Annular and Ram BOPs

Annular and ram BOPs are the individual preventers that make up a stack, sold as single units or spare bodies. This Category covers annular preventers, single, double and triple ram bodies, bonnets and operators, and ram blocks for pipe, variable bore, blind and shear service. A spare body of the model already on your stack shortens any maintenance outage.

How each preventer seals

An annular preventer drives a piston upward, which squeezes a steel-reinforced rubber packing unit into the bore. The packer closes on drill pipe, casing, a kelly, a tool joint or an open hole, and lets you strip pipe under pressure. Wellbore pressure acting on the piston helps hold some designs closed.

A ram preventer closes two opposed ram blocks with hydraulic operators in the bonnets. Pipe rams seal on one pipe size. Variable bore rams seal across a range of sizes. Blind rams close an open hole, and shear rams cut pipe in the bore, with blind shear rams cutting and sealing in one stroke. Mechanical or hydraulic ram locks hold the rams shut if closing pressure is lost.

Variants in this Category

Annular preventers, in spherical and wedge-type packer designs
Single, double and triple ram bodies, flanged, studded or hub-ended
Bonnets, standard or with large-bore operators or shear boosters for high shear forces
Ram blocks and top seals, sold as spares or to change a cavity's function

Key specifications

Parameter	Why it matters	Typical classes or units
Bore and pressure rating	Must match the rest of the stack	13-5/8 to 21-1/4 in., 5,000 to 20,000 psi
End connections	Must mate with adjacent bodies and spools	API 6BX flange, studded, hub
Closing ratio	Wellbore pressure the rams hold per unit of operating pressure	Ratio stated by OEM for each operator
Shear force capability	Sets the heaviest pipe the cavity can cut	Operator size and booster, from shear tests
Packer compound	Must suit mud type and temperature	Natural rubber, nitrile or neoprene
Temperature rating	Separate ratings for metal and elastomer parts	°F and °C per API 16A

Natural rubber packers suit water-based mud and low temperatures. Nitrile suits oil-based mud at higher temperatures, and neoprene suits oil-based mud in the cold.

Standards that apply

API 16A governs new manufacture, including design verification tests such as ram fatigue, packer fatigue and shear tests. API 16AR governs repair and remanufacture of drill-through equipment, so a recertified body should come with a 16AR report from a licensed facility or the OEM. API Standard 53 sets the in-service tests. Under 30 CFR 250.737, an annular is pressure tested to 70 percent of its rated working pressure or to MASP plus 500 psi, while rams go to rated working pressure or MASP plus 500 psi.

Where used preventers wear

Ram cavity seal seats and top seal areas, which pit and wash out
Ring grooves and any inlay of corrosion-resistant alloy
Bonnet seals, operator pistons, cylinder liners and tailrods
Ram lock mechanisms, which seize when not exercised
Annular piston, wear plate and the packer's steel inserts
Bolting on bonnets and flanges, especially after corrosion in storage

An inspection should measure cavities and seal surfaces against the OEM's wear limits, use magnetic particle testing on high-stress body areas, and finish with a low and high pressure test and a timed function test.

Documentation

Ask for the serial number history, the original certificate of conformity, the last 16AR repair or remanufacture report, and test charts. Get the manufacture date of every packing unit and seal. Elastomers age in storage, so a packer from an unused surplus body can still be past its shelf life.

Integration

A replacement body must match the stack's bolt pattern, height stack-up and outlet positions, or the choke and kill lines will not line up. Check the operator's closing volume, because a larger operator draws more fluid from the accumulators. A changed shear operator can push the stack's usable fluid volume below what API 16D sizing requires.

Refurbishment and the used market

Remanufacture to 16AR takes the body to bare metal, inspects it, rebuilds seal surfaces where needed and replaces every elastomer, then retests it. An unused surplus body of an out-of-production model can be the only quick source of a spare. Well-known families include Cameron U and TL rams, Shaffer SL and NXT rams, and Hydril GK and GL annulars. For whole assemblies, see BOP stacks.

FAQ

Frequently asked questions

What is the difference between an annular and a ram BOP?

An annular BOP seals with a rubber packing unit that closes around almost any shape in the bore, including an open hole. A ram BOP closes two steel ram blocks that seal on one pipe size, a range of sizes or an empty hole, or cut the pipe in the case of shear rams.

Should I replace the packing unit on a used annular BOP?

Yes, unless the Seller can show the packer's manufacture date, storage conditions and test history. Elastomers degrade with age, heat and ozone even unused, and the compound must suit your mud type and temperature. Budget for a new packing unit on almost every used annular.

Can a used ram BOP be recertified?

Yes, a used ram BOP can be recertified by the OEM or a facility licensed to API 16AR, which covers repair and remanufacture of drill-through equipment. The work includes strip-down, dimensional inspection against OEM limits, weld repair of seal areas where allowed, new elastomers and a pressure test.

What is a ram BOP closing ratio?

The closing ratio is the wellbore pressure a ram operator can close against, divided by the hydraulic pressure needed to close it. A higher ratio means the rams close against higher well pressure at a given operating pressure. The OEM states it for each operator and bonnet size.

Are variable bore rams a substitute for fixed pipe rams?

Variable bore rams seal on a range of pipe sizes, so one cavity can cover a tapered string. They can have a lower hang-off rating and different fatigue life than fixed pipe rams of the same body. Check the OEM data for each size in the range.

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