, technicians used a small boat to get to the enclosures and verify operation. The combination of quality weatherproof enclosures and proper planning for the installation resulted in the town’s infrastructure staying operational during the natural disaster.” DE Carol Brzozowski specializes in topics related to energy and technology.
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