INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Jobs

Why we stab Pin over the box is there any technical justifications

Why we stab Pin over the box is there any technical justifications

(OP)
Hello There

Can any one tell why we stap the pin over the box all the time while drilling and Runing in hole is there any justification of that


other question- what is the base of choosing the Threads on our BHA. Usually we use a mixture of the threads Crossing the drilling string; the fatique is one of reasings


what is the the most proper threading that need to used

Thanks

azouzzz

RE: Why we stab Pin over the box is there any technical justifications

The drillstring is generally run box up/pin down because it is easier to stab the pin connection into a stationary box connection. Generally, your point of view is above the connection so stabbing the pin into the box allows the operator a better view of what is going on. This results in faster trip times and less damage to the connections.

If for some reason, you had the connection above your line of sight, I guess the standard practice would be pin up and box down, but that is just not how a normal rig operates.

As for the connection types used in the Bottom Hole Assembly (BHA), yes, you are correct in that it is to minimize fatigue. The connections in the BHA are nearly always run in compression (as opposed to those in the drill pipe string which are under tension). The portions of the drillstring that are under tension tend to rotate about their own axis (at least as much as they can) as the tension tends to pull the string into alignment. Under compression, however, buckling can occur which can force the connection away from the center of rotation. When the axis of the connection is no longer aligned with the axis of rotation, the alternation forces due to bending are increased. In addition, the connection OD of the tools in the BHA can change dramatically while, in general, the ID of these tools is the same. The stiffness, or bending strength, of the box connection is dependent on the OD and the thread characteristics (lead, taper, thread length, etc...). The stiffness of the pin is dependent of the ID and the thread characteristics. To minimize the fatigue damage, you want to balance the bending strengths of the box and pin. This balance is known as the Bending Strength Ratio (BSR). See API RP7G, or other drilling handbook, for how to calculate the BSR and what range of BSR you should consider for your particular application.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close