Variable Spring Hanger: A variable spring hanger is a type of support used for piping systems. It is designed to allow for thermal expansion and contraction of the piping without causing damage. The variable spring hanger consists of a spring that is mounted between two flanges. The spring is designed to compress and expand as the piping expands and contracts.
Variable spring hangers are typically used in applications where the piping is subject to large temperature changes. They are also typically used in applications where the piping is subject to vibration.
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.
Advantages of using variable spring hangers
They allow for thermal expansion and contraction without causing damage to the piping.
- They are resistant to vibration.
- They are relatively inexpensive.
- They are easy to install and maintain.
Disadvantages of using variable spring hangers
- They can be bulky and take up space.
- They can be difficult to inspect and maintain.
- They can be damaged by impact or excessive vibration.
Constant Spring Hanger
A constant spring hanger is a type of hanger used to support piping systems. It is designed to provide a constant load on the piping, regardless of the temperature or pressure of the fluid being transported. This is in contrast to a variable spring hanger, which is designed to allow for thermal expansion and contraction of the piping without causing damage.
Constant spring hangers are typically used in applications where the piping is subject to vibration or where the piping is carrying a fluid that is corrosive or flammable. They are also typically used in applications where the piping is located in a sensitive area, such as a hospital or a laboratory.
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.
Advantages of using constant spring hangers
They provide a constant load on the piping, which can help to prevent vibration and fatigue damage.
- They are resistant to corrosion and wear.
- They are relatively inexpensive.
- They are easy to install and maintain.
Disadvantages of using constant spring hangers
They cannot accommodate thermal expansion and contraction of the piping.
- They can be bulky and take up space.
- They can be difficult to inspect and maintain.
- They can be damaged by impact or excessive vibration.