Barlow formula Archives - Low Cost Easy to Use Spreadsheets for Engineering Calculations Available at Engineering Excel SpreadsheetsLow Cost Easy to Use Spreadsheets for Engineering Calculations Available at Engineering Excel Spreadsheets

Where to Find an API 570 Piping Inspection Calculations Spreadsheet

To obtain an API 570 Piping Inspection Calculations spreadsheet, click here to visit our spreadsheet store. This Excel spreadsheet is intended for making piping inspection calculations from API 570 and API 574.. You can buy a convenient API 570 piping Inspection calculations spreadsheet for a very reasonable price. This spreadsheet calculates required minimum pipe wall thickness, long term corrosion rate, short term corrosion rate, remaining life, and maximum allowable working pressure (MAWP). It is available in either U.S. units or S.I. units. Read on for information about using an API 570 piping inspection calculations spreadsheet.

Formulas for API 570 Piping Inspection Calculations Spreadsheet

The required minimum wall thickness for piping being inspected must be the greater of the calculated pressure design wall thickness and the structural minimum wall thickness. The pressure design wall thickness is sometimes calculated with the Barlow formula and sometimes it is calculated with the ASME B31.3 formula. Both are shown below.

In the Barlow formula and the ASME B31.3 formula, P is the design fluid pressure in psig, D is the pipe O.D. in inches, S is the allowable unit stress of the pipe material in psi, E is a longitudinal quality factor, and Y is a coefficient that is a function of the pipe material and the operating temperature.

The structural minimum wall thickness is available in API 574 Table 6 for some pipe materials. The required minimum pipe wall thickness is the greater of the calculated pressure design wall thickness and the structural minimum wall thickness.

The long term corrosion rate and short term corrosion rate are calculated from values for the current measured pipe wall thickness, a previous pipe wall thickness or the initial pipe wall thickness and the time between the two. The remaining life of the pipe is calculated as the difference between the current measured pipe wall thickness minus the required minimum pipe wall thickness divided by the corrosion rate.

The maximum allowable working pressure for a pipe is calculated from the formula:

MAWP = 2SEt/D

In this formula, S, E, and D are as defined above and t is the measured pipe wall thickness in inches.

Example API 570 Piping Inspection Calculations Spreadsheet

An example API Piping Inspection Calculatons spreadsheet is partially shown in the image below. This Excel spreadsheet can be used to calculate the required minimum pipe wall thickness, corrosion rate, remaining life, and maximum allowable working pressure (MAWP). This Excel spreadsheet, as well as others for pipe flow calculations, is available in either U.S. or S.I. units for a very reasonable price in our spreadsheet store.

References:

1. American Piping Institute, AP! 570, Piping Inspection Code: In-service Inspection, Rating, Repair, and Alteration of Piping Systems, 3rd Ed, Nov, 2009

2. American Piping Institute, API 574, Inspection Practices for Piping System Components, 3rd Ed, Nov, 2009.

3. Bengtson, Harlan H., Spreadsheet for API Piping Inspection Calculations, an informational blog article at www.EngineeringExcelTemplates.com

The Barlow Formula for a Minimum Pipe Wall Thickness Calculator

The classic Barlow formula for calculating bursting pressure for a pipe is:

P = 2S*T/D_o where:

D_o is the outside diameter of the pipe with units of inches (U.S.) or mm (S.I.)

S is the strength of the pipe material with units of psi (U.S.) or N/mm² (S.I.)

T is the wall thickness with units of inches (U.S.) or mm (S.I.)

P is the fluid pressure in the pipe with units of psi (U.S.) or MPa (S.I.)

If the ultimate tensile strength of the pipe material is used for S, then P will be the bursting pressure, while P will be the pressure at which permanent deformation of the pipe begins if S is the yield strength of the material.

The Barlow formula can be rearranged to: T = /D_o*P/2S to use in a minimum pipe wall thickness calculator for the pipe wall thickness for a given bursting pressure or deformation pressure.

Calculation of Maximum Pipe Operating Pressure

The Barlow formula can be modified to calculate the maximum fluid operating pressure for a given pipe wall thickness and pipe diameter, by incorporation of a safety factor and corrosion allowance as follows:

P = 2S*(T – T_c)/SF*D_o

where SF is a safety factor (dimensionless) and T_c is a corrosion allowance in inches (U.S.) or mm (S.I.). This equation uses the outside pipe diameter in the calculations, which is convenient, because the outside pipe diameter remains the same for all of the schedules (wall thicknesses) for a given nominal pipe size. The calculation can be done using the outside pipe diameter (D_o) in an equation based on the inside pipe diameter, by using the relationship, D_i = D_o – 2T , to give the equation:

P = 2S*(T – T_c)/SF*(D_o – 2T)

An Excel Spreadsheet as a Minimum Pipe Wall Thickness Calculator

The Excel spreadsheet template shown below can be used as a minimum pipe wall thickness calculator or to calculate the maximum operating pressure in a pipe if the necessary other parameters are known/specified. Why bother to make these calculations by hand? This Excel spreadsheet and others for pipe flow calculations are available in either U.S. or S.I. units at a very low cost in our spreadsheet store.

Minimum Pipe Wall Thickness Calculator Spreadsheet

Low Cost Easy to Use Spreadsheets for Engineering Calculations Available at Engineering Excel Spreadsheets

At Engineering Excel Spreadsheets, we have low cost, easy to use spreadsheets for engineering calculations, including pipe flow, flow measurement, stormwater measurement, heat transfer coefficients, open channel flow, structural analysis of beams, and more.

Tag Archives: Barlow formula

API 570 Piping Inspection Calculations Spreadsheet