VIBRATION ISOLATION OF MACHINERY IN FACTORIES

There are many different machines in factories that generate vibrations and noise. If left untreated these can impair human well-being and cause damage to structures or entire buildings. This article aims to describe different methods for vibration isolation of such machines.

INSULATION OF PRESSES AND MACHINE TOOLS

A punch press due to the nature of the process results in high impact forces. These impacts generate a lot of noise and vibration if the press isn't properly insulated. The vibration intensity can disturb neighbouring buildings and cause noise complaints. In addition, strong vibrations place a strain on the press operator.

To reduce the vibration intensity of the press a low natural frequency of the system is required. To achieve this goal a low-stiffness isolation system, such as flexible springs, is necessary.

However, presses mounted on flexible springs are less stable because flexible springs allow for high deflections with relatively low loads. Unstable punching presses, in turn, are more difficult to control and can lead to lower end product quality (reduced punching quality) as well as operator uncertainty.

A solution can be to add more damping to the system to reduce this instability.

By combining low stiffness with high damping, both high vibration insulation and good stability can be achieved.

A case study of a punch press can be seen in the following link:

https://www.akustik.com/en-US/news/hydrpress/

USE OF INERTIAL MASSES

If machine stability is an important factor, using inertial masses can be a good solution. For even better stability vibration dampers can be installed at the center of gravity (see below).

If elastic mounting of the machine at the height of the center of gravity is not possible, an alternative with a larger/higher inertial mass can be used. Microcellular PU such as Sylomer® on the wall and floor can be a good solution (see below).

INSULATION OF PUMPS

Pumps are essential in many factories but they can also generate a lot of noise and vibration, both aspects can be harmful to workers' health and reduce productivity. Vibrations can damage both the pumps' mechanical components and other nearby machines, reducing their lifespan.

Therefore, noise and vibration insulation from pumps in factories is essential. Typical methods to achieve this goal include heavy inertial masses, vibration dampers, elastic layers, or a combination of all.

An inertial mass consists of a heavy concrete base to increase the mass and stability of the pump. This additional mass allows the use of vibration dampers that allow higher deflections to lower the natural frequency of the pumping system and reduce the vibration level to surrounding structures. This method is very useful for large pumps and high-speed pumps.

Vibration isolators are designed to dampen and isolate vibrations before they are transmitted to the concrete base below. Mounts for these types of installations typically use rubber or metal spring elements as the elastic material. They create a flexible connection between the pump and its base, preventing the transmission of harmful vibrations to surrounding structures.

Elastic layers such as rubber mats/blocks can be installed under the pump or under the inertial mass. When these elastic layers are enclosed in a fixed volume, they must shrink in size to function properly. Materials such as rubber do not allow for compression of their volume, making them unsuitable for this application. However, there are elastic materials such as Sylomer® that do shrink thanks to their microcellular structure with integrated air.

By combining these different methods correctly, vibration isolation, machine life and factory efficiency can be optimized.

You can learn more about the use of inertial masses in the following link:

INSULATION OF TRANSFORMERS

In modern industry, transformers are vital for supplying and distributing power throughout the factory. However, they produce vibrations and noise while running, which negatively impact their surroundings. Insulating these machines is essential to reduce such effects and ensure a healthy working environment.

The transformers produce vibrations and noise for the following reasons:

• - Oscillations of the network fundamental frequency: This frequency is the main frequency of the oscillations generated by the transformer. The mains frequency is 50 Hz in the largest part of the world and 60 Hz in the US and some other countries.
• - Magnetostriction: It is the main cause of transformer noise and is caused by the deformation of the magnetic core when exposed to a magnetic field. This oscillation produces a characteristic hum that can be very unpleasant at high levels. The frequency of this oscillation is twice the mains frequency.
• - Harmonics of the network fundamental frequency: Transformers also generate harmonics. These are oscillations with a frequency that is a multiple of the network frequency. This is caused by the nonlinear behavior of the core materials and magnetic saturation. The most common harmonics are the 3rd harmonic (150 Hz or 180 Hz), the 5th harmonic (250 Hz or 300 Hz), and the 7th harmonic (350 Hz or 420 Hz). These harmonics can occur when there are imbalances or nonlinear loads connected to the transformer.
• - Electromagnetic forces: The current flows through the transformer coils generate forces that can trigger vibrations in the transformer components (e.g. core and windings).
• - Mechanical vibrations: The cooling fan and oil circulation are also a cause of vibration and noise in large transformers.
• - Structural resonance: The transformer vibrations can be amplified if they coincide with the natural frequencies of the structural elements of the factory.
• - Subharmonic frequencies: Some transformer faults can produce subharmonic frequencies. These are integral sub-frequencies of the network frequency (e.g. 25 Hz or 30 Hz). These frequencies are associated with mechanical or electrical problems in the coils or core.

