How to Choose a Seismic Isolator Manufacturer: An Owner's Checklist

Why Manufacturer Selection Is an Owner's Decision

On most construction packages, the owner never sees the supplier list. Concrete, rebar, glazing: the contractor buys, the site engineer checks, life goes on. Seismic isolators are different. The bearings under your building are the single component your entire seismic strategy depends on, they are nearly impossible to swap out cheaply once the structure is up, and the price difference between bidders can reach 30 to 40 percent for what looks, on paper, like the same product.

It usually is not the same product. Two isolators with identical stiffness values on a datasheet can behave very differently after 200 cycles of loading, ten years of aging, or one real earthquake. The difference sits in things a datasheet does not show: rubber compounding, curing discipline, bonding quality, and above all, how honestly the manufacturer's test results were produced.

We work as an independent advisor on the owner's side of isolation projects, which means we sit through manufacturer evaluations regularly. This article is the checklist we wish every owner had before the first quotation arrives. It covers seismic isolator manufacturers generally, whether you are buying lead rubber bearings (LRB), curved surface sliders / friction pendulum bearings (FPS), or high-damping rubber bearings (HDRB).

1. Test Certification: The Non-Negotiable Filter

Start here, because it eliminates unqualified bidders fastest. A serious manufacturer can document type testing under at least one of the major frameworks:

• EN 15129 (Europe): The European standard for anti-seismic devices, mandatory for CE marking since it came into force in 2010. Type tests must be witnessed and certified by a Notified Body, an accredited third party, not the manufacturer's own lab. Ask to see the CE certificate of conformity and check that it covers the device type and size range you are actually buying, not just one small prototype from years ago.
• ASCE 7, Chapter 17 (USA): Section 17.8 requires prototype tests on two full-size specimens of each predominant type and size of isolator used in the design. These are project-specific tests under defined load and displacement sequences. If your project follows ASCE 7 or a derived code, the manufacturer must be able to pass these tests for your bearing sizes, and prior test records for similar units are the best evidence they can.
• ISO 22762: The international standard for elastomeric seismic-protection isolators, widely referenced for rubber bearing materials, tolerances, and test methods, particularly in Asian markets.

Three questions separate real certification from marketing:

• Who ran the test? Results from an independent, accredited laboratory or a Notified Body carry weight. Results from the manufacturer's in-house rig, unwitnessed, are a starting point at best.
• What was tested? A certificate for a 500 kN bearing says little about the 3,000 kN unit your hospital needs. Certification is type- and size-range specific.
• Will they test again for your project? Prototype testing of your actual bearing design, plus routine production testing of delivered units, should be priced into the offer, not treated as an exotic extra. A manufacturer who resists project-specific testing is telling you something.

2. Project References That Survive a Phone Call

Every manufacturer brochure lists landmark projects. The useful reference check goes further:

• Comparable projects: Same bearing type, similar load range, similar building class. A supplier with fifty bridge projects and zero hospitals is not automatically wrong for your hospital, but the burden of proof rises.
• Named engineers, not logos: Ask for the structural engineer of record on two or three reference projects and call them. Ten minutes on delivery punctuality, documentation quality, and how the manufacturer handled a non-conforming unit tells you more than any brochure.
• Post-earthquake performance: The strongest reference a manufacturer can hold is a building that went through a significant earthquake on their bearings and stayed in service. Ask directly whether any of their installed projects have been through a major event, and what inspection afterwards found.
• Years in isolation specifically: Rubber bearing manufacturing for bridges is related but not identical to seismic isolation. Look for a track record in seismic devices, not just elastomeric products in general.

