RockRoadRecycle staff writer
Many things affect construction, with new equipment and techniques being developed, but what is becoming more prevalent in virtually all operations is the development of clean air/dust control technology. This takes in many things, including new low emission engines from the likes of Caterpillar, Volvo CE and Deutz (among others) and the ability of equipment to work from generator or mains electricity. Also, many manufacturers are developing clean air solutions that mitigate the effects of dust and help produce a clean air working environment not just as an afterthought but rather endemic to all activities.
New OSHA regulations for silica dust control
Recent drivers of dust control equipment have been the new OSHA regulations for the control of silica dust. OSHA sets the personal exposure level (PEL) limit at 50 micrograms (µg) of respirable crystalline silica (RCS) per cubic meter (m3) of air (50 µg/m3) over an eight-hour, time weighted average. The new rules also stipulate requirements for exposure assessment, respiratory protection and methods for controlling exposure as well as medical surveillance, hazard communication and record keeping.
Invisible to the naked eye and able to travel long distances on ambient air currents, workers are often unaware of the lingering dangers and may take off protective gear, risking exposure and potentially contracting silicosis over time. Silicosis itself is a chronic and incurable disease that affects millions of workers across the world in a wide variety of industries.
With this in mind, OSHA’s Final Rule requires regular monitoring by the employer and sets personal exposure limits while suggesting engineering controls and particulate isolation as opposed to putting the entire onus of PPE on the employees. By doing this, regulators also limit fugitive dust emissions from leaving the site line and exposing the wider public. Non-compliance could result in fines, process disruptions and legal action by federal or state agencies or workers.
Engineering controls and isolation
Engineering controls include equipment that reduces or eliminates worker exposure to RCS. One company that has set out to help the construction industry address outdoor dust emissions from a wide range of activities is BossTek, through its DustBoss® line of atomized mist cannons. These use high-pressure water driven to a circular manifold at the end of a specialized cylindrical barrel with an industrial fan located at the rear. As the unit oscillates, the fan directs air through the cone shaped cannon and propels millions of tiny droplets — approximately the same size as the dust particles — covering an area of up to five football fields in size. The equipment has been used successfully for many years, proving its worth on demolition, construction, tunneling and civil engineering sites.
For outdoor isolation of particle emissions or for stack out conveyors and chutes where the cargo stream is exposed to open air currents, the system works by using point source suppression such as non-mechanical misting rings and spray bars. A misting ring encloses the stream in a curtain of atomized mist, preventing dust from migrating. Open-air discharge resulting in dusty blowback from impact can be suppressed by combining rings and spray bars to create a dust barrier. For hydrophobic materials such as coal, dosing pumps attached to both the mechanical and non-mechanical units can apply dust suppressing surfactants and crusting agents. The sprayed surfactant agents reduce the surface tension of water, improving its ability to wet surfaces and form fine droplets that reduce dust emissions.
Mobile dust suppression keeps demolition emissions from leaving site
An example of how the BossTek equipment can be used to minimize dust concerned River City Demolition. The company used a self contained and mobile DustBoss® DB-60 Fusion®, manufactured to suppress airborne dust created by the jaw processor and falling debris during the demolition of a five story concrete parking lot in a densely populated area. The result was an adjustable wide area control of airborne and surface dust that reduced the need for manned hoses, thereby maintaining air quality needed to comply with regulations.
Due to the close-in location and confined space of the project, River City crews decided to use a jaw processor to pulverize the concrete and take the parking lot decks down a section at a time. That helped avoid dust clouds from large sections falling at once, but still required a dust containment system. The BossTek-supplied DustBoss® DB-60 FusionTM is equipped with its own generator for locations without convenient access to power. All components are mounted on a road worthy trailer, providing River City crews with the versatility to position the fan-driven unit wherever it was needed on any given day.
The DB-60 Fusion forces water through a circular stainless steel manifold with 30 atomizing spray nozzles, then launches millions of tiny droplets with a powerful 25HP fan that produces 30,000 ft3 (849.50m3) of air flow. Atomized mist droplets of 50 to 200 microns in size are thrown out in a 200-foot (60m) cone at an adjustable zero – 50° elevation angle, capturing airborne dust particles and dragging them to the ground.
Rather than have personnel handling hoses to suppress the dust, the single atomized misting unit delivers 62,800 ft2 (5,834m2) of coverage, while using far less water than hoses and sprinklers. The unit is paired with a 45kW generator featuring a John Deere Tier III Flex engine enabling up to 24h of runtime. At just 80 inches (2.03m) wide, the system can be placed virtually anywhere dust suppression is needed and adjusted based on changes in wind or work activity. An optional dosing pump is powered from the standard 120V electrical outlet on the generator, allowing operators to precisely meter surfactants or other additives. The unit’s versatility makes it suitable for uneven ground as well as open spaces or tiered terrain.