Below you can see an example of harmonic oscillations of a transformer in a 50 Hz network:

Noise and vibration from transformers can have various negative effects in the factory environment:

• - Structural damage: The vibrations can cause fatigue of the ground and nearby structures, i.e. cracks or deformations over time.
• - Impact on devices: Vibrations can disrupt the functioning of sensitive equipment, such as precision machinery, measuring instruments or electronic systems.
• - Health effects: Long-term exposure to high noise levels can cause hearing damage and stress, which can affect workers’ health and productivity.
• - Environmental problems: In urban environments, noise can lead to neighbourhood complaints or legal complications.

To reduce the effects of noise and vibration from transformers, various insulation solutions can be used:

• - Installation of an inertial base above the vibration dampers An inertial mass consists of a heavy concrete base to increase the transformer's mass. This additional mass allows for the use of vibration dampers that allow for higher deflections to lower the transformer's natural frequency and reduce the vibration level to surrounding structures.



• - Application of elastic layers Elastic layers such as rubber mats/blocks can be installed under the transformer or under the inertial mass. When these elastic layers are enclosed in a fixed volume, they must shrink in size to function properly. Materials such as rubber do not allow for compression of their volume, making them unsuitable for this application. However, there are elastic materials such as Sylomer® that do shrink thanks to their microcellular structure with integrated air.



• - Acoustic encapsulation Acoustic encapsulation can be achieved by lining the transformer compartment with soundproofing materials. There are many different soundproofing materials available, such as mineral wool or the AMC acoustic absorber product line. However, proper ventilation is still important, so ductwork may be necessary. This ductwork can transmit sound if not properly insulated.
  
• It's important to select the right sound insulation materials. To do so, consider the sound insulation and sound attenuation curves of these insulation materials at a frequency twice the mains frequency.



• - Application of wall layers If it’s not possible to enclose the transformer, sound barriers can be installed between the transformer and the source of the vibrations. These insulation materials reduce sound transmission to surrounding areas.



• - Correct maintenance Proper maintenance of the transformer and its components (e.g. cooling fans and pumps) is essential to reduce noise and vibration. Misalignment or wear of moving parts can increase vibration and noise.

Standards

Most countries have standards that regulate sound and vibration levels in factories. ISO 1996-1:2003 specifies methods for measuring and evaluating ambient noise, and ISO 2631 regulates vibration levels for people. Compliance with these standards is important for the health of workers and protects industries from potential penalties.

INSULATION OF CONTROL CABINETS

You can find many machine control cabinets in a factory, insulating them is very important for several reasons, such as safety, correct functioning and service life of the electrical components.

• - Avoid damage: Vibrations can loosen screw connections or electrical components. Over time, this can lead to contact failures, sparks or short circuits.


• - Ensure proper functioning: Vibrations can also affect the accuracy of control cabinet measuring instruments and sensors. Protection systems such as differentials and circuit breakers can also be impaired during power outages due to vibrations.


• - Increased security risks: Vibrations can damage the electrical connections, which can become hot and thus increase the risk of fire. Vibrations can also damage cable insulation and other electrical components, increasing the risk of electric shock and short circuits.


• - Maintenance and service life: Frequent exposure to vibration can reduce electrical components' service life and increase maintenance frequency, resulting in unplanned downtime. A properly insulated control cabinet requires less preventative maintenance because the negative impact on connections and equipment is greatly reduced.

