US3936737A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Corrosion monitoring system
Assignee: C M S Inc
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Filing: 1975-04-10
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Granted: 1976-02-03
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Expires: 1995-04-10
Abstract
Abstract A corrosion measuring system is disclosed which includes a sensor supportable in a fluid within a vessel, such as a pipe. The sensor is generally tubular, one end of which is closed. The closed end comprises a measuring portion having a wall of relatively medium or heavy thickness. The measuring portion adjoins a relatively thick-walled outer end hub portion having a substantial radial dimension and a relatively low or negligible resistance. A resistive element is attached to the sensing element within the sensor. In combination with electrical circuitry, the probe produces readings representative of the corrosion of the sensing element which readings are correlated to the corrosion of the vessel. Another aspect of the invention relates to a multi-range bridge circuit for use with the resistive components of the probe. Effectively, the electrical resistivity of the measuring portion and the hub portion of the sensor are precalculated to be a low percentage, e.g. about 1 to 10 per cent, of the total resistance of these portions and the resistive element, so that effect of temperature variations compared to corrosion is negligible. The measuring section of the sensor is sized to be structurally sound and compatible with a predesignated bridge for a given material and anticipated corrosion rate to be useful in measuring corrosion over a plurality of ranges to produce a longer lasting probe. The method of determining the sensor parameters and the bridge components is also disclosed.
Inventors
- 👤 Fitch B. Jefferies, Sr.
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 01:16
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/02; G01N27/04; G01N27/041; G01N17/00; G01R; G01R27/00; G01R27/02
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
314 words
Apparatus for measuring corrosion of an electrically conductive material in a corrosive medium, said apparatus including probe means in combination with bridge circuit means, said probe means comprising: a closed end corrosion measuring portion made from such conductive material and adapted for insertion into said corrosive medium, said measuring portion being a first portion of a first electrical resistance element in said bridge circuit means, said measuring portion having a relatively low resistance, said measuring portion being subjected to fluctuation of temperatures in said corrosive medium; a hub portion adjoining said measuring portion and in electrical circuit therewith, said hub portion being formed from such conductive material and having a relatively thick wall compared to said measuring portion, and further having a very low resistance, said hub portion being a second portion of a first electrical resistance element in said bridge circuit means, said hub portion being subjected to temperature variations in said corrosive medium; a body portion adjoining said hub portion; a resistive element within said probe means and in electrical circuit therewith, said resistive element having a very low electrical resistance, a first portion of said resistive element being a third portion of a first electrical resistance element; first circuit means and second circuit means for defining a second portion of said resistive element as a second electrical resistance element in said bridge circuit means; additional circuit means connected to at least some of said first and second electrical resistance elements to provide electrical connections to said bridge circuit means; a source of electrical potential in said bridge circuit means for energizing said electrical resistance elements simultaneously, said bridge circuit including means for measuring the output voltage due to an imbalance in said bridge circuit means thereby to measure changes in the electrical resistance of the first portion of the first electrical resistance element to indicate the corrosion of said measuring portion.
Claim 2
Dependent Claim
314 words
Apparatus for measuring corrosion of an electrically conductive material in a corrosive medium, said apparatus including probe means in combination with bridge circuit means, said probe means comprising: a closed end corrosion measuring portion made from such conductive material and adapted for insertion into said corrosive medium, said measuring portion being a first portion of a first electrical resistance element in said bridge circuit means, said measuring portion having a relatively low resistance, said measuring portion being subjected to fluctuation of temperatures in said corrosive medium; a hub portion adjoining said measuring portion and in electrical circuit therewith, said hub portion being formed from such conductive material and having a relatively thick wall compared to said measuring portion, and further having a very low resistance, said hub portion being a second portion of a first electrical resistance element in said bridge circuit means, said hub portion being subjected to temperature variations in said corrosive medium; a body portion adjoining said hub portion; a resistive element within said probe means and in electrical circuit therewith, said resistive element having a very low electrical resistance, a first portion of said resistive element being a third portion of a first electrical resistance element; first circuit means and second circuit means for defining a second portion of said resistive element as a second electrical resistance element in said bridge circuit means; additional circuit means connected to at least some of said first and second electrical resistance elements to provide electrical connections to said bridge circuit means; a source of electrical potential in said bridge circuit means for energizing said electrical resistance elements simultaneously, said bridge circuit including means for measuring the output voltage due to an imbalance in said bridge circuit means thereby to measure changes in the electrical resistance of the first portion of the first electrical resistance element to indicate the corrosion of said measuring portion.
Claim 3
Dependent Claim
31 words
The apparatus as set forth in claim 1 wherein said bridge circuit means includes multi-range resistance means for bridge imbalance over a plurality of resistance values of said multi-range resistance means.
Claim 4
Dependent Claim
27 words
The apparatus as set forth in claim 2 wherein the resistance values of said bridge circuit means are predetermined to produce a predesignated plurality of bridge designations.
