VACUUMS

Common questions and answers

What size should I buy?

You should purchase a vacuum that has the capacity to handle the toughest vacuuming situation that you will run into.

Example: If you need to vacuum steel grit 500 feet horizontally at a rate of 5-10 tons per hour, this is significantly harder than vacuuming coal slag that same distance. This is primarily because of the difference in weight of the two medias. As a result of the greater density of steel grit, the SP or static pressure (amount of pull) that will be required is higher than coal slag.

In almost all situations today, it makes sense to purchase a machine that is CAPABLE of 27"Hg. You may not need it all the time, but when you do (for plugups) it is critical. The size in CFM will relate to the length of pull and tons-per-hour that you want to move. Contact Advantage SPS for specific recommendations on sizing.

In some situations, like marine work, the maximum hose size is defined based on the flexibility and routing it must take. For marine work, a 4" ID hose is most common. The only other variables are length of pull and density of material. For this work, a vacuum of 2-3000 CFM with a 27"Hg capability makes sense.

For highway work, where most pulls are horizontal and sometime quite long, a 3-5,000 CFM vacuum typically makes sense.

Remember, the longer the pull, the more CFM is lost to friction. You need EXTRA CFM to make up for that friction loss.

To decide what vacuum to purchase, you must know how you are going to use it.

What is the density (weight) of the material you intend to vacuum.

Each type of material has a density that is specific to that material. With sand or Black Beauty it is 100 pounds per cubic foot. With steel grit it is 265 pounds per cubic foot. For a material to be moved by a vacuum, it needs a certain velocity of air to start the movement (capture velocity) and keep the product moving. With sand it is approximately 3000 feet per minute (34 MPH) and with steel grit it is approximately 8500 FPM (96 MPH). If the required level of velocity doesn't exist, the material will "fall out" of the air stream and cause plugging of the vacuum line.

How does hose size relate to the size of the vacuum?

Some vacuums (Roots) need to get a certain amount of air to keep the rotors cool. The type of material that you are moving needs a certain velocity of air to keep it moving. The bigger the vacuum, the bigger the hose that is required to feed the air to the vacuum. The bigger the hose, the harder it is to handle. If you purchase a big vacuum and connect a small hose to it, you will restrict the flow of air, which causes increased friction, which will slow down the flow of air, which will cause the vacuum to run hotter.

How does hose size relate to the tonnage of material to be moved?

It takes air flow to move any material. The more air, the great the capacity to hold particles of material in suspension. To get the best performance, you need a proper "ratio" of air (CFM) to particles of material. If you use a small hose, it will restrict the air flow which will in turn restrict the amount of material that can be moved. To get the best production, use a hose size that can be easily handled by your men. Advantage SPS recommends using a 5" hose. It's not too big and not too small.

The net tons-per-hour production is a balance between hose size and handlability. An 8" hose can move a lot of material, BUT a human being can't easily move an 8" hose. Under actual jobsite conditions, a smaller hose will allow you people to actually move more material because they can more easily move the hose to the various piles and windrows.

How long a hose will you normally use.

The length of the hose will directly affect the level of friction, which will affect the level of vacuum that the rotors have to pull against. The concept of friction is just like a water or blast hose. The longer the hose, the lower the pressure at the outer end. To compensate for this, many contractors are now using "high pressure" compressors that produce more pressure. If you start with more pressure you will end with more pressure. With a vacuum, the length of the hose will determine how much friction is created. As the friction increases, the air flow will drop, making it harder to pick up the material you want to move. If you are going to use long hoses, you can bet that you will be creating a higher vacuum to begin with. If the material you are moving is heavy, like steel grit, it will push the vacuum even higher because it creates move friction.

What if I use pipe (steel, alum or plastic)?

If you use almost any pipe, the loss to friction will be much LESS than the typical spiral hose (ie: Kanaflex). As a result, you will move more material for the same manhours and fuel usage. This can be very significant, especially when the hose run is long (100's of feet). Because the friction will cause static electricity, you MUST ground the piping system to eliminate static discharge. This can be done with a copper rod driven into the ground with a strap clamped to the piping system

What happens if a vacuum gets too hot? (Roots designs)

The vacuum needs a certain amount of air to keep it from overheating. The tolerances of the rotors are measured in 10,000's of an inch. If the air flow is blocked, the rotors will overheat and eventually expand to a point where they contact the sides of the housing. When this happens, serious damage will result. If the rotors actually touch the sides of the housing, they may lock up without warning and twist off the drive shaft. At this point the vacuum is scrap and cannot be repaired. This damage happens to many contractors who have never used PD blowers before. After they replace one $20,000 blower, they will understand how critical cooling is to a vacuum.

What does 27"Hg mean?