AMC has developed a specific mount for these applications: the Akustik WF + Sylomer is a vibration-isolating mount for mounting on vertical surfaces (wall mounting). Thanks to its special design, the vibration damper can be loaded in shear.

INSULATION OF BRIDGE CRANES

Overhead cranes are found in many factories, they are necessary for moving heavy loads easily and safely. Correct vibration isolation of overhead cranes is important for the following reasons:

• - Structural safety: The vibrations generated by the movement of overhead cranes can affect the factory's structure, especially sensitive elements such as ceilings, walls, or foundations. If left uncontrolled, these vibrations can cause material fatigue, which over time can weaken the factory structure and increase the risk of damage and collapse.


• - Accuracy of machines: Many factories have precision machinery that is highly sensitive to vibrations. Vibrations from overhead cranes can affect other areas of the factory and disrupt manufacturing processes, reducing the quality of the final product and machine performance.


• - Staff safety: Excessive vibration can cause health problems for workers (e.g., dizziness, fatigue, and hearing loss). It is important to minimise vibration to ensure a safe working environment.


• - Service life of the bridge crane: If the overhead crane is not properly insulated, the service life of its components (e.g., motor, cables, wheels, or metal structure) may be shortened. This means more frequent and costly maintenance.


• - Noise reduction: Vibrations generate unpleasant noise when transmitted to surrounding metal structures. High noise levels can negatively impact the work environment and reduce worker concentration and efficiency.


• - Performance optimization: Vibration isolation improves the control of the overhead crane. Movement is more precise, reducing errors and increasing the efficiency of material handling in the factory.

Below you can see the structure of an elastically mounted bridge crane:

INSULATION OF POWER GENERATORS

Power generators (also known as generators) are necessary in many factories, but they can also generate a lot of noise and vibration. Emergency power generators, which operate as a backup power source when the power grid fails, are particularly important.

Generators need to be isolated for the following reasons:

• - Reduction of vibrations transmitted to the structure and the floor: Generators generate a lot of vibration during operation due to the internal combustion engines and other moving components. Vibration dampers isolate these vibrations and prevent them from being transmitted to surrounding structures, thus preventing potential damage to structures and people.
• - Extending the service life: The constant vibrations lead to faster wear of the generator parts (e.g. screws, welds, ball bearings or anchoring systems).
• - Noise reduction: Vibrations also generate noise, which is transmitted through the fixed connections. Using vibration dampers greatly reduces this structural noise transmission.
• - Compliance with standards: In many cases, there are standards that require noise and vibration control of generators. The use of isolators can help comply with these standards.

To reduce the vibration intensity of the machine, a low natural frequency is required. To achieve this goal, a low-stiffness isolation system is necessary, e.g., flexible springs or rubber vibration dampers.

A heavy inertial mass can also be used, this consists of a heavy concrete or steel base which increases the mass and therefore stability of the generator. This additional mass allows the use of low stiffness vibration dampers, which generally provide higher deflections and lower the generator's natural frequencies, thus reducing the level of vibration to surrounding structures. The diesel tank is often used to increase the base mass, this method is very useful for large generators.






For more technical information, download the AMC document here:

AMC - Isolation of gensets (PDF)





INSULATION OF WATER AND GAS PIPES

Water and gas pipes are necessary installations in factories and industrial buildings. Typical elements flowing through these pipes are water (cold or hot), compressed air and natural gas.

The insulation of water and gas pipes is very important for the following reasons:

• - Reduction of vibrations: A factory's pipes transport liquids or gases at high pressure, which generates a lot of vibration. These vibrations are transmitted through the structures throughout the factory, affecting both the machinery and installations. Pipe support reduces vibration transmission and protects these structures and equipment from potential damage, extending their service life.


• - Avoiding structural damage: If not properly insulated, the vibrations can fatigue the material of pipe walls or clamps and even cause cracks. This can lead to water or gas leaks.


• - Acceptance of thermal expansion: The pipes that carry hot and cold fluids are subject to thermal expansion due to temperature differences. If a pipe is elastically supported, the elastic support can absorb the thermal expansion without damaging the pipe or other structures.


