The service a pipe goes into decides its specification more than the shape of the pipe does. A pipe carrying water, a pipe carrying a sour wellstream and a pipe sitting at minus 45 degrees Celsius and below are the same object and three different purchase items.
Applications by service
| Service | What drives the specification |
|---|---|
| Oil & Gas | Where the pipe sits in the chain — casing and tubing inside the well, line pipe for gathering and transmission, fittings and the artificial lift string at surface. Each is bought to a different specification. |
| Pipeline Transmission | The design pressure under ASME B31.8 or B31.4 sets the wall thickness and the grade; the soil and the terrain set the coating. |
| Sour Service | Hydrogen sulphide. Selection is by hardness rather than strength, under NACE MR0175 / ISO 15156. |
| Construction | Four separate jobs — carrying water, carrying fire protection, carrying structural load and standing in the ground as a pile — each with its own specification. |
| Boiler & Heat Exchanger | Tube is bought by outside diameter and wall thickness, not by nominal pipe size and schedule. |
| Low Temperature Service | Impact toughness at the service temperature, not tensile strength. Below the transition temperature steel can fail by brittle fracture. |
How the service sets the specification
Four things about the service change what has to be bought. Ask them in this order, because each one narrows the answer the next one gives:
- PressureSets the wall thickness through the design code, and the wall thickness sets the minimum yield strength the grade has to meet.
- TemperatureNarrows the choice of material, and for low-temperature service replaces strength with impact toughness as the qualifying property.
- The fluidDecides whether corrosion resistance is a material problem or a coating problem. Sour service is a material problem, and it is solved by controlling hardness.
- The environmentDecides the external coating and, for buried pipe, the internal lining. Both are specified and inspected separately from the pipe.
Where to go next
- Steel pipe standards & grades – what each grade requires and how to choose between them
- Steel pipe and line pipe – seamless, ERW, LSAW and SSAW, black, galvanized and coated
- Casing and tubing – API 5CT OCTG with couplings and accessories
- Request a quotation – send the design conditions, quantity and destination port
Frequently asked questions
Does the application really change the pipe I need?
It changes the specification, and often the standard. The same nominal size can be bought to API 5L, ASTM A106 or ASTM A53, and the differences between those standards — chemistry limits, testing, tolerances — are what make them different purchase items. The service is what tells you which one applies.
Which grades are used for sour service?
Grades with a controlled hardness ceiling. The governing document is NACE MR0175 / ISO 15156, and hardness rather than strength is what qualifies the material. In casing and tubing the sour-service grade in common use is L80; in line pipe it is a low-carbon, low-manganese chemistry with the hardness controlled through the delivery condition.
How is low-temperature service qualified?
By a Charpy V-notch impact test carried out at the service temperature. The material is qualified by fracture behaviour, not by strength, which is why a stronger grade is not automatically a better answer when it gets cold.
What information do you need to quote an application?
The service, the design pressure or the design code, the operating temperature, whether the stream is sour, the size and quantity, and the destination port. Where the project has a specification, send that — it usually answers all of the above.
Tell us what the pipe has to do — the fluid, the pressure, the temperature and the environment — and we will come back with the specification it implies. Working from a service rather than a specification?
Request a quotation