How To...

How to Determine When to Use 2” vs. 4” Turning Vane

While SMACNA does address the maximum unsupported height of a vane, there are no rules spelled out in SMACNA as to when to switch from a 2” to a 4” vane when it comes to duct width.  A good rule of thumb would be that if there would be less than 4 turning vanes across the diagonal of the mitered elbow, then go to the smaller vane.  Further to that, if the elbow is so small that less than 4 two inch vanes would fit across the diagonal, the contractor should consider making a radius elbow for that application.  If there are less than 4 vanes in the elbow, the inner and outer voids at the heel and throat could cause enough turbulence to affect the overall performance of the elbow.  At four vanes and up, this effect is minimal versus the rest of the elbow cross section.

How to Calculate Amount Of Turning Vane Needed For Prorail

  1.  Determine the length of rail needed (distance across throat of elbow in inches) and divide the length by the distance between PROrail tabs - 2-1/8" if using 2" PROrail or 3-1/4" if using 4" PROrail. This will give you the number of pieces of turning vane needed.

  2. Determine the height of the turning vane in the elbow in inches.  Multiply the number of pieces needed (as obtained in step 1) by the height of the vanes.  This will give you the total inches of vane needed.

  3.  Divide the total number of inches needed (as obtained in step 2) by 120 (10’ vane is 120” in length).  This will tell you how many 10’ total pieces of vane to order.


Length of rail = 36”.  Divide 36” by 2.125” (2-1/8”). Answer = 16.94” or 17 pieces.

Height of vane = 18”. Multiply 17” x 18”. Answer = 306”. 

Divide 306” by 120” = 2.55 lengths of vane.  Round up final answer (unless it is a whole number).  2.55 is rounded up to 3 pieces of 10’ turning vane, or 30’. 

How to Use a Quick Sleeve in Place of an Access Door When Size is an Issue

Ductmate’s Quick Sleeve round duct connector can be used to access the inside of round pipe for cleaning, viewing, etc., when a standard access door will not work. Following are instructions when installing Quick Sleeves to access the inside of pipe.
  1. Use two Quick Sleeves.
  2. Cut about a one foot piece out of the pipe that you will need to access.
  3. Slide a Quick Sleeve on each open end of the installed pipe (not the piece you cut out).
  4. To complete the assembly, put the one-foot piece of pipe back in the opening it was cut out of and slide each Quick Sleeve over the cut openings of the pipe and tighten the bolt on the Quick Sleeve. This will give you an air-tight seal.
  5. When you want to access the pipe, loosen the bolt on each Quick Sleeve and slide the Quick Sleeves back over the pipe, away from the one-foot piece, remove the one-foot piece of pipe and this will give you plenty of access for cleaning, viewing, etc.
  6. To re-install the one-foot piece of pipe, follow the instructions in #4 above.


When installing our Quick Sleeve connector, it is recommended to have a support within 2-feet of each connection, especially as the duct gets larger.

The Quick Sleeve was designed for disassembly and reassembly without compromising the seal.

When the Quick Sleeve is tightened the rounded edge on the metal sleeve contacts the duct wall to provide rigidity.

The standard gasket used in the Quick Sleeve is polyethylene. If your application involves a higher temperature or chemicals, etc. we offer gaskets for these as well.

How to Determine Radius for Round Duct Access Doors

To determine radius for round duct doors, measure the duct opening if possible.  If duct diameter is not readily available, divide the duct circumference by 3.1416.

How To Calculate Ductmate Flange & Components Needed

Ductmate Frame List formula gives you the total lineal footage needed in a given duct line.

Formula: (Width of Duct in Inches + Height of duct in inches)/ 3 = total lineal feet of flange needed per joint

If you multiply this number by the number of joints of the same size needed, it will give you the total lineal feet for that given duct line.  Keep in mind that the number of joints needed is one more than the number of duct sections that you are fabricating. 


Duct size:                   40” x 30”                      

Feet per joint:             40 + 30 = 70 / 3 = 23.33 lineal feet (lf.) per connection

Number of Sections:     5 sections of duct

Number of Joints:         6

Total Flange Needed:    23.33 lf/joint x 6 joints = 139.98 lf.

You would order 140 lf. of Ductmate flange.

How to Calculate Component Quantities Needed

Corners: approximately (1) corner for every (3) lf. of flange

Cleat: approximately (1) 6” piece of cleat for every (4) lf. of flange

Gasket: approximately (1) lf. of gasket per every (2) lf. of flange

Nuts & Bolts: If using a bolted corner, you will need half the amount of nuts & bolts as corners ordered.

Example: a box of 250 corners would require 125 nuts & bolts. 

If using the no-bolt corner, the corner clips are in the box with the corners.  You don’t need to order the corner clips separately.

How to Select the Correct Spray Equipment and Spray Tip for PROseal Spray Duct Sealant

PROseal Spray can be applied using most commercial-grade paint sprayers. Graco’s 390 Airless Electric Sprayer is an entry level model perfectly suited for PROseal Spray. Whichever spray system you choose, make sure the pump is capable of supporting a minimum .021” tip size. Always follow spray equipment manufacturer’s instructions when using spray equipment.

For best results, use a Spray Tip with 2”- 4” fan pattern and minimum .021”-diameter orifice. Fan patterns are indicated by doubling the first digit of the Spray Tip model number. For instance, a 121 tip provides a 2” pattern and a 221 tip provides a 4” pattern. The last two digits of the model number indicate orifice diameter in thousands of an inch, i.e., .021”.

How to Attach Inner Rings for Double Wall Duct (using Spiralmate)

Click on Inner Ring Installation Instructions (PDF) to find out more.

How to Install an ULtimate Flat Access Door in a Duct Wrap System

Click on UL Door Wrap Install Instructions (PDF) and UL Door Wrap Written (PDF) to find out more.

How to Install Air Brace

Click on Air Brace installation (PDF) to find out more.


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