Annular and ram blowout preventers and BOP stacks · Bore and rated working pressure against MASP, stack make-up, ram types and locks, packing element temperature, accumulator and controls, pressure testing
A blowout preventer (BOP) is a large valve assembly on a wellhead that can close and seal the well during drilling or well work if formation fluids enter the wellbore. Annular preventers close a packing element around the pipe; ram preventers close rams (pipe, variable-bore, blind or blind shear) on the pipe or, for shear rams, through it. Ask three things first: what bore and rated working pressure the well needs, which preventers make up the stack, and which design standard and test regime apply.
Annular and ram-type blowout preventers and surface BOP stacks for drilling, workover and well service, with their locks and connections. Wireline and coiled-tubing pressure-control BOPs, inside BOPs, accumulator units, choke manifolds and BOP seals sold alone are outside this page except where compared.
01
In US offshore operations, BSEE's 30 CFR 250.730 requires the working-pressure rating of each BOP component (excluding annulars) to exceed the maximum anticipated surface pressure (MASP) for the operation, the BOP system to close and seal the wellbore to MASP, and compliance with API Standard 53 and with API Specifications 6A, 16A, 16C, 16D and 17D. Pipe and variable-bore rams must close and seal on any drill pipe, workstring or tubing in the hole under MASP. Section 250.733 requires a surface BOP stack of at least four remote-controlled, hydraulically operated BOPs: one annular, one with blind shear rams able to shear the tubulars and lines in the hole and then seal, and two with pipe rams. [1] [2]
Better Petro lists annular BOPs such as the FH18-21 with a 179 mm (7-1/16 in) bore at 21 MPa (3,000 psi), 8.4–10.5 MPa operating pressure and 1,350 kg, with 35 MPa (5,000 psi) and 70 MPa (10,000 psi) versions, built to API Spec 16A and NACE MR0175, with a standard nitrile packing element rated for 40–170 °F. It lists single and double ram BOPs such as the FZ18-21 at 179.4 mm (7-1/16 in) and 21 MPa (3,000 psi), 1.6 L opening and 2 L closing oil per cylinder, up to 5-9/16 in rams and 854 kg, with manual locking devices that keep rams closed if hydraulic pressure is lost. [5] [6]
Editorial calculation: 35 MPa is about 5,076 psi and 21 MPa about 3,046 psi, matching the nominal 5,000 and 3,000 psi classes. Compare the rated working pressure of each ram BOP with your MASP; under 250.730 each must exceed it. [5] [1]
Give the supplier the well type and location, bore size, rated working pressure needed (from MASP), stack arrangement (annular, blind or blind shear, pipe and variable-bore rams), tubular sizes to close on or shear, H₂S or CO₂ service, temperature range, top and bottom connections, ram locks, control system, applicable regulations and API specifications, and certification and test records required.
02
Section 250.735 requires every BOP system to have an accumulator sized and pre-charged to API Standard 53, an automatic backup charging system with an independent power source able to close and hold closed all components at MASP, at least two full control stations (one on the rig floor and one away from it), and locking devices on sealing rams, plus a wellhead rated above maximum anticipated wellhead pressure. Section 250.737 requires pressure tests when installed and at least every 14 days (30 days for blind shear rams), each test starting with a low-pressure test between 250 and 350 psi followed by a high-pressure test; for ram BOPs the high test equals the rated working pressure or MASP plus 500 psi, and for annular BOPs 70% of rated working pressure or MASP plus 500 psi, with MASP-based test pressures needing approval in the permit. [3] [4]
Editorial calculation: for a 5,000 psi annular BOP, 70% of rated working pressure is 3,500 psi; if MASP were 2,800 psi, the alternative MASP + 500 psi test would be 3,300 psi, subject to approval. A 5,000 psi ram BOP would be high-tested at 5,000 psi or, with approval, at 3,300 psi. [4]
Editorial note: these are US federal offshore rules; onshore and non-US wells follow their own regulations. Ask the supplier for API Spec 16A certification and factory test records.
03
Suppliers linked to this page list blowout preventers; each card links to the page reviewed.
The suppliers reviewed list annular and ram BOPs with wellhead and well-control equipment; ask each for bore and pressure ratings, ram types and shear capability, packing element and seal materials, design specification and certification, factory acceptance test records, and spare parts support.
04
This is a functional reference built from the sources cited; it is not one maker's design.
| Component | Role | Fix in the order |
|---|---|---|
| Annular preventer | Seals around varied pipe. [5] [2] | Bore; RWP; element. |
| Pipe and variable-bore rams | Seal on tubulars. [1] [6] | Sizes; RWP. |
| Blind shear rams | Shear and seal. [2] | Shear capability. |
| Ram locks | Hold rams closed. [3] [6] | Manual or remote. |
| Accumulator and controls | Close the BOPs. [3] | Volume; stations. |
| Choke and kill outlets | Circulate kicks. [2] [3] | Valves; ratings. |
05
A BOP quotation needs values for your well. The table explains each field, gives published values where a reviewed source states them, and says what to obtain from the supplier.
| Field | What it means and published values | Ask the supplier for |
|---|---|---|
| Rated Working Pressure (psi) | E.g. 3,000–10,000 psi; must exceed MASP. [5] [1] | RWP; test certificate. |
| Nominal Bore Size (in) | E.g. 7-1/16 in. [5] [6] | Bore. |
| Temperature Rating (°F) | E.g. 40–170 °F nitrile element. [5] | Rating by element. |
| Sealing Element Life | Wear in testing and use. | Expected life. |
| Closing Time (s) | Must hold up to wellbore fluids. [1] | Measured time. |
| Control System Pressure (MPa) | E.g. 8.4–10.5 MPa operating (annular). [5] | Pressure. |
| Ram Size Range (in) | E.g. up to 5-9/16 in. [6] | Ram sizes. |
| Weight (kg) | E.g. 854 kg ram; 1,350 kg annular. [6] [5] | Weight. |
| Hydraulic Operating Pressure (MPa) | Opening and closing. [6] | Pressure; oil volume. |
| Sealing Test Pressure (psi) | Low 250–350; high RWP or 70% (annular). [4] | Test records. |
06
Paste it into your enquiry below or into an email to a maker, then replace every bracket.
Well: [type; onshore or offshore; jurisdiction] Pressure: [MASP; required RWP] Bore: [size; connections] Stack: [annular; blind shear; pipe; VBR] Tubulars: [sizes to seal; to shear] Service: [H₂S; CO₂; temperature] Controls: [accumulator; stations; locks] Certification: [API 16A; test records]
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Explore company information and manufacturing capabilities, then discuss the scope of your project with a relevant supplier.
30 CFR 250.733 requires at least one annular, one blind shear ram and two pipe ram BOPs, all remote-controlled and hydraulically operated. [2]
30 CFR 250.737 requires a 250–350 psi low test then a high test (rated pressure or MASP + 500 psi for rams; 70% of rating or MASP + 500 psi for annulars), at least every 14 days. [4]
Sources checked 2026-10-11. BSEE's rules are US federal requirements for offshore operations; Better Petro describes its own BOPs.
Ask for use case, specification boundaries, supplier type, and RFQ preparation information for this product.
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