• How often does it run
• Does it run instead of another dust source so that the ventilation can divert back and forth - this will conserve energy and reduce the capital cost of the system.
• How much dust will it produce and how much air will it require to control and convey it.
• Is it combustible dust? If yes, the minimum duct velocity should be at 4000 FPM at a minimum. If it is a combustible metal then the velocity must be 4500 FPM or greater.
• Do not mix metals or noncompatible materials.

2. Locate each dust source and identify the size of the branch and the amount of vacuum required to establish the velocity through that branch.
3. Join the ducts with lateral T transitions on a 45 degree or less angle. The duct area of the combined branches should equal the area of the 2 branches. (Note (2) 4 " branches do not equal an 8" duct). 4" diameter = 12.56 square inches or .09 square feet. 6" diameter is 28.26 square inches or .20 square feet.
4. Continue this process until the duct is sized for conveying to the dust collector and add the sum of the CFM requirements. Be sure this translates properly to the trunk line of the duct (12" diameter @ 4000 FPM = 3,140 CFM.
5. Now you can size the dust collector and the fan.
6. The dust collector needs to have a conservative amount of surface area for good filter life and performance. A 1:1 ratio for a cartridge and a 3:1 with a bag at first glance may be too conservative but it can have very good benefits for operational costs, performance and energy management. This system will use 1 BHP for every 1.25" of fan static. More filter area will reduce the overall load on the fan and the equipment will operate at lower pressure drops reducing cleaning energy and wear and tear on the filters. The capital cost for the equipment will be higher but it will be able to handle additional capacity if expansion is required in the future.
7. To properly size the fan it needs to develop the vacuum necessary to provide the capture and conveying velocities. It must also be able to overcome the filters resistance to flow and the exhaust back pressures that exist. This includes after filters, silencers and rain shields. It is generally acceptable to design the fan to overcome twice what these add up to to allow for dust to collect on the filters. 50% of total fan energy can be consumed by dirty filters and still have the system perform to it's design rated flow. Using a VFD to control flow will help to prevent damage to the filters on start up. A dust collector with an under sized fan will perform well on start up but it will not perform well with dirty filters. A fan that has been designed to overcome dirty filters will move too much air on start up unless a VFD or the use of dampers is employed.  The use of the VFD will likely attract utility rebate dollars, and it will have a dramatic impact on the utility cost for running the system as well as provide peak performance for the system for a longer period of time.

We will be happy to design the system for you just contact us.

Dampers -to be interlocked or operaor controlled -isolation dampers -

Custom designed down draft & back draft hoods

dustcollectionconnection.com



Systems designed built and assembled on site by RPS

This system pictured below is on a wood dust application. It ranges in flow rates as designed by RPS from 4000 FPM to 5500 FPM with the entire shop in operation. Branch lines on seldom or irregularly used equipment are interlocked with the trunk line. When the equipment starts they open, the fan speeds up to provide flow for the additional capacity.  The 2 stage filter system is a cyclone separator with a baghouse on top. The baghouse is sized at a 10:1 because most of the particulate is filtered before being introduced to the filter. The filter is functioning at a plus 99% efficiency rate and the air is being returned to the building.

It has been in operation since 2008 and the filters continue to run at 1" delta P 16 months after commissioning the system. The fan inlet vacuum is 15" at low load with an external vacuum of 10.5". On this system, every 1" of differential pressure will equal 4.5 BHP or approximately 3000 watts of energy. Maintaining a low delta P is important to the overall energy savings that this system provides. Additionally, this system now returns the vast quantities of air that were exhausted prior to this unit being installed. The system is protected with a spark detection and spark extinguishing device as well as a high speed abort damper and explosion vent panels as designated in NFPA 664. This system replaced (4) dust collectors, (2) large and very loud inside dust collectors and (2) outdoor cyclones. The benefits included recovered floor space, cleaner and quieter shop conditions, lower energy expense for electric and heat, and lower disposal costs.

The hopper is connected to a closed loop conveying system that carries wood from a shredder and the dust collector and transports it to a trailer. The trailer is emptied approximately once every 4-6 weeks. The facility is now saving money on disposal costs due to the use of the shredder which reduces the bulk load size of the waste. Scarp wood was hauled away on a bi-weekly basis prior to this system being employed. The closed loop has a slip stream back to the baghouse to help maintain a balanced flow through the loop. Without this, the trailer would go positive and dust would blow out any cracks in the trailer. The clean air return line has the sagging hose, the slip stream can be seen ducted backwards into the return air duct. This is done to prevent drawing too much air out of the line and making the trailer go very negative. It also has a slide gate to provide additional flow control.