Pitch Diameter, Tap Drills, and the Logic Behind Our Unified Thread Calculator

Calculators & Tools, Standards & Codes

Every bolted flange, every stud, every tapped hole on a piece of pressure-control equipment depends on a thread that was cut correctly — and “correctly” starts with a handful of geometric relationships that are older and simpler than most of the software built around them. Our Unified Thread Calculator puts those relationships in one place:

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API 6A vs. API 17D: Surface Wellhead vs. Subsea Wellhead Standards

Design Engineering, Standards & Codes

API 6A and API 17D cover the same basic function — wellhead and tree equipment — but for two environments different enough that neither standard alone is sufficient for both. Here’s how they divide the work, and why a subsea well needs more than just “API 6A equipment installed underwater.” API 6A: the surface baseline

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Wellhead vs. Christmas Tree: What’s the Difference?

Design Engineering

“Wellhead” and “Christmas tree” get used interchangeably in casual conversation often enough that it’s worth clearing up — they’re two distinct pieces of equipment, built to somewhat different (though related) standards, doing two different jobs, and understanding the split matters if you’re specifying, reviewing drawings, or troubleshooting equipment. The wellhead: structure and pressure containment The

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What Does MAWP Mean? Maximum Allowable Working Pressure Explained

FEA & Simulation, Standards & Codes

MAWP shows up on every pressure vessel nameplate, every wellhead spec sheet, and nearly every FEA report scope — and it’s frequently confused with related-but-different terms like design pressure or operating pressure. Getting the distinction right matters, because MAWP is the number that actually defines the equipment’s legal and engineering limit. The definition Maximum Allowable

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API 6A Pressure Classes Explained: What Do 2,000–20,000 PSI Ratings Mean?

Design Engineering, Standards & Codes

A wellhead or tree component stamped “10M” or “15,000 psi” isn’t giving you a suggestion — it’s stating, per API 6A, the exact maximum pressure that component is qualified to hold, at a specified temperature, tested to a defined procedure. Understanding what those numbers actually mean (and don’t mean) matters for anyone specifying or reviewing

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What Is NACE MR0175 and When Do You Need Sour Service Materials?

Design Engineering, Standards & Codes

“Is this sour service?” is one of the first questions that should get asked on any wellhead or valve job — because the answer changes what materials are allowed, and getting it wrong isn’t a cosmetic mistake. It’s the difference between equipment that lasts its design life and equipment that cracks in service. What makes

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How Often Should a BOP Be Tested? API 53 Testing Intervals Explained

Design Engineering, Standards & Codes

A blowout preventer that hasn’t been tested recently is, for well-control purposes, a blowout preventer you can’t fully trust. API RP 53 sets out how often BOP components actually need to be function- and pressure-tested — and the honest answer is “more often than most people outside drilling operations would guess.” The two kinds of

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