An engineering critical assessment (ECA) – also known as fracture analysis – is a fitness-for-service procedure that uses fracture mechanics principles to determine the defect tolerance of safety critical items.
When evaluating the integrity of structures such as pipelines and pressure vessels, platforms, rigs and wind turbines, an ECA enables the user to make informed and confident decisions on the most appropriate remedial measures to take.
An ECA is used to decide whether a given flaw is safe from brittle fracture, plastic collapse, fatigue crack growth or creep crack growth under specified loading conditions. It can therefore be used:
·         During design, to assist in the choice of welding procedure and/or inspection techniques.
·         During fabrication, to assess:
o    a) the significance of known defects which are unacceptable to a given fabrication code; or 
o    b) the maximum critical flaw size, minimum fracture toughness or maximum operating stresses.
·         During operation, to assess flaws found in service and to make decisions as to whether they can safely remain, or whether down-rating, repair or replacement are necessary. 
There are standardised methods for ECA and these are now used routinely by the oil and gas, nuclear, aerospace,petrochemical and power industries to determine the safety of their structures. TWI has been deeply involved in the development of methods for conducting ECAs for more than 40 years, and can offer this service to its members on a consultancy basis. Our broad range of expertise and facilities, including advanced NDT, fatigue and fracture testingallows us to gather in-depth data as the basis for our ECAs.

ECA analysis to develop girth weld flaw acceptance criteria in accordance with the following codes:
·   API 1104 – Appendix A (19th and 20th editions)
·   DNV OS F101
·   DNV RP F108
·   BS 7910
·   API 579
Critical components assessed:
·   Flow lines including high pressure and high temperature (HP/HT)
·   Risers (SCRs, TTRs, hybrid, etc.)
·   Export pipelines
Pipeline installation methods include:
·   S-Lay
·   J-Lay
·   Reeled installation
Special ECA considerations:
·   Analysis, qualification and validation requirements for strain-based design, including reeling
·   Sour service ECA analysis and validation testing

Source :
http://www.microalloying.com/offshore-services/eca
http://www.twi-global.com/capabilities/integrity-management/engineering-critical-assessment/