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• April 22, 2025

What Is API 650 Standard? Storage Tank Design Explained

If you’re working in the world of industrial storage, you’ve probably heard about API 650 standard. But what does it actually mean? It’s not just some set of rules—it’s a vital standard that governs the design and construction of above-ground storage tanks, used to hold liquids like oil, water, and chemicals. So, what’s all the fuss about? Let’s dive in and break it down.

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So, What Is API 650 Anyway?

In simple terms, API 650 is a standard developed by the American Petroleum Institute (API) that tells you how to design, weld, and inspect large welded steel storage tanks. These tanks are typically used to store liquids at atmospheric pressure (not under high pressure). Think of them as the big guys you see at oil refineries, chemical plants, and water treatment facilities.

Why does this matter? Because these tanks need to be strong, durable, and built to last—especially when you’re storing dangerous or valuable liquids. That’s exactly what API 650 helps ensure.

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Why Should You Care About API 650?

Well, think about it: If you’re building a huge tank for storing liquids, you definitely don’t want it failing halfway through its life. API 650 standard gives you the exact specs you need to make sure the tank is safe, reliable, and up to the job. Plus, because it’s a widely recognized standard, it makes your job easier when you’re dealing with regulators or industry experts.

By following API 650, you’re also ensuring that your tank can handle the stresses and pressures that come with long-term storage. No leaks, no problems.

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When Do You Actually Use it?

So, when do you need a tank built to API 650 standards? Usually, if you need to store:

• Large amounts of liquid (think 50,000 gallons or more)
• Liquids that aren’t pressurized (so atmospheric pressure)
• Liquids like oil, water, and chemicals

If your storage needs are different, like storing low-pressure or refrigerated liquids (like LNG), then you’ll probably need something else—like API 620. Want to know more? Check out our post on Choosing the Right Tank Materials.

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What Materials Are Used?

Here’s the good news—API 650 standards doesn’t lock you into just one material. You’ve got a few options, like:

• Carbon steel (the most common choice)
• Stainless steel (good for corrosive materials)
• Aluminum (occasionally)

What you choose depends on what you’re storing. For example, if you’re dealing with something that’s corrosive, you’ll need materials that can hold up to that. Check out our guide on Sulfuric Acid Storage Tanks for more details.

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API 650 vs API 620 vs UL-142—Which One’s Right for You?

You might be wondering, “So, what’s the difference between API 650, API 620, and UL-142?” Here’s a quick breakdown:

Standard	Pressure	Use Case
API 650	Atmospheric	Oil, water, chemicals
API 620	Low to medium	Refrigerated products, LNG
UL-142	Low pressure	Aboveground fuel tanks

If you’re storing regular liquids at atmospheric pressure, API 650 is your go-to. But if you need to store refrigerated or pressurized liquids, API 620 might be a better choice.

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What Do You Need to Consider When Designing an API 650 Tank?

So, if you’re designing a tank under API 650, what should you be thinking about? Well, here are a few things to consider:

• Seismic design (important if you’re in an earthquake zone)
• Wind loading (because, yeah, tanks need to stand up to some pretty strong winds)
• Roof types (cone, dome, floating)
• Tank wall thickness (this impacts durability)
• Corrosion allowances (because no one wants their tank rusting out after a few years)

It sounds complicated, but that’s why you hire experts to make sure everything’s built to last.

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So, Should You Choose API 650 for Your Tank?

If you’re planning to store large amounts of liquid and need a reliable, safe, and cost-effective tank, then API 650 standard is probably the way to go. It’s the industry standard for a reason—it works, it’s recognized, and it’ll help you get the job done right.

At GSC Tanks, we know how important it is to have the right tank for your needs. Whether it’s API 650, FRP, or a custom solution, we’ve got you covered. Want to learn more about different tank options? Check out our blog on High-Quality Industrial Storage Tanks.

• API 650
• Guide to the API 650 Storage Tank Standard
• What Is API 650?