Bracing ⬇️
One way to control piping vibration is by adding bracing (i.e., restraints) to the system. This increases the mechanical natural frequency of the piping, thus ensuring that resonance due to low frequency excitation will not occur. It also limits large deflections that could be caused by slug flow, water hammer, etc.
When bracing addition is being considered, it must be confirmed that this will not adversely affect the thermal flexibility of the piping system. Adding restraints increases the system stiffness and can cause higher pipe thermal stresses and end-point reaction loads. New thermal flexibility calculations may be required to confirm that the design is acceptable after adding the restraints.
One way to control piping vibration is by adding bracing (i.e., restraints) to the system. This increases the mechanical natural frequency of the piping, thus ensuring that resonance due to low frequency excitation will not occur. It also limits large deflections that could be caused by slug flow, water hammer, etc.
When bracing addition is being considered, it must be confirmed that this will not adversely affect the thermal flexibility of the piping system. Adding restraints increases the system stiffness and can cause higher pipe thermal stresses and end-point reaction loads. New thermal flexibility calculations may be required to confirm that the design is acceptable after adding the restraints.
Snubbers ⬇️⬇️
Vibration amplitudes can be decreased by installing hydraulic or mechanical snubbers. These devices (e.g., dashpots or other frictional devices) increase the system damping by resisting rapid displacements, such as that resulting from vibration. However, they permit movement resulting from slow displacements, such as those from thermal movement. Thus, snubbers may be used in situations where bracing must be added to reduce or prevent vibration movements, but rigid restraints would cause unacceptable thermal displacement stresses or loads.
Vibration amplitudes can be decreased by installing hydraulic or mechanical snubbers. These devices (e.g., dashpots or other frictional devices) increase the system damping by resisting rapid displacements, such as that resulting from vibration. However, they permit movement resulting from slow displacements, such as those from thermal movement. Thus, snubbers may be used in situations where bracing must be added to reduce or prevent vibration movements, but rigid restraints would cause unacceptable thermal displacement stresses or loads.
Surge Suppressers ⬇️⬇️⬇️
Surge suppressers may be used to control surge or pulsation-induced vibration. A typical surge suppresser consists of a pilot operated valve which quickly opens after a power failure through the loss of power to a solenoid, or by a sudden large pressure reduction or increase at the surge suppresser. The open valve releases liquid from the line being protected, thus smoothing and reducing the pressure fluctuation. The valve is closed at a slower rate by using a dashpot in order to limit the pressure rise as the liquid flow is shut off.
Surge suppressers may be used to control surge or pulsation-induced vibration. A typical surge suppresser consists of a pilot operated valve which quickly opens after a power failure through the loss of power to a solenoid, or by a sudden large pressure reduction or increase at the surge suppresser. The open valve releases liquid from the line being protected, thus smoothing and reducing the pressure fluctuation. The valve is closed at a slower rate by using a dashpot in order to limit the pressure rise as the liquid flow is shut off.
Accumulators ⬇️⬇️⬇️⬇️
An accumulator is a pressure vessel that is partially or completely filled with a gas (usually inert). This vessel is then connected by pipe to the main line being protected. In the simplest case, the liquid in the pipe is in direct contact with the gas. In some cases, an elastomer membrane separates the liquid from the gas but transmits pressure between them. In other cases, a rupture disk forms a more rigid barrier between the gas in the accumulator and the liquid in the pipe. For the first two configurations, the device acts instantaneously to a rise in pressure at the gas/liquid interface. In the last configuration, the rupture disk delays the reaction time from 0.2 to 2.0 milliseconds since it must rupture before pressure is transmitted between the two fluids.
An accumulator is a pressure vessel that is partially or completely filled with a gas (usually inert). This vessel is then connected by pipe to the main line being protected. In the simplest case, the liquid in the pipe is in direct contact with the gas. In some cases, an elastomer membrane separates the liquid from the gas but transmits pressure between them. In other cases, a rupture disk forms a more rigid barrier between the gas in the accumulator and the liquid in the pipe. For the first two configurations, the device acts instantaneously to a rise in pressure at the gas/liquid interface. In the last configuration, the rupture disk delays the reaction time from 0.2 to 2.0 milliseconds since it must rupture before pressure is transmitted between the two fluids.
Temporary Restraints ⬇️⬇️⬇️⬇️⬇️
Cables or chains can be used to temporarily control large deflections caused by vibration in piping systems. The cable or chain is attached to the pipe, connected back to nearby structure, and tightened to stop the pipe movement. Quite often, even blocks of wood or scrap steel are used as wedges between the pipe or its supports and nearby structure to stop pipe movement. This approach is useful in stopping large amplitude vibration before it can damage the pipe, and to determine the best locations to place permanent bracing. This technique is not a permanent solution to a piping vibration problem.
Since the temporary restraints are installed while the system is in operation (and hot), their presence could restrict pipe thermal movement when the system is shut down. This should be considered when locating the restraints to determine if they would cause excessive thermal stresses or loads when the system is shut down. In extreme cases, it might be necessary to remove the restraints before or as the system is shutting down in order to permit free thermal movement.
