Heron Tower, London
Key Details
Acoustic consultant: Arup Acoustics
Acoustic enclosure: Powerplus Engineering Ltd, Colchester
Generator operating speed: 1500 rpm
Mountings: OS75/2000 Open Spring Mountings, MD/3 Silicone Fluid Viscous Dampers and Studflex Rubber Pads
Specified static deflection: Greater than 50mm
Achieved static deflection: 56.7mm
Isolator natural frequency: 2.09Hz
Calculated vertical isolation efficiency: 99.29%
Industry: Industrial solutions
The Building
Heron Tower is a 46-storey commercial skyscraper in the heart of London’s financial district, close to Liverpool Street Station. Built between 2007 and 2011, it combines 36 floors of flexible office space with restaurants and bars at the top and a 70,000-litre aquarium in the ground-floor lobby. With so many different uses under one roof, controlling noise and vibration from the building’s plant was a priority.
The Challenge
Arup Acoustics’ specification required spring-type isolators with a static deflection greater than 50mm, fitted with ancillary dampers. The dampers were needed to control excessive movement as each generator passes through the resonant frequency of its mounting system, which happens on every start-up and shutdown. The generators needed to run without transmitting vibration into the building, which houses offices, restaurants and an aquarium.
The Solution
We supplied a two-stage isolation system. In the first stage, each generating set sits on Open Spring Mountings and MD/3 Silicone Fluid Viscous Dampers, mounted on a shared intermediate steel support frame. In the second stage, the frame is isolated from the main structure by Studflex Rubber Pads in a mix of sizes and rubber compounds.
Ten OS75/2000 Open Spring Mountings (75mm deflection at 2000kg) each carry 1,511.6kg. This gives 56.7mm of deflection per mounting, exceeding the 50mm minimum, and an isolator natural frequency of 2.09Hz. The result is a calculated vertical isolation efficiency of 99.29% at 1500 rpm.
The whole system is covered by an acoustic enclosure designed by Powerplus Engineering Ltd of Colchester, a company we have worked with closely on a number of projects.
Explore Our Industrial Isolation Solutions
Need to isolate a generator or other heavy plant in your building? Contact Christie & Grey to discuss industrial vibration isolation solutions, including open spring mountings and silicone fluid dampers, tailored to your installation and acoustic specification.
FAQs
Why use a two-stage isolation system?
Two stages separate the machine from an intermediate frame, and the frame from the building structure. This gives high isolation efficiency and lets each type of isolator do a different job: springs handle the low-frequency vibration from the generators, while rubber pads help block higher-frequency vibration and structure-borne noise.
Why are dampers fitted alongside the springs?
Soft springs allow large movements when a machine passes through the resonant frequency of its mounting system during start-up and shutdown. Viscous dampers limit that movement without significantly reducing isolation at running speed.
What does 99.29% vertical isolation efficiency mean?
It means roughly 99.29% of the vertical vibration force generated at 1500 rpm is prevented from being transmitted to the supporting structure. This is a calculated figure based on the mounting system’s natural frequency and the generator’s operating speed.
Can this approach be used for other generators or building plant?
Yes. Open spring mountings and silicone fluid dampers can be specified for a wide range of generators and other heavy plant. Each project is assessed individually, taking into account the weight of the equipment, its operating speed and the project’s acoustic specification.
