Pipeline Integrity Management System (PIMS)
The primary concern for all operator is the mechanical integrity of pipeline throughout its lifetime. For that reason, it's important to apply a Pipeline Integrity Management System (PIMS) through technical processes & management controls that collectively ensure pipeline integrity.
The requirements for an effective integrity management system (IMS) are that it:
Complies with Company operating standards, recognized standards for integrity and local regulatory requirements for this type of asset.
Has achievable Key Performance Indicators (KPIs).
Can be readily communicated to all staff.
Is independently auditable.
Currently, the mains drivers for Pipeline Integrity Management are as follows:
Integrity Awareness
Safety & Reliability
Environment
Production Targets
Operational Costs
Ageing Assets
Extend Operational Life
Legislation, Codes & Guidance and Company Policies
Corrosion Growth Assessment
Why calculate a Corrosion Growth Rate (CGR)
•Key input into Integrity Management Decisions
•Repair / In field investigation Plans
•Effective mitigation planning
•Re-inspection intervals
Methods of Estimating CGRs
•Corrosion Models (Internal Sweet Corrosion)
•Coupons & Probes
•Historical Corrosion Rates
•Industry guidance on typical corrosion rates (e.g. NACE RP 0502, ASME B31.8S)
•Comparison of repeat inspection data
Introduction to the Damage Categories in Pipelines Operating at Stress Levels not Exceeding 30% SMYS
Superficial, severe and extreme damages that will require special attention.
All pipe damages have different types of categories that, at the same time, have different types of conditions that you can check in the tables below. However, we may face some conditions depending on the damage:
✔ Where corrosion damage is between Severe and Extreme Damage (in Grade B pipe or higher) an expert assessment level can be conducted.
✔ If the pressure is reduced; gouges can be categorized as superficial and dressed up to an additional 10% of the wall thickness.
✔ Any dent, which interferes with ILI, should also be removed.
✔ Spans require a span analysis to determine the critical span length for static and cyclic loading (Lcrit)
Feature Interaction
Corrosion may occur such that multiple areas of metal loss are closely spaced longitudinally or transversely. Defects are considered interacting if the failure stress of the combination of defects is less than that of any of the individual defects.
Various criteria exist and some have been incorporated into code guidance e.g., ASME B31.G (3t x 3t), B31.4 (1” axial, 6t circumferential).
POF Specifications and requirements for intelligent pig inspections of pipelines are widely used.
Detailed Rstreng River-Bottom Profile
• Detailed RSTRENG uses feature profile to make a more accurate estimation of feature area
• DNV RP F101 also contains a ‘complex’ feature assessment methodology
• First Step is to define worst-case profile. Often referred to as ‘River-bottom’ profile.
Normally, this method is applied after detect corrosion features that could be considered a threat to the pipeline integrity, in order to assess the more realistic condition and repair the real critical corrosion features.
Comparison of Corrosion Assessment Methods
There are many assessment methods to detect corrosion in pipelines.
When we know different assessment methods, it can be confusing which one is the right one for each case. That is why it is important to know the particularities of each one.
Original B31.G in one of the commonly used assessment methods. It is often used as a simple screening assessment. It is considered a conservative method resulting in unnecessary repairs, that’s why it was modified.
The less conservative methods are:
Modified B31.G / Simplified Rstreng
Rstreng (detailed)
DNV RP F101 (Part B)
The assessment methods have a similar defect shapes and are based on similar equations but have modifications in 3 factors:
Flow stress: it is defined as "the instantaneous value of the stress required to further deform the material, so that the metal continues to flow".
Folias / bulging factor: it a factor that considers the stress amplification at the ends of an axially oriented flaw resulting from outward radial deflection along the flaw.
Defect shape (factor to estimate actual corrosion area): it is the shape defined to identify the area where corrosion is most concentrated.
Code Guidance for Repairing Defects in Pipelines
We share a guide of repair methods prepared for the Pipeline Research Council International, Inc. This guide concentrates on the most common defects and the most commonly used methodologies.
The objective is to have an orientation on how to proceed in each situation, guided by industry best practices.
Difference Detween Type A and type B Sleeves
2 full encirclement sleeves that can act in different ways.
When we are talking about the repairing with a Type A sleeve, we are talking about a reinforcing consisting of two half shells that are placed around the defect, and joined by welding the side seams together. They work by providing a close or ‘snug’ fit to the pipeline, thereby reinforcing and restraining defects from bulging. Also, the ends are sealed to prevent water migration, and they are not suitable for circumferentially oriented defects.
The Type A sleeve does not provide pressure containment and is not suitable for leaking defects. However, the Type B sleeve provides pressure containment, therefore suitable for leaking and circumferentially oriented defects. Since the sleeve may contain pressure, it must have the same pressure carrying capacity as the carrier pipe, and requires live welding onto the pipeline.