Api buttress connection data sheet

The buttress thread form, also known as the breech-lock thread form, refers to two different thread profiles. One is a type of leadscrew and the other is a type of hydraulic sealing thread form. The leadscrew type is often used in machinery and the sealing type is often used in oil fields.

1. Connections must be clean and dry when applying
thread lock.
2. Apply a thin coating of thread lock on 50% of the
pin threads furthest from the pipe body.
3. Do not apply thread compound to pin or box.
Make Up
1. API Buttress connection is designed to be made up
to a final position, there is no final torque specified.
2. Make up acceptance criteria is defined based on the
relative position of the coupling face compared to the
triangle stamped on the pin end:
.Minimum Make up: One full thread turn before
triangle base.
.Maximum Make up: Triangle apex.

3. There is no torque specification for API Buttress
however torque values required to reach an acceptable
make up tend to be similar within the same batch of pipe.
4. In order to determine make up torque for the string
to be run:
.Make up the first 15 joints to the base of the stamped
triangle, taking note of the required torque for each joint.
.Calculate the average torque.
.Use the average torque to make up the string.
.Ensure all make ups are acceptable by checking the
coupling face position within the triangle.
5. It may occur that during the make up, the coupling
rotates on the mill end. This can be allowed provided
the coupling face on the mill end does not exceed the
apex of the triangle stamped on the mill end pin.


1. To avoid cross threading stab pipe in a smooth
controlled fashion ensuring the pipe is vertical when
doing so, continue to support and stabilise the pipe
throughout the stabbing and make up operation.
2. Upon commencement of initial rotation use low
RPM (5 RPM or below) in order to ensure the pipe has
not cross threaded during stabbing.
3. If cross threading is evident, immediately reverse
rotate the pipe slowly, break out and inspect both
4. Maximum spin in speed should not exceed 15 RPM.

1. Automatic stabbing system or stabber is highly
recommended to maintain the pipe in a vertical
2. Apply the back up tong jaw on the lower part, over
mill end, of the coupling.
3. Apply power tong in low RPM (3-5 RPM) to break
out the connection, ensuring the pipe is stabilised
during the break and spin out process.
4. Visual inspection is recommended to classify the
thread condition. Any rejected connections should be
clearly marked and segregated for further investigation.
5. Apply clean, dry thread protectors after applying
storage compound on clean, dry connections.
6. Storage / thread compound should always be
applied to connections post job, even rejects.

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