Piping corrosion monitoring system calculating risk-level safety factor producing an inspection schedule
First Claim
1. A corrosion monitoring method for monitoring the condition of the walls of corrodible piping and associated vessels in a process plant, comprising the steps of:
- dividing the piping and associated vessels of the plant into a plurality of circuits, wherein the elements of each of the circuits are expected to be exposed to a common corrosion environment;
establishing at least one inspection point within each circuit;
assembling corrosion data, said corrosion data comprising actual measurements of the wall thicknesses of the piping and associated vessels at each of the inspection points, said measurements being associated with corresponding times of measurement for each inspection point thus established;
determining for each inspection point the highest of several possible corrosion rates which can be expected to occur;
establishing a risk-level safety factor for each circuit, said risk-level safety factor being calculated from a plurality of factors comprising;
a design pressure for the circuit,a design temperature for the circuit,the degree of hazardousness to humans of the material in the piping and associated vessels of the circuit,the potential of said material to spontaneously ignite in the atmosphere, andthe location of the circuit relative to valued property likely to be damaged by a pipe wall failure in said each circuit;
calculating inspection dates one for each of the inspection points within each of the circuits from the determined corrosion rates taking into account the risk-level safety factor using a programmed digital computer; and
producing an inspection schedule for said piping and associated vessels from the calculated inspection dates.
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Abstract
A piping corrosion monitoring system is disclosed which is implemented by software run on a personal computer or the equivalent. The system generates inspection dates for individual piping and other elements, such as pressure vessels, in a process plant. The process plant is divided into circuits made up of piping and associated vessels expected to be exposed to a common corrosion environment. Corrosion data for individual inspection points within each circuit is used to estimate likely corrosion rates for other elements of the particular circuit. The estimated corrosion rates are used to calculate inspection dates for elements within the circuits. Also factored into the inspection date are the risk factors such as the toxicity of the substance being carried, the proximity of the circuit to valuable property or to control rooms, laboratories, or the like, and other factors relating to the security assigned to the circuit. The system evaluates a large number of possible corrosion mechanisms for each inspection point and chooses that which leads to the highest anticipated corrosion rate in calculation of the inspection date, thus providing a very conservative inspection date schedule, while not overinspecting circuits likely to exhibit low corrosion rates or in which failure would be relatively less critical.
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Citations
15 Claims
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1. A corrosion monitoring method for monitoring the condition of the walls of corrodible piping and associated vessels in a process plant, comprising the steps of:
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dividing the piping and associated vessels of the plant into a plurality of circuits, wherein the elements of each of the circuits are expected to be exposed to a common corrosion environment; establishing at least one inspection point within each circuit; assembling corrosion data, said corrosion data comprising actual measurements of the wall thicknesses of the piping and associated vessels at each of the inspection points, said measurements being associated with corresponding times of measurement for each inspection point thus established; determining for each inspection point the highest of several possible corrosion rates which can be expected to occur; establishing a risk-level safety factor for each circuit, said risk-level safety factor being calculated from a plurality of factors comprising; a design pressure for the circuit, a design temperature for the circuit, the degree of hazardousness to humans of the material in the piping and associated vessels of the circuit, the potential of said material to spontaneously ignite in the atmosphere, and the location of the circuit relative to valued property likely to be damaged by a pipe wall failure in said each circuit; calculating inspection dates one for each of the inspection points within each of the circuits from the determined corrosion rates taking into account the risk-level safety factor using a programmed digital computer; and producing an inspection schedule for said piping and associated vessels from the calculated inspection dates. - View Dependent Claims (2, 3, 4)
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5. A method of monitoring corrosion in a piping system, comprising:
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dividing a piping system to be monitored into a plurality of circuits, each circuit having a common corrosion environment;
designating at least one inspection point within each of the circuits;assembling historical data for piping wall corrosion in the vicinity of the inspection points; inspecting the piping wall thickness at selected inspection points within said circuits to determine the amount of actual corrosion at said points; comparing the actual corrosion at the individual points within each of the circuits at which said inspections have been made to corrosion estimated from rates based on said historical data; calculating, based on the corrosion at the inspected points and the historical data, estimated corrosion rates for inspection points within each of the circuits at which piping has not been inspected, wherein each of said estimates is selected as the maximum corrosion computed by a plurality of test cases, each test case employing a particular corrosion mechanism mode, said test cases including a model for corrosion of a pipe over a large area, such that said pipe tends to split open or collapse in service before corroding through a wall, and a model for corrosion of said pipe in a localized area, such that the pipe leaks prior to collapse thereof, said localized corrosion model incorporating a risk-level safety factor calculated from a plurality of factor comprising; a design pressure for the circuit, a design temperature for the circuit, the degree of hazardousness to humans of the material in the circuit, the potential of said material to spontaneously ignite in the atmosphere, and the location of the circuit relative to valued property that may be damaged by a leak; calculating inspection dates one for each of the inspection points within each of the circuits based on the estimated corrosion rates using a programmed digital computer, and producing an inspection schedule using the calculated inspection dates. - View Dependent Claims (6, 7, 8, 9, 10, 11)
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12. In a corrosion monitoring method for monitoring the condition of the walls of corrodible piping and associated vessels in a process plant, including the steps of dividing the piping and associated vessels of the plant into a plurality of circuits, establishing at least one inspection point within each circuit, assembling corrosion data including actual measurements of the wall thicknesses of the piping and associated vessels at the inspection points, determining for each inspection point the highest of several possible corrosion rates which can be expected to occur, calculating inspection dates one for each of the inspection points within each of the circuits from the determined corrosion rates taking into account a risk-level safety factor using a programmed digital computer, and producing an inspection schedule for the piping and associated vessels from the calculated inspection dates, the improvement comprising:
establishing the risk-level safety factor for each circuit by calculating said risk-level safety factor from a plurality of factors comprising; a design pressure for the circuit, a design temperature for the circuit, the degree of hazardousness to humans of the material in the piping and associated vessels of the circuit, the potential of said material to spontaneously ignite in the atmosphere, and the location of the circuit relative to valued property likely to be damaged by a pipe wall failure in said each circuit. - View Dependent Claims (13, 14, 15)
Specification