Cables or chains can be used to temporarily control large deflections caused by vibration in piping systems. The cable or chain is attached to the pipe, connected back to nearby structure, and tightened to stop the pipe movement. Quite often, even blocks of wood or scrap steel are used as wedges between the pipe or its supports and nearby structure to stop pipe movement. This approach is useful in stopping large amplitude vibration before it can damage the pipe, and to determine the best locations to place permanent bracing. This technique is not a permanent solution to a piping vibration problem.
Since the temporary restraints are installed while the system is in operation (and hot), their presence could restrict pipe thermal movement when the system is shut down. This should be considered when locating the restraints to determine if they would cause excessive thermal stresses or loads when the system is shut down. In extreme cases, it might be necessary to remove the restraints before or as the system is shutting down in order to permit free thermal movement.
1. Why to use a Spring Support?
⬇️ Any line operating at high temperature moves upwards/downwards (depending on the pipe configuration) due to thermal expansion. Any rigid support provided on such a line tends to lift pipe up/down and hence remain inactive during operating conditions. In such a case a flexible support (springs) is provided which is capable of taking the load in all the operating and cold conditions.The spring supports provides continuous support during expansion or contraction of the pipe.The spring support basically employs a spring element, which can get compressed or stretch-out depending upon the thermal movement of pipe and the corresponding loads.
⬇️ Any line operating at high temperature moves upwards/downwards (depending on the pipe configuration) due to thermal expansion. Any rigid support provided on such a line tends to lift pipe up/down and hence remain inactive during operating conditions. In such a case a flexible support (springs) is provided which is capable of taking the load in all the operating and cold conditions.The spring supports provides continuous support during expansion or contraction of the pipe.The spring support basically employs a spring element, which can get compressed or stretch-out depending upon the thermal movement of pipe and the corresponding loads.
2. Types of Spring Supports
⬇️ Depending on the loads to be accommodated and the magnitude & direction of the thermal displacement to be supported, spring supports are broadly classified as:
Variable effort springs
Constant effort springs
Some of the common terminology associated with the selection and procurement of any Springs are listed below:
Cold Load
Hot Load
Spring RateSpring
Travel
Load Variation or Variation
Pre-compression Length
⬇️ Depending on the loads to be accommodated and the magnitude & direction of the thermal displacement to be supported, spring supports are broadly classified as:
Variable effort springs
Constant effort springs
Some of the common terminology associated with the selection and procurement of any Springs are listed below:
Cold Load
Hot Load
Spring RateSpring
Travel
Load Variation or Variation
Pre-compression Length
3. Terminology
Cold Load:
This refers to the load on the spring hanger when the system is in standby or non-operating condition.
Hot Load:
This refers to the actual load on the spring hanger during operating conditions
Spring Rate/ Stifness:
This refers to the spring rate, force per unit length in N/mm, kg/mm, etc. determined from flexibility analysis.
Spring Travel:
(Installed to operating): This refers to the maximum vertical movement of the spring due to piping loads at operating conditions determined from flexibility analysis.
Load Variation or Variation:
This refers to the allowed variations between the hot load and cold loads.
Pre-Compression Length:
It is the initial compressing of the spring for sustained load.
Installation Height = loaded length – Pre-compression length
Cold Load:
This refers to the load on the spring hanger when the system is in standby or non-operating condition.
Hot Load:
This refers to the actual load on the spring hanger during operating conditions
Spring Rate/ Stifness:
This refers to the spring rate, force per unit length in N/mm, kg/mm, etc. determined from flexibility analysis.
Spring Travel:
(Installed to operating): This refers to the maximum vertical movement of the spring due to piping loads at operating conditions determined from flexibility analysis.
Load Variation or Variation:
This refers to the allowed variations between the hot load and cold loads.
Pre-Compression Length:
It is the initial compressing of the spring for sustained load.
Installation Height = loaded length – Pre-compression length
4. Variable effort spring
VES basically consist of a spring which can get compressed or expanded according to thermal movement of the pipe. However, this movement causes increase or decrease in supporting force depending on its stiffness & this differential load is transferred to the pipeThis load is less than that would be with the rigid support.In VES load variation is maintained generally within 25%.
In VES the loads increases with pipe movement.
VES basically consist of a spring which can get compressed or expanded according to thermal movement of the pipe. However, this movement causes increase or decrease in supporting force depending on its stiffness & this differential load is transferred to the pipeThis load is less than that would be with the rigid support.In VES load variation is maintained generally within 25%.
In VES the loads increases with pipe movement.
5. Types of VES/CES
Hanger type:
In hanger type spring support, the pipe is hung from the secondary support using hanger type spring, as shown. Clevis, Hanger rod, turn-buckle, pipe clamp, etc. are some other attachments associated with such a support.
Hanger type:
In hanger type spring support, the pipe is hung from the secondary support using hanger type spring, as shown. Clevis, Hanger rod, turn-buckle, pipe clamp, etc. are some other attachments associated with such a support.
