From 2000 PSI to 25000 PSI: How to Read the "Pressure Class" of Petroleum Equipment

2026-10-10 19:28:53 超级管理员 0

1. PSI and MPa: Two units for pressure

PSI stands for pound-force per square inch, and 1 MPa ≈ 145 psi. API Spec 6A defines rated working pressure classes of 2000, 3000, 5000, 10000, 15000 and 20000 PSI, corresponding to approximately 14, 21, 35, 70, 105 and 140 MPa respectively. 25000 PSI (around 172 MPa) represents cutting-edge ultra-high pressure, applied for ultra-deep wells in deep subsurface and deep sea.

20000 PSI equals roughly 138 MPa, equivalent to the weight of a compact car pressing on an area the size of a fingernail — this explains why pressure-containing components must be forgings and individually subjected to pressure testing.

2. Material Classes AA～HH: Classification of corrosion resistance

AA and BB cover carbon steel or low-alloy steel; CC and DD impose stricter requirements for stainless steel; EE, FF and HH are designed for H₂S-containing sour environments, with corrosion-resistant alloys selected in accordance with NACE MR0175 / ISO 15156. Wrong selection of material class may lead to sulfide stress cracking (SSC) in sulfur-bearing wells, resulting in catastrophic consequences.

3. Temperature Classes K～Y: Toughness for low temperatures, strength degradation for high temperatures

K (-60～82℃), L (-46～82℃), P (-29～82℃), R (ambient temperature), S (-18～66℃), T (-18～82℃), U (-18～121℃), V (2～121℃), X (-18～180℃), Y (-18～345℃). The low-temperature range assesses low-temperature impact toughness and resistance to brittle fracture, while the high-temperature range relates to strength degradation and ageing of non-metallic seals. The core challenge for ultra-low temperature Christmas trees is "withstanding high pressure without brittle failure at extremely low temperatures".

4. PSL and PR: Manufacturing requirements and performance verification

PSL 1～4 (including PSL3G): Product Specification Levels. Higher levels impose stricter requirements on material traceability, non-destructive testing and documentation. Higher PSL requirements apply to scenarios with higher pressure, H₂S presence, gas wells and densely populated areas.

PR 1 / PR 2: PR2 requires a full set of verifications including high and low temperature cycling, pressure cycling, endurance cycling, tensile, impact and hardness tests, and chemical analysis. API 6A explicitly stipulates that manufacturers without PR2 qualification are not permitted to produce surface safety valves.