Facilities Piping Inspection: Is Direct Assessment Enough?
Facility piping systems need a lot of resources to assure their integrity and avoid the failures that may lead to catastrophic events such as safety-related incidents that could cause injury to personnel or interrupted operations that could lead to financial losses. Operators routinely test systems for in-service damage such as corrosion, and direct assessment is a generally accepted methodology for examining the impact of external, internal, and stress corrosion on the integrity of underground pipelines.
However, direct assessment may not be ideal for aboveground pipelines, and with complex piping systems that contain both aboveground and underground pipe, operators may prefer a combined methodology that incorporates elements of direct assessment and the American Petroleum Institute’s (API) Piping Inspection Code. Juan Carlos Ruiz-Rico, a senior engineer at DNV GL, discussed this combined methodology at the API’s Inspection and Mechanical Integrity Summit in Galveston, Texas. Ruiz-Rico said that inspectors often face complexities when inspecting piping systems with aboveground and underground components.
“When we’re looking at facilities piping, you’re going to find several challenges. Normally, it’s a complex system. It’s not a simple system. With piping, you have different materials, thicknesses, and sizes. You have systems with soil-to-air interfaces. You could have electrical interference due to power lines located near your facility. Sometimes there is not enough information to establish an inspection point,” Ruiz-Rico said.
The methodology was developed in accordance to a number of recognized standards including API 570, which covers inspection, rating, repair, and alteration procedures for metallic and fiberglass-reinforced plastic piping systems. It also takes into account NACE standards such as ANSI/NACE SP0502, which outlines a standard external corrosion direct-assessment process for buried onshore ferrous pipeline systems. It is a four-step process: inspection planning, the inspection and direct examination period, post-assessment and intervention intervals, and the inspection program itself.
Inspection planning primarily involves data collection, both historical (data over the life of the system) and current, along with physical information of the system. This step is similar to the preassessment step of direct-assessment protocol, in which operators determine where operators define minimum data requirements to determine whether direct assessment is a feasible course of action.
“We collect all the information related to the piping system, including operational data, inspection, and maintenance information. All the information is collected in this respect. It is classified and analyzed,” Ruiz-Rico said.
The next step—execution of the inspection plan and the direct examination of the piping system—involves the collection of field data and the analysis of possible inspection protocols. Operators determine the type of inspections they want to run for the components of their systems, such as a visual inspection or an ultrasonic inspection. They may find new information that affects those decisions, like possible corrosion on a soil-to-air interface. Condition monitoring locations (CMLs), designed locations where thickness measurement inspections can monitor the presence and rate of damage and corrosion, are marked along the pipeline system. Ruiz-Rico said that the presence of CMLs allows for repetitive examination of specific locations during an inspection, which could provide better corrosion rate calculations.
In the post-assessment phase, operators compare the inspection data with the preinspection data. The findings from this phase lead to the inspection program, which is more of a blueprint for operators moving forward. This is the risk calculation part of the protocol: Operators consider the likelihood and possible consequences of damaged elements within a piping system. They can make an overall assessment of the facility and design mechanisms within their program to help mitigate risk.
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