Variable Spring Hanger

Related Topics

When required, PASS/START-PROF automatically performs  spring selection and compression analysis. The analysis generates  variable spring support and hanger properties. Select the standard spring database and the design state (operating or cold) in Project Settings.

This support applies one elastic vertical restraint and two fictional horizontal restraints at the specified point. It accounts for pendulum effects when hanger rods deviate from vertical (Fig. 1). Input the rod length. See "Custom Restraints".

    

Fig. 1

Properties

Property

Description

Name

Element name. Displays in 3D view when checked.

Weight

Spring weight applied to the pipe as a load.

Spring type

LISEGA spring type (21, 22, 25, 26). More...

Rod number

Minimum number of parallel spring chains required for structural integrity (1 to 10). Riser supports typically require at least two chains.
Doubling chains doubles allowable load and halves flexibility (doubles stiffness k). More...

Load range, %

Required load variation between operating and cold states. Typically 25-35%. Use lower values for equipment sensitive to nozzle loads (turbines, pumps). More...
Maximum allowable range for LISEGA and WITZENMANN springs is 25%.

Extended range

Enable to use extended load ranges.

Load safety factor, m

Safety factor for support load capacity: m = 1.0–1.3. Select based on design experience. Typically m = 1.0. Higher values increase spring count and overall height.
For springs compressed during thermal displacement, PASS/START-PROF automatically increases m by 15% per [1].

Allowable load

Maximum allowable load per chain for custom springs (type "Other").

Supporting force

Total supporting force required from all chains in the selected design state (Rop or Rcold).
R = 0 enables automatic force selection.
R ≠ 0 uses the specified value for manual load control. More...

Pre-compression force

Concentrated force Pз applied by spring compression during installation. More...

Flexibility, l

Flexibility (inverse of stiffness) per chain. Zero enables automatic calculation. Non-zero values use manual input. Must match values in the selected spring database. More...

Stiffness, K

Stiffness per chain K=1/l (inverse of flexibility).

Rod length, L, H

Hanger rod length. Zero disables pendulum effect (no fictitious restraints). See "Custom Restraints".

Test state

Account for springs locked during hydrotest.

Displacement range

Required when specifying stiffness manually, as multiple ranges can share the same stiffness value. More...

Check allowable loads

Verify steel structure loads when its capacity is less than the spring hanger capacity.

Note: When both "Flexibility" and "Supporting Force" are non-zero, PASS/START-PROF uses the input values without spring selection. More...

Menu and Toolbar Access

To insert this element, select a node and use: Insert > Insert Restraint > Variable Spring Hanger

Or click: or .

To view properties: