A flow coupling (or blast joint) in oil & gas is a heavy-walled tubular component installed in a well’s production string to protect against erosion from turbulent fluid flow, especially near restrictions like landing nipples or safety valves, by providing a thicker section to wear away before the main tubing fails, thereby extending completion life.
Key Characteristics & Function:
- Thick Wall: Has a much thicker wall than standard tubing, but the same outer diameter (OD) as couplings, maintaining flowpath integrity.
- Erosion Protection: Designed to withstand the abrasive action of rapidly moving oil, gas, and sand (produced fluids) that cause erosion at flow restrictions.
- Strategic Placement: Installed above and below components that create turbulence (e.g., sliding sleeves, chokes, safety valve mandrels).
- Extends Life: Doesn’t stop erosion but sacrifices its material to protect the rest of the tubing, making the completion last longer.
- Materials: Typically low-alloy steel but can be made from specialized materials like ceramics or carbide for extreme conditions.
Common Uses:
- Above/below safety valve mandrels.
- Above/below landing nipples.
- Near other flow-restricting devices.
- Below the wellhead during hydraulic fracturing to protect against abrasive frac sand.
