Vacuum Cleaners Information
Vacuum cleaners are capable of picking up large quantities of material and/or liquid in a wide variety of industrial applications. A vacuum is defined as a space in which the pressure of gas is low compared to the atmospheric pressure. The measure of vacuum is associated with pressure. Vacuum cleaners are responsible for removing pollutants and particulates from the air surrounding a work space.
The function of a vacuum pump is to withdraw gas from a designated volume so that the pressure is lowered to a value suitable for the purpose in hand. Vacuum cleaners use four basic systems for vacuum production:
Centrifugal blowers are used when only intermittent use is required. They can be powered with an inexpensive short-life, brush-type AC or DC motor. More information can be found at How to Select Centrifugal Pumps.
Turbine pumps are centrifugal pumps which generate pump pressure by using an impeller to apply centrifugal force to a moving media. They use turbine-like impellers with radially orientated teeth. Turbine pumps have high discharge pressures similar to positive displacement or multi-stage centrifugal pumps, as well as flexible operation like centrifugal pumps. They are best used in operations where high head, low flow, and compact design are desired. Read How to Select Turbine Pumps for more information.
Regenerative devices are similar to centrifugal blowers and pumps, but the chamber is designed to generate higher pressure. Rather than having only a single compression per stage (centrifugal types), individual air molecules pass through many compression cycles with each revolution. More information can be found at How to Select Regnerative Blowers. Regenerative blowers produce low vacuum (100 in. H2O in single-stage models) but very high flow capacity (up to several hundred cfm).
Positive displacement (PD) pumps create vacuum by isolating and compressing a constant volume of air. The compressed air exits one port and a vacuum is created at the port where the air is drawn in. More information can be found at How to Select Positive Displacement Pumps.
As the vacuum collects media it may be separated and stored by a separation system. Separation systems ensure that the pump and tubing do not become clogged or blocked as the device operates. There are several types of separation systems, including bag-type units, or cartridge-type units, and cyclone or centrifugal separators.
Bag-type separators, also known as bag-houses, are air pollution control devices, which use fabric filter tubes or cartridges to capture or separate dust and other particulate matter. They can be used in small household workplaces to large industrial facilities. Bag-type separators are available in a variety of bag sizes and types. They are very efficient when properly maintained and used in a relatively dry environment. For more information, visit How to Select Baghouses and Baghouse Filters.
Cyclone separators, also known as centrifugal separators, utilize gravity and a vortex to remove particulates from gaseous streams. They do not use filter media or moving parts. This lowers the pressure drop, operating cost, and maintenance required. Cyclone separators can withstand harsh operating conditions, and since separation in cyclones is a dry process they are less prone to moisture corrosion. These devices work by incorporating centrifugal, gravitational, and inertial forces to spin the media in order to remove fine particles suspended in air or gas.
Another specification to consider is the storage capacity of the separation system. The size of the bag or cyclone will determine how often it needs to be emptied or cleaned.
Vacuum Cleaner Types
Vacuum cleaners are used in a wide variety of industries and applications. The model selected should be based on the size of the facility, media vacuumed, the user, and the frequency of use. There are several unit types of vacuums:
A backpack vacuum is a self-contained unit that is designed to be worn on the back of an operator.
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Central vacuum system
A central vacuum system (CVS) defines the package of tubes, wall inlets, and accessories connected to a vacuum power unit to collect dust and other elements.
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Portable vacuums are designed to be moved by the operator during use. This category includes walk-behind and canister vacuums.
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Heavy-duty ride-on vacuums are usually designed to carry one operator. They can be used with indoor or outdoor applications.
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Large, vehicle transport units are designed to be moved by a vehicle. They can be trailer-mounted or truck-mounted.
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Vacuum Cleaner Specifications
Specifications for industrial vacuum cleaners include:
System power is specified in horsepower and indicates the power of the motor. The power output of the vacuum pump is provided by the manufacture in a pressure-flow curve, which also shows input power and speed requirements. By combining this data, the overall efficiency (both the volumetric and mechanical efficiency) can be evaluated. In order to do this evaluation, the free-air capacity of the pump at the required vacuum level must be divided by drive power at the condition. The result is proportional to the product of gage vacuum and air-flow rate represents efficiency. The vacuum power source depends upon the location and application of the vacuum. If a large number of vacuum generators are used in a small floor space than a centralized vacuum system is recommended. If a few vacuums are required to cover a large floor space, it is not practical to use electric vacuum pumps. Typically, industrial vacuums are powered by electricity, gasoline, diesel, or compressed air.
