SPED Pipe Support Design 1 — Questions and Answers
Question 1: What is the primary purpose of a pipe anchor in a piping system?
- To allow free thermal movement of the pipe
- To restrain all pipe movement in all directions at a fixed point (Correct answer)
- To support the dead weight of the pipe only
- To prevent corrosion at structural contact points
Correct answer: To restrain all pipe movement in all directions at a fixed point
An anchor restrains all translational and rotational degrees of freedom, fixing the pipe completely at that location.
Question 2: Which type of pipe support allows axial movement but restricts lateral movement?
- Anchor
- Guide (Correct answer)
- Constant-effort hanger
- Strut
Correct answer: Guide
A guide restrains lateral (transverse) movement while permitting axial displacement along the pipe centerline.
Question 3: Which MSS standard governs the materials, design, and manufacture of pipe hangers and supports?
- ASME B31.3
- MSS SP-69
- MSS SP-58 (Correct answer)
- ASME B16.5
Correct answer: MSS SP-58
MSS SP-58 specifically covers pipe hangers and supports — materials, design, and manufacture, including component types and load ratings.
Question 4: What is the primary advantage of a variable spring hanger over a rigid rod hanger?
- It provides greater lateral restraint under seismic loads
- It accommodates vertical thermal movement while continuously supporting pipe weight (Correct answer)
- It requires no periodic inspection or maintenance
- It is less expensive to procure and install
Correct answer: It accommodates vertical thermal movement while continuously supporting pipe weight
Variable spring hangers compress or extend as the pipe moves thermally, maintaining a changing but continuous support load throughout the travel range.
Question 5: Which pipe support device allows slow thermal movements but locks up rigidly under dynamic loads such as vibration or seismic events?
- Rigid rod hanger
- Dummy leg
- Snubber (Correct answer)
- Saddle support
Correct answer: Snubber
Snubbers (hydraulic or mechanical) permit gradual thermal displacement but engage and provide rigid restraint when subjected to rapid dynamic loading.
Question 6: What is a 'dummy leg' in pipe support design?
- A short pipe extension welded to the main pipe to transfer load to a structural support (Correct answer)
- A temporary wood block used during construction alignment
- A decorative cap on an unused pipe branch
- A type of constant-load spring hanger
Correct answer: A short pipe extension welded to the main pipe to transfer load to a structural support
A dummy leg is a stub pipe section welded perpendicular to the main pipe (often at elbows) to transfer pipe loads directly to grade or structural steel.
Question 7: According to MSS SP-69, support spacing tables are primarily based on which variables?
- Insulation color and pipe material only
- Pipe size, fluid specific gravity, and allowable sag (Correct answer)
- Ambient temperature and wind speed
- Pipe wall thickness and flange rating
Correct answer: Pipe size, fluid specific gravity, and allowable sag
MSS SP-69 span tables account for pipe outside diameter, pipe schedule, fluid weight (specific gravity), and a standard allowable mid-span deflection to limit sag.
SPED Pipe Support Design 1
What is the primary purpose of a pipe anchor in a piping system?