Variable Spring Hanger:
-Variables use coiled springs to support a load
and allow movement. The resistance of the coil to a load changes during
compression, which is why these devices are called "variables".
Constant Spring Hanger provides constant support force for pipes and equipment
subjected to vertical movement due to thermal expansion at locations where
maintaining a constant stress is critical. This constant resistance is
achieved by having two moment arms pivoted about a common point. The
load is suspended from one of these arms, and a spring is attached to the
other. With an appropriate choice of moment arms and spring properties, a
resisting force can be provided that is nearly independent of position.
Constant Spring Hanger:
- Constant support hangers are principally used to
support pipes and equipment subjected to vertical movement due to thermal
expansion at locations where transfer of stress to other supports or equipment
can be critical. The maximum recommended variation according to MSS standard
from the operating load is 25% for variable spring hangers. If the variation
exceeds 25%, a constant support hanger should be used.
The constant resistance to a load is achieved by combining a spring
coil with a cam which rotates about a main pivot point. The cam is designed
such that the distances from the main pivot changes to compensate for the
variable resistance during compression of the coil. The MSS standard provides
for a tolerance of 6% in the constant load through the travel range. Constant
support hangers are designed per MSS, ANSI, and ASME standards. The sizing of
constants primarily depends on the total travel and load.