API 5CT seamless casing and tubing from H40 through Q125, including sour-service grades (L80, T95, C110) and HPHT grades (P110, Q125). PSL-1 and PSL-2, BTC and premium connections, full MTC documentation.
Applications
→Production casing — primary pressure containment string in oil and gas wells
→Intermediate casing — isolation of formation zones and pressure containment
→Surface casing — protection of fresh water zones and structural support
→Tubing — conveyance of production fluids from reservoir to surface
→Sour service wells — L80, T95, C110 for H2S environments (NACE MR0175)
→HPHT wells — P110 and Q125 for high-pressure high-temperature applications
→CO₂ corrosive environments — L80 13Cr for high-CO₂ production strings
→Deep offshore wells — high-collapse P110 HC for deepwater collapse-critical strings
Standards & Certifications
API 5CT / ISO 11960—Specification for Casing and Tubing — all grades
NACE MR0175 / ISO 15156—Sour service qualification — L80, T95, C110
API 5C5—Connection performance qualification
API TR 5C3—Collapse, burst and tensile load calculations
EN 10204 3.1 / 3.2—Mill test certificate documentation
Connection Types
STC — Short Round Thread
API
Standard API. Shallow, low-pressure surface casing.
LTC — Long Round Thread
API
Higher tensile efficiency than STC. Moderate depth intermediate casing.
BTC — Buttress Thread
API
High collapse and tensile capacity. Standard for N80, L80, T95 and moderate-depth P110.
Premium Connections
ZC Patent
Metal-to-metal seal. Required for HPHT, deep wells, P110/Q125 and gas-tight applications. ZC-patented.
L80, T95, C110 — NACE MR0175 / ISO 15156 qualified
API 5CT Mechanical Requirements by Grade
Grade
Min–Max Yield MPa / ksi
Min Tensile MPa / ksi
Max Hardness
Heat Treatment
H40
276–552 / 40–80
414 / 60
—
None required
J55
379–552 / 55–80
517 / 75
—
None required
K55
379–552 / 55–80
655 / 95
—
None required
N80-1
552–758 / 80–110
689 / 100
—
Normalise or Q+T
N80Q
552–758 / 80–110
689 / 100
—
Q+T only
L80-1
552–655 / 80–95
655 / 95
23 HRC
Q+T only
L80 13Cr
552–655 / 80–95
655 / 95
23 HRC
Q+T only
T95
655–758 / 95–110
724 / 105
25.4 HRC
Q+T only
P110
758–965 / 110–140
862 / 125
None
Q+T only
C110
758–965 / 110–140
793 / 115
30 HRC
Q+T only
Q125
862–1034 / 125–150
931 / 135
None
Q+T only
API 5CT grades stocked and manufactured by ZC Steel Pipe. Grade selection is driven by well depth, H₂S environment, and pressure containment requirements.
Grade
Yield MPa / ksi
Tensile MPa / ksi
Max Hardness
H₂S Service
Typical Application
H40
276 / 40
414 / 60
—
✗ No
Shallow, low-pressure wells
J55
379 / 55
517 / 75
—
✗ No
Shallow oil and gas wells
K55
379 / 55
655 / 95
—
✗ No
Surface casing, conductor
N80-1
552 / 80
689 / 100
—
✗ No
Medium-depth sweet wells
N80Q
552 / 80
689 / 100
—
✗ No
Medium-depth sweet wells (Q+T)
L80-1
552 / 80
655 / 95
23 HRC
✓ Yes
Mild sour service
L80 13Cr
552 / 80
655 / 95
23 HRC
✓ Yes
CO₂-corrosive tubing strings
T95
655 / 95
724 / 105
25.4 HRC
✓ Yes
Moderate sour / deep wells
P110
758 / 110
862 / 125
None
✗ No
Deep HPHT sweet wells
C110
758 / 110
793 / 115
30 HRC
✓ Yes
Severe sour / HPHT sour
Q125
862 / 125
931 / 135
None
✗ No
Ultra-deep HPHT wells
Sour Service Grade Selection
Procurement Note — H₂S Grade Selection
Never substitute P110 or Q125 for a sour-service grade based on cost or availability pressure.
NACE MR0175 hardness limits exist to prevent sulphide stress cracking — a brittle fracture mode
with no ductile warning in H₂S environments. The correct escalation path is L80 → T95 → C110
depending on H₂S partial pressure and well depth.
API 5CT casing and tubing dimensions and weight chart. Common sizes from 4½″ to 20″ casing and 1.050″ to 4½″ tubing — OD, wall thickness, weight range, and applicable grades per API 5CT. Contact us to confirm availability for specific size/grade combinations.
