API 5CT C110 Casing Tubing
What is API 5CT C110 Casing & Tubing?
API 5CT C110 is a high-strength, restricted-yield casing grade designed specifically for Sour Service (H2S) environments. It belongs to Group 2 of the API 5CT specification.
C110 is engineered to bridge the gap between high strength and resistance to Sulfide Stress Cracking (SSC). While standard high-strength grades like P110 are brittle and fail instantly in H2S environments, C110 utilizes a highly controlled chemistry (Cr-Mo alloy) and rigorous Quench and Temper (Q&T) heat treatment to maintain a maximum hardness of 30 HRC. This allows operators to use high-strength strings in deep, high-pressure, sour wells.
Secure Your High-Pressure Sour Wells! Request a Quote for NACE MR0175 Compliant C110 Casing Today.
API 5CT C110 Casing & Tubing Color Code
To prevent catastrophic field errors, C110 has a unique color identification:
Pipe Body: One White Band + One Brown Band.
Couplings: The entire coupling is painted White with a Brown stripe in the center.
API 5CT C110 OCTG Pipe Chemical Composition
C110 requires a high degree of hardenability to ensure a uniform martensitic structure. The sulfur and phosphorus levels are kept extremely low to improve toughness and SSC resistance.
| Element | Requirement (Mass Fraction, %) |
| Carbon (C) | 0.25% – 0.35% (Typical) |
| Chromium (Cr) | 0.40% – 1.50% |
| Molybdenum (Mo) | 0.25% – 0.85% |
| Phosphorus (P) | ≤ 0.020% |
| Sulfur (S) | ≤ 0.005% (Critical for SSC resistance) |
| Silicon (Si) | ≤ 0.35% |
API 5CT C110 oilfield casing pipe Mechanical Properties
The "Restricted Yield" means the gap between minimum and maximum yield is very narrow (only 10,000 psi), ensuring the material behaves predictably under stress.
| Property | Value (Imperial) | Value (Metric) |
| Yield Strength | 110,000 – 120,000 psi | 758 – 827 MPa |
| Tensile Strength (Min) | 115,000 psi | 793 MPa |
| Hardness (Maximum) | 30.0 HRC | 286 HBW |
| Yield to Tensile Ratio | ≤ 0.93 | ≤ 0.93 |
API 5CT C110 casing pipes Size Chart
C110 is primarily used in deep production strings where high tension and collapse resistance are required.
| Outer Diameter (OD) | Nominal Weight | Wall Thickness | Inside Diameter (ID) | Drift Diameter |
| Inch (mm) | lb/ft | mm | mm | mm |
| 4-1/2" (114.30) | 11.60 | 6.35 | 101.60 | 98.42 |
| 4-1/2" (114.30) | 13.50 | 7.37 | 99.56 | 96.39 |
| 5" (127.00) | 15.00 | 7.52 | 111.96 | 108.79 |
| 5" (127.00) | 18.00 | 9.19 | 108.62 | 105.45 |
| 5-1/2" (139.70) | 17.00 | 7.72 | 124.26 | 121.08 |
| 5-1/2" (139.70) | 20.00 | 9.17 | 121.36 | 118.19 |
| 5-1/2" (139.70) | 23.00 | 10.54 | 118.62 | 115.44 |
| 6-5/8" (168.28) | 24.00 | 8.94 | 150.39 | 147.22 |
| 7" (177.80) | 26.00 | 9.19 | 159.42 | 155.45 |
| 7" (177.80) | 29.00 | 10.59 | 156.62 | 152.65 |
| 7" (177.80) | 32.00 | 11.51 | 154.78 | 150.81 |
| 7-5/8" (193.68) | 33.70 | 10.92 | 171.84 | 167.87 |
| 7-5/8" (193.68) | 39.00 | 12.70 | 168.28 | 164.31 |
| 9-5/8" (244.48) | 40.00 | 10.03 | 224.42 | 220.45 |
| 9-5/8" (244.48) | 47.00 | 11.99 | 220.50 | 216.53 |
| 9-5/8" (244.48) | 53.50 | 13.84 | 216.80 | 212.83 |
API Standard Length Ranges
C110 casing is supplied in three API "Ranges" to accommodate different derrick heights:
Range 1: 16.0 – 25.0 ft (4.88 – 7.62 m)
Range 2: 25.0 – 34.0 ft (7.62 – 10.36 m) - Most common for onshore.
Range 3: 34.0 – 48.0 ft (10.36 – 14.63 m) - Often used for offshore/deepwater.
NACE MR0175 Requirements for API 5CT C110 Casing Tubing
C110 is explicitly listed in NACE MR0175/ISO 15156 for use in H2S environments. To be compliant, it must meet these criteria:
Heat Treatment: Must be Quenched and Tempered (Q&T).
Hardness Limit: The hardness must not exceed 30 HRC in any part of the pipe (body, weld zone, or coupling).
SSC Testing (Mandatory): Each heat must pass Sulfide Stress Cracking (SSC) testing per NACE TM0177:
Method A (Tensile Test): Tested at 85% or 90% of specified minimum yield strength (SMYS).
Method D (DCB Test): To determine the fracture toughness ( KISSC ) in sour environments.
GNEE API 5CT C110 Casing Pipe process line
GNEE API 5CT C110 Oil well casing pipe test equipments
GNEE API 5CT C110 OCTG Casing Pipe certificate
FAQ
What is the difference between P110 and C110?
While both grades share a minimum yield strength of 110,000 psi, the critical difference is their performance in Sour Service ( H2S ) environments:
Environment: C110 is specifically designed for Sour Service ( H2S ); P110 is a general-purpose grade for Sweet Service (no H2S ).
Hardness: C110 has a strictly controlled maximum hardness of 30 HRC to prevent cracking. P110 has no mandatory API hardness limit and is highly susceptible to brittle failure in the presence of H2S.
Testing: C110 must pass mandatory SSC (Sulfide Stress Cracking) testing per NACE standards. P110 does not require this testing.
Chemistry: C110 uses a more expensive Cr-Mo alloy with very low Sulfur/Phosphorus to ensure toughness; P110 chemistry is less restricted.
What size casing should I use?
The size of the casing you should use depends on your well depth, geological conditions, and the size of the production tubing you plan to install.
Most wells follow a "nested" standard casing program:
Surface Casing (13-3/8"): Protects freshwater zones and provides initial structural support.
Intermediate Casing (9-5/8"): Used to seal off high-pressure zones or unstable formations before reaching the target depth.
Production Casing (7" or 5-1/2"): The final string that houses the production tubing.
Production Tubing (2-3/8" to 4-1/2"): Installed inside the production casing to bring oil/gas to the surface.
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