Mechanical and electrical equipment can generate a lot of vibration and noise, so having effective isolators in place is essential. Acoustic hangers are a standard solution, but they often don’t perform in the way intended, leaving you scratching your head when noise problems persist. To help you out of this dilemma, Jordi Femenia, sales manager and engineer at vibration control specialist Mason UK, outlines three of the most common problems with acoustic hangers.
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Spring hangers are used to isolate low-frequency noise from sources such as footfalls and mechanical vibration.
However, a non-specialist would fail to spot a poorly designed hanger or might match a good hanger to the wrong application.
With that in mind, here are some common problems to watch out for.
Insufficient misalignment capability
A properly engineered acoustic hanger should allow for approximately 30 degrees of sway in the drop rod.
As you can see in the image here, without that misalignment capability, you risk the rod making contact with the bracket and creating an acoustic bridge.
This is a must for mechanical and electrical services, where it is commonly the case that the drop rod is not in the centre.
Lack of deflection
People sometimes mistakenly think that having a very strong spring will deliver a better performance.
The opposite is the case. It would be a bit like replacing the shock absorbers on a Ford Fiesta with those that are designed for a Land Rover.
Let’s say you select a spring that can handle 100kg, but in your application, the actual load will only be 20kg.
A novice might think that by over-engineering, you guarantee a result when you are in fact making things worse.
If the spring is too strong you get no deflection. If you have no deflection, then you have no isolation.
Incorrect slenderness ratio
In architecture, the slenderness ratio refers to the ratio between the height and width of the building.
In structural engineering, it is used to calculate the propensity of a column to buckle.
When we are talking about acoustic hangers, slenderness refers to the ratio between the height and diameter of the coil.
If this is too high, then the spring is unstable and will potentially deform. It is therefore essential that the springs have the correct geometry.
A properly designed acoustic hanger will have design features that serve a purpose. For example, you might notice that Mason’s hangers look quite chunky.
This is to provide an effective misalignment capability and the correct slenderness ratio. Once you have a good hanger, you also need to match it to the application correctly.
Even a well-designed hanger will fail to isolate correctly if there is a lack of deflection, so a responsible manufacturer or installer should be aware of this factor, too and not simply sell a hanger without paying attention to the load it will bear.
Watching out for these three common problems should improve your chances of achieving the right isolation for mechanical and electrical equipment, but if you are in doubt, contact a specialist.
Mason UK provides anti-vibration solutions for mechanical and electrical equipment. To view the full range of spring hangers, visit mason-uk.co.uk
See more about acoustics on Skill Builder