Dnv-rp-f118 ~upd~ | PLUS • 2026 |

DNV-RP-F118 is Recommended Practice that provides guidelines for the qualification and validation

of Automated Ultrasonic Testing (AUT) systems used specifically for pipeline girth welds

. It is the industry benchmark for ensuring that advanced non-destructive testing (NDT) can accurately detect and size weld flaws during offshore and onshore pipeline construction. DNV - Global Core Purpose and Scope

The document establishes a standardized framework to verify that an AUT system—including the hardware, software, and the operator's procedure—is capable of meeting the performance requirements specified in codes like DNV-ST-F101 . It covers: DNV - Global System Qualification:

Proving the general capabilities of a new or modified AUT system. Project-Specific Validation:

Verifying that a qualified system performs correctly for a specific project's parameters (e.g., material type, wall thickness, and weld profile). DNV - Global Key Components of Qualification According to DNV-RP-F118

, a full qualification program typically involves five critical stages: Documentation Review: A thorough check of technical specs and system design. Methodology Review: Assessing the scanning strategy and operating procedures. QA System Audit:

Evaluating the quality controls for maintenance and field operations. Performance Data Analysis: Reviewing existing data on detection and sizing accuracy. Final Evaluation:

Drawing formal conclusions on the system's fitness for purpose. The "Trial Weld" Process

A central part of the validation involves scanning "trial welds"—physical samples containing intentionally induced flaws. POD (Probability of Detection):

The system must demonstrate a high probability of finding defects of a certain size. Sizing Accuracy:

The system's measured flaw height and length are compared against actual values (often confirmed via macro-sectioning or metallography) to determine "sizing error". Industry Context & Challenges

While DNV-RP-F118 provides a clear structure, experts note that achieving "general validity" across different projects can be difficult. Factors like ultrasonic coupling weld geometry material properties

(e.g., Corrosion Resistant Alloys) significantly impact results, often requiring repeated validation for new configurations. statistical methods

used to calculate the Probability of Detection (POD) within this practice?

Subject: Key Insights on DNV-RP-F118 – Recommended Practice for Pipeline and Riser Damage Assessment

Post:

If you’re working with subsea pipelines or risers, DNV-RP-F118 is a must-know recommended practice.

This DNV document provides a standardized methodology for:

Damage assessment of dents, scratches, corrosion, and ovality
Acceptance criteria based on remaining strength and fatigue life
Repair decision support – when to monitor, repair, or replace

Why it matters:
Non-conservative assessments can lead to unexpected failures; overly conservative ones drive unnecessary costs. DNV-RP-F118 helps balance safety and integrity with operational economics. dnv-rp-f118

Key takeaways from the RP:

Dent + scratch interaction – specific screening criteria for combined defects
Fatigue – simplified S-N approaches for dents in cyclic loading
Corrosion allowance – clear guidance on wall loss and remaining burst strength

Pro tip:
Always cross-reference with DNV-ST-F101 (subsea pipeline systems) for design requirements – RP-F118 complements the standard for in-service assessment.

Discussion question for the community:
Have you applied DNV-RP-F118 to a pipeline damage case? What was the biggest challenge – data availability, defect interaction, or repair criteria?

👇 Drop your experiences below. Let’s share lessons learned.

#SubseaEngineering #PipelineIntegrity #DNV #OffshoreEngineering #AssetManagement

DNV-RP-F118 is a recommended practice titled Pipe girth weld automated ultrasonic testing system qualification and project specific procedure validation

Its primary objective is to provide a standardized framework for verifying that an Automated Ultrasonic Testing (AUT) system can reliably detect and size flaws in pipeline girth welds, specifically to meet the rigorous safety requirements of the DNV-ST-F101 submarine pipeline standard. DNV - Global Core Purpose and Scope

The practice was established to ensure consistency in how AUT systems—which have largely replaced radiography in offshore projects due to their efficiency and lack of radiation hazards—are qualified. It focuses on two critical performance metrics: Probability of Detection (PoD):

Demonstrating that the system will find flaws of a critical size. Sizing Accuracy:

Ensuring the system can accurately measure flaw height and length, which is vital for Engineering Critical Assessments (ECA). Key Qualification Stages According to DNV guidelines , a full qualification program typically includes: Technical Documentation Review:

Assessing the AUT system's design and operating methodology. Repeatability Testing:

Verifying that the system yields consistent results across multiple scans of the same weld. Temperature Sensitivity:

Testing the system's performance at project-specific temperatures (e.g., up to 70°C for some deepwater projects). Reliability Testing:

This is the most intensive phase, involving the inspection of "seeded" defective welds. Data Analysis:

Comparing AUT results against "ground truth" data, often obtained through high-precision Immersion Ultrasonic Testing (IUT) or Destructive Testing (DT). Statistical Requirements

DNV-RP-F118 is known for its strict statistical thresholds to ensure high confidence in the data: PoD Criterion:

A system is generally considered qualified if it demonstrates a 90% Probability of Detection with a 95% confidence level for the largest acceptable defect. Sample Size:

While basic statistical confidence might start at 29 samples, RP-F118 often requires significantly more—sometimes upwards of 91 samples for complex weld types like double V submerged arc welds—to provide adequate evidence of detection. Document Evolution

DNV-RP-F118 provides a structured, statistically based framework for validating Automated Ultrasonic Testing (AUT) systems, shifting focus toward Probability of Detection (PoD) and accurate sizing in pipeline welds. It ensures technical confidence in detecting critical defects by requiring rigorous performance demonstrations, which can be optimized through simulation technologies like CIVA. For more details, visit www.extende.com AUT Pipeline testing with CIVA - Extende Why it matters: Non-conservative assessments can lead to

Precision in Every Pulse: A Guide to DNV-RP-F118 for Pipeline Girth Welds

In the world of offshore pipelines, the integrity of a girth weld isn’t just a technical requirement—it’s a lifeline for safety and environmental protection. Ensuring these welds are flaw-free falls heavily on Automated Ultrasonic Testing (AUT)

. However, an AUT system is only as good as its validation, which is where DNV-RP-F118 comes into play. What is DNV-RP-F118? DNV-RP-F118 is a Recommended Practice (RP)

that provides a rigorous framework for the qualification and project-specific validation of AUT systems. It serves as the practical bridge to the requirements found in DNV-ST-F101 Appendix E

, ensuring that weld inspections are consistent, reliable, and compliant with international offshore standards. Why Does It Matter?

Unlike manual inspections, AUT relies on complex algorithms and mechanical setups. DNV-RP-F118 ensures that: Detection is Proven

: It moves beyond "best guesses" to require statistical evidence of flaw detection. Accuracy is Quantified

: The system must accurately size flaw length and height, often using advanced techniques like "Tip Echo" assessments or "MaxAmp" for embedded flaws. Safety is Standardized

: By following a set validation procedure, operators can have high confidence that flaws of a critical size will be detected before they lead to failure. The Power of Numbers: Statistical Confidence One of the most critical aspects of DNV-RP-F118 is its demand for statistical confidence . For example: Sample Size

: While some might think a handful of examples is enough, this RP requires significantly more. A minimum of 29 samples

is often cited just to reach basic statistical confidence (e.g., 90% Probability of Detection with 95% confidence). Complex Welds

: For more complex configurations, like double V submerged arc welds, the recommendation can jump to a minimum of 91 samples Implementation in the Field

Leading engineering firms use this practice to qualify advanced technology. For instance, the Applus+ RTD IWEX

system was subjected to trials specifically according to DNV-RP-F118 to document its performance for Corrosion Resistant Alloy (CRA) pipeline girth welds. This process involves: Technical Documentation

: Establishing clear records during engineering and construction. Trial Welds

: Using welds with induced imperfections to test the system's limits. Third-Party Witnessing : Often involving DNV experts to verify the results. The Bottom Line DNV-RP-F118 isn't just a checklist; it's a mindset of cost-effective safety

. By standardizing how we validate AUT systems, the industry reduces the risk of subsea failure and ensures that "good enough" is replaced by "statistically proven".

Are you looking to implement a specific AUT qualification for an upcoming offshore project?