Casing — Common Sizes
OD (in)
OD (mm)
Weight Range (lb/ft)
Wall Range (mm)
Common Grades
Typical String
4½
114.3
9.50–15.10
5.21–8.56
N80, L80, T95, P110
Production casing / tubing
5
127.0
11.50–18.00
6.43–9.19
N80, L80, T95, P110
Production casing
5½
139.7
14.00–23.00
6.98–10.54
L80, T95, P110, C110
Production casing — most common
7
177.8
17.00–38.00
6.91–14.27
N80, L80, T95, P110
Intermediate / production casing
7⅝
193.7
24.00–45.30
8.33–15.11
L80, T95, P110, C110
Intermediate casing
9⅝
244.5
32.30–58.40
8.94–15.11
N80, L80, P110
Intermediate casing
10¾
273.1
32.75–65.70
7.09–13.84
J55, K55, N80
Surface casing
13⅜
339.7
48.00–72.00
8.38–12.19
J55, K55, N80
Surface casing
16
406.4
65.00–109.00
9.53–15.88
J55, K55
Conductor / surface
20
508.0
94.00–133.00
11.13–15.88
H40, J55
Conductor pipe
Tubing — Common Sizes
OD (in)
OD (mm)
Weight Range (lb/ft)
Wall Range (mm)
Common Grades
1.050
26.7
1.14–1.80
2.41–3.91
J55, N80
1.315
33.4
1.70–2.90
2.90–4.55
J55, N80
1.660
42.2
2.30–3.40
2.90–4.85
J55, N80
1.900
48.3
2.75–4.70
3.18–5.08
J55, N80, L80
2⅜
60.3
4.00–6.40
3.18–5.54
J55, N80, L80, T95, P110
2⅞
73.0
6.40–10.40
5.51–7.82
J55, N80, L80, T95, P110, C110
3½
88.9
7.70–12.95
5.49–8.31
J55, N80, L80, T95, P110
4
101.6
9.50–14.00
5.74–8.38
N80, L80, T95, P110
4½
114.3
9.50–15.10
5.21–8.56
N80, L80, T95, P110, C110
Procurement Note — Size Confirmation
The tables above show common API 5CT sizes. Not every size/grade combination is held in stock — ZC Steel Pipe is order-to-make. Send us your full specification (OD, weight, grade, connection, PSL, quantity) and we will confirm availability and lead time within one business day.
ZC Steel Pipe manufactures casing and tubing exclusively by the seamless process. All grades from N80Q through Q125 are produced by quench and temper heat treatment for controlled yield and hardness.
1
Billet Inspection
Continuous cast or rolled billets inspected for surface defects and internal quality before entry to the pipe mill.
2
Hot Rolling / Piercing
Billets heated to rolling temperature and pierced on a mandrel mill or push bench to form the seamless mother tube.
3
Sizing & Straightening
Hot-rolled tube sized to target OD and wall, then hot straightened for dimensional conformance.
4
Heat Treatment
Q+T grades (N80Q, L80, T95, P110, C110, Q125) quenched and tempered in continuous furnace lines to achieve the API 5CT yield band and hardness ceiling.
5
Cold Straightening
Post-heat-treatment straightening to API 5CT straightness limits.
6
End Finishing
Pipe ends machined to customer connection specification — STC, LTC, BTC, or premium thread profile. Thread protectors fitted before dispatch.
7
Inspection & Testing
Full mechanical testing, NDE, dimensional inspection and MTC documentation. Third-party inspector witness available throughout.
Production process — casing pipeProduction process — tubing pipe
All ZC Steel Pipe casing and tubing is tested and documented per API 5CT. PSL-2 orders include mandatory NDE and impact testing. Third-party inspection to EN 10204 3.2 available on request.
1Tensile test — yield strength, tensile strength, elongation per API 5CT
2Hardness test — Rockwell HRC per grade requirement; NACE qualification survey for sour service grades
3Charpy impact test — PSL-2 mandatory; SR2 at project-specified temperature
4Hydrostatic pressure test — per API 5CT mill test pressure formula
5Dimensional inspection — OD, wall thickness, straightness, length per API 5CT
6Non-destructive examination — full-length UT or EMI body scan (PSL-2); end-area UT
7Visual inspection — internal and external surface, thread form and finish
8Chemical composition analysis — heat analysis and product analysis per API 5CT
9Third-party inspection — SGS, Bureau Veritas, TÜV on request (EN 10204 3.2)
PSL-1 vs PSL-2 Testing Requirements
Requirement
PSL-1
PSL-2
NDE — pipe body
Not mandatory
Full-length UT or EMI
NDE — pipe ends
Not mandatory
Mandatory UT
Charpy impact test
Not mandatory
Mandatory per Table C.36
Dimensional tolerance
Standard API
Tighter OD, wall, straightness
Traceability
Heat number
Heat + pipe number per joint
Hardness survey (SR15)
Optional
Required for NACE qualification
MTC format
EN 10204 3.1 typical
EN 10204 3.1 or 3.2
Recommended for
Sweet wells, shallow depth
All sour service; HPHT; IOC projects
Click any image to view full size.
API 5CT casing pipe — mill production
Casing pipe yard storage
Casing pipe ends and threading
Tubing pipe — production
Casing and tubing — bundled supply
Mill inspection and loading
BTC buttress thread connection
Premium connection close-up
Casing & tubing well application diagram
Sour service and high collapse casing
API 5CT casing pipe weight calculator and burst pressure calculator. Calculate pipe weight per metre (kg/m) or per foot (lb/ft) from OD and wall thickness. All formulas per API 5CT / TR 5C3.
Pipe Weight per Metre
Formula: W = 0.02466 × t × (OD − t) kg/m | API 5C3
Internal Yield Pressure (Barlow)
Formula: P = 0.875 × (2 × Yp × t) / OD | API 5C3 Barlow with 87.5% wall tolerance
Quick Unit Converter
Results update as you type.
These calculators are provided as engineering reference tools. Always verify critical design values against full API 5CT / TR 5C3 calculations before use in casing design.
Supply Enquiry — Casing & Tubing
Tell us your grade, OD, weight, connection, PSL level and delivery port. We will respond within one business day with availability and lead time.