Bottom support type: In bottom support spring, the pipe is resting on the top of the spring load plate, as shown. This type of spring support is also known as ‘CAN’ Type or ‘F’ Type spring.
Hanger type or bottom support type is selected based on pipe layout and the space availability for mounting.
Hanger type or bottom support type is selected based on pipe layout and the space availability for mounting.
6. Selection of Variable effort spring
⬇️ Determine the required effort & pipe movement (up or down) from installed to operating condition.
Select the smallest spring size from the vendor catalogue which has the operating load within the working travel.
Ensure the spring selected can accommodate the preset to operating travel within the working range.
This is done by moving up & down the chart from the operating load by the amount of travel.
If the spring selected cannot accommodate the movement try a larger spring size or the next travel range.
Check the variation in supporting effort for the selected spring.
If this exceeds the allowable variation then choose the next travel range and go back to Step 3 above.
If the variation is less than half of the allowable then a smaller travel range may be acceptable.
Choose a smaller travel range and go back to step 4.
If the variation exceeds the allowable selection then a constant effort support is required or possibility of routing changes to be studied.
⬇️ Determine the required effort & pipe movement (up or down) from installed to operating condition.
Select the smallest spring size from the vendor catalogue which has the operating load within the working travel.
Ensure the spring selected can accommodate the preset to operating travel within the working range.
This is done by moving up & down the chart from the operating load by the amount of travel.
If the spring selected cannot accommodate the movement try a larger spring size or the next travel range.
Check the variation in supporting effort for the selected spring.
If this exceeds the allowable variation then choose the next travel range and go back to Step 3 above.
If the variation is less than half of the allowable then a smaller travel range may be acceptable.
Choose a smaller travel range and go back to step 4.
If the variation exceeds the allowable selection then a constant effort support is required or possibility of routing changes to be studied.
7. Constant effort spring
Whenever load variation exceeds 25% or exceeds the specified maximum load variation percentage in a variable hanger, then a Constant Effort Spring is selected.
In CES the load remains constant when the pipe moves from its cold position to hot position.
Thus irrespective of travel the load remains constant over complete range of movement.
The pipe is supported by a drop rod connected via turnbuckle to the end of the lever arm.
The spring coil applies a force to the trunnion arm of the lever which tends to pull the lever-arm UP against the load of the pipe.
The geometry of the lever arm provides a balance btw the pipe load & spring force. The pipe may therefore move due to thermal expansion while being supported with a nominally constant force through this travel range.
Whenever load variation exceeds 25% or exceeds the specified maximum load variation percentage in a variable hanger, then a Constant Effort Spring is selected.
In CES the load remains constant when the pipe moves from its cold position to hot position.
Thus irrespective of travel the load remains constant over complete range of movement.
The pipe is supported by a drop rod connected via turnbuckle to the end of the lever arm.
The spring coil applies a force to the trunnion arm of the lever which tends to pull the lever-arm UP against the load of the pipe.
The geometry of the lever arm provides a balance btw the pipe load & spring force. The pipe may therefore move due to thermal expansion while being supported with a nominally constant force through this travel range.
8. Selection of Constant effort spring
Determine the load to be supported by hanger as well as the actual travel, ie. The actual vertical movement of the pipe at the point of hanger location, refer load-travel table.The total travel for constant supports should be equal to “actual travel” plus 1” or 20% whichever is greater. After determining the size, consideration of availabl
room for suspending the pipe and hanger will indicate whether a vertical or horizontal hanger is desirable. After hanger size & design are determined, the type of constant support to be used depends upon the physical installation required by the suspension problem.
Determine the load to be supported by hanger as well as the actual travel, ie. The actual vertical movement of the pipe at the point of hanger location, refer load-travel table.The total travel for constant supports should be equal to “actual travel” plus 1” or 20% whichever is greater. After determining the size, consideration of availabl
room for suspending the pipe and hanger will indicate whether a vertical or horizontal hanger is desirable. After hanger size & design are determined, the type of constant support to be used depends upon the physical installation required by the suspension problem.
9. General notes & guidelines
Any re-adjustment of spring element shall be carried out only when the line is full with the fluid or its equivalent in density to balance the weight of piping and the preset load of spring. The adjustment of hanger type spring element is done by rotating turn buckle or adjustment nuts provided in the hanger rod. During hydraulic testing, flushing or chemical cleaning of the pipeline, the spring must be kept under locked condition or protected against overloading due to weight of testing / flushing fluid, by providing temporary.
After re-adjustment it is important to check whether sufficient range is available on scale for required movement of the pipe during operation.
Any re-adjustment of spring element shall be carried out only when the line is full with the fluid or its equivalent in density to balance the weight of piping and the preset load of spring. The adjustment of hanger type spring element is done by rotating turn buckle or adjustment nuts provided in the hanger rod. During hydraulic testing, flushing or chemical cleaning of the pipeline, the spring must be kept under locked condition or protected against overloading due to weight of testing / flushing fluid, by providing temporary.
After re-adjustment it is important to check whether sufficient range is available on scale for required movement of the pipe during operation.