What is the difference between LTC and STC threads?

29, Apr. 2024

 

API OCTG Connections: API Certified Casing Threads

API Connections

We manufacture a complete range of API-certified connections.

U. S. Steel Tubular Products manufactures a complete range of American Petroleum Institute (API) certified casing thread types, including short round thread casing (STC), long round thread casing (LTC) and buttress thread casing (BTC). STC and LTC both feature a non–runout design of round threads, each with eight round crested threads per inch. BTC has a square thread with a flat root and crest, a runout design, and five buttress threads per inch.

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Each thread type is suited for a specific well condition. STC is a good choice for shorter length casing applications that do not involve high axial loads or bending. LTC is well suited for situations where some axial load is encountered but overall well conditions do not include extremes of temperature or pressure. BTC is an excellent connection for use in well situations involving higher axial loads and moderate internal pressures and temperatures.

U. S. Steel Tubular Products’ other API connections include non–upset end tubing (NUE) and external–upset end tubing (EUE). Both offer eight or ten round threads per inch and a non–runout design of round threads. NUE is well suited to light duty, general purpose applications.

EUE can be deployed for general purpose drilling and production applications where internal pressures are moderate.

U. S. Steel Oilwell Services Threading Services

U. S. Steel Oilwell Services specializes in complex threading of OCTG. We provide API and premium threading of OCTG , ranging in size from 3-1/2” to 20” outside diameter. Tubing and casing threading services encompass bucking, torque turn, saw cutting, and full-length drift.

We provide threading through U. S. Steel Oilwell Services – Offshore Operations, Houston and through Patriot Premium Threading Services in Midland, Texas.

U. S. Steel Tubular Products OCTG Distributors

U. S. Steel Tubular Products are available through authorized distributors. See our complete list of U. S. Steel Tubular Products OCTG product distributors and authorized agents.

Typical API Thread Connections – STC, LTC and BTC

What standard API Thread Connections for Choice

The floating collar and shoes are available in different API certificated thread connections, including Short Round Thread (STC), Long Round Thread (LTC) and Buttress Thread (BTC).

Connection strength and tightness are two main coupling technical indicators. Both LTC and STC threads use lead, zinc, copper, graphite or silicone oil composition to improve seals, but those seals only work under temperature of 60 °C to 95 °C. Also for STC coupling, if under huge external pressure and axial tensile stress, when heavy impact or bent happens, the threading will be likely to slippage. Both of those two type of threading are not suitable for heavy oil thermal recovery, ultra deep well and heavy corrosive environment.

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LTC (Long Thread) type.

It is also has a non-runout design of round thread. Each has eight round crested thread per inch, which is same as the STC type.

LTC thread is easy to process, good tightness, strong connection strength, simple maintenance and low price.

LTC thread is widely used in oil and gas industry and is well suited for situations where some axial load is encountered but overall well conditions do not include extremes of temperature or pressure.

STC thread type.

It is features with a non-runout design of round thread. Each has eight round crested threads per inch.

STC threads can withstand strength of the tubular 60% to 80% of the pipe strength. STC thread is a good choice for shorter length casing applications that do not involve high axial loads or bending.

BTC type.

It is designed to improve axial tensile or axial compressive load capacity and to provide leakage resistance performance.

It is an excellent connection for use in well situations involving higher axial loads and moderate internal pressures and temperatures.

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