Choosing Pipe Supports

Q: Which standards or codes apply?

reduce the span for gas-filled lines that later run liquid-full (hydrotest), for valves/heavy fittings (support adjacent), and at changes of direction. Never let a long span create a liquid pocket on a draining line.

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Quick pick (TL;DR)

Carry weight → rest/shoe.
Allow axial, restrain sideways → guide.
Fix the pipe → anchor (defines expansion zones).
Vertical thermal movement → variable spring (load change ≤ 25%) or constant spring (sensitive equipment, < ±6%).
Insulated hot lines → welded shoe; add a PTFE slide plate to cut friction.

Step 1 — Support functions

Type	Function
Rest / shoe	Carries weight; allows sliding.
Guide	Axial free, lateral restrained.
Anchor	Fixes the pipe; defines zones.
Variable spring	Vertical movement, ≤ 25% load change.
Constant spring	Constant load, sensitive equipment.

Step 2 — Support spacing

Limited by sag/deflection. Suggested max spans for water-filled straight CS pipe:

Size	Max span (water)
DN25 (1″)	~ 2.1 m
DN50 (2″)	~ 3.0 m
DN100 (4″)	~ 4.3 m
DN150 (6″)	~ 5.2 m
DN200 (8″)	~ 5.8 m
DN300 (12″)	~ 7.0 m

Frequently asked questions

What should I know about Choosing Pipe Supports?

Carry weight → rest/shoe. Allow axial, restrain sideways → guide. Fix the pipe → anchor (defines expansion zones). Vertical thermal movement → variable spring (load change ≤ 25%) or constant spring (sensitive equipment, < ±6%). Insulated hot lines → welded shoe; add a PTFE slide plate to cut friction.

Which standards or codes apply?

reduce the span for gas-filled lines that later run liquid-full (hydrotest), for valves/heavy fittings (support adjacent), and at changes of direction. Never let a long span create a liquid pocket on a draining line.

Note — Reduce span near valves, at bends, and for hydrotest-filled gas lines.

Step 3 — Spring selection

Variable vs constant

Variability rule load variation % = (spring rate × travel) / hot load × 100 Decision variation ≤ 25% → variable spring (cheaper) variation > 25% → resize or use constant spring near pumps/turbines (low nozzle load) → constant (< ±6%)

Step 4 — Friction & attachment

Steel friction ≈ 0.3; PTFE slide ≈ 0.1.
Insulated → welded shoe (height = insulation).
Hot lines → welded shoe; check local stress.

Support spacing lookup (MSS-SP-69)

Recommended maximum span

MSS-SP-69 suggested max spans — water vs gas/vapour service.

Nominal size

Service

Straight horizontal std-wall runs — reduce at valves, bends & for thin-wall pipe.

Common mistakes

Rigid rest where the pipe lifts → use a spring.
Ignoring friction load.
Spans too long → sag/vibration.

Requisition & datasheet

Function, loads/movements, shoe, attachment.
Spring loads; friction; standard.

Standards — MSS-SP-58 / SP-69; ASME B31.1 spans.