Choke and Kill Manifolds

Choke and kill manifolds are the valve and choke assemblies that control flow out of a shut-in well and carry kill mud into it. This Category covers skid-mounted choke manifolds, kill manifolds, drilling chokes, remote choke panels and spare gate valves. They are pressure-rated equipment tied to the BOP's rating, so the pressure class comes first when you compare units.

How the manifold works

Choke and kill lines leave the BOP below the closed preventers and run to a manifold on the rig floor or cellar deck. During a kick, you route returns through an adjustable choke and hold back-pressure on the well while circulating it out. Downstream, flow goes to the mud-gas separator, the shakers or an overboard line. The kill side lets you pump into the well through the BOP when circulating through the drill string is not possible.

Configurations

Choke manifolds with two or more chokes in parallel, usually one manual and one or more remote hydraulic chokes
Combined choke and kill manifolds on one skid
Standalone kill manifolds and cement or test manifolds
Remote choke control panels with choke position, standpipe and casing pressure gauges

Key specifications

Parameter	Why it matters	Typical classes or units
Working pressure upstream	Must at least equal the ram BOPs	5,000 to 20,000 psi (34.5 to 138 MPa)
Working pressure downstream	Often one class lower than upstream	psi, MPa
Bore	Flow capacity and erosion velocity	2-1/16, 3-1/16, 4-1/16 in.
Material class	Sour service and corrosion	API 6A AA to HH
Temperature class	Elastomer and steel limits	API 6A letter classes such as P, U or X
Product specification level	Testing and traceability depth	PSL 1 to 4

API 53 expects the choke manifold, up to and including the chokes, to carry a working pressure at least equal to the rated working pressure of the ram BOPs.

Standards and certification

API 16C covers choke and kill equipment, including manifolds, drilling chokes and choke and kill lines. API 6A covers the gate valves, flanges and fittings, and assigns material class, temperature class, PSL and performance requirement. Sour service parts must meet NACE MR0175 / ISO 15156. In US waters, 30 CFR 250.737 requires the choke manifold to pass the same low and high pressure tests as the ram BOPs, at least every 14 days.

Failure modes and inspection

Erosion drives most failures. Fast, sand-laden flow cuts the piping immediately downstream of the chokes, tees, bends and target blocks. Choke trims, stems and seats wear, and gate valve gates and seats wash out. Ring grooves corrode when flanges sit broken out.

Ultrasonic wall thickness readings at every erosion point, compared with minimum wall
Visual and dimensional checks of choke trim, gates and seats
Hydrostatic body and seat tests to rated working pressure
Magnetic particle testing of welds and high-stress fittings
Function and calibration checks of the remote choke panel and its position indicator

Documentation

Ask for certificates of conformity with the 16C or 6A monogram, the material and PSL of each component, ultrasonic thickness surveys, hydrostatic test charts and the valve maintenance log. A panel or remote choke should come with its calibration records.

Integration

The upstream connections must match the choke and kill line outlets on your stack or the rig's flexible lines. Downstream, check bore and pressure against your mud-gas separator, buffer tank and overboard lines. The skid footprint and weight must suit the space you have. The remote panel must be compatible with the choke actuators, air or hydraulic.

Refurbishment and the used market

A refurbishment replaces choke trims, valve gates, seats and seals, surveys wall thickness and ends with a hydrostatic test. A used manifold rated for your BOP pressure is a sound buy when your own unit is under-rated or eroded. Unused surplus suits a fixed rig design. NOV and Cameron build complete manifolds and drilling chokes, and many rigs carry gate valves from other API 6A licensees. Downstream equipment is under gas separators, and the pump side under standpipe manifolds and rotary hoses.

FAQ

Frequently asked questions

What pressure rating does a choke manifold need?

The choke manifold, up to and including the chokes, needs a working pressure at least equal to the ram BOPs it serves under API 53. The downstream section is often one class lower, because the chokes take the pressure drop. Your well control plan and regulator may set further limits.

Can a used choke manifold be used in H2S service?

Only if every wetted part is made from sour-rated materials. Check the API 6A material class on the nameplates and certificates, and confirm the parts meet NACE MR0175 / ISO 15156. You cannot upgrade a standard-service manifold to sour service with paperwork.

What wears out first on a choke and kill manifold?

Choke trims and the piping just downstream of the chokes usually wear first, because high-velocity, sandy flow erodes them. Gate valve seats and gates follow. Ultrasonic wall thickness readings and valve service records show how much life remains.

How often is a choke manifold pressure tested?

In US federal waters, the choke manifold is pressure tested with the BOP, at installation and at least every 14 days under 30 CFR 250.737. The high test goes to rated working pressure or to MASP plus 500 psi, after a low test of 250 to 350 psi.

Looking for choke and kill manifolds?

Tell us what you need and we will find out what is available. We reply within one business day.

Enquire