Piping - Canadian Woodworking Magazine

Dust Collection: Piping, Fitting & Flex Hoses

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Piping



Last issue we looked at fans, the heart of the dust collection system. This issue, let’s look at piping, fittings and flex hoses.
 
In the following photos, I will point out the different types of piping available and help you to identify and select hoses and fittings to build a system which will work safely and efficiently for you.
 
Piping is made from either plastic or steel. There are different types of piping available in each:

Plastic
• ABS plumbing pipe (black- for water and vents)
• PVC sewer pipe (generally white and thinner than ABS)

Steel
• spiral lock pipe
• snap lock pipe (one longitudinal seam)
 

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In order to determine which type of piping is best for dust collection, the first thing to realize is that the material that we are handling is, in fact, a fluid. Do not confuse the term “fluid” with “liquid”. The two are not the same and they act differently when they travel through piping. We are dealing with a fluid, which is primarily air with dust or shaving particles suspended in it. When conveying a fluid, the object is to keep all the directional changes as gentle and gradual as possible, in order to keep the particles suspended. With this in mind, let’s compare the elbows in the photo to the left.

The correct fitting for dust collection is on the left: a 3” ABS long radius elbow. It is better than the short radius PVC elbow beside it. Do not be deceived by the smooth exterior of the flex hose 90 – it is smooth on the outside but very restrictive and rough on the inside. The rough interior would interfere with the suspension of the particles in the air.

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Heating and ventilating piping.
 
On the left is an adjustable HVAC 90-degree elbow. Next are two 45-degree elbows, joined by a short piece of straight pipe. To the right is a DSW long radius die stamped welded elbow. Using the HVAC 90-degree elbow is like adding 10 feet of straight pipe to your system and it also hinders the flow of shavings. The DSW long radius elbow is totally smooth inside and is like adding 6 feet of pipe. The less expensive alternative would be the set-up in the center with the two 45-degree elbows.

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Galvanized snap-lock smoke pipe and spiral seam pipe - Note that both pipes are smooth inside.

Flex pipe comes in various materials, each of which has been designed to convey specific substances. For dust collection, we are looking for three things: a smooth interior surface, flexibility and strength, so that it won’t collapse under vacuum.

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On the left we see pipe which is not acceptable because of how rough it is inside. This plastic big “O” style hose is fine for drainage but not dust removal. The next hose to the right is a length of wire-reinforced rubberized cloth hose. It is not totally smooth inside either but, as you can see, it is better. Next in line is a plastic hose with plastic reinforcing. It is the most available plastic hose and it comes in 3, 4, 5 and 6 inches. It can also be found with wire reinforcement. This hose is basically smooth inside. The last piece of hose shown is aluminum spiral. A spiral hose, which is not smooth on the inside, acts as a long cyclone; the air will spin, throwing the dust and shavings to the outside, eventually plugging the hose.
 
To summarize, when it comes to piping in dust collection, select materials which will create gradual and gentle directional changes and which have smooth inner surfaces. The right materials will keep particles suspended in the air to give you a safe and efficient dust collection system.
 



CHESTER VAN NESS is a Dust Removal Consultant in Scotland, Ontario
Chester Van Ness

(519) 484-2284