Seismic Restraint

Seismic restraints are categorised in three groups; seismic isolators, seismic snubbers and seismic bracing. Based on the vibration isolation component seismic isolators can be rubber or spring type. Seismic snubbers are relatively simple components that come in various types and sizes. Acrefine offers steel wire rope based seismic bracing products, which have very versatile use. All of these products are designed to limit the non-structural component movement during earthquakes or high winds.

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Seismic Restraint

Earthquakes and high winds can cause significant damage in many different ways to structures of all types. However, the damage that natural disasters can cause to electrical and mechanical systems in buildings can be especially extensive.

This is particularly true in the case of mechanical systems that have not been properly restrained and held in position. If equipment is knocked off its supporting structure because of building movement, both property and lives can be threatened. When bearing this in mind, it’s clear that the expense of seismic restraining such equipment properly is relatively insignificant. Especially when compared with the cost of repairing or replacing damaged equipment and system downtime due to the seismic event.

Here at Acrefine, we supply seismic restraint systems that limit equipment movement, keeping it safe during seismic events. When our systems are used correctly, risks will be significantly reduced, and long-term costs of repairing damaged equipment will be minimised.

An Overview of Seismic Restraints

There are three different categories of seismic restraints – seismic bracing, seismic isolators, and seismic snubbers. All perform the same task – of restraining equipment during seismic events. However, they achieve this goal in different ways.

Seismically restrained vibration isolators may be either spring or rubber types. Meanwhile, a seismic snubber is a fairly simple component available in several sizes and types. Here at Acrefine, we also offer seismic bracing products based on a steel wire rope construction. These are very versatile. We design our products to limit the movement of non-structural components during high winds or earthquakes.

What are Seismic Isolators?

A Seismic Isolator, or more precisely Seismically Restrained Vibration Isolator, may either be a rubber or spring type. It eliminates any need for a Seismic Snubber as it uses a ductile steel housing which provides all directional restraint. Isolators with a spring and top plate or stud are most commonly used.

When restraining large equipment like cooling towers, generators, or chillers, a seismic isolator with a top plate should be used. That is because these isolators are capable of handling extremely heavy weights and provide optimal vibration isolation. They’re also more suitable for resisting large seismic forces. Fans, pumps, and other small equipment are more suitable to be installed with stud isolators. These have a more limited load capacity, but offer good vibration isolation and excellent seismic restraint performance.

A seismic rubber isolator is needed for applications which require high-frequency vibration isolation. They can also be used in areas that are less sensitive to vibration or noise.

An Overview of Seismic Isolators with Top Plates

These spring type seismic isolators achieve vibration isolation by using springs sandwiched between bottom and top plates. Their steel housing gives protection from earthquakes by resisting the seismic forces in every direction. These isolators’ most distinctive feature is a top plate. This allows support beams or equipment bases to be easily placed in position, hence act as a seismic restraint.

For low-frequency vibrations, standard springs that have 25mm, 50mm, or 75mm deflections should be used. It’s also possible to have several spring layouts in one housing so extremely heavy equipment can be isolated. Diesel generators, cooling towers, chillers, transformers and similar equipment are used with these isolators.

What are Seismic Isolators with a Single Stud?

These spring type seismic isolators achieve vibration isolation by using one spring, encapsulated in a ductile steel housing. This gives optimal protection from earthquakes due to its ability to resist seismic forces in every direction. These isolators have a distinctive feature – the single stud which allows the support or equipment based to be directly installed. Thus, there’s no need for any extra nuts or bolts. And you have the seismic restraint you need.

For combatting low-frequency vibrations, standard springs with 25mm, 50mm, or 75mm deflections are needed. The isolator’s load capacity will be limited by the spring’s capacity, and therefore, these products suit medium or small equipment. Small chillers, pumps, and fans are all suitable for use with a single stud isolator.

When are Seismic Isolators with Rubber Mounts used?

A seismic rubber isolator limits equipment movement in every direction caused as a result of seismic events. There is a steel housing around the mount, and the equipment will be directly bolted into the embedded steel insert. As a result, all-directional seismic restraint is provided for both vertical and lateral forces.

The rubber elements used in this type of seismic isolator are categorised by Shore A Hardness. This corresponds to their varying load ranges. Medium and small mount sizes have three groups, namely 40, 50 and 60 Shore A hardness. Their load capacity is up to 900kg.

What are Seismic Snubbers?

A seismic snubber is the most commonly-used protection from earthquake damage for MEP equipment. Seismic snubbers are available in several different sizes and shapes. However, all have a load resisting surface with a special protective rubber layer.

Commonly, these items are used together with a vibration isolation product such as spring mounts or pads. If there are no concerns about vibration isolation, a seismic snubber can be used alone as a seismic restraint. It is capable of resisting seismic forces either in multiple or single directions.

How does Seismic Bracing work?

There are two distinct types of seismic bracing product – steel wire rope braces and rigid braces. Single rigid braces are capable of working either under compression loading or tension. They’re ideal for use with sprinkler and fire fighting piping. Nevertheless, steel wire rope braces are a cost-effective solution despite the fact they’re only capable of resisting tension loads. That is why two braces are required at a single seismic restraint point.

Rigid bracing is only suitable for use if vibration isolation won’t be necessary. The only available alternative in such cases will be steel wire ropes. They’re speedy to install while also offering excellent flexibility. Most commonly, seismic bracing is used when protecting suspended MEP services like ducts, cable trays and pipes. It’s also frequently used for suspended equipment like AHU, FCU, and fans.

Here at Acrefine, we supply an extensive range of high-quality seismic restraint products to suit a broad spectrum of needs. Whether you need seismic bracing products, seismic snubbers, or seismic isolators, we have the solution you’re looking for.