Fitness For Service

ETD Consulting assesses the fitness for service of plant components and material under operating conditions, which can confirm that a material or component is safe to use, give advanced warning of in-service failures and resolve disputes between suppliers and operators.

This can help the plant operators in reducing cost by avoiding costly unplanned outages and at the same time minimise excessive maintenance or premature inspection, as well as reassuring operators of the quality of components. ETD Consulting has excellent expertise in the use of standardised approaches such as those outlined in API 579.

ETD's Approach to Fitness-For-Service

Typically components are designed for 100,000 hours service. Plants operators are faced with an increasing array of ageing plants and equipment, in many cases close to or even beyond the original design life. Furthermore,  damage accumulates with service time. This damage accumulation may be accelerated by a number of factors - for instance, poor design/fabrication, or possible changes in the service environment.

Once the plant reaches its design life, or if the operating conditions change, a fitness for service review needs to be implemented. As well as this plant operators often require assurances that material or components provided to them meet their requirements, requiring a fitness for service review. ETD Consulting implements this assessment in a staged way, as follows - 


Step 1: Preliminary Fitness-For-Service Assessment and Inspection

A level I fitness for service assessment is normally implemented before any on-site assessment or laboratory-based work commences. Initial calculations are usually based on design information and any other information that can be derived from historic inspection, operating data or component/material specification. The results of these calculations are combined with ETD Consulting’s experience of assessing plant and material, to enable us to undertake a preliminary and conservative fitness-for-service review. Normally, the assessment is performed using API 579 and relevant material specifications (BS, ASTM, EN). This assessment allows ETD Consulting to identify those components that are fit for further service and those that require further evaluation. Based on the results of step 1, an inspection strategy for the key components in the plant is then drawn up. 

Step  2: Implementation of the Inspection Program

The focused inspection program on critical components defined in Step 1 is then implemented, either by the client or by a team supervised by an ETD Consulting engineer. Normally, an inspection technique with automated data collection will be recommended, to ensure that a permanent record of the findings is available. In the case of newly manufactured materials and components, ETD Consulting can perform either direct inspection of the components or lab based work on samples provided by the client. This stage might involve NDE or mechanical testing.

Step 3: Final Fitness-For-Service Assessment  

Following completion of the step 2 assessment, the data will be compiled and a fitness-for-service evaluation will be implemented.  Depending on the findings, this may involve all three Levels (i.e. stage 1 to 3) of FFS assessment, with stage 3 being the most detailed calculational phase, involving finite element modelling to refine the stress analysis of the component investigated or material tested using the data gathered during step 2.