• - Improving energy efficiency: The elastic bearings also help maintain the temperature of the transported fluids and reduce thermal losses. This increases system efficiency and reduces energy consumption for heating and cooling the fluids.


• - Personnel protection: The vibration and noise from improperly insulated cables can affect workers' health (hearing damage and stress). Good insulation reduces these vibration and noise levels, creating a safer and more pleasant working environment.


• - Noise reduction: The elastic mounting reduces the transmission of noise caused by the fluids, pumps, valves and other components.


• - Easier maintenance: The use of elastic supports allows easy access to the pipes for maintenance and repairs because these systems are often modular and can be expanded frequently.



See below an example of a water pipe that is elastically mounted to absorb thermal expansion due to temperature differences:

	Akustik Pipe Omega Sylomer	More information
	Akustik Pipe Mount	More information
	EP+ Sylomer	More information
	Pipe Riser Isolation	More information







INSULATION OF INDUSTRIAL WASHING MACHINES

Industrial washing machines are often located in residential buildings, therefore noise problems with neighbours can arise. In addition to the actual running noise of a washing machine, disturbances such as the drum hitting during reversing, doors opening/closing or the noise of the water flowing in can lead to complaints.

Washing machines are a major source of vibration and noise because they require the rotation of an eccentric mass. In addition, the rotation frequency is usually quite low, meaning isolating these low-frequency vibrations is very complicated.

To isolate low frequencies, a natural frequency lower than the excitation frequency is needed. Therefore vibration dampers with a low stiffness are required, this however results in a very unstable installation. Since washing machines operate at all frequencies, all natural frequencies and natural vibration modes are reached.

To solve this, a solution can be to install an inertial base beneath the machines. This increases the mass, which means more energy is needed to move the total mass.

Below you can see some washing machines installed on an inertial base. The inertial base is mounted on an elastic Sylomer® layer.








Another option for elastic mounting of the inertial base is vibration dampers that are concreted into the inertial base. See an example below:

The heavier the mass of the inertial base, the better the vibration insulation.





INSULATION OF HEATING, VENTILATION AND AIR CONDITIONING (HVAC) SYSTEMS

HVAC machines are absolutely essential in offices and buildings where people work. They ensure the right room temperature is always maintained. Other applications aren't intended for people, but rather for products that need to be cooled.

HVAC equipment contains components such as fans, motors and compressors that generate vibration and noise. If they are not properly insulated vibration and noise can be transmitted, reducing component lifespan and compromising comfort.

Proper selection of vibration isolators is key to achieving good vibration isolation values in HVAC equipment. Installation of the vibration isolators is also critical to achieving optimal results.

Each application is different and has its own specific characteristics. In fact, there are many factors that can affect vibration transmission, such as the materials used in the structure (wood or concrete), the location of the machine (ground level or on the roof) and the type of room adjacent to the machine room (sensitive or insensitive to noise and vibration). While it's difficult to define all the problems that can arise, we have highlighted some common ones here and describe how to avoid them.

1.- RIGIDITY OF THE BASE PLATE WHEN USING SPRING ELEMENTS

The base plate should be rigid to avoid significant deformation when mounted on the vibration dampers.






This problem can be solved by reinforcing the base plate with structural profiles or by increasing the number of vibration dampers in the most heavily loaded zones.

2.- STIFFNESS OF THE BRACKETS

The stiffness of the clamps should be at least ten times that of the vibration dampers themselves. If the clamps are more flexible, they can reduce vibration isolation and, in extreme cases, damage the vibration dampers.

3.- SIZE OF THE CONTACT SURFACE UNDER AND ON THE VIBRATION DAMPERS

The vibration dampers should be installed so that they have a sufficiently large contact surface. This surface must also be smooth in all areas that come into contact with the isolator to avoid damage to the vibration dampers, particularly rubber surfaces.






4.- WIDTH OF THE SUPPORT PROFILES WHEN USING TSR VIBRATION DAMPERS

To ensure that the elastic properties of the vibration dampers meet expectations, the load must be distributed across the entire elastomer surface. If the contact surface is too small, steel profiles must be added. These steel profiles must be stiff enough to resist deformation under the load.






