GENERAL QUESTIONS

Do I need a permit to install a dust collector?
Check with your local code enforcement agency, but in most cases you do need a permit. You can get fined for installing the dust collector without getting prior authorization.   Top

What is the efficiency of a dust collector?
A properly sized dust collector is 99.9% efficient by weight (of inlet loading) down to one micron. This means if the dust collector loading is 100 pounds per hour, the bags will capture 99.9 pounds of the dust that is over one micron. This is a minimum efficiency figure. Pleated elements and special fabrics can improve efficiency.   Top

SILO FILTER VENT COLLECTORS

Why do I need a dust collector on top of my silo?
Approximately 50 pounds (or more) of dust are exhausted into the atmosphere. A properly sized dust collector will capture this dust and return it to the silo.   Top

How do I size the dust collector for my silo pneumatic filling operation?
When designing a dust collector for a silo, the following information is required: fill line size; quantity of lines filling at one time; air flow and pressure; loading time and material handled. Most applications use a single 4" or 5" diameter fill line running at 350 cfm @ 12-15 PSI for approximately 45 minutes. The material handled is either cement, flyash, or sand. A mechanical shaker dust collector with 250 sq.ft. of cloth area will be adequate for these applications.   Top

When do I shake the bags on my mechanical shaker silo filter vent?
You only turn the shaker motor on when there is no air flowing through the bags. Once the fill process has stopped, then you shake the bags for one minute.   Top

I just overfilled my silo. Have I damaged the dust collector?
If you have just overfilled your silo, inspect the dust collector before you do anything else.  Open the door and see if the bags have been damaged or are full of product. Do not turn on the shaker motor or more damage may occur. If the bags have a lot of dust in them, but are not ballooning out, shake each bag down by hand until all the dust is removed. If you are lucky, the bags will be OK. If the bags have ballooned out, or if some of the bags have come off the tubesheet, replace all of them. Once the bags are stretched out, the weave in the bag loosens, allowing dust to pass through. The dust can get into the motor and other shaker parts, wearing them out also.   Top

How do I prevent overfilling my silo?
Griffin has a complete series of overfill control systems for all silo filling operations.   Top

Do I need a pressure safety valve?
Whenever a silo is being filled by a pneumatic offloading system (pressure blower), high pressure is forcing material into the silo. The pressure safety valve, or "pop-off valve" will allow the pressure to escape preventing any additional damage.   Top

What is the pressure safety valve set at?
The Griffin Environmental pressure safety valve is preset to relieve pressure at +14" water gauge or .5 PSI.   Top

Do I need a fan on my silo filter vent when I pneumatically load the silo?
For normal operation with a sealed silo, a fan is not necessary. If the silo is totally sealed, the air from the filling operation can only go in one direction through the dust collector. If the dust collector is too small, or not maintained properly, the pressure safety valve will pop open. But if the collector is sized properly, a fan is not needed. However, if the silo has holes in it, or is being fed by a screw conveyor, bucket elevator, or air slide then you will need a fan to keep negative pressure in the silo.   Top

I have a lot of moisture in my silo filling operation.  Is there a better bag available?
The standard bags in a mechanical shaker silo filter vent are 9-oz. woven polyester sateen. For high humidity or high moisture applications you should use a 5-oz. siliconized dacron bag. This material feels like a silk shirt.   Top

I have a two-compartment silo. Can I use one dust collector?
You can use a single fan-assisted dust collector. You also need to install intervent ductwork between the two compartments. This ductwork is twice the diameter of the fill pipe and designed like an inverted "V" with a minimum 45º angle to allow the dust to fall back into the silo. You can also use this approach if you have two silos. Remember, always put the collector at the highest point on the silo. If handling cement and flyash, put the collector on the flyash silo. If both silos are being filled at the same time, be sure to provide a collector to handle both silos.   Top

I am offloading from a rail car. What dust collector do I use?
Generally you would use a pulse jet, continuous cleaning dust collector. On occasion, when compressed air is not available, you may be able to use the 72-CS two-compartment mechanical shaker collector. This collector allows one compartment to shut down and shake while the other side is on-line.   Top

BATCHER VENT COLLECTORS

I have a weigh hopper but don't know what size batcher vent to use.
When picking the right dust collector for a weigh hopper, the rule of thumb is 50 cfm per cubic yard. For example, a 3-cubic yard weigh hopper would require a dust collector that would handle 150 cfm.   Top

