In the API 5L standard, common suffixes and letter combinations for line pipe include R, N, Q, M, S, O, X, and others; however, it is important to note that these do not all belong to the same category of suffixes, and their meanings depend on the steel grade, manufacturing process, and standard version.
1. Common API 5L Line Pipe Suffixes and Their Meanings
| Suffix or Identifier | Meaning | Description |
|---|---|---|
| PSL1 | Product Specification Level 1 | Product Specification Level 1 |
| PSL2 | Product Specification Level 2 | Product Specification Level 2, with stricter quality control requirements |
| R | As-rolled | Hot-rolled condition |
| N | Normalizing / Normalized | Normalized or normalized-rolled delivery condition |
| Q | Quenched and Tempered | Quenched and tempered condition |
| M | Thermomechanical Rolled | Thermomechanically rolled condition |
| S | Sour Service | Requirements for service in acidic environments, typically involving H₂S environments |
| O | Offshore Service | Additional requirements related to offshore engineering; specific details are subject to the provisions of the standard |
| X | High-Strength Steel Grade Designation | e.g., X42, X52, X65, X70, etc. |
2. Specific Representations of Suffixes for API 5L Steel Grades
In API 5L, some steel grades use letter suffixes to indicate the delivery condition. Common combinations are as follows:
| Steel Grade Designation | Delivery Condition |
|---|---|
| L245 or X42 | Basic steel grade designation without a delivery condition suffix |
| L245N or X42N | Normalized or normalized rolled |
| L245Q or X42Q | Quenched and tempered |
| L245M or X42M | Thermomechanically rolled |
| L360N or X52N | Normalized or normalized rolled |
| L360Q or X52Q | Quenched and tempered |
| L360M or X52M | Thermomechanically rolled |
| L415M or X60M | Thermomechanically rolled |
| ... | ... |
3. Common Special Requirement Suffixes in API 5L
(1) S: Typically used to indicate sour service requirements, such as line pipe conforming to relevant sour service specifications.
In API 5L PSL 2 line pipe, “S” may serve as an additional identifier for sour service and is used in combination with the delivery condition letter.
For example:
| Steel Grade Suffix | Meaning |
|---|---|
| X52NS | Normalized condition + sour service requirements |
| X52QS | Quenched and tempered + sour service requirements |
| X52MS | Thermomechanical rolling + sour service requirements |
| BNS | Normalized condition + sour service requirements |
| BQS | Quenched and tempered + sour service requirements |
| BMS | Thermomechanical rolling + service requirements for acidic environments |
Specific requirements for acidic environments should be confirmed in conjunction with the relevant appendices of API 5L and the technical procurement specifications.
(2) O: Relates to additional requirements specific to offshore engineering and should not be simply regarded as a generic steel grade suffix for all API 5L products.
PSL2: Is not a steel grade suffix, but rather a product specification level, indicating more stringent technical requirements than PSL1.