How to Setup a Variable Spring Support

Variable spring supports allow vertical pipe displacement due to thermal expansion or contraction, and support the weight of the pipe system. In a variable spring support, load varies at a constant rate with the vertical travel. For that reason, they are used when the vertical movement is of a low or medium range (up to 50-75 mm).

Basic Setup

Before proceeding, check Understanding Support Datasheet topic for a better knowledge on information architecture.

Step 1: Enter basic data

First of all, select Variable on ‘Type of Support’ combo box.
Define ‘Single/Double Type’ configuration (if double, select how you will enter loads on ‘Load Calculations’ field, by support or spring).
Enter ‘Operational Load (Hot Load)’ value. If you prefer entering ‘Preset Load (Cold Load)’ value, click on the Lock icon to unlock this field and lock Hot Load.
Enter ‘Vertical Movement (+/-)’ value. Positive or negative values are allowed.

Advanced Setup

Choosing the spring series

The catalogue offers four series of variable springs. All four cover the same load range in the same number of sizes; what differs is how much travel they have and therefore how stiff they are. A series with twice the travel has half the spring rate.

Series	Travel	Stiffness	Use when
CVC	short	stiffest	movement is small and space is tight
CV	standard	reference	general purpose
CVL	long	softer	variability on CV is too high
CVLL	extra long	softest	large movement, low load

If you let the software choose, it proposes from the whole catalogue. If you select the series yourself, it selects within it.

Travel reserves

Leave Travel Reserve Up and Travel Reserve Down blank to accept the default margins. Define them when the stress analysis is provisional, when a client specification requires a stated reserve, or when the support will be hard to reach for adjustment.

See Travel and travel reserves.

Variability limit

Max Allowed Variability can be set for the whole project on the project datasheet, or overridden for one support. The individual value wins. If you leave both blank the software applies its own default (25 %).

See Hot load, cold load and variability.

Entering the cold load instead of the hot load

Click the lock icon beside Preset Load (Cold Load) to make it the input and lock Operational Load (Hot Load). The software then works the relationship in reverse. Useful when the specification you are working from states the installed load.

Reading the proposal

The software always proposes a model if any candidate passes the load and travel filter — including candidates that exceed the variability limit or sit outside the recommended travel band. The proposal is a starting point, not a validation. Read the warnings on the datasheet before accepting it.

When a variable spring is the wrong answer

Variable springs suit vertical movements up to roughly 50–75 mm. Above that, variability becomes hard to control even on the softest series, and a constant spring support is normally the right choice.