Rectangular Duct And Fittings Flashcards
This is found on the front of a circumference ruler?
Inches and stretch outs on the bottom
What can be used to find a specific angle?
Protractor
What is the purpose of cross breaks?
To reinforce metal usually 12 inch and over
What is the difference between a net and gross pattern
Net means no allowances
Gross is with allowance
When using a box and pan brake what steps must be taken before using?
Adjust fingers and clamping pressure
Why do we cross brake?
For stiffness
At what measurement should we start cross breaking?
Over 12 inch
A curved cheek should have what for a Pittsburgh allowance on its curved portion?
3/16
What allowance is used on a straight portion of duct for a Pittsburgh joint?
1/4
What are the heel and throat called
That join the cheeks together to make an elbow?
Runners or wrappers
What should you do to a wrapper or runner before putting on the pittsburgh?
Pre roll it
What is the allowance per end for slip and drive of duct?
1/2
What should be done to the transition sloping end on the 1 inch ends?
Kinks or correction bends
Where is the TDC put on a piece of duct?
Raw edge
Where is the drive put on a piece of duct?
Short side
What is one reason for using a proprietary connection?
Adequate seal for high pressure system
To adjust blanks and patterns for growth you remove how much?
1/16 per joint
What is the purpose of a canvas connection?
To provide isolation of sound
Can fire dampers be modified?
No
How much smaller is a first damper made to fit in a sleeve?
1/4
Hoe much of the fire damper sleeve should stick through the wall minimum and maximum?
Min 3 inch
Max 6 inch
When connecting a fire damper sleeve to the duct work what must it have?
A break away joint
What is the minimum gauge of a fire damper sleeve?
22 ga
