API 5CT T95 occupies a precise and critical position in the OCTG grade ladder: it is the only standard API grade that combines 95 ksi yield strength with qualification for moderate H2S sour service under NACE MR0175. Where L80 lacks the pressure containment for deep or high-collapse wells, and P110 is excluded from any H2S environment, T95 fills the gap — provided it is specified and inspected correctly. The grade's defining procurement complexity is the hardness trap: the difference between API 5CT's 25.4 HRC limit for T95 Type 1 and NACE MR0175's 22 HRC ceiling is wide enough to contain fully API-compliant pipe that is non-conforming for sour service.
ZC Steel Pipe supplies API 5CT T95 casing and tubing to PSL-2, Type 1 and Type 2, with full MTC documentation and sour service hardness qualification. We supply to operators and EPC contractors working in sour and mixed service wells across Africa, South America, and Southeast Asia. This guide covers everything required to specify T95 correctly — grade mechanics, type selection, NACE hardness trap, comparison against L80 and P110, and complete purchase order guidance.
What Is API 5CT T95?
T95 is defined in API Specification 5CT / ISO 11960 as a casing and tubing grade with a minimum yield strength of 655 MPa (95,000 psi). Three characteristics position it uniquely in the API grade ladder:
Bridging yield — at 95 ksi minimum, T95 delivers meaningfully higher collapse and burst resistance than L80 (80 ksi) while remaining below the hardness threshold that disqualifies P110 from sour service. The yield band of 655–758 MPa gives designers pressure containment that L80 cannot reach.
Mandatory Q+T with hardness ceiling — T95 must be produced by quench and temper heat treatment, and API 5CT imposes a maximum hardness limit — 25.4 HRC for Type 1. This hardness ceiling is what makes NACE MR0175 qualification possible, unlike P110 which has no hardness limit.
Two types with different hardness limits — Type 1 (25.4 HRC max per API) and Type 2 (22 HRC max per API, directly aligned with NACE). The type distinction is the single most important variable in T95 procurement for sour service wells.
Mechanical Properties
| Property | T95 Type 1 | T95 Type 2 |
|---|---|---|
| Minimum yield strength | 655 MPa (95,000 psi) | 655 MPa (95,000 psi) |
| Maximum yield strength | 758 MPa (110,000 psi) | 758 MPa (110,000 psi) |
| Minimum tensile strength | 724 MPa (105,000 psi) | 724 MPa (105,000 psi) |
| Maximum hardness (API) | 25.4 HRC | 22 HRC |
| Maximum hardness (NACE) | 22 HRC required for H2S | 22 HRC — directly met |
| Heat treatment | Q+T — mandatory | Q+T — mandatory |
| Min elongation | Per API 5CT formula | Per API 5CT formula |
| Charpy impact (PSL-2) | Per API 5CT Table C.36 | Per API 5CT Table C.36 |
The yield band — 655 to 758 MPa — is tightly controlled by design. A T95 pipe cannot exceed 758 MPa yield; a heat producing above that value is non-conforming and must be rejected. Verify both limits on the MTR.
The NACE Hardness Trap — Type 1 vs Type 2
This is T95's defining procurement complexity and the source of most specification errors.
NACE MR0175 / ISO 15156-2 permits carbon and low-alloy steel tubulars in H2S sour service only up to 22 HRC maximum hardness. API 5CT permits T95 Type 1 up to 25.4 HRC. The gap between these two limits — 22.1 to 25.4 HRC — is a zone where pipe is fully API-compliant but NACE non-conforming.
A T95 Type 1 pipe produced at 24 HRC meets API 5CT in every respect. It fails NACE MR0175 qualification for H2S service. In a sour well, that pipe is a well integrity risk that only becomes apparent after the string is run.
| Hardness | API 5CT Status | NACE MR0175 Status |
|---|---|---|
| ≤ 22.0 HRC | Conforming (T1 and T2) | Conforming |
| 22.1–25.4 HRC | Conforming (T1 only) | Non-conforming — not permitted in H2S |
| > 25.4 HRC | Non-conforming | Non-conforming |
Safe specification paths for sour service:
- Specify T95 Type 2 — API hardness limit is 22 HRC, directly aligned with NACE. No gap.
- Specify T95 Type 1 + SR15 — Supplementary Requirement 15 mandates NACE hardness qualification on every heat. Requires MTR confirmation of individual hardness survey results, not just compliance with the 25.4 HRC API limit.
Do not accept a T95 Type 1 order for a sour service well based solely on the mill's API 5CT compliance statement. The compliance statement covers the 25.4 HRC API limit, not the 22 HRC NACE limit.
Chemical Composition
API 5CT specifies maximum element limits for T95. Many international project specifications and IOC technical addenda add tighter restrictions.
| Element | API 5CT Max % | Notes |
|---|---|---|
| Carbon (C) | 0.35 | Lower C preferred in project specs for sour service toughness |
| Manganese (Mn) | 1.90 | Controlled for hardenability consistency |
| Silicon (Si) | 0.45 | Deoxidiser |
| Phosphorus (P) | 0.020 | Tighter than N80/P110 — important for sour service fracture toughness |
| Sulphur (S) | 0.010 | Low S required — sulphide inclusions are crack initiation sites in H2S |
| Nickel (Ni) | 0.99 | Limits — higher Ni can reduce HIC resistance |
| Chromium (Cr) | 1.10 | Limits |
The S limit of 0.010% for T95 is significantly tighter than the 0.030% permitted for N80 and P110. This reflects the sour service context — sulphide inclusions in the steel matrix are preferential sites for hydrogen-induced cracking in H2S environments.
