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 test
- Function test — operating each BOP component (rams, annular, choke and kill valves) through a full open-close cycle to confirm it actually moves and seals, without necessarily applying full rated pressure.
- Pressure test — pressurizing the closed component to a specified test pressure (typically low-pressure and high-pressure stages) to confirm it holds without leaking.
Typical intervals per API RP 53
Exact requirements vary with well type, regulatory jurisdiction, and specific equipment, but the general API RP 53 framework calls for:
- Function tests — weekly for surface BOP stacks, and before critical operations such as running casing or drilling out a shoe.
- Pressure tests — at minimum every 21 days for surface stacks, and always after any seal, ram, or component replacement, after disconnecting a pressure-containing seal, and before drilling into a zone with anticipated higher pressure.
- Accumulator response and pressure checks — regularly verified to confirm the system can close all functions and still retain the required minimum reserve pressure (200 psi above pre-charge, per API 53).
Subsea stacks generally follow similar principles but with testing intervals and procedures adapted for remote operation and the added complexity of the LMRP and riser system.
Why the interval matters more than it might seem
A BOP’s entire job is to work correctly on the one occasion it’s actually needed — during a kick, when the well is already in an abnormal state. Elastomer seals degrade with time, temperature cycling, and exposure to well fluids; a ram that functioned perfectly on installation can fail six months later without ever having been used. Regular testing is how that degradation gets caught before it matters, not after.
What this means for equipment design and re-qualification
Frequent testing has design implications too: BOP components need to be qualified for repeated cycling without unacceptable wear, and test ports, gauges, and access need to be designed in from the start rather than retrofitted. When older BOP stacks or components are being re-qualified for continued service or a different pressure rating, documented test history is often as important as the physical inspection — see our related post on legacy wellhead equipment re-qualification.
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