Transitional Fittings And Pipe Tees Flashcards
How are pipe tees identified
By the angle and diameter of the stub and the diameter of the body
How is the type of seam determined
By the pressure class and material thickness of the ducting system
What is the formula to calculate the stretch out of the cylinder
3.14xdiameter of the cylinder
Why is it necessary to number the plan views and patterns properly
Miter line may turn out not correct
What methods can be used to divide the stretch out on the round stub
Dividers
Slope line method
Mathematically
Why is it important to lay out all patterns as inside patterns
Inside patterns will place all the scribe lines inside the fitting
Why is notching necessary
For ease of assembly and equiptment may be damaged do to layers of metal not being removed
Why is it a good idea to start spot welding at the center of the lap seam
Eliminate buldging or buckling between spot welds
What should you do to the metal of the body before folding the hooks for a grooved seam
Ends of material should be rolled slightly to reduce flat spots at the seam
When cutting the hole in the body you should cut directly on the line
T or F
False
Why is it useful to know the fabrication technique when measuring a fitting to be installed
To know if a given fitting is practical or not
When fabricating a transitional fitting which type of lock is commonly used
Pittsburg is the most common
What type of fitting is needed if a duct changes size in both dimensions and sometimes also changes direction
Transition/transitional fitting is needed
List three places where transitional duct fittings could be used
Reduced airflow
Increased airflow
Accommodate architectural requirements
Which rectangular duct ratio of width to depth moves air most efficiently
1:1
Which duct size ratio should be maintained to optimize airflow
1:1
What should be done to a duct that is approaching 4:1 width to depth ratio
Should be transitioned back to square or round ASAP
List two factors that may make transitional fitting fabrication impractical
Layout skills
Cost of fitting
What knowledge is required when developing patterns for a transitional fitting
Triangulation and how to develop patterns
What affects the overall cost of developing patterns for a transitional fitting
Labour and layout costs
List two options that can be used to avoid a complex transitional fitting
Change duct sizes to something that does not require a transitional fitting
Transition done in two fittings
Why is it not recommended to use multiple fittings connected together in a medium to high pressure duct system
Cause turbulence, noise and pressure loss in airstream
When would we used the specialized term flat on back/ flat on top
A transitional fitting that shows flat on one of the cheeks
When would we used the specialized term “on center “
When A transitional fitting that has equal amounts of change on both sides
What is the allowance for a raw edge duct connection
No allowance is added to the completed pattern
list two scenarios where we would use a raw edge duct connection
The duct or fittings are welded
When manufactured duct connectors are applied to the end of the duct or fitting
Where would we most commonly use a slip and drive duct connection and what is the allowance added to the end of the duct
Square duct, 1/2” allowance
What is the technical term used for cp connection
Standing drive
Why is cp connection primarily used on a larger duct
Adds strength and rigidity
Where do we primarily use a hammerlock connection
Joining a smaller piece of duct to a larger piece of duct
What is the allowance added to the edge of a duct to accept a hammerlock connection
3X width of the seam
List three fittings that hammerlock connections are sometimes used on
Duct connection collars
Plenum take off
Tee branches
List three things that can be done to a slip joint to stiffen long/wide duct connections
Extra folds
Flat iron
Angle iron
What adjustments need to be made to the end of a duct fitting that is to be fabricated with either a standing drive cp or a hammerlock seam
No adjustments
Other than the slip and drive connection S plus D list one more transverse duct connection that requires an adjustment to the net pattern
Proprietary connection
When fabricating a transitional duct fitting that has a proprietary duct connection what determines the amount we need to shorten the net pattern for development of the fitting
Size of slelected proprietary flange
How are fittings drawn on blueprints by engineers
Net patterns
What standards do most prints or job specifications state that all ductwork must be constructed meet
SMACNA
When developing patterns why do we thrive to keep all of the layout lines on the inside of the fitting
Taking Pride in the work
List two ways we can add the allowances used to join ducts together on our change cheek
Measure allowance perpendicular to the net pattern line
Use a compass to scribe arcs on either end
Why is it recommended to calculate and pre cut the wrappers when developing the fitting
Saves time
When fabricating a transitional duct fitting, why do we use an angle transfer notch on some of the angled sides
Removes material that will interfere with the duct connection
What formula can be used to find the sloped side of a triangle
Pythagorean theorem
What strategy can be used in a shop to eliminate much of the triangulation work associated with developing patterns for a flat sided transition
Cut lists, calculations done before metal is cut, to determine cut lengths
