The String is composed of multiple sections of Pipes. A "stand" typically comprises two to three drill pipe joints, each around 60 to 90 feet in length. Each joint of pipe is referred to as a "single." According to API, there are three ranges of drill pipe length: R1, R2, and R3.
Five classes of drill pipe indicate the amount of wear a pipe joint has sustained during its lifetime.
Drill Pipe Class
- New
- Premium or class 1
- Class 2
- Class3
- Scrap
All new pipes become premium class as soon as they are used. The new pipe indicates it is directly from the manufacturer and has never been used. As soon as a joint of the new pipe is picked up for use on a rig, it is re-classified as premium or class 1 pipe. Interestingly, this allows the manufacturers a broader set of tolerances, with the pipe having to conform to the requirements for Premium grade rather than the new specification.
Criteria For Determining The Class
Once the drill pipe has been used, normal wear and other use-related defects cause it to lose some of its original strength. API has developed inspection criteria to determine the extent of damage. These criteria are used to assign the pipe to "classes" according to the extent of the damage. The inspection examines the following conditions with all the criteria having to be met for a drill pipe to gain the specific class.
- O.D. wall wear.
- Fatigue cracks.
- Dents and mashes.
- Stress-induced diameter variations. Stretched or shot.
- Internal corrosion and pitting.
- Internal erosion and wear.
- Corrosion cuts and gouges, longitudinal and transverse.
- Internal fatigue cracks.
- Any evidence of fatigue cracks or washouts and the pipe is designated as scrap.
- Slip area mechanical damage. Crushing, necking, cuts and gouges.
Identification Marks
Code marks, which are stenciled on the tool joint pin to identify drill pipe and string, record the following information:
- Manufacturers' symbols.
- Month connections welded on.
- Year connections welded on.
- Pipe mill code.
- Pipe steel grade.
Sometimes a mill slot plus one circumferential groove, about 3/8″ (9·5mm) wide, is milled onto the pin end of drill pipe grades higher than "E", but be in the habit of checking, as this can vary from contractor to contractor and rig to rig. A series of letter and number codes will be present on all API drill pipes, giving manufacturing data such as date of manufacture, manufacturer's code, and the grade of steel
API re-facing benchmarks show the position of the original shoulder so an inspector can determine if too much re-facing has occurred
The re-facing benchmark is positioned 1/8″ from the makeup face. The tolerance on this measurement is ±1/16″. Once re-facing has taken place such that 1/16″ of the make-up face has been removed, the joint must be re-cut or belled, and split boxes become a risk.
The API benchmark is only present at one location around the circumference of the tool joint. The API benchmark will not show if re-facing is uneven around the makeup face area. Proprietary benchmarks are available. The figure below shows the Grant-TFW benchmark. As it is a continuous line, it shows how perpendicular the re-facing is and how much has occurred.
As a professional drilling tool manufacturer certified by API Q1 system, Vigor continues to provide high-quality drill pipe products that meet API 5DP/API 7-1 standards for the global oil and gas industry. Our innovative "360° whole-process quality assurance system" includes three core values:
Technology-first service model
A team of engineers with more than 10 years of oilfield service experience provides simulation analysis of drilling conditions, and customizes drill pipe selection plans based on well depth structure, formation characteristics and drilling parameters to ensure that product performance and operation requirements are accurately matched.
Visual tracking of the whole production cycle
From raw material procurement (using Baosteel/Tata special pipe blanks) to finished product delivery, customers can view 28 key quality control nodes in real time through the ERP system: heat treatment curve verification, non-destructive testing report, and uptake test data.
Our service network has covered 26 oil-producing countries, and has provided products to 37 international energy companies such as Saudi Aramco, ExxonMobil, and Schlumberger, and achieved an industry-leading NPS value of 58 in the 2023 customer satisfaction survey.
To inquire about project cooperation proposals, please call +86-029-81161513 or visit www.vigordrilling.com/ submit a technical request form. Our engineering team will provide a customized solution within 2 hours.
For more information, you can write to our mailbox info@vigorpetroleum.com & mail@vigorpetroleum.com
