Battery Limits

Let's talk about ISBL & OSBL

Just in case you are working in a project and wonder, What is a Battery Limit?

and moreover...

why is it important to understand the difference between Inside vs. Outside BL.

Check the Video here:

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Or simply read...

🔍 What’s the Invisible Line in Every Plant?

It’s called the Battery Limit, and it divides your plant into two major zones:

• ISBL and OSBL.

🏭 ISBL (Inside Battery Limits)

• 🧪 Core units like reactors, columns, tanks
• 🧷 Everything in the P&ID
• ⚙️ Directly involved in the process reaction and transformation

🏗️ OSBL (Outside Battery Limits)

• 💡 Utilities like cooling towers, steam, power, roads
• 🧯 Infrastructure that supports but doesn’t transform
• 🛢️ Think: Tank farms, flare systems, pipe racks

💰 Why It Matters?

1. Cost Control – Avoid hidden costs from poor planning
2. Modular Design – Build smarter with clearer module boundaries
3. Project Phasing – Tackle ISBL first, OSBL later (or reuse existing)

⚠️ Common Mistakes to Avoid

• 🚫 Ignoring OSBL utility needs
• 📅 Not defining the limits early
• 🔌 Poor integration between ISBL & OSBL (no power, wrong specs, chaos!)

👷‍♂️ Engineers, don’t work in silos!​
🤝 Collaboration between ISBL & OSBL teams is key to smooth operations

🧠 Pro Tip:​
That "invisible line" might not show up in a drawing… but if you ignore it, you’ll feel it in your project delays and budget overruns!

Final thoughts

Hey guys, hope you enjoyed the content, I'll be sending more quick tips/commentary on common aspects of Process Engineering & Plant Design.

BTW, 📣 Share your battery limit war stories in the YouTube Video comments!

Looking forward for crazy stories!

Please don't hesitate to contact me (by replying to this e-mail) if you have any doubt, question or comment at all!

See you later!

Emmanuel Ortega

a.k.a. Chemical Engineering Guy

113 Cherry St, Seattle, WA 92768
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