Electricity- Electric vacuums are very efficient, as much as four times more efficient than compressed air driven vacuum generators. They are best option if constant vacuum flow and a high flow rate at higher vacuum levels are required.
Compressed air- Compressed air powered pumps require a high volume of compressed air for proper operation. If a facility requires several of these devices, they may have trouble maintaining adequate supply pressure. Often, extra or backup compressors need to be maintained online to keep up with the site requirements.
Airflow refers to the velocity of the air stream created. This is also known as the rate of air removal. The flow rate is determined by the volume of air exhausted with no pressure difference across the pump. Most manufactures provide curves showing free air delivery at rated speed for vacuum levels. These levels range from 0 - in. Hg (open capacity) to maximum vacuum rating.
Image Credit: Flow Rate vs. Pressure
Vacuum pressure is commonly referred to as static pressure (SP) or water lift. In vacuum systems, vacuum pressure is used in discussions of pressure differential across a filter media. The maximum vacuum rating is generally given in absolute pressure in mmHg or vacuum in inches Hg. Continuous and intermittent vacuum ratings are determined for standard atmospheric pressure which is 29.92 in. Hg. The rating is determined by the formula:
Va = (Vo * Pa) / 29.92
Va = adjusting vacuum rating, in. Hg.
Vo = original vacuum rating at standard conditions, in. Hg.
Pa= anticipated atmospheric pressure at the application site, in. Hg.
Maximum number of inlets or operators the device can support refers to the size of the system. Some important specifications to consider are that the more inlets or operators the system has the more power, pressure, and filters are needed. Consider the space and access to resources such as power to determine the fewest number of vacuums needed to adequately handle the task.
The type of media in the system is important to consider when selecting an industrial vacuum. Vacuum cleaners can handle an assortment of media types including liquids (wet), gas, and solid particulate matter (dry). It is critical to ensure that the selected vacuum can effectively collect the system media because using an improper vacuum can cause serious equipment and facility damage. Some devices can be used with abrasives, coolants and oil mist, explosive media, fine powders, general cleaning, litter pick-up, non-free flowing media, metalworking chips and fluids, reclaiming and recycling, spill recovery, toxic media, and welding fumes.
An important component of a vacuum cleaner is the type of filter used to collect the media. Most vacuums use a mechanical filter which is a physical device used to capture and retain particles. The barriers can be made of cloth, polyethylene, and/or paper filters. There are four factors which affect the mechanical filtration: the particle size being collected, the air velocity or speed of the particle, the filter material, and the running time of the filter. Filters are available in a wide range of efficiencies. Two of the most efficient filters are the HEPA and ULPA filters.
High efficiency particulate air (HEPA) filters are replaceable, extended-media, dry-type filters in a rigid frame. They have a minimum particle collective efficiency of 99.97 percent for a 0.3 micron particle, and a maximum clean filter pressure drop of 2.54 cm (1 in.) water gauge when tested at rated air flow capacity.
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Ultra low penetration air (ULPA) filters are extended-media, dry filters that are mounted in a rigid frame. They have a minimum particle collection efficiency of 99.999 percent for particles greater than or equal to .12 micron in size. ULPA filters are more efficient than HEPA filters and are often used in facilities that manufacture microelectronics.
Vacuum cleaners differ in terms of features such as:
Cleanroom suitability- A cleanroom vacuum cleaner is designed specifically for cleanroom applications. Cleanrooms, including laboratories and hospitals, require very high quality (free of particulates and pollution) air to prevent contamination. This usually requires the inclusion of a HEPA filter or better.
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Duty cycle- Continuous duty vacuums are rated for 100% duty cycle (constant use). This is important for facilities, such as wood shops, where particulates and pollution can be deposited on the machinery or operators. A high number of particulates in the air could be a potential fire and health risk. When selecting a continuous duty vacuum, consider the power required to run the device.
Instrument panel- The unit is equipped with an instrument panel for user operation. The instrument panel may be equipped with an alphanumeric keypad, gauges, safety switches, on-off switches, or timer controls.
Vacuum cleaners can be found in industries such as agriculture, automotive, food and beverage, health care, pharmaceutical, utilities, and in the manufacturing or manipulation of textiles, pulp and paper, plastics and rubber, and electrical and electronics. Vacuums are used to collect particulates which could cause a fire if exposed to a spark, to absorb dangerous fumes from chemicals, to keep the work air clean so operators can see and breathe safely, and to keep equipment clean and free of debris. Industrial vacuum cleaners can be especially important where high air quality is important, such as in the manufacturing of delicate materials like microelectronics, or pharmaceuticals.
Chambers, A. Modern Vacuum Physics. Boca Raton: Chapman & Hall/CRC, 2005. Print.
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