Pipe Support and Hanger
General / GeneralDefinition
Pipe supports and hangers carry the weight of piping, fluid, insulation, and components while controlling thermal expansion movements, preventing excessive stress, and maintaining equipment nozzle loads within allowable limits. A piping system without proper supports will sag, vibrate, overstress at connections, and eventually fail from fatigue or static overload. Pipe support design is a specialized discipline within piping engineering that combines structural analysis, thermal expansion calculation, and field installation experience.
Working Principle
Pipe supports serve two primary functions: weight support and restraint. Weight supports carry the gravitational load of the pipe, fluid, and components. Rigid supports fix the pipe at a specific location. Spring supports (variable spring hangers) allow vertical thermal movement while maintaining a nearly constant supporting force — the spring compresses or extends as the pipe moves. Constant-effort hangers use a cam and spring mechanism to deliver exactly the same supporting force throughout the entire travel range, critical for high-temperature systems with large vertical expansion. Restraints (guides, anchors, limit stops) control thermal expansion direction, direct movement toward expansion loops or bellows, and prevent vibration.
Key Components
| Rigid support | Fixed attachment; allows no movement (anchor) or limited movement (guide) |
| Variable spring hanger (VSH) | Coil spring support; force varies slightly with travel |
| Constant effort hanger (CEH) | Cam-spring mechanism; constant force over full travel range |
| Guide | Allows axial movement, restricts lateral or rotational |
| Anchor | Fixes pipe in all directions; absorbs thermal expansion forces |
| Sway brace / snubber | Restricts dynamic movement (seismic, water hammer) but allows slow thermal movement |
Types & Variants
| Support Type | Movement Allowed | Force Variation | Typical Application |
|---|---|---|---|
| Rigid hanger | None (fixed point) | N/A | Cold lines, anchor points |
| Variable spring (VSH) | Vertical thermal movement | Up to 25% force variation | Medium-temp steam, hot water (up to 650F) |
| Constant effort (CEH) | Large vertical movement | Less than 6% variation | High-temp steam (650F+), large expansion |
| Sliding support | Horizontal movement (low friction) | N/A | Bottom-supported pipe racks |
| Sway brace | Dynamic restraint only | N/A | Seismic zones, safety-related piping |
Materials
Support steel: ASTM A36 carbon steel for general service, galvanized or painted for corrosion protection. ASTM A572 Gr 50 for higher-strength supports. Stainless steel supports (304, 316) for corrosive or high-temperature environments where carbon steel would degrade. Springs: ASTM A228 music wire or chrome-vanadium steel for variable springs; alloy steel for constant-effort springs. Friction-reducing pads: PTFE (Teflon) sliding plates reduce friction coefficients from 0.3 (steel-on-steel) to 0.05 (PTFE-on-steel). Insulated supports: calcium silicate or high-density polyurethane blocks for cold and cryogenic service.
Applicable Standards
ASME B31.1 (Power Piping) and B31.3 (Process Piping) define support design requirements and allowable stresses. MSS SP-58 (Pipe Hangers and Supports — Materials, Design, and Manufacture) is the primary product standard. MSS SP-69 (Selection and Application) provides guidance. MSS SP-127 (Bracing for Seismic) covers sway brace and snubber design. ASCE 7 provides seismic load requirements. Manufacturer catalogs (Anvil, Lisega, Piping Tech) are the primary references for sizing and selection.
Applications
Power plants: constant-effort hangers on high-pressure main steam lines that expand vertically 6-12 inches between cold and operating conditions. Refinery process piping: variable spring hangers on hot oil