Fitness For Service

Fitness for Service (FFS) is a standard used in the petrochemical industry that is applied to in-service equipment in order to determine its ability to continue in service.

Why Should We Use It?

Fitness for Service has the potential to save clients hundreds of thousands and even millions of dollars. This is because FFS has the potential to show that existing equipment can continue service in conditions that may have previously been thought to necessitate a shutdown.

So What's Involved?

Fitness for Service, as governed by API-579, is broken down into fourteen (14) parts
and three (3) levels.  Each part, after Part 1 (Introduction) and Part 2 (Procedure), relates to a 
type of damage.  For example,  Part 3 is Assessment of Existing Equipment for Brittle Fracture 
and Part 11 is Assessment of Fire Damage.

There are three levels to Fitness for Service.  As the level increases, the complexity and  
information  required  via  inspection  increases  while  the  level  of  conservatism decreases.



  • Level  1  - A level 1 assessment uses a combination of screening curves, tables and a few computations.  It is quicker and more conservative than the next two levels.

  • Level  2  - A level 2 assessment is less conservative than a level 1 assessment. The  amount  of  time  required  can  be  substantial  and  the  computations  per- formed  start  to  become  complex.   This  level  sometimes  requires  the  use  of specialized software.

  • Level  3  -  A  level  3  assessment  typically  involves  the  use  of  Finite  Element Analysis (FEA) to model and replicate the loading scenarios found in the field. It is the least conservative and most complex component to FFS.

Engineering Design Services LLC can provide support for any level of analysis needed. Do you have a piece of equipment that may need an analysis performed? Reach out to speak with one of our Fitness for Service Consultants!

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Coverage Areas

Assessment of:

  • Existing Equipment for Brittle Fracture

  • General Metal Loss​

  • Local Metal Loss​

  • Pitting Corrosion

  • Hydrogen Blisters and Hydrogen Damage

  • Weld Misalignment and Shell Distortions

  • Crack-Like Flaws

  • Components Operating in the Creep Range

  • Fire Damage

  • Dents, Gouges and Combinations thereof

  • Laminations