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2020

By Tom Coolidge and Tom DeWitte

 

We were struck recently in reading NACE International’s estimate of the money spent each year on corrosion-related costs for monitoring, replacing, and maintaining U.S. metallic pipe networks. The estimated annual tab is $7 billion for gathering and transmission pipelines and another $5 billion for gas distribution pipelines. That’s $12 billion each year!

 

Metallic pipe has been around for a long time. It has been used by the gas utility and pipeline industries since the 1800s when cast iron pipe first replaced wooden pipe. Advances in metallurgy through the years have steadily resulted in different types and better quality of metal for pipe networks. Today there is a lot of metallic pipe of one kind or the other in the ground. In fact, even after much cast iron and other metallic distribution pipe have been replaced by plastic pipe, there remains today several hundred thousand miles of in-service metallic pipe in America’s gas and hazardous liquids transmission and distribution networks. Much of it is old, and all of it is subject to corrosion.

 

Most people understand that if you put iron or steel in contact with moisture and oxygen, the metal will begin to rust or corrode. What most people do not understand is that this basic electro-chemical process can be slowed or even halted.

 

Gas utilities and pipelines understand that, though. That’s why today they dedicate considerable human and financial resources to the cause of cathodic protection. They do it because they are committed to safe operations, and they do it for regulatory compliance as cathodic protection has been required for much of America’s pipe networks since 1971.

 

This is the first blog of a series that explores how ArcGIS provides capabilities for the management of cathodic protection networks.

 

Protecting the Pipe from Corrosion

There are several methods to protect metallic pipe buried in the ground. One method is to apply a coating to the pipe to form a barrier between the metal pipe and the corrosion-causing mixture of water and air.

Coated Metallic Pipe

 

This is very common for natural gas and hazardous liquid carrying pipelines.  But it is not perfect, as a single scratch through the coating layer diminishes the protection.  A second method is to manipulate the same electro-chemical process which causes corrosion to instead protect the pipe from corrosion.  This method is called cathodic protection. Two common forms of cathodic protection are galvanically-protected and impressed-current protection.

Galvanically Protected

 

We Need a Sacrifice

A galvanically-protected cathodic protection system is also called a passive-cathodic protection system.  It is passive in that no foreign electrical energy is needed.  Galvanic protection works by connecting a more electrochemically active metal into the system than the pipe system which is being protected.  This electrochemically active metal is simply a hunk of metal buried in the ground near the pipe system. This component is called an anode. Common materials for anodes are zinc and magnesium. In a galvanic protection system, the anode gives up electrons to the pipe system.  This sacrifice of electrons results in the anode corroding instead of the pipe system.

Impressed Current Cathodic Protection

Charge It

Impressed-current cathodic protection systems are typically used to protect large pipe systems such as transmission pipelines.  The rectifier inserts direct current (DC) voltage into the cathodic protection system.  A rectifier cable connects the rectifier’s positive terminal to the anodes within the anode bed.  A second rectifier cable connects the rectifier’s negative terminal to the pipe system.

 

The Electric Circuit

The foundational concept to keep in mind when trying to understand cathodic protection is that the components of a cathodic protection system are connected to form an electric circuit.  If the circuit is broken, then the metallic pipe system components will lose their protection and the rate of corrosion will accelerate. If not corrected, the pipe system components will weaken and eventually fail.

 

Soil Is A Conductor

With cathodic protection, it is important to remember that the soil between the anode and the metallic pipe acts as a conductor.  The soil as a conductor of electricity completes the electric circuit connecting the anode to the metallic pipe.

 

Material Type Matters

The material of the pipe system components is critical to a cathodic protection system.  Some materials such as polyethylene (Plastic PE) are non-conducting and act as insulators. These insulating materials break the electric circuit.

Cathodic Protection System With Insulating Plastic Pipe

 

In addition to plastic pipes and plastic components acting as insulators and breaking the electric circuit, metallic components can be manufactured so that they, too, can be insulating devices or junctions.

Cathodic Protection Systems Separated By An Insulating Valve

 

Managing Cathodic Protection Data with UPDM

Management of the cathodic protection components in a Geodatabase is not difficult.  The anodes, rectifiers, and test points are typically modeled as point features.  The test lead wires; bonding lines, and rectifier cables are modeled as line features. Utility and Pipeline Data Model (UPDM) 2019 provides a template data model for managing these cathodic protection components.

 

Where data management of the cathodic protection systems gets challenging is the defining and maintaining of the cathodic protection zone.  The cathodic protection zone is the combination of pipeline, pipe devices, pipe junctions, cathodic protection devices, and cathodic protection lines, which together form an electric circuit.

Cathodic Protection System

Conclusion

Data management and analysis of cathodic protection systems was a challenge in legacy geospatial systems.  Entering the information has always been a straight forward process.  Maintaining an intelligent representation of the cathodic protection system has historically been the challenge.

With the utility network combined with the UPDM 2019 configuration, maintaining and analyzing a cathodic protection system is now an intuitive process. 

 

About This Blog Series

This blog article is the first of a three-part series explaining how the Esri ArcGIS platform with the Utility Network Management Extension and the Utility and Pipeline Data Model (UPDM) can be utilized to manage a digital representation of a cathodic protection system.  It is intended to provide GIS professionals and IT administrators with enough knowledge of how a cathodic protection system works to be able to correctly configure and deploy UPDM and the utility network.

