Definition
Internal Flush Connection — An Internal Flush (IF) connection is an API rotary-shouldered connection whose bore is nearly flush with the drill pipe tube's internal diameter, minimizing internal upset and turbulence for efficient fluid flow.
Also known as: internal flush connection, IF connection, internal-flush thread
What Internal Flush means
The Internal Flush (IF) connection is a classic API rotary-shouldered connection whose internal bore is machined close to the drill pipe tube’s own internal diameter — leaving the flow path essentially “flush” through the connection. This smooth transition reduces turbulence and pressure loss where fluid passes from the tube into the tool joint.
IF connections are named by pipe size, such as 3-1/2 IF or 5 IF. Because the IF bore is generous, several IF connections are dimensionally interchangeable with NC connections (for example 4 IF with NC46 and 5 IF with NC50), a relationship the NC series formalized.
Characteristics
- Flush bore — minimizes flow restriction and internal erosion at the connection.
- Internal upset — the pipe is upset internally to provide the metal needed for the connection.
- Interchangeability — many IF connections map directly to an NC equivalent.
Renting IF-connection tubulars
IF connections and their NC equivalents remain common in rental inventory. We supply drill pipe and drill collars with IF or matching NC connections — contact us to confirm compatibility before you make up your string.