27"Hg represents the maximum vacuum level that the vacuum can produce (29"Hg is a perfect vacuum). In layman's terms, this the how much "suction" it can create. For many years most vacuum systems had a maximum level of 15"HG. This meant that they could pull suction to a level of 15" of Mercury (Hg). When a vacuum is operating and the material is flowing smoothly, the vacuum level might be in the range of 4"-12".

If the operating vacuum level is 4"-12"Hg, why do I need 27"HG?

If everything always stayed at a constant flow, a 15"HG capability would be all you need. The problem is that operators don't always keep a constant flow of material. If an operator puts the end of the hose into a pile, the suction will fill up the end of the hose. It's like eating too much, it takes more time to digest the large quantity. The same is true with a vacuum hose.

When a plug occurs in the hose, the vacuum level rapidly rises as the spinning rotors try to pull hard enough to keep air flowing. Because the grit is so heavy, it is very hard to get the flow going again. If the vacuum has a 15"Hg maximum, when the reading hits 15" a vacuum relief valve will pop and relieve the vacuum by letting air come directly into the vacuum line right in front of the rotors. This is because the rotors must have a flow of air to keep cool. With a 27"Hg system, the vacuum level rises because of the plug until at a certain point, probably in the 22"-24" range the plug breaks loose and air begins to flow again. This is why you need a 27"HG machine. You need to have the CAPABILITY to handle the WORST CASE SITUATION - A PLUG-UP.

With a 15" machine, the vacuum relief valve may trip before the plug has been broken loose. This makes it almost impossible to break the plug and get air flowing again. Without air flowing, you can't vacuum.

Two hoses or one?

While a 6” hose will move more grit, it is harder to handle. Users have shown that 5” hoses will allow the operator to get more ACTUAL production because it was easier to handle.

Will a “Y” work to create two hoses?

It will until one hose plugs with grit for some reason. If this happens, the other hose will take all the flow. To unplug the plugged hose, the other operator will have to stop the airflow in his line to cause airflow in the plugged line. This can be overcome to some degree by using an oversized vacuum for this work. A 5000 CFM vacuum can support a 6" hose with a "Y" to two 4". If plumbing allows, two 5" hoses can also be run if they run back to the receiving hopper.

Is there a solution?

If the airflows are monitored and automatically balanced to keep a uniform airflow in each hose, plugging will be avoided. To do this requires an automated system to be able to react as quickly as is required.

Continuous vs. Intermittent vacuuming.

If you set up your system to vacuum continuously, you will want to calculate the amount of grit that will be vacuumed each minute and each hour. Usually it will be the grit that is falling from blast nozzles that are operating continuously. Each #7-#8 nozzle will use about one ton of steel grit per hour. In general, continuous vacuuming will allow you to use a smaller vacuum.

If you are going to need to vacuum a large amount all at once, you should again determine the amount you expect to vacuum in one hour. If your hourly amount is 1-10 tons, an 1800 CFM vacuum will probably do the job. If you need to vacuum over 10 tons per hour, a 3500-5000 CFM system should be used.

Will vacuuming small amounts continuously cause any problems?

Yes, when only small tonnage's are vacuumed each hour, the velocity of the particles will be very high. When the velocity is high, the energy of each particle will be highest. Each time that particle hits the hose or internal surface, it will cause wear. When the hose is filled with particles, the particles will hit each other and actually protect the wearing surfaces.

When the ratio of particles to air is very low, high rates of wear can be expected. To have a high air to particle ratio is wasteful in many ways. On a big vacuum, slowing down the RPM can cause the same problems as too small a hose.

Wear on internal parts will be very high causing higher than normal operating costs.

Fuel is wasted moving air not material.

So what size do I need?

As you can see, there are many variables that factor into selecting the right vacuum for the job. Generally, you should purchase a vacuum that will be utilized at 60-90% of capacity while running at 90-100% recommended RPM. Running a PD blower at full RPM is better than running it too slow. Better to have too much air flow than too little.

PD blowers are designed for 24 hour per day operation 365 days per year in stationary mounting situations. They are very durable machines if subjected to continuous duty operation with a constant load. They must have only clean, dry air passing through the rotors.

In mobile operations, PD blowers seldom last as long as stationary mounted units. This is because in mobile applications they are routinely subjected to poor maintenance, variable vacuum levels, widely ranging ambient temperatures and a variety of abuse that doesn't occur in a stationary mount situation.

In general, Advantage SPS recommends that only 27" Hg vacuums be purchased if you intend to vacuum steel grit. With a 15" Hg machine you run the risk of running out of vacuum if you are vacuuming a long run. If you need to vacuum under 10 tons per hour, a 2000 CFM unit will work well. If you need to vacuum over 10 tons per hour, a 3500-5000 CFM unit makes sense.

