The Essentials Of Maintaining Pure Vacuum Sweepers

Pure vacuum sweepers are used across the United States by municipalities and sweeping contractors alike. Operating like a giant vacuum cleaner, these sweepers remove debris from the surface and deposit it into a debris hopper. The fan air is then exhausted out of the body. Use of 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 also reduces any dust generated by the broom motion.

Combining a low-maintenance design with an extra-wide sweeping path and short wheelbase, the Whirlwind sweeper from Elgin Sweeper offers a pick-up performance and flexibility that allows the operator to select one nozzle or two, and 28- or 36-inch side brooms for a maximum sweep path of 12 feet. Ideally suited for sweeping uneven roads and jobs involving dirt, sand, millings and leaves, the Whirlwind can also be used for routine catch basin cleaning.

Pure vacuum sweepers, like the Whirlwind, use vacuum to convey the debris into the hopper and rely on filtration to clean the air stream before being exhausted to the atmosphere. These sweepers rely upon air movement established at an impeller and an intact vessel to contain and maintain the integrity of the air stream as it lifts the debris from the sweeping surface and its conveyance into the containment area or hopper. The air stream on a pure vacuum sweeper must be exhausted after the impeller to keep the vacuum system working optimally.

For a vacuum sweeper to work, several components must work in unison to develop and maintain the air stream. Any defects in any one of the components involved can and will affect the sweeper’s ability to capture and convey the material.

Impeller

An impeller rotates and creates air flow that can be managed at a suction nozzle to capture and convey the debris from the sweeping surface. The addition of side brooms and a center broom mounted under the sweeper before the suction nozzles assist the vacuum system in cleaning debris from the streets. As the side brooms rotate, the dirt and organics from the street and gutter are moved into the path of the suction nozzle.

The impeller creates a vacuum (low pressure) area under the nozzle and atmospheric pressure rushes in to fill the void. Street debris is captured in that rush of air and transported into a hopper. The air stream through the suction nozzles and the suction tubes moves very rapidly, and when it enters the eight-cubic-yard hopper, the air stream slows down, allowing the heavier debris to fall out of the air stream and onto the floor of the hopper.

Periodic inspection of the impeller is essential for its function and longevity. It is recommended that impellers be inspected every 50 hours of operation—and more frequently if water is not consistently being used. Impeller inspections identify discrepancies, such as holes in the vanes caused by the accelerated erosion of the metal. Wear of the vanes causes deteriorated suction performance over the life of the impeller.

Also look for missing weights. Elgin Sweeper impellers are dynamically spin balanced for vibration-free operation during sweeping. Abrasion from carryover is the number one cause for impeller wear, loss of weights and failure. Any time the operator notices an unusual vibration, the impeller must be inspected. All vacuum sweeper manufacturers provide inspection access into the impeller housings.

Caution must be observed during impeller inspection, as wear and erosion of the vanes will result in extremely sharp edges. Gloves must be worn during the impeller inspection to prevent injury and infections from any dirt remaining on the impeller. The impeller should be rotated with a gloved hand for a thorough, 360-degree inspection. Some sweepers require “barring” the auxiliary engine over to thoroughly inspect the impeller. Remove the keys and lockout/tagout the sweeper during impeller inspections. A running impeller can cause injury, so protection is crucial. Inspect the housing while inspecting the impeller. Any discrepancies with the liner will require a new liner.

Hopper

The first stage of filtration is the hopper. As previously described, the air stream drives the heavier debris through the suction nozzles and the suction tubes and falls onto the floor of the hopper. The use of water is important to filtration as wet material is heavier than dry debris and will filter out of the air stream more completely.

Screens

The second stage of filtration relies on two screens positioned in front of the impeller inlet. Material that is light in weight but has a large surface area can remain suspended in the airstream as it exits the hopper through the two large screens. These screens capture this light-weight debris and prevent it from being ingested by the impeller, which could accelerate wear and possibly cause the impeller to be unbalanced. If debris has become entangled in the impeller, it must be inspected and cleaned in accordance with all published information. If repairs are deemed necessary due to damage and wear, the impeller must be removed and replaced with a new impeller.

