API Spec 7 geometric tolerance for shouldered connections

[ak762]

I represent connections in drawing with reference to API Spec 7.
But I confused a little because did not find info or skip it regarding to geometric tolerance for shoulder.
If shoulder surface is critical for joint what's about secure Box interface and move it inside about 5mm from practical side.
I would appreciate if anyone enlighten this points with API Spec 7.
I have found requirements for shoulder surface in Russian GOST. It is stated perpendicularity no more 0.1mm to thread axis and flatness no more 0.07mm
But we work with API standards only.

 

[redpicker]

API Spec 7 is obsolete.

You will now find the requriements for rotary shoulder connections in API Spec 7-2 (ISO 10424-2). Specifically, 7-2 requires the shoulder contact faces to be in a plane and square to the thread axis to within 0.05mm (0.002 inches). This is the same requirement that was found in sections 10.2.1 - 10.2.2 of the 40th edition of API Spec 7.

rp

 

[ak762]

Thank you for pick me in right direction.
Concerning to protection shoulder for box thread. Is there something rational in this idea from points of drilling operation or it is impractical to protect this sealing surface with such design?

 

[redpicker]

I don't understand your question.

Can you ask your ask your quesiton using different wording?

rp

 

[ak762]

My assumption was that if shoulder surface have sealing functionality then would be good to protect it from wear or notch when tubes make up during drill operation at rig. It can be achieved different ways and one of them move shoulder inside at box end as I've shown in sketch. I've refused from this idea now after got additional info.
As I understand now during transportation to rig tubing ends protected with plastic caps. When tubes make up at rig it is not so useful because wipe and clean flat surface much easy then stepped. Anyway I would appreciate if someone add additional pros&cons to my 1-st idea with protect design.

 

[redpicker]

You are correct that the shoulder seal needs protection during service. That is the function of the OD bevel on both the male and female connections. This provides protection to the seal from impact damage to the OD, and allows OD wear without affecting seal area.

The problems with your design is that it is customary to have the OD of both members match. With your drawing, the OD of the male connector would have to have a smaller OD to fit the recess of the female side. With the male connector being smaller in OD, you are sacrificing bending strength.

rp