DNV-RP-F118 establishes a framework for qualifying Automated Ultrasonic Testing (AUT) systems, ensuring reliable flaw detection and precise sizing for pipeline girth welds. It focuses on statistically validating inspection procedures to guarantee safety, optimize cost-efficiency, and comply with offshore project requirements. For more technical details on AUT validation, visit NDT.net. AUT Pipeline testing with CIVA - Extende not a mandatory statutory code. However

DNV-RP-F118 is a Recommended Practice (RP) titled "Pipe girth weld automated ultrasonic testing system qualification and project specific procedure validation." Its primary objective is to provide guidelines for ensuring that the qualification and validation of Automated Ultrasonic Testing (AUT) systems meet the requirements of the offshore pipeline standard DNV-ST-F101 Appendix E. Core Objectives

System Qualification: Document the reliability, repeatability, and accuracy of an AUT system for detecting and sizing defects in pipeline girth welds.

Procedure Validation: Offer a recommended scope for project-specific validation to ensure consistent performance across different materials and project parameters.

Standardization: Provide a fair basis for evaluating different AUT systems to ensure they comply with fracture mechanics-based acceptance criteria (e.g., Engineering Criticality Assessment). The Qualification Process

The RP outlines a structured 11-stage program for procedure qualification:

Technical Review: Evaluation of system documentation and operating methodology.

Quality Assurance: Review of development and maintenance systems.

Performance Data: Analysis of existing detection and sizing accuracy data.

Parameter Identification: Evaluation of significant variables and their variability.

Repeatability & Reliability: Planning and executing test programs to prove consistent results.

Supplementary Testing: Using Non-Destructive Examination (NDE) and destructive testing to verify findings.

Data Analysis: Establishing the Probability of Detection (PoD) and sizing accuracy. Statistical Requirements

A critical component of DNV-RP-F118 is its demand for statistical evidence.

Sample Size: It requires significantly more than the basic minimum of 29 samples to achieve high confidence levels (e.g., 90% PoD with 95% confidence).

Weld Types: For specific types like double V submerged arc welds, the RP recommends a minimum of 91 samples. Key Considerations

Part 5: Fabrication, Installation, and Inspection

Myth #3: "Visual inspection is sufficient for F118 compliance."

Reality: Visual inspection (by ROV or diver) is the minimum. The RP requires quantitative NDT (MFL, ACFM, UT) at defined intervals, especially for chain segments that have experienced abnormal loading events (e.g., storm overloads).

Phase 3: Data Interpretation and Reporting

Noise Filtering: A significant portion of the RP deals with filtering out "false positives" caused by tool noise (wireline rubbing against the pipe) or background environmental noise.
Reporting: The final report must clearly state the probability of a leak, the precise coordinate/depth of the anomaly, and the confidence level of the finding.

4.1 Design Workflow

A typical riser design project following F118 proceeds as:

Define design premises: Water depth, metocean data (waves, current profiles, wind), vessel RAO (response amplitude operators), fluid properties.
Global dynamic analysis: Using software like OrcaFlex, DeepLines, or Riflex. Simulate time-domain responses for 10,000+ wave combinations.
Cross-section checks: Calculate stress, strain, and utilization ratios per limit states, applying partial safety factors.
Fatigue damage accumulation: Rainflow counting of stress cycles + S-N curves. Validate that total damage < 1.0 with required safety factor.
Interference analysis: Ensure minimum clearance between adjacent risers, mooring lines, and vessel hull (often 0.5–1.0 m).
Installation analysis: Check lay tensions, curvature, and free-span vibrations.
In-service inspection plan: Define NDT intervals, hot-spot locations, and acceptable flaw sizes based on fracture mechanics.

1. Executive Summary

DNV-RP-F118 is a recommended practice developed by DNV (Det Norske Veritas) that provides technical guidelines for the use of wireline-deployed tools to detect and locate leaks in pipelines and risers. As oil and gas infrastructure ages, the integrity of pipelines becomes a critical safety and environmental concern. This document outlines the methodology, planning, execution, and interpretation of data for wireline leak detection surveys, ensuring a standardized and reliable approach to integrity management.

1.1 Definition and Status

DNV-RP-F118 is a Recommended Practice, not a mandatory statutory code. However, in the offshore industry, "Recommended" often means "required." Classification societies, flag states, and operators universally reference it as the state-of-the-art guideline for riser systems attached to floating units.

Full Title: Recommended Practice DNV-RP-F118 – Risers for Floating Production Units
Latest Edition: October 2017 (with occasional amendments and links to DNVGL-ST-F201)

6. Summary Table