What Is Cold Springing (Cold Pull)?

Cold springing (also called cold pull) is a piping installation technique where a pipe spool is deliberately fabricated shorter than its installed length, then pulled or forced into position during erection. This introduces a controlled pre-stress in the cold (ambient) condition that partially offsets the thermal expansion loads that develop when the system reaches operating temperature.

The result is a reduction in equipment nozzle loads and anchor forces at operating temperature, at the cost of introducing loads in the cold condition.

How Cold Springing Works

Condition	Without Cold Spring	With 50% Cold Spring
Cold (ambient) installation	Zero stress, zero load on nozzles	Pipe is pre-stressed; nozzle sees ~50% of thermal load (in reverse direction)
Hot (operating) condition	Full thermal expansion load on nozzles and anchors	Nozzle load reduced by ~50% (expansion partially absorbed by cold spring)
Cold after first cycle	Some residual stress due to relaxation	Relaxation may reduce cold spring effectiveness over time

Code Treatment (ASME B31.3 and B31.1)

Aspect	ASME B31.3 (Process Piping)	ASME B31.1 (Power Piping)
Credit for stress range	No credit—cold spring does not reduce the displacement stress range (S_E)	No credit for stress range
Credit for reactions (nozzle loads)	Allows 2/3 credit for cold spring in calculating reactions at equipment nozzles	Allows 2/3 credit per para. 119.10
Cold spring factor (C)	C = fraction of total expansion absorbed by cold spring (0 to 1.0)	Same definition
Maximum recommended	Typically 50% cold spring (C = 0.5)	Typically 50-100%
Documentation	Must be shown on piping isometric	Must be noted on drawings

The 2/3 credit factor accounts for the uncertainty that full cold spring may not be achieved in the field due to fit-up tolerances and weld shrinkage.

Cold Spring Calculation

The cold spring gap (the amount the spool is shortened) is:

Gap = C x delta_total

Where:

• C = cold spring factor (typically 0.5)
• delta_total = total thermal expansion of the pipe run between anchors (mm or in.)

For carbon steel pipe at 400 deg C, the thermal expansion is approximately 5.1 mm/m. A 20 m run with C = 0.5 would require:

• delta_total = 5.1 x 20 = 102 mm
• Cold spring gap = 0.5 x 102 = 51 mm

The spool is fabricated 51 mm short and pulled into position during installation.

When to Use Cold Springing

Situation	Cold Spring Recommended
Equipment nozzle loads exceed allowable	Yes—reduces operating loads by up to 2/3 x C
Stress range exceeds allowable S_A	No—cold spring does not reduce displacement stress range per code
Large thermal movement at anchor or restraint	Yes—balances forces between cold and hot conditions
High-temperature steam or process lines (>300 deg C)	Often used on long runs to turbines, boilers, and heat exchangers
Cryogenic service	Less common; thermal contraction may be addressed by expansion loops instead

Common Mistake

Assuming cold spring reduces the displacement stress range. Per ASME B31.3, cold springing only affects reaction forces (nozzle loads), not the stress range used for fatigue evaluation. A system that fails the stress range check cannot be fixed by cold springing alone—routing changes or expansion loops are needed instead.

Pro Tip

Specify cold spring on the piping isometric with a clear callout showing the gap dimension, direction, and the closure weld location. The construction team must verify the gap before welding and record the actual achieved cold spring in the as-built documentation.

Cold springing is typically applied in coordination with pipe support design and is documented in the system stress analysis package referenced by the pipe class specification.

Read the full guide to pipe class specifications