3. Engineering Support During Design

Isolator procurement is not a commodity purchase where design finishes first and buying starts after. Bearing properties (effective stiffness, damping, displacement capacity) feed directly into the structural analysis, so the manufacturer's engineers and your design team will iterate together. Evaluate:

• Responsiveness at tender stage: If preliminary property sets and technical answers take three weeks now, imagine the pace once they have your deposit.
• Property modification transparency: Modern codes require designers to account for how bearing properties vary with aging, temperature, and manufacturing tolerance (upper and lower bound properties, often via lambda factors). A competent manufacturer states these ranges openly; a weak one only publishes nominal values.
• Willingness to say no: Good suppliers push back when a requested bearing sits outside their comfortable production envelope. The ones who accept every specification without discussion are the ones whose bearings fail prototype tests six months later, with your schedule absorbing the delay.

4. Lead Time and Production Capacity

Isolators sit on the critical path more often than owners expect. Foundations cannot be closed out without them, and a bearing delay stops the whole structure. Pin down:

• Realistic delivery, in writing: Depending on manufacturer backlog, bearing size, and testing scope, delivery commonly runs several months from order to site, and prototype testing can add more if a design iteration fails. Get the full chain (design freeze, prototype test, production, production testing, shipping) as dated milestones in the contract, with delay remedies.
• Where testing happens: If prototype tests must run at an external laboratory, lab queue time is part of your schedule. Ask which lab, and what slot the manufacturer has actually booked.
• Factory visit: For any significant order, visit the plant before signing. You are looking for a real production line with quality control stations and test rigs, not a trading office with a catalogue. An hour on the factory floor is the cheapest due diligence in the whole project.

5. Warranty, Design Life, and What Happens After Handover

Isolators are designed to serve for decades, typically matching the building's design life, yet many supply contracts carry only a short workmanship warranty. Negotiate:

• Warranty length and scope: What exactly is covered, for how long, and what voids it. Clarify who pays for removal and reinstallation if a bearing must be replaced, since that cost usually dwarfs the bearing itself.
• Inspection protocol: A written schedule for periodic visual inspection, and a defined procedure for post-earthquake inspection, including who is qualified to perform it.
• Replaceability: Confirm the design allows individual bearings to be jacked and replaced, and that the manufacturer will still support that operation, with documentation and compatible units, decades from now. Ask how they support buildings they isolated twenty years ago; the answer is revealing.

6. Local Presence and Service

A technically excellent manufacturer on another continent, with no local partner, becomes a problem the first time something needs attention on site: installation supervision, a damaged unit in transit, a question during bearing placement. Check for a local engineering office or an established local representative, installation supervision included in the offer (not billed by the travel day), and language and documentation compatibility with your site team and permitting authorities.

7. Reading the Price

Once the filters above are applied, price comparison becomes meaningful. Compare offers on scope, not the bottom line: does the price include prototype and production testing, delivery, installation supervision, spare units, warranty terms? A bid that is 25 percent cheaper but excludes testing and supervision is usually not cheaper.

The Owner's Checklist

One structural note on process: keep at least three qualified manufacturers in play until the design properties are frozen. Beyond the obvious price leverage, it protects the schedule. If your single supplier fails a prototype test or slips production, having a second qualified bidder with a recent offer shortens recovery from months to weeks.

Sources & References

• EN 15129 (2009). "Anti-seismic devices." European Committee for Standardization (CEN). CE marking via Notified Body certification.
• ASCE/SEI 7-22 (2022). "Minimum Design Loads and Associated Criteria for Buildings and Other Structures," Chapter 17, Section 17.8: Testing. American Society of Civil Engineers.
• ISO 22762. "Elastomeric seismic-protection isolators." International Organization for Standardization.
• Ferroni, D., & Vazzana, G. (2012). "Certification of anti-seismic devices according to the European Standard EN 15129:2009: Tasks for manufacturers and notified bodies." 15th World Conference on Earthquake Engineering, Lisbon.
• FEMA P-58 (2018). "Seismic Performance Assessment of Buildings." Federal Emergency Management Agency.

Also available in Turkish: Sismik İzolatör Üreticisi Nasıl Seçilir? on sismikizolasyon.com