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Dnv-rp-f118 !new! -

DNV-RP-F118 is a Recommended Practice (RP) titled "Pipe girth weld automated ultrasonic testing system qualification and project specific procedure validation". It provides a uniform guideline for qualifying Automated Ultrasonic Testing (AUT) systems to ensure they meet the rigorous safety and performance requirements of the offshore and energy industries. Core Objective

The primary goal of DNV-RP-F118 is to ensure that any AUT system used for pipeline girth weld inspection is capable of identifying imperfection dimensions (sizes, shapes, and positions) with consistent accuracy. This is especially critical for submarine pipeline systems governed by the DNV-ST-F101 standard. Key Features and Scope

DNV-RP-F118 is a critical Recommended Practice (RP) titled "Pipe Girth Weld AUT System Qualification and Project Specification Procedure Validation". It serves as a technical framework for qualifying Automated Ultrasonic Testing (AUT) systems used specifically for submarine pipeline girth welds. Core Purpose and Scope

The document provides the industry-standard methodology for proving that an AUT system can reliably detect and accurately size flaws in pipeline welds. It is most frequently used in conjunction with the DNV-ST-F101 (formerly OS-F101) code for submarine pipeline systems. Key Technical Requirements

The standard focuses on statistical confidence in flaw detection. Some of its most notable requirements include:

Statistical Evidence: It requires a high level of confidence in the Probability of Detection (PoD). For instance, a common benchmark is achieving a 90% PoD with 95% confidence. dnv-rp-f118

Sample Size: To reach this level of confidence, the standard recommends significant sample sizes. While a basic statistical sample might require 29 samples, DNV-RP-F118 often recommends much higher numbers—such as a minimum of 91 samples for double V submerged arc welds—to ensure reliability.

Qualification Components: The process involves a thorough review of technical documentation, operating methodology, and quality assurance systems. The Qualification Process

According to the guidelines, qualifying an AUT system typically involves:

Repeatability and Reliability Tests: Planning and executing programs to ensure the system performs consistently.

Supplementary Testing: Combining AUT results with other Non-Destructive Testing (NDT) and destructive testing to verify accuracy. DNV-RP-F118 is a Recommended Practice (RP) titled "

Sizing Accuracy: Establishing not just if a flaw is detected, but how accurately the system can measure its dimensions. Where to Find the Full Text

The official, up-to-date full text is available through the DNV (Det Norske Veritas) Rules and Standards portal. While some summaries or older research papers referencing the process can be found on sites like Scribd or ResearchGate, the most authoritative version for professional project validation should be sourced directly from DNV.

Phase 3: Vendor and Inspection Contract Alignment

Ensure your ROV inspection contractors, NDT (non-destructive testing) providers, and chain manufacturers are quoting against DNV-RP-F118 specifications. Demand that:

  • ROV camera focal lengths and lighting meet RP’s defect detection resolution.
  • All mooring chain UT reports include backscatter analysis for flaws beyond normal probes.

6.1 Offshore Wind and Hydrogen

While DNV-RP-F118 was written for hydrocarbons, it is increasingly used for:

  • Dynamic power cables for floating wind turbines (though DNV-ST-0145 is more direct, F118 provides fatigue guidance).
  • Hydrogen risers – embrittlement concerns require stricter flaw acceptance per F118’s annex on sour service.

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). ROV camera focal lengths and lighting meet RP’s

Part 4: Practical Application – How Engineers Use DNV-RP-F118

3. Key Methodologies Covered

The RP details several physical principles used to detect leaks via wireline. The choice of method depends on the product in the pipeline (gas or liquid) and the operational conditions.

Phase 1: Gap Analysis

Compare your current integrity management system against the RP’s 45+ specific requirements. Common gaps include:

  • Lack of a documented risk-based inspection (RBI) strategy for moorings.
  • Absence of fatigue life tracking for individual chain segments.
  • No formal procedure for pipeline walking assessment near mooring anchors.

2.2 Risk Assessment

A quantitative risk assessment (QRA) is central. The RP introduces a risk matrix that considers:

  • Probability of failure (PoF): Corrosion, third-party damage (e.g., anchor drag), material defects, fatigue.
  • Consequence of failure (CoF): Hydrocarbon spill volume, repair cost, production loss, environmental sensitivity.

For a mooring line, failure probability is heavily influenced by fatigue and wear. For a pipeline, it might be corrosion or spanning.