Standard Sizes
| OD (inches) | OD (mm) | Common Weights (lb/ft) | Typical Application |
|---|---|---|---|
| 4½ | 114.3 | 9.50–13.50 | Tubing, small production casing |
| 5 | 127.0 | 11.50–18.00 | Production casing, deep sour wells |
| 5½ | 139.7 | 14.00–23.00 | Production casing — most common T95 size |
| 7 | 177.8 | 17.00–38.00 | Intermediate and production casing |
| 7⅝ | 193.7 | 24.00–39.00 | Intermediate casing, deep sour wells |
| 9⅝ | 244.5 | 32.30–53.50 | Intermediate casing |
| 10¾ | 273.1 | 32.75–55.50 | Surface and intermediate casing |
T95 vs L80 vs P110 — Grade Selection
| Property | L80-1 | T95 Type 2 | P110 |
|---|---|---|---|
| Min yield strength | 552 MPa (80 ksi) | 655 MPa (95 ksi) | 758 MPa (110 ksi) |
| Max yield strength | 655 MPa (95 ksi) | 758 MPa (110 ksi) | 965 MPa (140 ksi) |
| API hardness limit | 23 HRC | 22 HRC (T2) | Not specified |
| NACE MR0175 | Yes — mild sour | Yes — moderate sour | Not permitted |
| Heat treatment | Q+T mandatory | Q+T mandatory | Q+T mandatory |
| Collapse resistance | Baseline | Better than L80 | Best of three |
| H2S compatibility | Mild | Moderate | None |
| Typical well depth | < 3,500 m | 2,500–5,500 m | 3,000 m+ sweet |
Choose L80 when the well contains H2S at mild concentrations, depth and pressure are moderate, and L80's 80 ksi yield provides adequate pressure containment.
Choose T95 when H2S is present at moderate levels and well depth or pressure requirements exceed what L80 can contain. T95 is also the correct grade when reservoir data shows H2S but P110's yield is needed for collapse — T95 fills that gap.
Choose P110 when the well is fully sweet (no significant H2S), depth is deep to ultra-deep, and maximum collapse and burst capacity governs the casing design.
PSL-1 vs PSL-2 for T95
| Requirement | T95 PSL-1 | T95 PSL-2 |
|---|---|---|
| NDE of pipe body | Not mandatory | Mandatory — full length UT or EMI |
| NDE of pipe ends | Not mandatory | Mandatory |
| Dimensional tolerances | Standard API | Tighter |
| Heat and pipe traceability | Heat number | Full heat + pipe number per joint |
| Charpy impact testing | Not mandatory | Mandatory |
| Hardness survey (SR15) | Optional | Strongly recommended for sour service |
| Typical use | Non-sour moderate wells | All sour service applications |
For any T95 order destined for an H2S environment, PSL-2 is the minimum acceptable specification. PSL-1 T95 lacks mandatory NDE and impact testing — gaps that are unacceptable in sour service completions. Most IOC and NOC project specifications require PSL-2 for all T95 as a baseline.
Connection Types for T95
| Connection | Suitability | Notes |
|---|---|---|
| STC | Not recommended | Low tensile efficiency — undersized for T95 string loads |
| LTC | Limited use | Acceptable only for light, shallow applications |
| BTC | Standard | Correct choice for most T95 sour service casing strings |
| Premium | Required for deep/HPHT sour | Metal-to-metal seal required for gas-tight and high-load applications |
BTC is the working connection for T95 in the majority of sour service applications. Premium connections are required when well conditions add high axial load, bending, thermal cycling, or gas-tight seal requirements to the already demanding sour service environment.
What to Check on a T95 MTR
| MTR Item | What to Verify | Why It Matters |
|---|---|---|
| Yield strength | 655–758 MPa — both limits | Over-yield above 758 MPa is non-conforming — reject |
| Tensile strength | Min 724 MPa (105 ksi) | Confirms Q+T microstructure achieved |
| Hardness | Type 1: ≤ 25.4 HRC API, confirm ≤ 22 HRC if sour; Type 2: ≤ 22 HRC | The NACE trap — individual hardness values must be recorded |
| Heat treatment | Q+T confirmed — reject any other | T95 cannot be produced by normalising or N+T |
| Sulphur | ≤ 0.010% for T95 | High S indicates sour service fracture risk |
| SR15 record | Hardness survey results by joint or heat | Required for NACE compliance confirmation |
| NDE records (PSL-2) | Full-length UT or EMI body scan confirmed | Absence = PSL-1 regardless of labelling |
| Charpy impact (PSL-2) | Values, temperature, specimen size | Confirms adequate toughness in sour environment |
How to Specify T95 on a Purchase Order
A complete T95 sour service purchase order must include:
- Standard — API 5CT or ISO 11960
- Grade and type — T95 Type 2 (preferred for sour) or T95 Type 1 + SR15
- OD and nominal weight — e.g. 5½ inch × 17.00 lb/ft
- Connection type — BTC or premium connection designation
- Range — R1, R2, or R3 (most strings are R3)
- PSL level — PSL-2 mandatory for sour service
- Supplementary requirements — SR2 (Charpy at project temperature), SR15 (NACE hardness qualification)
- Quantity — in joints or metric tonnes
- Delivery port — for freight and lead time planning
- MTC level — EN 10204 3.1 or 3.2
- Third-party inspection scope — witness hardness testing, NDE, dimensional inspection
References
- API Specification 5CT — Specification for Casing and Tubing (American Petroleum Institute)
- ISO 11960 — Petroleum and Natural Gas Industries: Steel Pipes for Use as Casing or Tubing
- NACE MR0175 / ISO 15156 — Materials for Use in H2S-Containing Environments in Oil and Gas Production
- API TR 5C3 — Technical Report on Equations and Calculations for Casing, Tubing, and Line Pipe