Guides

Technical guides for oil and gas equipment buyers

Short, accurate explanations of the standards and specifications behind oil and gas procurement.

API 6A vs API 6D: What's the Difference?

API 6A covers wellhead and Christmas tree equipment rated in psi; API 6D covers pipeline valves rated in ASME classes. Here is how to tell which standard applies.

NACE MR0175 / ISO 15156: Sour Service Equipment Explained

What sour service means, when NACE MR0175 / ISO 15156 applies, and how it affects materials for valves, pipe, wellheads and bolting.

API 6A PSL, PR, Temperature and Material Classes Explained

A practical guide to specifying API 6A equipment: product specification levels (PSL 1–4), performance requirements (PR1/PR2), temperature classes (K–V) and material classes (AA–HH).

API 5CT Casing & Tubing Grades Explained

A guide to API 5CT casing and tubing grades, from J55 to Q125, including which grades are suitable for sour service and what the color bands mean.

Flange Standards, Pressure Classes and Ring Gaskets

ASME B16.5 vs B16.47 vs API 6A flanges, pressure classes, RF and RTJ facings, and how to choose R, RX or BX ring gaskets.

How to Write an RFQ for Oil & Gas Equipment (and What Documents to Expect)

A checklist for writing a complete oil and gas equipment RFQ, covering specifications, standards, certification (EN 10204 3.1/3.2), inspection and test plans, and the documentation package.