standard
API Specification 17D Explained: Subsea Wellhead and Tree Equipment
A plain-language, image-supported guide to API Specification 17D: what it covers, which subsea equipment uses it, how PSL and validation fit together, and what the pressure testing requirements mean in practice.
Published Jun 29, 2026 - Maintained by Ashish Kapoor
This technical page is maintained by Ashish Kapoor, a project engineering lead. Use it as a learning and calculation-review aid, then verify critical work against current standards, project documents, supplier data, and competent engineering review.
Found an assumption, unit, formula, or standards-reference issue? Send the page URL through the contact page so it can be corrected.
Illustrative image only: a generic subsea tree and ROV scene, not an API figure and not a proprietary equipment drawing.
API Specification 17D is the API standard for subsea wellhead and subsea tree equipment. In simple language, it explains how subsea wellheads, mudline wellheads, drill-through mudline systems, vertical trees, horizontal trees, tubing hangers, connectors, valves, chokes, and associated tools should be designed, validated, manufactured, factory tested, marked, preserved, and shipped before offshore use. Cross reference: API 17D, Section 1 and Section 4.1.
This article is an original engineering explanation. It does not reproduce API's protected tables, figures, or standard text. Use it as a map, not as the legal or technical source of record. For design, procurement, inspection, FAT, or project acceptance, always verify every requirement in the official licensed copy of API Specification 17D and the project specification.