Duct Construction Quiz Flashcards
Duct reinforcements can be attached to the duct wall with screws, rivets or welds at a maximum of?
2” from the ends and spaced a maximum of 12”
Ducts themselves are usually strong enough to permit maximum hanger spacing of?
8’-10’ but ultimately refer to SMACNA standards (TQ)
The most popular round transverse joints are?
Slip and lap joints
All saddle fitting should be sealed at all pressures. True or False
True
A minimum of three screws must be used up to what size of round duct?
14”
What is the maximum spacing between screws that should be used on round duct
15”
What is the shelf life of water based duct sealants?
6 months
Tapes tend to lose adhesion as they age and therefore their service life is questionable.
True or false
True
What are the 7 static pressures and their pressure classes
1/2”wc low
1”wc low
2”wc low
3”wc medium
4”wc medium
6”wc medium
10”wc high
If there is no pressure class specified by the designer what is the assumed pressure?
1”wc
All variable volume duct upstream of VAV boxes has a _______ basis of compliance when the designer does not give a pressure class
2”wc
What are the three pressure classes?
High class A
Medium class B
Low class C
Water column (WC) and water gauge (WG) are the same thing. True or false
True
What needs to happen to the size of duct when they are acoustically lined?
They need to be upsized to accommodate the insulation
The ABC states that all ductwork and fittings should be built and installed as per what standards?
SMACNA
ASHRAE
Aluminum duct should be approximately how much thicker or thinner than galvanized iron?
44% thicker
Residential duct systems are generally low-pressure consisting of a ____ water column (wc) with lower velocities and less than ____ feet per minute (fpm)
1/2” WC
1000 FPM
Fibrous ducts can be used in systems that operate up to ___wc and ___ feet per minute (fpm).
2” wc
2400 fpm
Industrial duct systems are designed and constructed according to what is conveyed in the airstream and the operating temperatures and pressures. The design of industrial duct systems begins with an accurate appraisal of the characteristics of material to be conveyed. These characteristics are
abrasiveness, concentration and corrosiveness.
According to SMACNA, duct construction standards define relationships between static pressure, wall thickness, width and durability. This ensures that ducts have adequate
strength and acceptable deflection limits.
When duct is located in conditioned space leakage is less or more of a factor than duct located outside conditioned areas?
Less
The impact of duct leakage depends on what 4 things?
-Duct location
-length
-design
-pressure
What type of round girth joint is typically used on round pipe over 60” round?
Companion flange
