Sizing Information - Duct Incorporated

Sizing a Pipe System

DUCT INCORPORATED offers assistance for those who need help designing a piping system. We can help determine the correct pipe size and configuration that will supply the flow you need. Please contact us at 1 877-BUY-DUCT for assistance.

USING THE CFM/FPM CHART:
The following chart allows you to pick the correct pipe for the required CFM.

To prevent waste material from dropping out of the air stream, each type of material needs to be conveyed at different velocities. (See table on page 28.) For example, some waste materials flow well at 4500 feet per minute (FPM). Reviewing the chart, a 4” pipe will convey 395 CFM at 4500 FPM. This means that a 4” pick-up on a machine will use 395 CFM from the filtering system; or, if you know that a machine will require approximately 400 CFM to remove the waste, you should use a 4” pipe for that purpose.

Air Volume in Ducts in Cubic Feet per Minute (CFM)
	2000	2500	3000	3500	4000	4500	5000	5500	6000	6500	7000
3	100	125	150	170	195	220	245	270	295	320	345
4	175	220	260	305	350	395	440	485	525	570	615
5	275	340	410	475	545	615	680	750	820	885	955
6	395	490	590	685	785	885	980	1080	1180	1275	1375
7	535	670	800	935	1070	1205	1335	1470	1605	1735	1870
8	700	875	1050	1220	1395	1570	1745	1920	2095	2270	2445
9	885	1105	1325	1545	1765	1990	2210	2430	2650	2870	3090
10	1090	1365	1635	1910	2180	2455	2725	3000	3270	3545	3820
12	1570	1965	2355	2750	3140	3535	3925	4320	4710	5105	5500
14	2140	2675	3205	3740	4275	4810	5345	5880	6415	6950	7485
16	2790	3490	4190	4885	5585	6285	6980	7680	8380	9075	9775
18	3535	4420	5300	6185	7070	7950	8835	9720	10600	11485	12370
20	4635	5455	6545	7635	8725	9815	10910	12000	13090	14180	15270
22	5280	6600	7920	9240	10560	11880	13200	14520	15840	17160	18480
24	6285	7855	9425	10995	12656	14135	15710	17280	18850	20420	21995
26	7370	9210	11055	12900	14740	16580	18420	20270	22110	23950	25800
28	8550	10685	12820	14960	17100	19230	21310	23500	25650	27780	29920
30	9800	12260	14700	17170	19625	22080	24530	26990	29440	31890	34350
32	11160	13950	16750	19541	22330	25120	279120	30700	33490	36380	39070

Sizing Branches

Example:
When working from your machines back toward the filter, you have a 5” drop that rises and joins with a 6” drop (see diagram below). How do you figure what size branch you’ll need?

The 5” pipe carries 615 CFM at 4500 FPM (see chart above). The 6” pipe needs 885 CFM at the same velocity of 4500 FPM. Added together, there is a total of (615 + 885) 1500 CFM coming together.

Referring back to the chart under the 4500 CFM column, 1500 CFM is not listed, but is close to the 1570 CFM listed for an 8” pipe. This states that the 5” joined with the 6” requires an 8” pipe to carry the combined material at the correct velocity. The branch will need to be 8” on the downstream end reducing down to a 5” with a 6” branching off of it. This would be listed as an 8-5-6 branch.

Ducting Branch Sizing 1

Example: When working from your machines back toward the filter, you have a 5” drop that rises and joins with a 6” drop (see diagram below). How do you figure what size branch you’ll need?

he 5” pipe carries 615 CFM at 4500 FPM (see chart above). The 6” pipe needs 885 CFM at the same velocity of 4500 FPM. Added together, there is a total of (615 + 885) 1500 CFM coming together.

Modular Clamp Together Ducting for All Applications

Design Assistance - Sizing Suggestions

Sizing a Pipe System

Sizing Branches