Technical guide
API 6A PSL, PR, Temperature and Material Classes Explained
Product Specification Level (PSL)
The PSL sets the level of quality control, testing and traceability. PSL 1 is the baseline. PSL 2 adds tighter controls. PSL 3 adds full traceability, more NDE and longer hydrotest holds. PSL 3G adds gas testing. PSL 4 is the highest level, used for critical HPHT and sour gas wells.
Performance Requirement (PR)
PR1 is the standard requirement. PR2 requires design validation testing (pressure and temperature cycling, and load testing), which is typical for gas and critical service.
Temperature classes
| Class | Range |
|---|---|
| K | −60 °C to 82 °C |
| L | −46 °C to 82 °C |
| P | −29 °C to 82 °C |
| R | Room temperature |
| S | −18 °C to 66 °C |
| T | −18 °C to 82 °C |
| U | −18 °C to 121 °C |
| V | 2 °C to 121 °C |
Ratings that span two classes are written as combinations. For example, "P-U" means −29 °C to 121 °C.
Material classes
| Class | Service | Body / bonnet | Pressure-controlling parts |
|---|---|---|---|
| AA | General service | Carbon or low-alloy steel | Carbon or low-alloy steel |
| BB | General service | Carbon or low-alloy steel | Stainless steel |
| CC | General service | Stainless steel | Stainless steel |
| DD | Sour service | Carbon or low-alloy steel | Carbon or low-alloy steel |
| EE | Sour service | Carbon or low-alloy steel | Stainless steel |
| FF | Sour service | Stainless steel | Stainless steel |
| HH | Sour service | CRA | CRA |
Sour classes are followed by the maximum allowable H2S partial pressure, or "NL" for no limit (for example, DD-NL or HH-1.5).
Frequently asked questions
What PSL should I specify for a sour gas well?
Most operators specify PSL 3 or PSL 3G with PR2 for sour gas wells, and PSL 4 for HPHT or critical wells. Follow your company's specification, which usually defines the minimum PSL by well category.
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