Water sources can vary and the unit requires a constant supply pressure of just 10psi (.069bar). The water is delivered to the atomized misting unit through a hose with a cam-and-groove quick disconnect coupler leading to the booster pump. The pump adds approximately 150psi (10.34bar), with a maximum of 205psi (17.23bar), depending on the inlet pressure. For use with a non-potable water source, the DB-60 can be equipped with a number of filter options.
Another manufacturer who has specialized in producing dust mitigation systems is U.S.-based JH Fletcher, which has undertaken massive strides in developing and applying clean air technology for its tunneling equipment as well as quarrying, mining and general construction. Currently the company offers enclosed operator compartments as an option on all its drilling jumbos, with most being available with built-in air conditioning and heating systems for mobile equipment. The company’s systems have been purpose-designed for enclosed operator cabs, with filters for both recirculated air and the make-up air using a high efficiency filter. The jumbos may also be equipped with an exhaust purifier as well as Tier IV engine options.
JH Fletcher also manufacturers a mobile dry scrubber, which is an independent vehicle designed to filter air and direct it back out into the main air stream. For its roof bolting equipment they offer operator air canopies. Air is pulled through a fan, filtered and then pushed down over the breathing zone of the person working beneath the canopy. Atlas Copco’s Epiroc division and Sandvik Mining and Rock Technology have both ensured that their equipment is also able to protect operators from dust and other emissions.
The increasing demand for clean air/dust control technology for underground operations has seen developments from manufacturers whose business is primarily focused on providing technology for a clean working environment. Not all of these companies are well known.
Engart Global specifically focuses on equipment and services aimed at dust management primarily in the field of optimizing dust extraction equipment and solving dust related problems. One such solution is its wet dust extractor unit. This enables users to maintain the proper air volumes required to alleviate fumes from equipment and to control the dust emissions generated during tunneling. The dust extractor allows the air exhausted from a tunnel to be free from air-borne particulate while providing better visibility and controlling unhealthy particulate levels in the tunnel operation.
These developments mean compliance with increasingly stringent work place regulations — as with the new U.S. silica emissions — but also increase productivity by improving visibility and worker conditions.
The age of the machine
Robotic developments are also providing clean air dust control solutions. This is not just in the case of providing equipment to work underground in tasks that may negatively affect human workers but also in the provision of specialized equipment to minimize or remove contaminated air. Swedish company Husqvarna seems to be at the forefront of these developments with a dust reduction accessory available for all its DXR robots. The accessory supplies water to the tool sufficient to bind the airborne dust, contributing to a better working environment and reducing the risk of the operator breathing harmful dust particles. The accessory also provides a more efficient and economical way of working by eliminating auxiliary equipment or extra workers engaged in binding airborne dust. Beyond the environmental benefits, the dust reduction kit has a unique and effective water management system.
One of the best ways to control dust is by using enough water while wet cutting/drilling to bind the dust directly at the source. However, this leads to the production of slurry and in order to remove this, Husqvarna has developed a slurry collector which may be attached to a specially developed slurry vac. In addition, the company has also developed a line of dust extractors designed to meet strict emission regulations. These are ideal for many applications as they are compact and equipped with one, two or three powerful single-phase electric motors with separate cooling, capable of running continuously. Husqvarna now supplies the most advanced and versatile portable air cleaners available on the market, which complement dust and slurry management equipment as well being ideal for other applications where good air quality is essential.
Easy to use air scrubbers can further clean air in enclosed areas: plug it in, turn it on and it’s ready to clean the air. When used in addition to a dust suppression system, it helps ensure the workspace is well protected against airborne dust particles. Husqvarna’s A-line features two of the most advanced and versatile portable air scrubbers available on the market. They are tested and certified for use as both air scrubbers and negative air machines, making them the ideal complement to dust and slurry management equipment as well as other applications where air quality is essential.
The A600 and A1200 are equipped with an efficient filter system and provide superior air quality when dealing with concrete, fine sanding or gypsum dust. The number of air cleaners needed for a particular job site can be calculated so that the entire air volume on the worksite is filtered at least six to eight times each hour.
Features include quiet and efficient operation; ready for ducting; lightweight cabinet with sturdy aluminum frame and metal locking casters with a metal mesh protecting the filter area; and two stage air filtration with a pre-filter made of pleated polyester catching the larger dust fractions before the air enters the individually tested HEPA filter ensuring 99.97 percent efficiency at 0.3 microns.
Single-phase dust extractors
The Husqvarna S-line (S 13, S 26 and S 36) consists of professional dust extractors designed to meet strict demands. These compact, lightweight machines are equipped with one, two or three powerful single-phase electric motors with separate cooling, capable of continuous workday running. This makes them suitable for all construction, abatement and restoration jobs as well as for use with electric power tools.
Furthermore, a dust extractor can also act as a substitute for a cube vac, with this being primarily due to jet pulse cleaning of the conical main filter that ensures dust is continuously removed. A Longopac® collecting bag further enables the machine to be emptied quickly and simply, while individually tested and certified HEPA filters provide superior and safe dust collection, even on fine sanding and gypsum dust. Longopac bags are completely sealed, meaning that the operator never comes in contact with the dust.
