Disclaimer

Last updated: July 2026

CalcHub is an engineering aid provided by LM Technologies AS. It is designed to support, not replace, the judgment of a qualified engineer.

Calculations are performed in accordance with API 579-1/ASME FFS-1, as implemented by LM Technologies AS. CalcHub is not affiliated with API or ASME. It is not endorsed by or produced by either organization. Every assessment result displayed or exported by CalcHub states the specific standard section or equation it was calculated from, so results can be independently checked against the published standard.

You, the user, are responsible for:

  • Verifying that all inputs entered into CalcHub are correct and applicable to your equipment.
  • Confirming that the assessment level, method, and damage mechanism selected are appropriate.
  • Having a qualified engineer review any result before it is used to support an operating, inspection, or repair decision.

Who should prepare and review an assessment

CalcHub supports Level 1 and Level 2 assessments only. Use of the software does not transfer responsibility away from the equipment Owner-User or the engineers and inspection personnel involved. In practical terms, the API 579-1/ASME FFS-1 personnel framework means:

  • Suitable background: The Owner-User should confirm that each participant's training and practical experience are appropriate for the difficulty of the work and the consequences of getting it wrong. Participants must be able to show that they can perform their assigned tasks. See paragraph 1.5.1.
  • Engineering authority: The engineer responsible for the assessment must understand the selected method, be permitted to carry out that engineering work under local rules, and satisfy any additional competence requirements set by the Owner-User. The engineer should also have a high degree of familiarity with API 579-1/ASME FFS-1, including its scope, applicability limits, data requirements, and Level 1 and Level 2 procedures. See paragraphs 1.4.3 and 1.5.4.
  • Level 1: A suitably qualified member of the plant inspection or engineering team may complete the screening calculation. If it is prepared by inspection personnel or another specialist who is not acting as the responsible engineer, it should receive engineering review before anyone relies on the result. See paragraphs 1.4.3.1 and 2.4.1.1.
  • Level 2: The more detailed Level 2 calculation should be handled by a Plant Engineer or FFS specialist with relevant assessment experience. That person should understand the equipment and service conditions, and should involve other specialists where their own expertise is not sufficient. See paragraphs 1.4.4 and 2.4.1.2.
  • Relevant specialist input: The damage mechanism and calculation may call for support from materials, mechanical or structural, inspection, fracture mechanics, nondestructive examination, or process engineering specialists. See paragraph 1.4.3.2.

There is no single worldwide credential or fixed experience period that covers every assessment. Local legal requirements and the Owner-User's own competence rules determine what is acceptable in each case. CalcHub does not check a user's qualifications and cannot serve as the required technical review.

Selected API 579 applicability limitations

The points below are CalcHub's summary of several important boundaries in the standard. They are included as warnings, not as a substitute for reviewing all requirements in the applicable API 579-1/ASME FFS-1 procedure.

  • Part 4, Level 1 and Level 2: When metal loss is close to a Type C component, check the clear distance from the edge of the damaged area to the nearest weld associated with the structural discontinuity. Figure 4.6 defines the minimum as Lmsd ≥ 1.8√(D·tc). See paragraph 4.2.6(e) and Figure 4.6.
  • Part 5, Level 1 and applicable Level 2: For the local-metal-loss route, Equation 5.10 uses the same separation check: Lmsd ≥ 1.8√(D·tc). The internal-pressure Level 2 method in paragraph 5.4.3.2 refers back to this Level 1 criterion. Do not extend it to a different Part 5 route without checking that route's requirements.
  • Part 9, Level 1: The simplified cylinder and sphere screening route covers axial and circumferential cracks whose plane is normal to a principal stress direction. It also assumes that the crack is separated from a major structural discontinuity by at least 1.8√(D·t), using inside diameter D and current wall thickness t. This restriction belongs to the Level 1 geometry rules in paragraph 9.2.2(e)(1)(v); it is not a general Part 9 Level 2 condition.
  • Part 10, Level 2: Do not use the separation equation above as an entry criterion for the CalcHub creep calculation. Paragraph 10.2.2.2(d), together with the damage list in paragraph 10.2.2.1(d), places components with crack-like flaws outside the supported Level 2 route.

LM Technologies AS disclaims all liability, to the extent permitted by applicable law, for decisions made on the basis of CalcHub's output. CalcHub is provided "as is," without warranty of any kind, express or implied, including but not limited to fitness for a particular purpose.

Questions about this disclaimer can be sent to the contact address on our Terms page.