The exam covers basic piping geometry, standard material degradation tracking, and pressure design basics. Calculation types are split into the following operational categories:

1. Core API 570 Calculations (Usually Closed-Book)

These questions track the life and degradation of an active piping system. You must memorize these basic formulas.

Corrosion Rates ($CR$): You will be given historical wall thickness measurements over a span of years. You have to calculate either the Long-Term ($LT$) or Short-Term ($ST$) rate:

• Remaining Life ($RL$): Determining how long the pipe can stay in service before hitting its minimum required thickness (tmin​):

  RL=Corrosion Ratetactual​−tmin

  ​​

• Inspection Intervals: API 570 rules dictate that the next thickness measurement inspection must happen at 21​ of the remaining life or the maximum code interval (e.g., 5 years for Class 1, 10 years for Class 2), whichever is less.

2. Pressure Design & Pipe Wall Thickness (ASME B31.3 – Open Book)

These questions test your ability to look up code properties (like allowable stress or joint quality factors) and calculate limits for a straight pipe section.

• Pressure Design Thickness ($t$): Using the modified Barlow’s formula from ASME B31.3:

  t=2(SEW+PY)PD​

  Where:

  • $P$ = Internal design gauge pressure

  • $D$ = Outside diameter of the pipe

    Low Cost Easy to Use Spreadsheets for Engineering Calculations Available at Engineering Excel Spreadsheets

  • $S$ = Allowable stress value from ASME B31.3 Appendix A (Table A-1)

  • $E$ = Quality factor (weld joint or casting factor)

  • $W$ = Weld joint strength reduction factor

  • $Y$ = Coefficient from ASME B31.3 Table 304.1.1 (dependent on material type and temperature)

• Minimum Required Thickness (tm​): Adding mechanical allowances (like thread depth) and a specified corrosion allowance ($c$) to your pressure design thickness:

  tm​=t+c

3. Piping Blanks (ASME B31.3 Par. 304.5.3)

You will often be asked to calculate the minimum required thickness for a permanent blank (blind) installed between two flanges to isolate a line.

• Trick to watch for: You must look up the correct gasket inside diameter (dg​) or use the value directly provided in the question.

4. Flange Ratings & Working Pressures (ASME B16.5)

These don’t require heavy algebra, but they do require multi-step lookups that candidates often trip over:

• Given a specific flange Material Group, Flange Class (e.g., 150, 300, 600), and a Design Temperature, you must use the ASME B16.5 Pressure-Temperature tables to find the Maximum Allowable Working Pressure (MAWP).

• Determining the required system hydrostatic test pressure based on the limit of the flange versus the pipe.

5. Hydrostatic & Pneumatic Test Pressures (ASME B31.3)

You must be able to calculate the target pressure required to leak-test a modified or repaired piping system.

• Hydrostatic Test Pressure:

  Test Pressure=1.5×P×SD​ST​​

  (Where ST​ is the allowable stress at test temperature, and SD​ is the allowable stress at design temperature).

• Pneumatic Test Pressure:

  $$\text{Test Pressure}=1.1\times P$$

💡 Key Exam Trap: “Mill Tolerance”

On open-book ordering or calculation problems, pay close attention to whether the question mentions nominal pipe thickness vs. minimum minimum wall thickness. New manufactured pipes have a standard mill undertolerance of 12.5%. If a question asks you to verify if a new pipe schedule is adequate, you must multiply the nominal wall thickness by $0.875$ before using it in your comparison checks.