What Factors Affect Cost in Seismic Springs?

Are you looking for seismic springs to reduce pump vibrations, but have no idea what they’re going to cost you?

They’re a small product but have a massive impact on the noise levels of your plantroom, so it’s understandable that you may be confused about the pricing scale.

If you’re not quite sure what seismic springs are all about, we suggest you read “How Seismic Springs Work” to get the most out of this article.

The cost of seismic springs isn’t just black and white – a variety of factors can lever the price up or down. We’ve been supplying seismic springs to the HVAC industry for over 20 years, and have documented 5 main factors as being influential over their cost:

1. Weight
2. Quantity
3. Deflection
4. Retrofitting
5. Standard vs Seismic

At the conclusion of this article, you will feel confident discussing the different qualities of seismic springs with a vendor while understanding how cost moves up or down depending on your choices.

WEIGHT

The heavier the pumpset, the larger the individual spring mounts. Bigger spring mounts cost more, as they’re made for heavier loads and therefore have to be stronger than smaller ones. To get a more exact idea of price, you’ll have to contact a contractor to discuss what size springs the weight of your pumpset will require.

QUANTITY

The obvious one – the more springs you need, the higher your overall spring cost is going to be. Bigger pieces of equipment, such as condenser water and chilled water pumpsets larger than 110kW, will require more point loads and therefore more springs than smaller mechanical equipment.

DEFLECTION

Deflection to a certain mm will often be specified by the consultant. The higher the deflection, the more expensive the seismic spring.

Note that on the ground floor, 25mm deflection will always suffice. On a raised floor, a heavier equipment slab (such as a chiller) may be in the middle of a room and be 10m between support columns, therefore having the potential to bend or “deflect” by another 25mm or so. A consultant might specify 50mm deflection to allow for this potential bend. Springs with high deflection capacity will always be bigger and therefore more expensive than those with the normal 25mm deflection.

The reason for this difference in price is because springs have the same operating height as their diameter. The ratio between loaded height and diameter needs to be 1:1 to make them laterally very stiff. For example, a requirement for 50mm deflection would need a spring that is 130mm in diameter, whereas a 25mm deflection spring would need a far smaller diameter. The general size difference between these two deflections makes for very different prices, with larger diameters resulting in higher prices.

RETROFITTING

Retrofitting is a technique used to strengthen existing structures to ready them for excessive motion. In this case, jobs where seismic springs have not been specified or supplied may require them down the track, meaning we have to go to site and rebuild the existing springs to a seismic quality.

When standard springs have been supplied originally, the outrigger or base is usually smaller to suit the smaller spring brackets. this makes the retrofit more difficult, as fitting bigger springs and their brackets to a too-small base makes the job more difficult.

Having seismic springs retrofitted is inconvenient and therefore very expensive, so it’s advisable to make suitable enquiries with a head contractor so he may review the specifications carefully and determine whether the site actually requires seismic restraints. Retrofitting may only be necessary if your plantroom is in a highly earthquake-prone area.

Here’s what retrofitting looks like:

In this case, the customer initially required 50mm deflection, open-cup springs. These were sent to site with the pumps and mounted accordingly. Later on, the customer preferred 25mm deflection seismic springs. If we had not ordered packers to insert under the seismic brackets and make the new springs align with the original base, the customer would have been forced to redo all the pipework to accommodate lower connections.

If seismic events occur and the requirements for damage control have not been met with the appropriate equipment, enormous added expenses will be needed to repair damaged pipes and water infrastructure. Seismic risk must be assed and relevant construction codes adhered to by the consultant to reduce potential future damages and costs.

STANDARD VS SEISMIC

Standard spring arrangements decrease your overall spring cost, whereas seismic springs will be priced higher because of the extra protection they offer. Our standard option consists of a spring housed in a rubber floor-mounted retainer and a top retainer, which includes an adjusting bolt. These springs have no additional mounted bracketing that anchors the spring, which the seismic spring does include.

Seismic restraints aren’t required for all pumps on all sites. You may get the required vibration control from standard springs due to the size or weight of your equipment. Either way, you should speak to a professional contractor before confirming this decision.

Where flexible mounting devices (such as spring mounts) are used, they should be fitted with restraining devices to limit the horizontal and vertical motions, inhibit the development of resonance in the flexible mounting system and prevent overturning.

Though pricing is hard to determine when there are so many factors at play, we hope this guide has given you an idea of which characteristics will affect the cost of your seismic springs.

Got more questions? Let us know here.