Seeking the perfect precast concrete transformer foundation supplier? A transformer foundation’s sole purpose is to provide a stable, level platform for the heavy transformer load; to safely trap any oil leaks; and to do the job for decades without any settling, cracking or damage to the equipment on top. If it is, no one will see it. If it doesn’t, then the issue is not necessarily one of the concept of using a precast foundation, it is almost always one of the suppliers who designed and fabricated it.
This guide explains the process for assessing a transformer foundation supplier for precast concrete transformer foundations, and how you can be sure that you’re getting a foundation that can support critical electrical infrastructure in a reliable fashion, rather than one that will cause issues for equipment that cannot afford to be taken offline.
The Decision of Which Supplier to Choose is More Complex Than Just the Base Size and Price Tag
The price per unit, weight bearing and base dimensions are the first things that most buyers compare. Yes, it’s a good place to start, but it does not include the part that really matters: how the supplier calculated and reinforced the unit for the specific transformer weight, size and oil containment needs of your equipment, versus a generic size that is close.
The load of transformer foundations is heavier and more concentrated than most equipment pads, and the effects of a problem foundation are much broader than the concrete foundation itself. An irregular or settling foundation can cause transformer bushings and connections to become strained and a small leak can become a problem for the environment and safety. A supplier who considers the design of the transformer foundation to be a true structural and containment engineering project takes the actual equipment specification and regulatory requirements into account at the outset, rather than just treating it as a “heavy-duty concrete pad.” One that does not will provide a foundation that may appear solid on delivery but that will cause problems once the transformer is in service.
Understand the Different Types of Foundations and What is Required for a Given Type of Project
Equipment size and site needs differ significantly so it helps to know which type of transformer foundation your project requires before you start comparing suppliers.
Pad Mounted Distribution Transformer Foundations
Smaller distribution transformers typically used for residential and light commercial applications are supported by pad mounted foundations. These will require precise dimensional fit to the particular transformer footprint and standard utility clearance requirements around the transformer.
Substation Power Transformer Foundations
Large power transformers typically have a lot more fire barrier and oil containment requirements for their substation foundations, and the heavier the transformer. These require foundations designed specifically for the weight distribution of the transformer, and also for the regulatory containment requirements of the site, as the scale and consequences are much greater than in smaller distribution applications.
Foundations with Integrated Oil Containment
Alternatively, a containment basin or bund may be integrated into the precast foundation structure, to retain the total amount of oil in the transformer should it leak or burst. Such containment volume must be calculated to an accuracy of the transformer’s actual capacity of oil, and refer to a certified reference to the applicable containment standard.
Vault and Below-Grade Transformer Foundations
In dense urban areas, transformers installed in vaults or in the ground are supported by vault or below-grade foundations. These require structural design for load of the transformer and surrounding soil and ground water pressures, along with containment and drainage detailing appropriate for a below grade installation.
After determining which category best matches your transformer and site needs, you can limit your suppliers to the manufacturers who can account for true engineering experience with that particular application.
Inquire on Their Structural Design and Load Calculations
A transformer foundation manufacturer who knows and cares about this transformer will design a foundation that will take into account the actual weight, footprint and load distribution of your transformer, rather than a “heavy duty” transformer foundation size that is assumed to be adequate. This should include a specific reinforcement designed to carry a specific design load to the transformer’s specifications.
Find out what the foundation’s load and soil bearing capacity are, if the design is based on a specific transformer type and size, and if they can give you the calculation for the load rather than a generic catalogue transformer size. The supplier that communicates with your equipment’s actuals is speaking your language. A provider that only offers an average size (according to the norm of the transformer types) is worth a closer look.
Review the Design and Compliance of Their Oil Containment Design
In the case of transformer foundations, one of the most important, and regulated, features is its ability to store oil. If containment is provided as part of the precast structure, or instead with a separate containment system, ask if the design provides containment, asks how much containment volume is provided relative to your transformer’s oil capacity, and asks what regulatory standard the containment design references.
When the supplier is prepared to explain how their containment design fulfills your project’s unique regulatory criteria, they are showing you real engineering behind the product. If a supplier offers a description of containment without a volume calculation or reference to a standard, it is a warning to scrutinize and proceed carefully, because there can be some serious effects on the environment and safety if containment is not adequate.
Review Their Manufacturing Quality Control
It is possible for two foundations to have similar specifications on paper but be different in performance based on the way they’re cast. Inquire about how units are cast, the curing process and time, and what inspections are carried out before a unit is given for dispatch.
This is a key dimensional factor, as all the points for mounting the transformer, the locations of cable entry points and the dimensions of the containment basin must match the equipment being installed. Request the supplier’s tolerance on these critical dimensions and how they assure them prior to delivery, because if the foundation is marginally off tolerance, it can cause a lot of trouble when installing the equipment.
Request Project-Specific Engineering, Not a Standard Catalogue Size
A good supplier will ensure that the foundation design is verified with your actual transformer specification and site conditions and not just the closest catalogue match. That should include a check for proper weight, footprint, and cable access of your particular transformer, verification of containing the volume of oil required by your actual equipment, and instructions on what additional requirements your particular transformer may have for the specific regulatory jurisdiction of your site.
Suppliers working with your specific equipment and regulatory requirements will be able to spot mismatches before the foundation is cast instead of after when it’s delivered and it just doesn’t fit the transformer or meet the containment requirement for your site. If you do not have a supplier who will simply tell you that they don’t offer a size chart that could be used to match your particular specifications, then you are taking a chance on your own judgment to find out if there is any gap.
Verify Installation and Handling Requirements Precast Concrete Transformer Foundation Supplier
Installation requirements vary widely depending on foundation size and foundation type. Substation-scale pad-mounted foundations are significantly larger and heavier than the typical site foundation, and may best be handled by available lifting equipment, with careful planning for the excavation and backfill work.
Obtain information from your supplier regarding the lifting and handling requirements for your particular foundation; the recommended backfill, its compaction and the necessity for compaction; and if the supplier has any installation instructions or coordinates directly with the electrical contractor installing the transformer. If you find out halfway through the job that the cable entry points are not matching up with the conduit routing is a very expensive mistake to make.
Investigate Their Referrals and History
Design calculations and containment specifications tell you what the supplier states their foundations can do. Installed projects provide you with actual information about the projects that have been installed. Request samples of foundations provided for other transformers of the same type and capacity and information on the performance of such foundations, such as their leveling, stability, and containment, in years of service.
Reliability is what a supplier with a consistent track record saying about their engineering discipline is saying much more than a catalogue listing.
Some of the Red Flags That Could Be Noticed Precast Concrete Transformer Foundation Supplier
Few warning signs reappear with less reliable transformer foundation suppliers:
- Lack of any supporting load calculation specific to your transformer.
- Answers that are general, like “containment volume” or “meets the regulations.”
- Unwillingness to compare the dimensions to your exact specifications.
- A distinct price that is significantly lower than that of their competitors, with no explanation provided for the discrepancy.
None of these should exclude a supplier, but two or three of them can indicate that the foundation is supporting the critical, high-value electrical equipment and there are real environmental and safety implications, so it’s best to slow down and engage your electrical and structural engineers directly before committing.
Integrate Everything Into a Single Unit Precast Concrete Transformer Foundation Supplier
Wise selection of the precast concrete transformer foundation supplier depends on the details of the supplier designing specifically to your transformer, not just a generic heavy duty pad, with actual engineering calculations and careful manufacturing; backed by real engineering calculations and careful manufacturing.
Do it right, and the foundation does just what it’s supposed to – keeps critical electrical equipment level, stable and safely contained for the life of the installation.