 

The second blog article will go into detail on the configuration of UPDM to manage the components which makes up the cathodic protection system.

 

The third blog article will explain how the utility network uses its capabilities to model the cathodic protection system.

 

PLEASE NOTE: The postings on this site are our own and don’t necessarily represent Esri’s position, strategies, or opinions.

By Tom Coolidge and Tom DeWitte

 

Gas utility and pipeline GIS data management is increasingly important.  With a pipe network typically geographically widespread, topologically complex, and buried underground, the performance of many tasks and workflows, in a wide range of functional areas and roles, necessarily involves application software operating on a digital model of the pipe network and the surroundings through which it passes.

 

These models are only as good as the data available to them.  Today’s pipe network GIS typically contains extensive and detailed information about each and every component of the physical network, what is going on within it, the natural and man-made surroundings through which the pipe network passes, and activity occurring around it.

 

Models most often are built from that data in one of two ways – depending upon whether the objective being examined is around “where is it located” or “how is it connected.”  Linear referencing is the model building method for the first, connectivity modeling for the second.  While both methods create a network model, they do it in different ways.

 

Before arrival of the shared centerline feature class with ArcGIS 10.8/Pro 2.5, pipe network modelers to satisfy both modeling needs had to create and maintain multiple digital mirror representations of their real pipe network.  One of these was defined by linear referencing.  Linear referencing is a language that expresses pipeline attribute and event locations in terms of measurements along a pipeline, from a defined starting point.  The network model in Pipeline Referencing is established by the sequence of strictly increasing or decreasing measures on a continuous, unbroken non-branching run of physical pipe.

 

Another was defined by connectivity.  Connectivity describes the state where two or more features either share a connectivity association, or the collection of features are geometrically coincident at an endpoint (or midspan at a vertex), and a connectivity rule exists that supports the relationship.  For those to whom connectivity associations is a new term, they are used to model connectivity between two point features (Device or Junction) that are not necessarily geometrically coincident. An example of this in a pipe system is a ****** bolted to a valve.  There is no pipe component between the ****** and the valve in the physical world.  Now with connectivity associations in the utility network, this point to point connectivity can be correctly modeled in the digital world.

 

Traditionally, each of these ways was enabled by a separate set of data – one for linear referencing and another for connectivity modeling.

 

Multiple types of operators manage natural gas or hazardous liquids pipe networks and face the challenge of needing to create and maintain multiple models.  One type is vertically-integrated gas companies.  They span all or part of the way from the wellhead to the customer meter and typically operate an integrated pipe network that includes multiple subsystems – for example, transmission and distribution subsystems.  Historically, these subsystems have been modeled separately.

 

Transmission pipelines also face the same challenge, not because they operate multiple subsystems, but because the range of application software their GIS needs to support requires access to both kinds of models.

 

Moreover, all types of operators are searching for better interoperability among software systems at the enterprise level.  They also are experiencing the convergence of information technology and operations technology systems.

 

For all these reasons, a better solution to the need to create and maintain multiple digital models of the real pipe network is needed.

 

The Solution: Unified Pipe Data Management

Esri’s vision for pipe network operators is to create a single representation of the entire pipe network that mirrors the real network and can support both types of model building.  This removes the traditional barriers between industry subsystems – for example, between transmission and distribution subsystems – that result in data silos.  A single representation also enables users to work with that digital network just as they do with the real network.  Linear referencing and connectivity modeling now can be performed on the same single network representation.  We call this new data management capability: Unified Pipe Data Management.

The solution for vertically-integrated gas companies also is the solution for standalone transmission pipeline operators that, while they don’t operate multiple industry subsystems, have a need for both types of models to satisfy the data input requirements of the range of application software being supported by their GIS.

 

A single representation of the pipe network requires a unique data organization approach to store the entire pipe system—from wellhead to meter—and support the information model requirements of the ArcGIS Utility Network Management extension and Pipeline Referencing. Esri’s Utility & Pipeline Data Model (UPDM) 2019 is a data model template that provides this data organization.

 

Benefits Of Both Extensions Working On the Same Geodatabase

The ability for Pipeline Referencing and the ArcGIS Utility Network Management extensions to work on not just the same geodatabase but the same feature classes within the enterprise geodatabase, provides important benefits to pipe network operators.  First, the two extensions bring important advancements in essential industry-specific data management into Esri’s core technology.  This relieves the need for Esri business partners to fill capability gaps and frees them to extend the capabilities further and focus on adding value to uses of the data.  At the same time, it gives pipe network operators the opportunity to mix and match application software built on ArcGIS from multiple Esri business partners.  In addition, the ability for both extensions to work on the same geodatabase simplifies staff training, provides better management of high-pressure distribution pipe, and improves scalability and performance for operators of larger pipe networks.

 

Summary

For decades pipe organizations have had to either implement multiple models stored in separate data repositories or had to settle for one data management method over the other.  With the release of ArcGIS 10.8/Pro 2.5, a single digital representation of the physical pipe system can be created and maintained.  This reduces IT administration and support costs by allowing server systems and database licenses to be consolidated.  For data editors, the process is simplified by providing a single editing experience regardless of where the edit occurs across the vertically-integrated pipe system.  For end users, using the pipe system data is simpler because there is only one representation of the pipe system to work from.

 

One is better than more.

 

PLEASE NOTE: The postings on this site are our own and don’t necessarily represent Esri’s position, strategies, or opinions.