How does the batcher vent work?
The batcher vent is ducted to the exhaust of the weigh hopper. The shaker motor of the batcher vent is wired to the weigh hopper discharge valve. When the silo dumps product into the weigh hopper, the dust enters the batcher vent. After the silo discharge valve closes, the material in the weigh hopper is weighed. When the weigh hopper discharge valve opens, the batcher vent shaker motor turns on. The discharge valve is open for approximately 15-30 seconds which is enough time to shake down the bags.   Top

Can I vent my weigh hopper to a central dust collector?
Most weigh hoppers have a 6" diameter exhaust vent. By positioning a flared circular hood over the vent, you can capture the dust that escapes from the weigh hopper. The hood cannot be attached to the weigh hopper and must be designed for 500 cfm.   Top

MECHANICAL SHAKER COLLECTORS

When would I use a mechanical shaker collector?
It is used when periodic shutdown is possible for cleaning the bags. During normal operation, when the magnehelic gauge reaches a 6" pressure drop, it is time to shut down the baghouse and shake the bags. A silo filling operation with a standard tank truck takes about 45 minutes to complete. At the end of this cycle the bags need to be cleaned.   Top

VECT-AIRE

What makes the Vect-Aire different from other cartridge collectors?
It is the only true down flow collector with vertically mounted cartridges. This means the dust cannot lay on the cartridges like it does with other horizontal and angled cartridge collectors.   Top

How do you change cartridges in a Vect-Aire?
The cartridges are removed from the side access door.   Top

GRIFFIN-AIRE

What applications is the Griffin-Aire designed for?
The Griffin-Aire is designed specifically for woodworking where the majority of the dust is chips and shavings. For sanding and other operations generating fine dust particles, another type of dust collector would have to be considered.   Top

Why is the Griffin-aire a positive pressure design?
The positive pressure design helps in many ways. It aids in the flow of the dust down the bags to help keep them clean. It prevents water from being drawn into the housing, unlike negative systems. And it reduces the amount of ductwork needed.   Top

PULSE JET COLLECTORS

When would I use a pulse jet collector?
The pulse jet collector was designed for continuous-duty applications where shutdown for cleaning is impractical. The pulse jet collector uses compressed air to clean the bags and the bags can be cleaned while on line.   Top

What are the requirements for using a pulse jet collector?
To be able to use a pulse jet collector, you will need 110/1/60 for the controls, 230-460/3/60 for a fan (if required) and 90 PSI of compressed air (at the dust collector) to clean the bags. The airflow requirement depends on the type of pulse jet collector you get.   Top

What size compressed air line do I need?
The recommended compressed air line size, from the compressor to the dust collector, is ¾" diameter for the first 75' of pipe with ¼" diameter increases for each additional 50' increment.   Top

When would I use a high entry inlet?
Although an added expense, a properly sized high entry inlet serves many purposes. It is necessary when filtering light density dust. Hopper inlets keep the dust airborne so it re-entrains on the bags. The high entry inlet allows the dust to flow around the bags and settle in the hopper. Dust under 30 pounds per cubic foot and low micron size dust (<10 micron) falls into this category. If you have a dust loading of over 5 grains per cubic foot, you may require a high entry inlet. In cases where the upward velocity (velocity between the bags) exceeds 300 feet per minute, you need a high entry inlet.   Top

NOVA

When would I use the NOVA high temperature dust collector?
The NOVA is used when the design temperature exceeds 550º F. The maximum operating temperature of the NOVA is 1650º F.   Top

What kind of bags are in a NOVA collector?
The NOVA does not use bags. It uses ceramic elements that are designed for high temperature dust collector applications.   Top

CLEAN-A-BATCH

What models are available?
Two standard models are available. The U-48 and U-80. Both collectors use 8" diameter X 107" long bags.   Top

Why 8" diameter bags?
We use 8" diameter bags for several reasons. The bigger 8" diameter allows for a lower velocity at the tubesheet which reduces the abrasion on the bag. It also allows the dust to fall faster; prevents bridging during the shake-down cycle; and reduces the quantity of bags to change.   Top

How often do I shake the bags?
For a standard concrete batch plant operation, shutdown for cleaning is once or twice per 8-hour day. Normally at lunch time and always at the end of the day. An optional pressure differential switch can alert the operator that the collector has reached a 6" pressure drop and needs to be shut down and cleaned.   Top

PLEATED BAG COLLECTORS

When would I use a pleated bag collector?
Pleated bag collectors are becoming more popular. An important advantage is that it can be used in areas that are dimensionally too restrictive for a conventional collector.   Top

What is the maximum temperature for pleated bags?
The maximum temperature for the spun bond polyester pleated bag is 200º F and the maximum temperature for the spun bond Nomex pleated bag is 365º F.   Top