3 min read

Inertia bases are simple devices that offer effective results. However, there is some contention as to whether they are necessary in the modern day. 25 years ago, most pumps did not have Variable Speed Drives (VSDs), and as a result, inertia bases were essential in preventing vibration, noise and instability from occurring as pumps would suddenly go from stagnant, to fully operating – causing jarring noise and violent vibration in the pump’s surrounding area. This was especially problematic in raised plantrooms. 

With VSDs, however, pumps can gradually power up and power down, leading some to believe that inertia bases are no longer necessary, as there is no longer a sudden and drastic change in system torque. 

What Is an Inertia Base? 

Inertia bases are housings used to support and safeguard the machinery in an HVAC system, and can accommodate a variety of equipment depending on specification and design. Inertia bases may contain only the system’s pumps, and can also include the system’s chillers and ancillaries. 

The inertia base also protects the pump-to-pipe joints, reducing the starting torque transferring to the pipes. 

Inertia bases are available in two primary configurations: standard spring and seismic spring.  

Standard Isolators vs Seismic Isolators 

Vibration Isolators reduce transfer of vibration from the pump to the underlying structure,

thus reducing noise and vibration in the structure.

Inertia bases can be isolated using several types of isolators: elastomeric mounts, open springs, and housed springs. A subset of housed springs is seismically rated springs.

The only difference between standard springs and seismic springs is that seismic springs are rated to provide support in all directions, should there be an earthquake. Seismic springs are worth considering as it is becoming a lot more common for seismic rating to be required by AS 1170. 

Even if your project does not strictly require seismic springs, it doesn’t hurt to know that your pumpset will remain in position during an earthquake!   

What does an inertia base prevent? 

In pumping systems, the main vibrating force is created by the imbalanced forces on the rotating assembly (the impeller shaft assembly, motor rotor assembly and the coupling assembly). An additional disturbing force occurs due to the changing momentum of the pumped liquid as operating conditions change. This causes unpleasant and noisy vibrations coming from the pump. 

When paired with a correctly designed acoustic isolation system, transfer of vibrations to the structure below and above are minimised, however, the vibration energy remains at the pump. Theaddition of an inertia base increases the pumpset’s mass, therefore reducing the residual vibrations and movement at the pump set itself. Inertia bases are highly effective vibration and noise reducers that aid the stability and low-noise operation of all the machinery that it supports.

By lowering the machinery’s centre of gravity, increasing overall pumping mass and strongly holding various components in place, pump vibration and noise is significantly reduced, increasing system efficiency and reliability. 

The inertia base’s primary weapon against vibration and noise is to make the equipment’s mass exceed the mass of any disturbing vibrating forces created within the system as it operates. 

Do I still need an inertia base when I have a VSD? 

If you are working with a raised plantroom in a high rise building, inertia bases are definitely worth consideration, as regulatory bodies have strict restrictions on noise levels, and raised plantrooms are more conducive to vibrating forces. 

As Masterflow has assured clients for years now, inertia bases are often not necessary in basement plantrooms, however, you may have a basement plantroom that includes noise restrictions. If you are unsure as to whether your basement plantroom requires an inertia base, reach out to Masterflow and we’ll be happy to help. 

While VSDs are removing the urgent need for the use of inertia bases, there is always the risk that a system will be suddenly switched on or off due to human error or an operational choice. Regardless, there is still a noticeable difference in noise level when a raised plantroom without an inertia base is compared to a raised plantroom with one. 

As time goes on, end users are becoming more and more interested in low-noise environments, making it a favourable decision to use inertia bases if you are interested in optimising the end user experience whilst minimising vibration. 

Masterflow Inertia Bases

Masterflow’s inertia base plates are designed to comply with Natspec requirements. Natspec, also known as the National Building Association, is a nonprofit organisation with the objective of improving the construction quality and productivity of the built environment through leadership of information. 

Their requirements for inertia bases state that the mass of the baseplate must be equal to the mass of the pump and driver rotating element, and a spring deflection of 25mm. We recommend using a minimum concrete density of 2400kg/m3.

Typically, inertia bases are filled with concrete on-site by the builder. Upon request and in prefabrication jobs, Masterflow incorporates steel reinforcement mesh and outriggers as standard. Crucially, Masterflow performs alignment checks before pump sets are dispatched, and performed again after installation is complete. In accordance with our principle ‘better by degrees,’ Masterflow ensures that our pumps are free from alignment issues. 

If you’re in need of an inertia base for an upcoming project, contact Masterflow for an inertia base tailored to your needs.