Tips for Vibration Isolation

 

The main concern for all engineers is to ensure that their machine or the appliance runs as efficiently as possible - to that end, vibration isolation systems are usually top of the list. 

Every piece of machinery, from the smallest laptop to a huge band saw, vibrates. Obviously, the amplitude of these vibrations varies significantly. These vibrations can create friction, imbalances, excessive noise and even failure in some mechanical devices. For heavy industrial applications, these vibrations can pose a significant risk to productivity and safety.

Causes of Abnormal Vibrations

Before we can tackle minimising these vibrations, we need to understand the cause. These can vary and can result from combined factors. These factors generally include:

• Wear

For example, a roller bearing can become pitted, a drive belt can break down or gears could chip. A result is a machine that is going to vibrate. Vibrations caused by additional factors can also result in wear and can go on to cause premature failure. Excessive operational stresses can develop that go on to change the balance condition, or even thermal expansion can cause misalignment which can cause wear. 

 

• Loose Connections

It’s common for bolts and screws to become loose over time - this is why regular machine or equipment maintenance is vital. Bearings can quite often loosen after severe wear, or if they’re not tightened to their mounts, causing vibrations to damage components. Other causes can be cracked welds, piping or ductwork problems – the list is very long. More often than not, loose connections happen when rotating components have not been fitted correctly.

• Misalignment

For example, if the rotating shafts are out of line, vibrations can occur. When a shaft and motor are not parallel, angular misalignment occurs. Minor vibrations can result, but large angular differences are another matter entirely and can cause significant damage to the machine. Misalignment can happen during assembly or over time because of thermal expansion.

• Imbalance

With components that rotate, the machine’s axis must be balanced. Picture a washing machine when the weight of laundry is not evened out. An imbalanced axis creates a centrifugal force, causing the machine to vibrate. As machine speed increases, so does the impact of the imbalance. In some applications, the imbalance can be caused by manufacturing defects such as machining errors, or maintenance issues such as dirty fan blades. In addition to machine vibrations, the imbalance can significantly reduce bearing life.

Industrial Machines and Isolating Vibrations

The most common and cost-effective methods for controlling vibrations in machines or equipment is a vibration isolation system - specifically, special mounts which are designed to absorb the vibrations. 

 

• What to Consider

Think about the weight, size, and centre of gravity of the machine or equipment that you want to isolate. Size – or shape—dictates the type of attachment and space available for the chosen vibration isolator. Centre of gravity matters, because isolators of different load capacities might be required at different points on the machine, depending on the weight distribution.

You should also determine what types of dynamic disturbances need to be isolated. For instance, random vibration tests are common for automotive and transport applications. Shipping containers, too, may need a good deal of vibration testing. Shock tests are important, depending on the equipment. They’re especially beneficial in helping to determine if a product can survive a crash or is dropped to the ground.

The environment also matters. If the isolator will be subjected to grease or UV light, then you will need a material that can stand up to these factors. Temperature is extremely important, as it can change the performance of the isolator.

Different vibration isolators used in various applications tend to fall into the following categories:

• Rubber mounts; typically used in engines and generators.
• Oil; typically used in engines and hydraulic systems. 
• Foam and polyurethane; typically used in automotive applications, building and construction.
• Spring mounts; typically used in heavy industrial machinery such as boilers, fans, pumps and compressors.