When necessary, START-PROF runs an automatic spring support springs selection and analysis of their compression. The analysis produces variable spring support and hanger properties. For this, the standard and one of states for selection, operation or cold, must be chosen in Project Settings.
A support places one elastic vertical restraint and two fictional horizontal restraints on the restrained point, taking into account the pendulum effect when hanger rods are displaced from the vertical position (fig. 1). Rod length must be input. See "custom restraints".
Fig. 1
Property |
Description |
Name |
Element name. If checked then it shown in 3D view |
Spring type |
LISEGA spring type (21, 22, 25, 26). More... |
Rod number |
Spring chain
(rod) number - minimum structurally sound number of parallel
spring chains in a support (from
1 to 10).
For example, a variable
spring support on a riser must have
at least two spring chains, since it is not structurally sound
with one. The number
of spring chains indicated in START-PROF output will be no
less than that in input data, but may be higher if two chains
are insufficient for allowable load conditions. |
Load difference, % |
Required
relative load difference. Equal
to the correlation of differences in support loads in operation
and cold states and loads in operating mode. Usually 35% is recommended. For
pipelines connected to equipment sensitive to effects from
Piping forces (turbine,
pump, etc.), less than 35% is recommended.
More... |
Load safety factor, m |
Support load safety factor m
= 1 ÷
1.3 (load cannot
exceed carrying capacity).
Specific value is selected
based on Piping design, installation and commission experience.
Usually m = 1 is
recommended. If
m > 1, the number of springs in the support and the
overall spring chain height increase. |
Allowable load |
Allowable load (for one chain) for custom springs (standard type - "other") |
Supporting force R (Rop or Rcold) |
Supporting force value (for
all chains) - required
force, created by variable spring hangers in operation
Rop or
cold Rcold Piping states (depending
on selection state input in Project Settings). |
Flexibility, l |
Flexibility or stiffness of one chain. If flexibility and stiffness is input as 0, an automatic calculation is done. If the value is not 0, chain composition selection and calculation of supporting forces in operation and cold states is done, where flexibility value must match the value in the springs database selected in Project Settings. More... |
Stiffness, K |
Stiffness is the inverse value of flexibility K=1/l |
Rod length, L, H |
Hanger rod length. If the value is 0, pendulum effect is not considered (fictitious restraints are not set, see "custom restraints") |
Test state |
In some cases, springs may be temporarily locked during testing, which must be taking into account in the analysis |
Displacement range |
Spring displacement range. Must be specified if spring stiffness is specified manually because several displacement ranges could have the same stiffness value. More... |
Note: If both "flexibility" and "supporting force" are not 0, the input values are used in START-PROF analysis without selection for the corresponding spring. More...
To insert an element, select the desired node and use: Insert > Insert Restraint > Variable Spring Hanger
or press the or toolbar icon.
To view properties of an existing element:
Double-click the element in the 3D view
Select the element and press the toolbar icon