How clean must the air be that goes through a vacuum?

It must be VERY clean. As was mentioned earlier, the rotor tolerance is measured in 10,000's of an inch. Any dirt flowing through the system will cause wear on the rotors and bearings. Excessive dirt can cause premature failure in as little as 10 hours of use or as much as 2000 hours of use.

What is a final filter?

A final filter is normally a paper or polyester cartridge placed in the air flow between the main bank of air filters and the PD blower. The final filter is designed to catch particles that get past the main filters for a variety of reasons. A loose bag-cartridge or broken bag-cartridge are the most common reasons for leakage.

What is a differential pressure gauge?

A differential pressure gauge shows the difference in pressure between the clean and dirty sides of a filter. If the filter is dirty, the differential is high. With a high differential, air flow is being restricted due to plugged pores on the cartridge material. Typically, a differential of 5" of water is normal. Over 10" it indicates that you are not cleaning the fitlers properly. The pulse system may not be working properly. This gauge effectively tells the operator if the filters are being cleaned properly. Some systems automatically shutdown the vacuum if the level rises above a set position.

The main filter bank. Cartridges or bags?

It doesn't really matter as long as the designer has set up a proper ratio for the specific conditions. New materials, valves, etc. all have an effect on air flow and cleaning methods. If a system is properly designed, the differential pressure should range between 0-5" water (different than Mercury) during normal operation. If the differential climbs steadily, something is wrong.

Some manufacturers claim to have miracle cartridges that last "forever". Is this for real?

Four paper manufacturers make virtually all the "paper" for all the companies that make cartridge filters. The "paper" is available in a variety of types. To get longer filter life, polyester fibers are added to the mix of paper. Advantage SPS uses a polyester blend (plastic fibers). No filter will last forever. If the pulse cleaning system is set properly, they should last 1-3 years DEPENDING ON THE LEVEL OF DUST LOADING, MAINTENANCE, MOISTURE LEVELS, ETC.

How long will the cartridge last?

Filters wear out for three reasons. 1. The repeated pulses of air that clean the filter will cause the filter paper to fatigue and then rip open. 2. If the dust collector is improperly designed, the dust coming into the filter will cause it to wear by abrasion. When this happens, the filter will begin to leak. 3. Over time, the filter paper will become saturated with dust. If the dust is wet it can actually stick to the paper and not fall off when the pulse of air hits the inside of the cartridge.

How important is particle size efficiency? 1 micron or 2 micron?

VERY IMPORTANT. A dust collector was specified to collect the hazardous dust in a filter and deposit it into a hopper. The goal is to catch the dust particles, NOT let them pass. Regulations are becoming very strict about filter efficiency. Advantage SPS systems are designed to the following specification using the ASHRAE 52-76 test procedure:

100% particle efficiency by weight on particles 5 micron (large particles)

100% particle efficiency by weight on particles 2 micron

99.9% particle efficiency by weight on particles 1 micron

99.8% particle efficiency by weight on particles .5 micron (very small particles)

State DOT and consulting engineers are very concerned that the money they spend to specify dust collection GETS THEM COLLECTION OF THE HAZARDOUS DUST. They don't want to find that the fan or vacuum is exhausting a steady steam of small dust particles. Expect to see filter efficiency specified on projects.

What is HEPA? Do I need it?

HEPA (High Efficiency Particulate Assimilator) was developed during in the 40's to address very high levels of filtration. Addition of a HEPA stage to a typical dust collector will increase the static pressure by 1" of water. HEPA is typically used where hazardous materials like asbestos are being vacuumed.

What if I want to put my vacuum on a flatbed trailer or mount it on a truck frame?

Advantage SPS vacuums are designed to clamp down to a wide variety of trailers. On normal or single drop flatbeds (depending on vacuum size), they can be turned four different ways to allow you to position the dump valve where you want it.

How much maintenance does it take to keep a machine going?

Mobile vacuums don't require a great deal of maintenance. As long as the pulse cleaning system is working properly, the filters will work as they should. Over time, timer boards, diaphragm valves and filters will require some attention. PD blower lubricant levels should be checked daily.

When Advantage SPS vacuums don't work properly, it is usually as simple problem. Failure to empty the dust from the hopper hourly, failure to turn on the pulse timer, failure to turn on the pulse air and other oversights are the most common reasons for problems.

How important is it to empty dust from the filters?

It is critical. The dust collected by the filters is very fine. If it is not removed from the system, it will "re-entrain" back on the filters and cause premature failure. For this reason, we use a valving system that dumps the dust every few minutes into a 55 gallon drum. It does this WITHOUT shutting down the vacuum.

What is the effect of cycled dumping where the vacuum flow stops every so often?

The effect is that all production stops when this happens. All air flow stops and all grit stops. When it starts back up additional wear takes place inside the hose. Most importantly, you lose production that you are paying for. Vacuuming is a very expensive process when all costs are figured in; equipment, fuel, wearing parts, hose and labor. With only 6 minutes lost every hour, your vacuuming costs will be increased by 10% or more. Over the life of a project, this amounts to a significant amount of money.

How important is an inline cyclone before the filters?

We believe it is very important. Mistakes happen, hoppers get overfilled. If this happens, grit can come in direct contact with bags or cartridges and cause premature failure. If a cyclone exists before the filters, it will catch the grit and give you some time to correct the mistake. In normal operation, an inline cyclone will reduce the load on dust on the filters which extends their life. At Advantage SPS, we like to think of the cyclone as a "safety hopper" that protects and filters from direct contact with dust and grit particles.

What is the difference between blowers, vacuums and pumps?

They are all the same device if they use a rotary lobe design to move air. Because most units are used to "blow" air under positive pressure, they are called blowers. If the suction side is used they may be called vacuums blower or pumps. A pump can either create a postive or negative pressure.

What is the difference between Roots vacuums and Hibon vacuums?

Roots, now owned by Dresser Industries has been in business in the US for many years. They pioneered the positive displacement blowers in the the United States. Most blowers that are sold are used in stationary installations for positive air generation such as aeration systems in water treatment facilities. Mobile usage is a very small part of their business. The national service center is located in Connorsville, IN.

Roots:

Lobes: two (2), lower frequency, tougher to silence

Oil galleries: small, quarts

Running temperature: 50-100 degrees F hotter than Hibon

Full blocked air flow: overheating will occur

Hibon, based in France, is a major supplier of blowers in Europe and has also been in business for many years. They have aggressively pursued a variety of pump innovations as they have expanded their markets worldwide. Their move to a 3 lobe design with 27"hg ratings comes at a time when contractors are seeking ways to increase production and cut noise levels. Their North American service center is located in a new, state of the art facility in Montreal, Canada. US service centers are located in Pennsylvania and California. Mobile applications worldwide represent a bigger part of their business than it does for Roots.

Hibon:

Lobes: three (3), higher frequency, easier to silence

Oil galleries: large, gallons

Running temperature: 50-100 degrees F cooler than Roots

Full blocked air flow: internal cooling design prevents any overheating

Why does Advantage SPS use only Hibon vacuums?

The one feature that we feel is critical is the internal cooling design. This prevents any chance of overheating even if airflow is blocked 100% for an extended period of time. Prior to this Hibon design innovation, blower overheating was something that was only detectable with a discharge air sensor and safety interlock. If this failed, your operators could easily damage the blower without knowing it. Because the repair cost is easily into thousands of dollars, we have decided that ANYTHING that reduces the chance of failure is valuable to the end user.

A BETTER VACUUM:

27" Hg vacuum capability provides the power you need for steel grit recovery

Don't get fooled by the CFM rating. A 3500 CFM vacuum with only a 15"Hg rating won't do the work that a 27"Hg machine can. With steel grit, you need muscle(suction) AND CFM for long hose runs. Steel grit is 2.5 times heavier than sand. If you have ever used a vacuum, you know that with long hose runs, 15"Hg just isn't enough power to get the job done.

Largest hopper for longer filter life, direct dumping into 55 gallon drums

A large hopper will allow the incoming air to drop to a lower velocity as the dust laden air hits the filters. If the velocity is too high, the dust can actually wear holes in the filter units. The lower the velocity, the less filter abrasion. Hopper valve dumps directly into a 55 gallon drum for safe, hands-free disposal.

Unique design offers the most compact and flexible system

Only Advantage SPS offers a 2700 CFM system that will fit in an 8'x8'x8’ space on either a flatbed or twin I-beam trailer. Using a computer designed hopper, this unit packs more power in a smaller space than anything on the market today. The PDV-2700 is so flexible, it can be turned 4 different ways on the trailer of your choice. It’s the perfect size for mounting on the gooseneck of a single drop trailer.

Top removal of polyester cartridge filters, many types of filters available

Top removal means you can stand on a safe platform while you easily loosen and lift filters out. A wide variety of options are available from Advantage SPS.

Largest final filter protects the machined vacuum parts

All vacuum air gets a final filtering through a 300 square foot polyester cartridge before it passes through the machined rotors. This protects the high tolerance surfaces from dirt which can cause immediate damage to these critical parts.

Many possible options to enhance and improve performance

Everything from self-contained compressors to automated vacuum collection tanks are available to make this machine a grit recovery workhorse.