Washing or flushing these screens should be done with them in their down service position. Since all debris washed from the top side is flushed into the empty hopper, the hopper should be washed after the screens. The impeller inlet should also be washed out. It is easier to identify potential problems with the sweeper and make the necessary repairs when the machine is clean.

Diffuser

The final stage of filtration happens at the diffuser location. On the Whirlwind sweeper, the diffuser is located over the left rear set of dual tires. The diffuser is a conduit used to route the air stream
out of the impeller housing, along the hopper floor, externally, and exhausted behind the left rear tires. The exhaust conduit terminates with a clean out and some large diameter holes to catch any carryover material that may get past the filtration.

Any carryover material remaining in the air stream past filtration can be controlled by the use of water, sweeping speeds and impeller RPM. If the diffuser is continually filling and needs to be cleaned out, the first step is to verify that the water tank is full and the spray nozzles are delivering enough atomized water to moisten the debris. This controls dust and makes the debris heavier and also acts as a lubricant. Wet debris is less abrasive to wear components, ensuring a longer service life.

An impeller speed that is too fast does not allow the air stream to slow down enough when it reaches the hopper to separate the debris. Sometimes, just reducing the impeller speed a couple hundred RPM will be enough to ensure the filtration process works. The impeller speed should only be fast enough to convey the material to the hopper.

Suction nozzle

To make the vacuum sweeper work effectively, the setup and maintenance of the suction nozzle is important. The illustration to the right displays the adjustments necessary to make this suction nozzle perform at its peak efficiency.

On the Whirlwind suction nozzle, there are six adjustments that assist the air stream as it enters the nozzle. Deck height is established by placing shim plates between the caster and the nozzle’s mounting location for the casters (identified as “A” in the illustration to the right), which is 6 7/8 inches from the top of the deck at the rear of the nozzle.

The front of the deck is 3/16 of an inch higher than the rear of the deck and is made by adjustment (labeled “B” and “C” in the illustration). This serves to allow the nozzle to ingest the debris as the nozzle moves forward. The raised positioning of the front of the deck makes it easier for debris to be sucked in.

The rear curtain ground clearance should be ¼ inch off the ground. The suction nozzle will work best if there is a pathway for the air stream to enter the nozzle from all sides. This adjustment is made by placing a ¼-inch spacer under the curtain, loosening the curtain mounting bolts (identified by “D” in the illustration) and retightening once the ¼-inch air gap has been established.

The inner air curtain (labeled “E” in the illustration) has the same ¼-inch measurement as the rear curtain. The adjustment is made by loosening the mounting bolts, placing the ¼-inch plate and retightening.

The nozzle shutter opening spring tension (labeled “F” in the illustration) features a cotter pin that locks the adjusting hex nut once the adjustment has been made. The cotter pin should be removed and the hex nut rotated clockwise until the shutter just begins to open. The hex nut should be backed off until the shutter just closes. Then the cotter pin should be reinstalled to complete the adjustment of the shutter opening.

The same procedure will be followed for adjusting the rear and under curtain. Place a ½-inch plate or square stock under the curtain to loosen the mounting bolts and allow the curtain to touch the plate or stock and retighten the mounting bolts.

Seals

The rest of the checks will be the same as the regenerative or any other air product that relies on a contained air stream to deliver material to hopper or container. Rear door seals and mating surfaces must be cleaned at every dump, any inspection door accessing the hopper must be inspected and discrepancies to those seals will require adjustment or replacement. Transition seals from the suction nozzles into the hopper must be cleaned when dumped and inspected at regular intervals. The integrity of the airstream and the vacuum being created must be in excellent working order for vacuum machines to work effectively and efficiently.

Maintaining a pure vacuum sweeper will keep the machine running in new or near-new condition for a longer period of time. With this type of sweeper, it’s always important to sweep with the proper amount of water, not just for dust suppression, but also to maintain the overall integrity of the machine.

As with any type of sweeper, lack of maintenance and neglect are very harmful to the machine’s overall performance. Every sweeper manufacturer publishes service intervals in their operations and service literature. These guidelines must be closely followed to keep the sweeper on the road and out of the garage.

For more information on pure vacuum sweepers available from Elgin Sweeper, please contact your local Elgin Sweeper dealer, or visit www.elginsweeper.com to find a dealer near you.

Story by Jimmy Broyles, CBT supervisor ESG University, Elgin Sweeper

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