Three common oversights in the installation of antivibration mounts
When it comes to isolating and attenuating vibration and noise, the general consensus is that correct specification delivers optimized performance. But is that enough? Or are we compromising performance during the installation process?
Here, Geert Leustermans, Market Manager for General Industry and Distribution at Trelleborg’s Industrial Antivibration Solutions operation, considers three common oversights during the installation of antivibration mounts.
Best practice for the specification of antivibration mounts is well documented. Product choice has never been more abundant, and leading manufacturers are digitising the product selection process with convenient smart phone apps. Together, this means that facilities engineers are well equipped to make informed choices when it comes to reducing harmful vibration in moving machinery.
Manufacturers of antivibration technology continue to invest heavily in developing solutions which deliver optimized performance throughout the product lifetime. In order to reap these benefits, however, it is vital that engineers avoid a number of installation pitfalls which may impact negatively upon performance.
These include poorly installed mounts, vibration short circuits and any contributing parasitic stiffness. Let’s look at each of these in more detail:
Poorly installed mounts
Before beginning the installation process, ensure all surfaces are clean, dry and free from debris. To maintain correct alignment when lowered on to the mounts and also to prevent damage to the asset or individual during the installation, the equipment being mounted should be lifted carefully onto sufficient supports.
Whilst it may be tempting to lift the equipment just enough, always consider how much space is required to freely access the fixing points. Where possible, space should be created to allow installation engineers free access to these areas. This is essential to facilitate a more effective mount installation.
Once the area has been correctly prepared, the process for installing most antivibration mounts is generally uncomplicated, but due care and attention must be given to the accuracy and positioning of the fixing points, as well as the orientation of the mount and its components.
The top and bottom fixing points should be parallel to one another and horizontal before they are fixed into place. When tightening each fixing point, avoid rotating the top of the mount relative to its base – the orientation of the entire mount, in plan view, should be either longitudinal or lateral rather than an abstract angle.
Vibration short circuits
Like many other systems, the successful installation of resilient mounts will be dependent on minimizing weaknesses, especially when the machine is in motion. Many of these weaknesses occur during the installation process and are preventable. If left unattended, the performance of the antivibration mount will be hindered.
These ‘short circuit’ issues can be attributed to two main factors – lack of due diligence and insufficient planning. Things to consider under lack of care would be that the transit chocks have been removed from the mount prior to installation, the guards at each end have been unlocked and that no tools become jammed beneath the set once the equipment is lowered onto its new mount. These may seem like obvious points to check, but they are common occurrences and will have a profound impact on the performance of your mount investment.
Lack of planning can lead to numerous installation challenges, including the use of incorrect assembly bolts or the poor positioning of floor plates. If the assembly bolts are too long, they may come into contact when the mounts are loaded or when the machine is switched on and starts to move.
Likewise, when the set is in motion, the floor plates may meet which will impact how much vibration and noise can be isolated.
Contributing parasitic stiffness
More often than not the image of plant sitting atop antivibration “springs” is not an accurate reflection of real world applications. Almost all machinery will have other connections such as exhaust outlets, electrical cables, water inlet or outlet pipes, hydraulic piping, compressed air tubing and earthing straps.
Each additional connection contributes a level of stiffness to the equipment and will have a parasitic effect on the performance of the mounting system. Particular attention must be given to any hydraulic hoses and exhaust bellows, which are the worst culprits when it comes to altering the performance of an antivibration mount, due to their high levels of tensile strength and the fact that they are connected furthest away from the centre of gravity.
Machinery with multiple additional connections can still be successfully mounted onto an antivibration mount, but changes will need to be made. Each additional connecting point will need to be replaced with a flexible alternative, ensuring that the specified material has a multi-directional stiffness which is significantly lower than the antivibration mounts selected. This re-specification process will also ensure the mount can correctly isolate excessive vibration.
Optimizing the performance of any antivibration solution requires best practice in both specification and installation, but the benefits do not end there. Following installation best practice can improve product longevity and reduce the likelihood of unplanned mount maintenance and machine downtime, which of course translates to a more profitable application.
For more information on the specification and installation of antivibration mounts and other antivibration solutions, visit http://www.trelleborg.com.