Pipe Support Design Flashcards

What is a 'pipe shoe' support and why is it used on insulated piping?

Answer: A support element welded or clamped to the pipe to elevate it from structural steel, preventing insulation crushing

A pipe shoe raises the insulated pipe off the support steel so the insulation is not crushed and the vapor barrier is maintained, while transferring load to the structure.

Per ASME B31.3, which characteristic distinguishes a non-integral pipe support attachment from an integral one?

Answer: Non-integral attachments grip or clamp externally without altering the pipe wall; integral ones are welded to or through the pipe

Integral attachments (lugs, trunnions, welded pads) become part of the pressure-boundary analysis, while non-integral clamps and straps engage the pipe externally without affecting its structural integrity calculation.

MSS SP-69 serves what purpose in the context of pipe support engineering?

Answer: It provides selection and application guidance for choosing the correct hanger or support type for given conditions

MSS SP-69 (Pipe Hangers and Supports — Selection and Application) guides engineers in matching the appropriate support type (hanger, rest, guide, anchor, etc.) to specific piping conditions and service requirements.

For high-temperature piping services above 750°F (399°C), which material consideration is most critical when selecting pipe support components?

Answer: Selecting Cr-Mo alloy steel with adequate creep resistance and retained high-temperature strength

Carbon steel suffers significant strength loss and creep deformation at elevated temperatures; chromium-molybdenum alloy steels (e.g., P11, P22) are specified for their superior high-temperature mechanical properties.

What is a 'trunnion support' and for what type of piping is it commonly used?

Answer: A short cylindrical pipe stub welded perpendicular to the main pipe to transfer loads to structural support, used on large or heavy piping

A trunnion is a stub cylinder welded to the pipe (often at an elbow) that acts as a pivot point resting on a structural cradle, efficiently transferring large loads from heavy or large-diameter piping to the supporting structure.

Which method of support is most appropriate for buried underground piping to prevent differential settlement and point loading?

Answer: Properly compacted granular bedding providing continuous, uniform support along the pipe length

Continuous granular bedding (per AWWA or project specification) distributes the pipe load uniformly, eliminates point contacts, and accommodates minor soil movement without overstressing the pipe.

When a pipe support weld attachment (such as a lug) is made directly to an alloy steel pipe, which additional fabrication requirement commonly applies per ASME B31.3?

Answer: Preheat and potentially post-weld heat treatment (PWHT) per the applicable P-number requirements

ASME B31.3 requires preheat (and PWHT where specified) for weldments based on the pipe's P-number material group, carbon equivalent, and wall thickness to avoid hydrogen cracking and meet mechanical property requirements.