5.- DECOUPLING OF A STRONGLY VIBRATING PIPELINE

If the vibration level of a pipeline is high, it can be reduced by adding damping to the system. A good way to achieve this is to use an inertia plate connected to the vibration isolators (see below). This reduces the vibration energy and isolates the supported system. Sylomer bands can also be used around the pipe itself and also under the vibration dampers to reduce the transmission of high frequencies.








6.- INSTALLATION OF AIR CONDITIONING AND REFRIGERATING EQUIPMENT WITH A HIGH CENTER OF GRAVITY

Machines with a high center of gravity tend to be unstable during dynamic situations. Resolving this instability with rigid vibration dampers also reduces vibration isolation.

However, good stability and vibration isolation can be achieved if additional stabilisers are correctly implemented. It's important that the stabilisers only operate when dynamic loads are present, during static operation of the equipment they should have minimal force applied.






Another option is to use vibration dampers with compression limiters. Below you can see large fans mounted on vibration dampers which have an internal buffer built in, this limits the deflection.






If additional stability is required, spring elements with hydraulic damping can be a solution. Below you can see an earthquake-resistant spring element with hydraulic damping:








7.- ELASTIC CEILING SUSPENSION OF AIR CONDITIONING OR REFRIGERATING UNITS






When a machine is elastically suspended from the ceiling, it is important that only vertical loads are applied to the hangers. Horizontal loads, such as when the weight distribution is uneven, can potentially create acoustic bridges. Although some acoustic hangers have rubber parts to prevent metal-to-metal contact, it is recommended that the screw not come into contact with these rubber parts.








BOX-IN-BOX INSULATION OF OFFICES NEAR MACHINERY

Machinery in factories can generate a lot of impact and airborne noise. Therefore, it's recommended to properly insulate offices near these machines.

Impact sound is the sound emitted by a solid object when it contacts another object. Factory machinery typically can generate high levels of impact noise, particular large hydraulic presses for example.

Airborne sound is sound that propagates through the air. Typical sources of airborne sound are speech, television, radio, or traffic noise. When airborne sound encounters an obstacle, part of it is transmitted as solid-state sound, and another part is reflected (echo). The sound transmitted as solid-state sound is later converted back into airborne sound when these solid objects radiate it.

It can be important that both the impact and airborne sound levels are not transferred into the ceilings, walls, and floors of surrounding offices.

Typically, a light structure requires less energy to excite than a heavy structure. Therefore, adding mass is one of the most effective solutions for improving sound insulation, as it gives the structure more inertia.

The use of absorbent materials (e.g. mineral wool) provides additional mass and sound absorption (i.e. the conversion of sound into heat). This helps improve impact and airborne sound insulation.

The correct materials inside an office space should also be considered for optimal soundproofing. The floor covering for example is very important for impact sound insulation because it determines how quickly a falling object changes speed. However, this floor covering has a much smaller effect on airborne sound insulation. A very soft floor covering can be very effective against impact sound, but floor coverings that are too soft are impractical.

Decoupling of an office space to the surrounding factory can be achieved through the box-in-box design.







There are various materials available for building a box-in-box system. Depending on the requirements, wet solutions (e.g. concrete, mortar, etc.) or dry solutions are used.

Some solutions require more space for their installation, which means a loss of living space volume, while others are more compact.

The level of mass has a major influence on impact and airborne sound insulation. The effect of the box in box solution is generally greater in lighter structures than in heavy structures. When choosing the right products for a box-in-box solution, you should consider several factors:

• - Fastener type. Examples with different fastening types:







• Stored weight. It usually depends on a few elements:
  • - Plasterboard
  • - Insulating materials (e.g. mineral wool)
  • - Profiles and strips
• Available volume. There are products that require very little space, but others require much more:




Low-profile acoustic hangers (little space)	High-profile acoustic hangers (lots of space)





• Acoustic performance requirements. These depend on the country and building type. Acoustic hangers and other acoustic insulation products play an important role in acoustic results, but there are also other important factors:
  • Structure of the building
  • Correct installation. This factor can have a more important role than the product selection. If the installation is not done correctly, the following problems may occur:
    • - Acoustic bridges
    • - Overloaded acoustic hangers
    • - Sloping floors, walls or ceilings
    • - Unstable floating floors
    • - Breakage of the floating floor or plasterboard ceiling



