Application Deep-Dive
Choke Body Machining — Trim Seat Precision, Bore Machining, Alloy Selection
Choke bodies control pressure by throttling flow through a precision seat. Seat wear and body erosion are the failure modes; both are set at machining time. This guide covers choke body and trim machining — materials, tolerances, and the alignment discipline that determines field life.
What choke bodies do
The choke throttles flow between the wellhead and downstream production equipment. Adjustable-choke bodies contain a moving stem or plug that meters flow across a precision seat. Fixed chokes use interchangeable trim inserts.
Failure modes: seat erosion from abrasive flow, body wash-out from high-velocity impingement, corrosion pitting in aggressive fluids. All accelerated by machining defects at the seat or bore surface.
Materials
| Alloy | Where used |
|---|---|
| Inconel 625 | Erosion + corrosion resistance for standard chokes |
| Inconel 718 (aged) | Higher-pressure or extended-life applications |
| Super Duplex 2507 | Chloride-heavy service |
| Tungsten carbide | Trim inserts (fixed or replaceable) for maximum erosion life |
| 17-4 PH | Body material where corrosion resistance is adequate |
Machining scope
- Choke body machining — Flange faces, through-bore, seat pocket per design print.
- Seat machining and finish — Critical feature — typical ±0.0002" tolerance and 16 μin Ra finish.
- Bore-to-seat alignment — Concentricity of bore and seat controls flow uniformity and seat wear.
- Trim mating surfaces — Precision-fit to matching trim (adjustable stems, fixed inserts).
- Fluid passages — Radiuses per design to reduce erosion at flow direction changes.
The seat is everything
Choke seat geometry, finish, and alignment to the mating trim determines field life more than any other single feature. Poor concentricity between bore and seat creates asymmetric flow that erodes one side of the trim first. Rough seat finish creates local turbulence and erosion.
Frequently asked questions
Where can I get choke bodies CNC machined in Texas?
B&R Productions in New Waverly, TX machines choke bodies regularly. Direct number for RFQs and rig-down work: (936) 291-7827.
How long does choke bodies machining typically take?
Depends on quantity and material availability. Standard work: 1–3 weeks. Emergency turnaround: same-day to 3 days when material is on the shelf. Call to discuss your specific job.
What material is standard for choke bodies in sour service?
Inconel 625 or Inconel 718 for high-strength requirements. Super Duplex 2507 for chloride-heavy applications where the extra corrosion resistance matters.
Can you machine choke trim seats and mating surfaces?
Yes — precision seat machining with CMM verification of concentricity and finish.
What tolerance is typical on a choke seat?
±0.0002" to ±0.0005" on critical sealing surfaces with 16 μin Ra or better surface finish. Concentricity to the mating bore held within 0.0005" TIR.
Do you machine choke bodies from customer-supplied forgings?
Yes — routine. Provide forging + MTR + print.