Claim 5
Dependent Claim
79 words
The apparatus as set forth in claim 3 wherein the size of the measuring portion of the probe is determined as a function of the resistivity of its material, the length of the sensing portion, and the anticipated corrosive rate of the corrosive medium on the conductive material to produce a resistance value which is compatible with at least one of said predesignated bridge circuit means so that said bridge circuit means can be balanced over said predetermined multiranges.
Claim 6
Dependent Claim
22 words
The apparatus of claim 1 wherein said sensing portion is of a generally tubular construction and is integral with said hub portion.
Claim 7
Dependent Claim
75 words
The apparatus of claim 1 wherein the combined resistance value of said first and said second portions of said first electrical resistance element is on the order of about one to ten percent of the combined electrical resistance of said first and said second electrical resistance elements to render negligible the effect of the resistance changes caused by the temperature fluctuations of said corrosive medium as opposed to the corrosive effects of said sensing elements.
Claim 8
Dependent Claim
36 words
The apparatus as set forth in claim 6 wherein the physical size of the sensing portion is partially controlled by the gage factor of the gridge circuit which is at maximum for a fully active bridge.
Claim 9
Dependent Claim
12 words
The apparatus of claim 1 wherein said resistive element is a wire.
Claim 10
Dependent Claim
66 words
The apparatus of claim 3 wherein said predesignated plurality of bridge designations are characterized about as follows: Designation Ranges Output Gage Factor
______________________________________
A 10 100 mV DC 1.003643
B 10 200 mV DC 1.007299
C 10 500 mv DC 1.018349
D 10 1.0 V DC 1.037037
E 10 2.0 V DC 1.075472
F 10 5.0 V DC 1.200000
G 10 10.0 V DC 1.444444
______________________________________
Claim 11
Dependent Claim
33 words
The apparatus of claim 1 wherein the wall of the hub portion is sufficiently thick to permit a weld thereon which will not affect the precalibration of the resistance of the hub portion.
Claim 12
Dependent Claim
229 words
A sensor for a probe for measuring corrosion of an electrically conductive material in a corrosive medium, comprising: a sensing portion which includes a measuring portion made from a conductive material and adapted for insertion into a corrosive medium, said measuring portion when new having a predetermined wall thickness and a very low resistance, said measuring portion being adapted to constitute a first active portion of a leg of the bridge circuit; and a hub portion made from a conductive material in electrical circuit with said measuring portion, said hub portion having a relatively large wall thickness and a very low resistance, said hub portion being adapted to constitute a second inactive portion of said leg of said bridge circuit; resistive element means in electrical circuit with said sensing portion for providing from a portion thereof a reference resistance in another leg of said bridge circuit, another portion of said resistive element means being a third inactive portion of said leg of said bridge circuit; circuit means for providing a source of power to and for sensing the resistance of said measuring portion, said hub portion and said resistive element means; and said sensor being further characterized in that said measuring portion and said hub portion constitute about 1 to about 10 per cent of the combined resistance of said leg and said another leg of said bridge circuit.
Claim 13
Dependent Claim
229 words
A sensor for a probe for measuring corrosion of an electrically conductive material in a corrosive medium, comprising: a sensing portion which includes a measuring portion made from a conductive material and adapted for insertion into a corrosive medium, said measuring portion when new having a predetermined wall thickness and a very low resistance, said measuring portion being adapted to constitute a first active portion of a leg of the bridge circuit; and a hub portion made from a conductive material in electrical circuit with said measuring portion, said hub portion having a relatively large wall thickness and a very low resistance, said hub portion being adapted to constitute a second inactive portion of said leg of said bridge circuit; resistive element means in electrical circuit with said sensing portion for providing from a portion thereof a reference resistance in another leg of said bridge circuit, another portion of said resistive element means being a third inactive portion of said leg of said bridge circuit; circuit means for providing a source of power to and for sensing the resistance of said measuring portion, said hub portion and said resistive element means; and said sensor being further characterized in that said measuring portion and said hub portion constitute about 1 to about 10 per cent of the combined resistance of said leg and said another leg of said bridge circuit.
Claim 14
Dependent Claim
31 words
The sensor as set forth in claim 11, wherein said measuring portion has an integrally closed end, is made from the same material as said hub portion, and is integral therewith.
Claim 15
Dependent Claim
27 words
The sensor as set forth in claim 11, wherein said resistive element is a wire secured to an end of the hub portion opposite said measuring portion.
Claim 16
Dependent Claim
26 words
The apparatus as set forth in claim 1 wherein said resistive element is located within said body portion and in electrical circuit with said hub portion.
Claim 17
Dependent Claim
28 words
The apparatus as set forth in claim 1 wherein said resistive element is located within said closed end measuring portion and in electrical contact with said measuring portion.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-02-02 | 1979-08-04 | 1980-02-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-02-02 | 1983-08-04 | 1984-02-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-02-02 | 1987-08-04 | 1988-02-03 | $7700.00 | Window Closed / Lapsed |