In the 160 years since the mechanical street sweeper was patented, equipment has become much more sophisticated. No longer used just to keep streets free of vermin-attracting litter, sweepers that remove microscopic-sized pollutants are helping many communities meet stormwater requirements in all types of conditions and temperatures. Here is a summary of the most popular types.
1. Mechanical broom
How it works: A main broom picks up debris that’s sent to a conveyor and ultimately lands in a hopper.
Major benefits: Uses less fuel than other types of sweepers because it doesn’t require high horsepower airflows. It is not sensitive to high street crowns or rough damaged street surfaces. Able to remove larger and heavier debris than other technologies. All current available models may be off-loaded into trucks and containers for transport.
Primary applications: Construction debris and granular materials such as millings and gravel; the heavy build-up encountered after flooding; annual yearly spring cleanup, and general municipal sweeping.
Potential drawbacks: Highly complex and higher levels of maintenance required. Removes less fine dust than air-based technologies.
2. Regenerative air
How it works: Full-sized models use a blast of air the width of the sweeping head to dislodge and lift surface material into an airstream that moves the material across the sweeper into a vacuum hose, where it’s lifted into the debris hopper. In general recirculating mode, the amount of vacuum airflow is equal to the amount of pressurized airflow, causing the air to continually flow through a “regenerative loop.” Units frequently use a vacuum enhancer valve to limit the amount of air volume recirculated through the blast nozzle, causing air pressure under the sweeping head to move from balanced flow to vacuum. Increasing the sweeping head’s vacuum level assists in picking up litter, leaves, and other light debris.
Major benefits: A self-contained air stream means nothing is vented or exhausted back into the atmosphere.
Primary applications: This standard configuration is used for most municipal applications – i.e. streets, parking lots, and some alleyways. They aren’t the “best-selling/most popular” design. For example major municipalities such as Los Angles, New York, and Chicago all rely almost exclusively on mechanical sweepers.
Potential drawbacks: Requires a very flat pavement surface, so it shouldn’t be used on uneven and pothole-filled streets. Debris must be small to enter head.
3. Pure vacuum
How it works: Operating like a giant vacuum cleaner, pure vacuum sweepers remove surface debris and deposit it into a debris hopper. The fan air is then exhausted out of the body. Using water in the hopper or at the side brooms helps prevent fine particles from being pulled through the vacuum fan and exhausted into the free air, and reduces any dust generated by the broom motion. These sweepers rely on air movement provided by an impeller and a sealed hopper to maintain a steady air stream that lifts debris from the sweeping surface and conveys it into the containment area or hopper.
Major benefits: Provides the most efficient removal of material directly under the suction nozzles, typically resulting in up to 99% removal of all particles. Because pure vacuum sweepers only use energy in the suction direction, the pressure discharge side simply vents to the atmosphere.
Primary applications: Pure vacuum sweepers better serve roadways with inconsistencies, such as those with several potholes. On a typical rough and potholed roadway, pure vacuum sweepers capture and keep more particulates out of the air. With an extended nozzle that can reach the curb, it is ideal for efficient street gutter cleaning.
Potential drawbacks: Due to the high-power density nozzle design, the suction nozzle entrance area limits the size of debris to dirt, gravel, sand, leaves, organics and small pieces of asphalt, bricks, and concrete.
