In general, these helipads are designed for regional referral hospitals and usually serve a large population. The main objective is to allow a helicopter to pick up a critically ill patient and land at the hospital within 15 to 30 minutes of flight time. This extends the effective coverage radius to rural or hard-to-reach areas located many kilometres away. They can also be used for inter-hospital transfers, in which patients are generally transferred from smaller medical centres to hospitals with a higher level of technological specialisation.
Hospital helipads must be isolated using anti-vibration mounts, especially when they are built as elevated structures on the roof of the hospital building itself.
Helicopter landing and take-off generate extremely powerful low-frequency vibrations (caused by the helicopter blades) that can travel through the hospital's concrete or steel structure. In addition, aircraft landing and take-off also generate dynamic loads that must be isolated.
Regulations applicable to hospitals concerning noise and vibration isolation require these helipads to be properly isolated.
- To protect medical equipment in operating theatres, MRI and CT rooms, laboratories, etc.
- To safeguard patient well-being. Hospitals require a low-noise, vibration-free environment to support patient rest and recovery.
- To ensure the structural safety of the building. The continuous dynamic impact of aircraft causes long-term fatigue in the building's construction materials.
How do AMC FZH2M+Sylomer® anti-vibration mounts work?
To solve this problem, a structure known as a "floating slab" is created and isolated using anti-vibration mounts. The helipad therefore does not rest directly on the hospital structure; instead, an intermediate isolation and damping stage is installed.
This intermediate stage is created by installing mounts that must meet specific dimensional requirements and a target natural frequency, normally low, established by means of an acoustic measurement.
The AMC FZH2M+Sylomer® mount is one of the available solutions which, following the appropriate calculation and correct sizing, enables optimum isolation of these helipads. These mounts are integrated into the slab itself and consist of a metal housing containing springs, a Sylomer® base and a threaded lifting spindle.
The purpose of this anti-vibration system is to decouple the floating slab by means of height-adjustable mounts. The AMC FZH2M+Sylomer® mount can achieve a very low natural frequency of approximately 4-5 Hz and provides a highly effective solution across the entire frequency range. The internal springs isolate low excitation frequencies, while the Sylomer® base isolates medium-to-high frequencies. The inclusion of this Sylomer® base offers a major advantage over other solutions without it, where vibration can be transmitted through the spring coil itself at medium-to-high frequencies.
Installation steps for AMC FZH2M+Sylomer® mounts
The following steps are carried out during installation:
- A resilient perimeter strip is installed around the slab to prevent noise and vibration transmission through the slab edge. AMC uses 25 mm thick Sylomer® SR11 for this resilient strip.
- First, a plastic release sheet (polyethylene) is laid over the base floor.
- The mounts are distributed at a previously calculated spacing (this distance will vary depending on the slab thickness, stiffness and supported load).
- The reinforcement mesh is installed over the side lugs of the mounts, ensuring that no acoustic bridges are created around the slab perimeter, where the acoustic strip has previously been installed.
- The helipad slab concrete is poured around and over the housings, leaving the screws accessible.
- Once the concrete has cured, the plugs are removed from the AMC FZH2M+Sylomer® mounts to access the thread into which the levelling screw is inserted.
- The mounts are levelled according to a predefined pattern, and the slab level is checked using a laser. An air cavity is created beneath the raised slab.
The final result is a well-isolated floating slab that prevents noise and vibration from being transmitted to the hospital through the installation of approximately 300-350 AMC FZH2M+Sylomer® mounts, based on a hypothetical helipad area of approximately 350 m².
United Kingdom
