According to API RP 7G (Recommended Practice for Drill Stem Design and Operating Limits), drill pipe is classified based on its physical condition and the amount of wear on the pipe body.
4 recognized classes
New Class
Condition: This pipe is unused and meets the original manufacturing specifications (API Spec 5DP).
Wall Thickness: Has 100% of its original wall thickness (minus allowable manufacturing tolerances).
Identification: Usually identified by the manufacturer's markings and lacks any wear bands.
Premium Class
Condition: This is the most commonly used pipe in the industry. It has been used but is still in excellent condition.
Wall Thickness: Must have a minimum of 80% of the original wall thickness remaining.
Identification: Indicated by two white bands painted on the pipe.
Usage: Standard for most drilling operations where high pressures and tensions are expected.
Class 2
Condition: This pipe has significant wear compared to Premium Class.
Wall Thickness: Must have a minimum of 70% of the original wall thickness remaining.
Identification: Indicated by one yellow band painted on the pipe.
Usage: Typically used in shallow wells or lower-stress drilling environments where high performance is not critical.
Class 3
Condition: This pipe is heavily worn and nearing the end of its useful life.
Wall Thickness: The wall thickness has fallen below 70% of the original.
Identification: Indicated by one orange band painted on the pipe.
Usage: Generally considered unsafe for standard drilling operations. It is often relegated to "structural" use or very low-pressure service.
Comparison Table
| Class | Remaining Wall Thickness (RWT) | Color Code (Industry Standard) | Reliability |
| New | 100% | No Bands / Brand Markings | Maximum |
| Premium | 80% or more | 2 White Bands | High (Industry Standard) |
| Class 2 | 70% to 79% | 1 Yellow Band | Medium |
| Class 3 | Less than 70% | 1 Orange Band | Low / Reject |
| Scrap | Unusable | 1 Red Band | Scrap |
API Drill Pipe Classification & Selection Guide
(Based on API RP 7G Standards)
| Class | Remaining Wall Thickness (RWT) | Industry Color Code | Structural Integrity | Selection Advice & Typical Applications |
| New | 100% | No Bands (Stenciled markings) | Maximum | Deepwater, HPHT (High-Pressure High-Temp), and Critical Exploration Wells. Offers the highest safety factor for extreme conditions. |
| Premium | Min. 80% | 2 White Bands | High (Industry Standard) | The preferred choice for most drilling operations. Ideal for horizontal wells, deep wells, and complex formations. Best balance of performance and cost. |
| Class 2 | 70% - 80% | 1 Yellow Band | Medium | Shallow wells, workover operations, or low-stress sections of the drill string. Cost-effective, but not recommended for high-torque or high-angle wells. |
| Class 3 | Less than 70% | 1 Orange Band | Low (Unsafe) | Prohibited for drilling operations. Typically downgraded for structural use, such as piling, handrails, or construction supports. |
| Scrap | Critical Damage | 1 Red Band | None | Disposal only. Severe physical damage or wall thickness insufficient for any pressure or load-bearing use. |
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FAQ
What is the API standard for drilling?
API standards in the drilling industry primarily refer to a series of technical specifications developed by the American Petroleum Institute (API), among which the core standards directly related to drilling operations are API 5DP and API 7K.
What are the different grades of drill pipe?
The main grades of drill pipe, according to the API 5DP standard, are classified into four categories: E75, X95, G105, and S135. These grades represent the minimum yield strength of the steel-the higher the number, the greater the strength-and are suitable for more complex or deeper well conditions.
