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Third Year > Duct Construction > Flashcards

Duct Construction Flashcards

1
Q

Which one of these three things do you not need for pressure testing ?

Static
Leakage class
Leakage coiffecant
Velocity

A

Velocity does not matter for pressure testing

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2
Q

What is the best leakage class for pressure testing ?

A

Class a

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3
Q

What is the easiest joint to weld in light gauge sheetmetal ?

A

Standing seam
Flange

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4
Q

What to do to veins when under a high pressure ?

A

Weld or solder

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5
Q

What’s is the included angle of turning vanes on a 90 degree elbow ?

A

90 degrees

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6
Q

What’s the smacna rules for screws when installing turning veins in duct ?

A

12” on center

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7
Q

What does a two peice streamline used for ?

A

Goes around an obstruction

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8
Q

Where do we find specs for duct pressure classifications ?

A

Contract drawings

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9
Q

When no pressure classes are specified by the designer what pressure do we use ?

A

1” wc

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10
Q

For variable volume duct upstream of vav boxes what pressure do we use when designer does not give us a specific one ?

A

2” wc

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11
Q

What are the 7 pressure ratings ?

A

10” wc
6”wc
4”wc
3”wc
2”wc
1”wc
1/2”wc

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12
Q

What are the pressure ratings for medium pressure ?

A

6”wc
4”wc
3”wc

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13
Q

What are the pressure ratings for low pressure ?

A

2” wc
1”wc
1/2” wc

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14
Q

2” acc 30x20 duct sized labeled on prong what size duct should we build ?

A

34x24

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15
Q

What are the seal classes ?

A

A b and c a is the best c is the worst

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16
Q

What percent is aluminum thinker than galvanized iron ?

A

44%

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17
Q

How many inches of water colum are residents duct systems usually ?

A

1/2” wc with low velocities less than 1000 fpm

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18
Q

What must be done before you can begin to design the ductwork ?

A

Load calculations and overall type of distribution system

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19
Q

What organization gives u answers on how to construct duct work ?

A

Smacna

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20
Q

What are some types of transverse joints

A

Slip and drive
Tdc
Big end small end pipe

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21
Q

What’s another name for transverse joints ?

A

Gerth joints

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22
Q

What’s the gerth joint for spiral pipe ?

A

Beaded sleeve joint

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23
Q

What’s the shelf life of sealants ?

A

Less than 6 months

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24
Q

What is the minimum amount of screws that should be placed along a diameter of 14” or less and must be used uniform intervals of atkeast 15” along the circumference?

A

Minimum 3 screws

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25
What weld can be used for all pressure classes ?
Butt welds
26
What is the strongest weld on round ?
Butt weld
27
What joint is used in round ducts over 60”in diameter to help retain circular shape ?
Flange joint
28
What’s the maximum hanger spacing ?
8ft or 10ft intervals
29
What may you require to do for hangers on wider ducts ?
Trapeze bar
30
What may installing intermediate hangers prevent ?
Any portion of the duct from sagging
31
What is the range of the ductwork static pressure classifications ?
1/2” to 10” wc
32
The letters STD indicate standard (non-variable volume) air duct construction requirements? True or false
True
33
The letters STV indicate the standard construction classification for variable volume ducts ? True or false
True
34
Beaded sleeves that join transverse round ducts must be ?
At least the same gauge as duct and minimum 4” long
35
By how many inches should round duct transverse joints that are beaded and crimped be slip into one another ?
1”
36
What is most commonly used for round duct reinforcements ?
Angle rings
37
SMACNA refers to the part of a fitting collar that slips into the large end of spiral pipe. What is this part called ?
Spigot
38
All duct constructed for 1” wc and 1/2” wc pressure classes must meet which seal class ?
Class c
39
Does aluminum duct meet the requirements for equivalent strength and rigidity as galvanized duct ?
No aluminum is two gauges heavier
40
What can not be used in commercial when wc is 2” and 2400 feet per minute ?
Fibrous duct
41
For industrial duct systems pressure can range from above or below how many “ of wc ?
30” wc
42
For industrial what are the three characteristics of materials to be conveyed?
Abrasiveness Concentration Corrosives
43
Duct Designers must apply construction standards that are appropriate to specific situations the types of material being used and duct system features. What are the features ?
Joint seams Reinforcements Duct support
44
When selecting a transverse joint it must be coincidentally with the following as outlined by Smacna . What 4 things to consider ?
Static pressure class Applicable sealing requirements Materials involved Duct support intervals
45
Liquid sealants that have high percents of solvents (30% to 60%) may what ?
Shrink when drying
46
What sealant has excellent adhesion and elasticity and even some have fabric embedded in them ?
Mastics
47
What sealant is usually used for fillets grooves and flanges ?
Mastics
48
What is made from a friable material such as elastomer butyl that are made from open or closed cell rubber and are used for planted joints?
Gaskets
49
Why is tape a questionable sealant
Tends to loose adhesion as it ages
50
What should be done to all saddles ?
Seal them
51
How do we attach angle rings to the duct wall ?
Screws Rivets Tack welds
52
Rectangular longitudinal seams will vary according to what 3 things ?
Material thickness Duct size Local trade prefences
53
Rectangular duct external reinforcements must be a maximum distances of _” from the ends and spaced at a maximum of _”
2” 12”
54
What are the 4 types of rectangular duct external reinforcements ?
Angle Hat section Zee channel U/ framing channel
55
The duct hanging system is normally made up of three components what are they ?
The upper attachment The hanger itself Lower attachment
56
Selecting the proper hanger system requires that you?
Transfer the load of ductwork’s weight to hanger system and secure it to building structure useing proper fasteners
57
Most popular round transverse joint seam ?
Slip Or lap type
58
Maid advantage of high velocity duct systems ?
Thier smaller
59
Is duct leakage more of a factor through an unconditioned space or a conditioned space ?
Unconditioned
60
Unless otherwise stated a mitre elbow is based on Smacna standards and what else should be taken into consideration ?
Velocity
61
Unless otherwise stated a mitre elbow is based on Smacna standards and what else should be taken into consideration ?
Velocity
62
Compaion flange also know as van stone flange is used for round when ?
When round is over 60”

Third Year (10 decks)

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