Questions and Answers
How can dog legs be avoided when making offset bends?
Maintaining the centerline for all bends.
How can the shoe be prevented from creeping when making bends on short lengths of conduit?
Screwing a coupling onto the conduit.
Which of the following will produce an offset in a conduit run?
Given a 30 degree kick with a hypotenuse of 10 inches and knowing the cosecant of 30 degrees is 2, what is the side opposite the kick?
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What are the two dimensions an electrician must know when making a 90 degree stub bend?
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What is the maximum diameter of rigid pipe that hydraulic benders can bend?
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What is a single change in direction of less than 90 degrees called?
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One of the characteristics of aluminum conduit is that it is:
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What is the first step in calculating the radius of a bend when making concentric bends in conduit of different sizes?
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Which of the following is a type of bending shoe?
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What does springback refer to in conduit bending?
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Which combination of bends between pull points is allowed by the NEC?
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What is the developed length for an elbow bend in 5 inch conduit if the center line radius is 20 inches?
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Why does the NEC specify the minimum radius of conduit bends?
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How much conduit is needed if the rise is 15 inches, the leg length is 10 inches, and the gain is 8.6 inches?
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Where do you make your first mark when making a 14 inch stub-up in 1 inch RMC with a bender deduct of 10 inches?
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Which of the following is true when joining PVC conduit?
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In which installations are PVC expansion couplings seldom required?
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When making a 15 inch offset with two 30 degree bends and an offset multiplier of 2, what is the distance between bends?
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How many bends are required for a conduit run that must pass over a pipe and then over a rectangular duct?
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Study Notes
Conduit Bending Overview
- Dog legs can be avoided in offset bends by maintaining the centerline for all bends.
- To prevent shoe creep on short conduit lengths, screw a coupling onto the conduit.
- An offset in a conduit run can be produced by making two kick bends in opposite directions.
Bending Techniques and Calculations
- For a 30-degree kick with a 10" hypotenuse, the side opposite the angle (rise) is 5".
- The two essential dimensions for a 90-degree stub bend are the desired rise and take-up distance.
- Hydraulic benders can bend rigid pipe up to 5" in diameter.
- A change in direction of less than 90 degrees is referred to as a kick.
Material Characteristics
- Aluminum conduit is known for its lightweight properties.
Bending Radius and Methods
- To calculate the radius of concentric bends in conduits of different sizes, start by determining the radius of the innermost bend.
- A segmented bending shoe is one type of bending shoe used in conduit bending.
Bending Behavior and Regulations
- Springback refers to the conduit’s tendency to relax to a looser bend angle once the bender is released.
- NEC regulations allow for a combination of two 45-degree offsets, an elbow, and three 15-degree kicks between pull points.
- The developed length for an elbow bend in 5" conduit with a center line radius of 20" is 31.4".
- The minimum radius of conduit bends is specified by NEC to prevent damage to insulation on conductors during pulling.
Length and Marking Calculations
- For a rise of 15", leg length of 10", and gain of 8.6", the total conduit needed is 16.4".
- For a 14" stub-up in 1" RMC, with a bender deduct of 10", the first mark should be made 4" from the end of the conduit.
Joining and Installation Guidelines
- When joining PVC conduit, the cementing operation should not exceed 20 seconds.
- PVC expansion couplings are rarely necessary in underground installations.
Offset Bending Details
- To create a 15" offset with two 30-degree bends and an offset multiplier of 2, the distance between bends is 30".
- A conduit run that must pass over a pipe and a rectangular duct requires a total of seven bends.
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Description
Test your knowledge on conduit bending techniques with these flashcards. Learn how to avoid dog legs, prevent bending creep, and understand offsets in conduit runs. Perfect for students and professionals in electrical installation.
