Certified Pipefitter Rigging, Hangers, and Supports Questions and Answers — Questions and Answers
Question 1: A vertical steam pipe (riser) must be supported at each floor level it passes through. Which type of support is specifically designed to clamp onto the pipe and transfer the pipe's dead weight to the building's structure at that elevation?
- Clevis Hanger
- Roller Support
- Riser Clamp (Correct answer)
- Pipe Saddle
Correct answer: Riser Clamp
A Riser Clamp is specifically designed for supporting vertical runs of pipe. It clamps tightly around the pipe, and the clamp itself rests on the floor or structural steel, thereby transferring the weight of the pipe section to the structure.
Question 2: A high-temperature piping system is expected to have significant vertical movement due to thermal expansion. To avoid transferring stress to sensitive equipment, the support must provide a consistent lifting force throughout the entire range of movement. Which hanger is best suited for this application?
- Rigid Rod Hanger
- Variable Spring Hanger
- Constant Support Hanger (Correct answer)
- U-Bolt Anchor
Correct answer: Constant Support Hanger
A Constant Support Hanger uses a mechanism of springs and levers to provide a consistent supporting force throughout its full range of travel. This is critical for applications with large thermal movements, as it prevents transferring variable loads to nozzles or other hangers. A variable spring hanger's supporting force changes as the pipe moves.
Question 3: When using a two-leg sling bridle to lift a 2,000-pound pipe, what happens to the tension in each sling leg as the horizontal angle between the sling and the pipe decreases (i.e., the slings become flatter)?
- The tension decreases
- The tension remains 1,000 pounds
- The tension increases significantly (Correct answer)
- The tension is unaffected by the angle
Correct answer: The tension increases significantly
As the sling angle relative to the horizontal load decreases, the tension on each sling leg increases dramatically. At a 90-degree angle (vertical lift), each sling supports half the load. At 30 degrees, the tension on each sling is equal to the full weight of the load. This is due to the vector forces involved in the lift.
Question 4: A pipefitter is installing a trapeze hanger using 1/2-inch threaded rods to support a group of pipes. According to common standards like MSS SP-58, what is the correct practice for securing the nuts on the threaded rods?
- The rod should be flush with the top of the nut.
- The rod must extend fully through the nut with some threads visible. (Correct answer)
- The nut should be tack welded to the rod for security.
- Only a single nut is required below the trapeze channel.
Correct answer: The rod must extend fully through the nut with some threads visible.
For a threaded rod connection to achieve its full rated strength, the rod must be fully engaged with the nut. Best practice and standards require the rod to pass completely through the nut, with at least a few threads visible beyond the nut, ensuring full engagement and a secure connection.
Question 5: Which of the following is the primary purpose of a variable spring hanger?
- To rigidly anchor the pipe and prevent all movement.
- To guide the pipe's lateral movement.
- To provide a constant, unchanging supporting force.
- To support a pipe's weight while allowing for vertical thermal movement. (Correct answer)
Correct answer: To support a pipe's weight while allowing for vertical thermal movement.
A variable spring hanger is designed to support the dead weight of a pipe system while accommodating vertical displacement caused by thermal expansion or contraction. Unlike a rigid support, it allows movement, and unlike a constant support, its supporting force varies as the spring compresses or extends.
Question 6: A rigging plan requires lifting a 4,000 lb load with a two-leg sling bridle where the slings are at a 60-degree angle from the horizontal. What is the approximate tension on each individual sling leg?
- 4,000 lbs
- 2,309 lbs (Correct answer)
- 2,000 lbs
- 2,828 lbs
Correct answer: 2,309 lbs
The formula for tension on each leg is (Total Load / Number of Legs) / sin(Angle). In this case, it is (4,000 lbs / 2) / sin(60°). Since sin(60°) is approximately 0.866, the calculation is 2,000 lbs / 0.866, which equals approximately 2,309 lbs per leg.
Certified Pipefitter Rigging, Hangers, and Supports Questions and Answers
A vertical steam pipe (riser) must be supported at each floor level it passes through.
Which type of support is specifically designed to clamp onto the pipe and transfer the pipe's dead weight to the building's structure at that elevation?