Introduction

Tensile strength of threaded pipes is a crucial factor that determines the lifespan of the well. Premium threads provide superior tensile strength and are improvement over the API standard. They are proprietary threading oil drill-pipe couplings.

Importance of Accurate Measurements

Failure of threads in an oil-field pipe can lead to catastrophe, with damage to life and property. Leads, Pitches, diameters, tapers and angles must be uniform with tight tolerances as well as free of occlusions and defects. Manufacturers need measuring systems in place to ensure they meet quality requirements. One of such measuring system used for this purpose is the Profile Projector.

Measurements on Profile Projectors

Measuring thread profile parameters on a profile projector is easy as it the crystal clear projection of the thread profile onto the screen and the use of highly precise linear glass scales ensure that the results are accurate. However the skill of the technician operating the Profile Projector is also very important because his visual accuracy in probing the points using cross-hairs is a factor affecting the measured results. However the use of Optical Edge Detector technology in Profile Projector where the software automatically detects edges eliminates errors resulting from probing points.

For premium threads which are large in size and are heavy, the Horizontal Profile Projector is best suited as its workstage can carry big heavy parts. Also, it has feature called the Helix angle where in the angle of the premium thread can be aligned to the light rays to make the measurements more easy.

For External threads dimensions such as leads, pitches, diameters can measured directly. The premium thread is placed on the movable workstage with the profile of the thread projected on the screen. The stage is then moved in the X or Y direction with the cross hair on the screen probing the points. The movement is captured in real-time by the glass scales and the results are displayed either on a Digital Read Out or DRO or in a Computer running the Metrology Software.

The Metrology Software has an added advantage of capturing and saving the drawings of the thread and also can give Pass/Fail results instantly using the fed-in tolerances.

Internal Threads can be measured indirectly by using a silcon gel. The gel takes shape of the internal threads and then measurements can be done on a profile projector.

Conclusion

The criticality of premium thread measurements necessitates that the measurements are accurate which can be achieved on a Profile Projector