Airflow™ tool holders have also been developed to increase airflow across tools to improve diamond cutting and life. At the same time, the increased airflow creates a cyclone effect in the grinder head and enables the dust extractor to pull dust off of the floor more effectively.
Epiroc, through its SB hydraulic breakers, has also taken measure to ensure its equipment protects operators from dust emissions through an integrated water-spraying channel. The SB hydraulic breakers series are said to be the industry’s only breakers equipped as standard with an integrated channel for water spraying. A feature is designed to improve the working environment on construction and demolition sites around the world. The use of an integrated water channel ensures that operators of SB breakers can spray water at the source of dust creation to keep dust levels down. This helps to improve the working environment, enhances visibility and prevents dust from seeping into the bushings. For U.S. customers, the water-spraying feature can assist in compliance with OSHA’s final silica rule dust regulations. SB breakers are also designed to protect operators and equipment by reducing noise and vibration.
Rammer has also been at the forefront of dust control advances for its range of hydraulic breakers and demolition attachments. For hammers, the company has developed a special water jet system designed to suppress airborne materials or dust during hammer operation. The Rammer water jet system consists of a hydraulically driven water pump and specially designed hammer housing equipped with necessary spray nozzles and water supply lines. The hydraulically driven water pump is powered by either the hammer supply circuit or from another high-pressure hydraulic source from the carrier. Depending on the installation, Rammer Jet Pump is activated by either the operator or automatically in conjunction with the hammer operation.
The Ramair air flush system is designed to prevent dirt from entering the hammer’s tool chamber and keep the tool grease flowing towards the lower tool bushing. The air flush system is most beneficial in applications where the material is highly abrasive and dusty, but is also beneficial when the hammer working position is horizontal or above — such as tunneling and scaling applications. The Ramair system consists of a hydraulically driven air compressor fitted on the carrier, hoses for the hydraulics and compressed air and a built-in channel in the hammer’s power cell. The air compressor is powered by the hammer supply circuit and is activated during hammer operation.
Rammer has also developed a special AGW unit specifically designed for the company’s PRO hammers which are ideal for tunneling applications, heavy demolition and quarrying.
Advanced systems Europe leading the way?
Many European countries have had stringent, enforced dust control legislation in place for years. This has led to the development of systems and solutions purpose-designed for limiting the effects of hazardous airborne emissions, such as dust from concrete floor grinding and polishing which may contain asbestos. Blastrac has recently launched four new single-phase dust extractors with such features as a permanent reverse air pulse filter cleaning system, which delivers high suction performance with sealed airflow that gives increased productivity.
The Italian manufacturer of equipment for concrete floor grinding and polishing, Klindex, is also involved in the development and manufacture of high-efficiency dust extractors. Klindex recently launched two new models in its Supervak series, X2 and X3, which according to Klindex are the only single-phase industrial dust extractors with an embedded cyclonic pre-separator system. The Supervak X series is equipped with an automatic airpulse cleaning system tank, with air blasts regulated by an electronic timer that keeps filters clean. A pre-separator cyclone is integrated into the drum, which can hold over 90 percent of the dust collected in plastic bags. The drum is shock proof, and has a very futuristic design fully produced in Italy.
Last year Scanmaskin launched two new industrial vacuum cleaners, ScanDust 8000 and ScanDust 3600. The machines are equipped with Hepa filters that take care of any unhealthy particles, as well as being fitted with a filter guard that informs the user when to clean the filter. In order to keep the filters as clean as possible, its “jet-pulse” system cleans using pulses. The machine’s coarse filter package is made of polyester with a high degree of separation. The design and filter area of the two new machines are also designed to maximize suction capacity, with both the ScanDust 3600 and ScanDust 8000 being fully constructed in steel as well as fitted with non-marking powerful, durable and puncture-free tires and comes equipped with Longopac.
Some years ago in Sweden, a new dust extraction technique for the construction industry was launched. The technology in itself was not new, but offered a very efficient way to control dust particles in the air by ionizing the air in the workplace. The ionized air makes the dust particles lump together and through increased weight they fall to the floor ,making them easy to be sucked up by a dust extractor. The company Renluftsteknik AB has used the technique in its Oxysan series of air cleaners that was launched on the Swedish market some years ago. There are now four models in the Oxysan series: Oxysan 200, Oxysan 1000 and the larger Oxysan 2000 and Oxysan 4000. The complete Oxysan range has been upgraded recently and the industrial ionizers today can cover a workplace area from 20m2 to 400m2. The technology is 100 percent ozone free and not only eliminates hazardous dust, but also odors and bacteria, making it useful in many types of environments.
The above outline some of the developments that have occurred in equipment designed to make construction — above or underground — a safer and healthier place to work. There is little doubt that many of these developments are being driven by increasing concern by companies regarding the welfare of their workers at the sharp end of their operations. However, manufacturers are rising to the challenges being presented, and are now producing equipment and solutions which will be refined to further improve working conditions.