API Casing Color Code

To determine the strength of various casing materials, API has designated defined grades. This grading system consists of a letter and number as P-110, L-80. The number is an arbitrary one (e.g. K-55) representing the min yield strength of the casing (Casing performance Properties), the number is an arbitrary one (e.g. N-80). There are also non-API casings that we use in special cases as deep wells or in high-corrosive environments. The API has defined a color code for the different grades of steel used for making casing and collars. These are shown below.

Grade	Color Coating on Couping	Color Band on Couping	Color Band on Pipe Body	Drawing
H-40	Black	–	–
J-55	Green	Letter “J” (Yellow)	One Green band
K-55	Green	–	Two Green bands
N-80	Red	–	One Red band
L-80	Red	One Brown band	One Red band and One Brown band
L80-CR9	Red	Two Yellow bands	One Red band, One Brown band and Two Yellow bands
L80-CR13	Red	One Yellow band	This API Casing Color Code had One Red band, One Brown band and One Yellow bands
C-90	Purple	–	One Purple band
C-95	Brown	–	One Brown band
T-95	Silver	–	One Silver band
P-110	White	–	One White band
Q-125	Orange	–	One Orange band

In the design of casing and tubing strings, the minimum yield strength of the steel is taken as the basis of all strength calculations

Grade	Minimum Yield Strength (PSI)	Maximum Yield Strength (PSI)	Min Tensile Strength (PSI)
H 40	40,000 PSI	80,000 PSI	60,000 PSI
J 55	55,000 PSI	80,000 PSI	70-95,000 PSI
C 75	75,000 PSI	80,000 PSI	70-95,000 PSI
N 80	80,000 PSI	110,000 PSI	100,000 PSI
L 80	80,000 PSI	95,000 PSI	100,000 PSI
C 90	90,000 PSI	105,000 PSI	100,000 PSI
C 95	95,000 PSI	110,000 PSI	105,000 PSI
P 110	110,000 PSI	140,000 PSI	125,000 PSI
Q 125	125,000 PSI	150,000 PSI	135,000 PSI