• Acoustic hangers with springs offer the highest deflection. Their effect is particularly noticeable in large voids, because the acoustic insulation of ceilings with small voids is highly dependent on the stiffness of the air.
• With Sylomer solutions, a small void has a lesser effect on the acoustic results. When the void is large, solutions which combine Sylomer and springs achieve the best results.
• Rubber hangers are the most cost effective solution however the acoustic performance is lower when compared to Sylomer and spring options for small voids.


• Price
  • - Price is an important factor in all projects.
  • - Sometimes using a more expensive acoustic hanger can reduce the total number of hangers required, therefore reducing the overall cost and installation time.
  • - Typically, solutions with rubber hangers are the cheapest of the three options. The middle option would be a solution with Sylomer^®, but the price difference to the rubber solution is small. The most expensive solutions are the acoustic hangers with springs.




ISOLATION OF SENSITIVE MACHINES NEAR PRODUCTION MACHINES

The problem with vibration-prone machines in factories isn't always that they generate vibrations. There are machines that generate almost no vibration, but are sensitive to vibrations generated by other machines.

Examples of such machines are coordinate measuring machines (CMMs) or grinding machines.

Coordinate measuring machines (CMM)	Machine tools






In these cases, the goal is to protect these machines from vibrations, which we can call passive insulation.

To properly isolate these sensitive machines it is necessary to know the system’s key data, such as mass, center of gravity position, and main excitation frequency. It is also necessary to decide whether the machine will be mounted on elastic vibration dampers or whether elastic layers will be used underneath the machine.

Using this data, a calculation is performed. To achieve a good level of insulation, the following factors are most important:

• - Low natural frequency
• - Low stiffness of the vibration dampers
• - Low rubber hardness (if rubber is used)
• - Correct storage positions

To achieve a good level of isolation of the system, it is necessary that the natural frequency of the system is smaller and as far as possible from the excitation frequency.

A solution that works very well is the elastic mounting of the machine with an inertial mass:

1. Inertial mass made of concrete 2. Structural soil





INSULATION OF GOODS LIFTS

Goods elevators are not only necessary in factories, but also in other areas such as supermarkets.

If they aren't properly insulated, they transmit sound and vibrations to the structure, other machines, and also people. This can lead to long-term health problems if not correctly resolved.

There are several ways to insulate freight elevators. The principle behind all these solutions is to replace all rigid connections between the freight elevator and the structure with flexible connections. These solutions are briefly described below:

• - The base of the goods elevator should be placed on a resilient layer. Ensure that there are no acoustic bridges.
• - Connect the rails and the structure elastically.

You can learn more about freight elevator insulation in the following link:

View AMC Advice #19






INSULATION OF PASSENGER LIFTS

Passenger elevators are also a source of noise and vibration in factories and office buildings.

They have two main sources of vibration:

• - Motor: The elevator motor generates vibrations during operation. To isolate it, a base is required that can be elastically decoupled from the main structure. This requires knowing the weight and available bearing positions, as well as the force exerted by the suspension cables on the bearings.








• Rails: The rails transmit vibrations when the elevator moves. The rails can also be decoupled by adding an elastic element to their attachment points. In addition, the base of the rails can be supported to isolate all vibration transmission points.

You can learn more about passenger elevator insulation in the following link:

INSULATION OF FACTORY AND GARAGE DOORS

Factory and garage doors generate noise and vibration. If not properly insulated, they can be very disruptive to workers and neighbours.

When doors are rigidly connected to the building structure, they can transmit sound and vibrations to the structure. Therefore, it is recommended to decouple the doors from the structure with elastic means.

There are different methods to achieve this decoupling:

1) Decoupling the rails and the horizontal beam above

2) Decoupling the motor

A) The motor of vertically opening doors is usually fixed to the ceiling. It can be suspended from the ceiling using SRS + Sylomer®. Spring acoustic hangers can be decoupled.