Rudenberg’s Formula for the Placement of an Anode Ground Bed

Contents

Introduction

This formula considers the attenuation of the pipe to determines the required structure voltage based on the current output.

Rudenberg’s formula is very theoretical just using pipe parameters. Other factors to be considered include the presence of foreign metallic structures, accessibility and availability of a power source which are not included.

V_x=\frac{0.0381\rho}{\pi y}\log_{10}\frac{( y+\sqrt{y^2+x^2} )}{x}

V_x=\frac{0.0381\rho}{\pi y}\log_{10}\frac{( y+\sqrt{y^2+x^2} )}{x}

Where:
V_x — Potential at X in volt caused by grounds anode current
I — Ground anode current (Amps)
ρ — Actual soil resistivity (0hm / cm)
y — Length of anode in earth (ft)
x — distance from ground anode (ft)

If x > 10y then: V_x=\frac{0.0521\rho}{x}

V_x=\frac{0.0521\rho}{x}

Case Guide

Part 1: Create Case

Select the Rudenberg’s Formula for the Placement of an Anode Ground Bed application from the Cathodic Protection Module
To create a new case, click the “Add Case” button
Enter Case Name, Location, Date and any necessary notes.
Fill out all required parameters.
Make sure the values you are inputting are in the correct units.
Click the CALCULATE button to overview results.

Input Parameters

Ground Anode Current (amp)
Actual Soil Resistivity (ohm-cm)
Length of Anode in Earth (ft)
X – Distance from the Ground to Anode (ft)

Part 2: Outputs/Reports

If you need to modify an input parameter, click the CALCULATE button after the change.
To SAVE, fill out all required case details then click the SAVE button.
To rename an existing file, click the SAVE As button. Provide all case info then click SAVE.
To generate a REPORT, click the REPORT button.
The user may export the Case/Report by clicking the Export to Excel icon.
To delete a case, click the DELETE icon near the top of the widget.

Results

Potential at X Caused by Ground Anode Current (volt)

References

NACE Standard Practices 0169 – Latest Edition “Control of Corrosion on Underground or Submerged Metallic Piping Systems”
ISO 15589-2 Petroleum and Natural gas Industries Cathodic Protection Pipeline Transportation Systems
Pipeline Corrosion and Cathodic Protection, Third Edition, Gulf Publishing Company

FAQ

ASME B31G Original/Modified and RSTRENG?

ASME B31.G Original and Modified (0.85) are Level 1 assessment along with most other metal loss calculations that are limited to pits and short lengths of pitting clusters. RSTRENG is a Level 2 metal loss calculation; however, it is not limited just to pits, but most lengths of pitting i.e., 2500 mm (100 inches) using interaction rules that is not uncommon on some pipelines. Check Out
Preventative and Corrective Measures to Control Corrosion Pitting?

A corrosion rate needed to set the re-inspection interval, reassess the performance metrics and their current applicability, plus to ensure the assumptions made are correct. At each direct examination where corrosion pitting is found, the operator should measure and record each pitting cluster. Check Out
Estimating Internal Corrosion Rates?

Internal corrosion is most likely to occur where water first accumulates. Predicting these locations of water accumulation serve as a method for prioritizing local examinations. Predicting where water first accumulates requires knowledge about the multiphase flow behavior in the pipe requiring certain data. Check Out
Estimating External Corrosion Rates?

All corrosion defects found during each direct examination should be measured, documented, and remediated as needed. At each excavation, the pipeline operator should measure and record generic environmental characteristics (such as soil resistivity, hydrology, drainage etc.). Check Out

Updated on December 15, 2023

Tagged: Calculations Cathodic Protection

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