Dust Collectors on Concrete Batch Plants Come in Three Basic Types:

1. Shaker Type - Low Capacity Dust Collectors that are normally installed on cement and fly ash silos. This unit draws in dust laden air by an electric blower or by displaced air passing through into a single filter bag compartment. To clean, the bags are shaken by an electric motor driven shaker assembly
   
2. Reverse Air - Medium Capacity units. This unit usually consists of two or three filter compartments. To clean, the air reverses in one compartment while the other compartment or compartments still cleans dust laden air.
   
3. Jet Pulse - This system allows for continuous cleaning of all filter elements. Dust collected in filter cartridges is removed by surges of air sequences a few seconds apart.
   

Any type of dust collection equipment requires proper installation and maintenance. If the dust collector is installed, turned on, and forgotten about until it stops working, it may be too late for repairs. At that point the dust collector may have to be rebuilt or even scrapped.

Several tools can help you troubleshoot a dust collector:

1. Opacity Monitor
2. Pressure Drop Monitor
3. Flow Monitor

The most valuable tools, however, are your eyes, ears, nose, and brain. Use them to establish a good baseline of normal operating data so you can quickly identify the causes of problems that occur.

Typical Routine Maintenance:

Daily Maintenance:

1. Check pressure drop
2. Monitor air flow rate
3. Observe outlet, visually or with a continuous monitor
4. Monitor cleaning cycle
5. Check compressed air on jet pulse dust collector

Weekly Maintenance:

1. Spot check bag connection condition
2. Check all moving parts on shaker dust collector
3. Check fan for material build up
4. Inspect duct collector body for rust and holes

Quarterly Maintenance:

1. Thoroughly inspect the bags
2. Check ducting for dust build up
3. Observe dampen valves for proper seating
4. Check gaskets on all doors

Yearly Maintenance:

1. Check all welds and bolts
2. Check hopper for wear
3. Replace high wear parts on cleaning system
   

Basically, filter bags fail one of two ways: By physically tearing and ripping, or by blinding, in which case the filter bags become plugged and severely limit the flow of the gas stream. 

The most common cause of bag failure is overfilling the cement or fly ash silos, and excessive transport truck blower pressure. The following tips should be followed:

1. Inspect high level bin level indicators and visual / audible signals for proper operation to avoid silo overfill.
2. Install Anti-Overfill system on silo fill lines which works with high level bin indicators to positively eliminate accidental overfilling of silos by transport operator.
3. Shaker mechanisms should be run for two to three minutes after filling silo. Pulse Jet Dust Collectors should be operated according to manufactures instructions.
4. Transport truck blower pressure should not exceed 10 P.S.I. to avoid silo and dust collector damage. 
   

Possible causes of short bag life included:

1. Failure at Filter Bag Top
1. Excessive bag tension
2. Poor top cuff design
3. Chemical attack
   
   
2. Failure at Filter Bag Middle
1. Bag to bag abrasion
2. Bag to structure abrasion
   
   
3. Failure at Filter Bag Bottom
1. Poor bag to thimble connection
2. Poor thimble design
3. Inlet dust abrasion
4. Lack of bag tension
5. Lack of bottom cuff
6. High air to cloth ratio
   
   
4. Failure at Anti-Collapse Rings
1. Poor ring cover fit
2. Poor ring cover stitching
3. Bag to bag abrasion
4. Excessive reverse air flow
5. Rapid reinflation after bag cleaning or reverse air system
6. Insufficient null time before reversing flow
   
   
5. Seam Failure
1. Excessive blower pressure
2. Excessive air to cloth ratio
   

Inspecting and changing bags takes a long time and is the highest maintenance cost in a dust collector. Bag failures occur at varying times depending on the operation of the collector. The longer the time between bag change-outs the lower the maintenance cost to the owner.

It is important to keep track of the bag failure rate. This can be helpful in correcting any condition that would cause premature bag failure. In addition, it is helpful in scheduling a complete bag change-out at a convenient time.

SAFETY BULLETIN

This notice is issued to advise you that some previously accepted shop practices may not be keeping up with changing Federal and State Safety and Health Standards. Your current shop practices may not emphasize the need for proper precautions to insure safe operation and use of machines, tools, automatic loaders and allied equipment and/or warn against the use of certain solvents or other cleaning substances that are now considered unsafe or prohibited by law. Since many shop practices may not reflect current safety practice and procedures, particularly with regard to the safe operation of equipment, it is important that you review your practices to ensure compliance with Federal and State Safety and Health Standards.

Always be sure proper guarding is in place for all pinch, catch, shear, crush and nip points.

Always be sure that all personnel are clear of the equipment before starting it.

Always be sure the equipment is properly grounded.

Always turn the main electrical panel off and lock it out in accordance with published lockout/tagout procedures prior to making adjustments, repairs, and maintenance.

Always wear appropriate protective equipment such as safety glasses, safety shoes, hearing protection and hard hats.

Always keep chemical and flammable material away from electrical or operating equipment.

Always maintain a safe work area that is free from slipping and tripping hazards.

Always be sure appropriate safety devices are used when providing maintenance and repairs to all equipment.

Never exceed the rated capacity of a machine or tool.

Never modify machinery in any way without prior written approval of the Besser Engineering Department.

Never operate equipment unless proper maintenance has been regularly performed.

Never operate any equipment if unusual or excessive noise or vibration occurs.

Never operate any equipment while any part of the body is in the proximity of potentially hazardous areas.

Never use any toxic flammable substance as a solvent cleaner.

Never allow the operation or repair of equipment by untrained personnel.

Never climb or stand on equipment when it is in operation.