Oil drill pipe is seamless tubing which was used to rotates the drill bit and circulates drilling fluid in the well. API spec. 5DP specifies the technical delivery conditions, size, weight, grade, material properties and other requirements for drill pipe. The standard gives us the guidelines for inspection & classification of your used drill pipe string. Dill pipe can be divided into following levels, classes and grades:

PSL-1: Specifies wall thickness, impact strength, and yield strength requirements specific to the material grade.

PSL-2: Additional mandatory requirements.

PSL-3: Additional mandatory requirements.

Drill pipe class defines the physical condition of the drill pipe in term of dimension ,surface damage and corrosion.

Class 1(New class) : Brand new (never used) and the strongest.

Premium(used pipe): The remaining wall shall not be less than 80% of the new specified wall. Premium Class drill pipe has become the NORM in the industry for drilling

Class 2: The remaining wall shall not be less than 70% of the new specified wall.

Class 3: The wall thickness is less than the minimum for class 2.

Drill pipe grades defines the Minimum yield strength and gives the requirements for the properties of the material :

E-75: Minimum Yield Strength (psi) 75000 .Grade E is utilized in medium depth wells from 10,000 to 15,000 feet.

X-95: Minimum Yield Strength (psi) 95000.

G-105:Minimum Yield Strength (psi) 105000

S-135：Minimum Yield Strength (psi) 135000

Among them, grades X, G and S belong to high strength drill pipe grades. The higher the steel grades, the higher the strength of the drill pipe (yield strength, tensile strength, torsional strength, anti-extrusion strength, etc.).