Patent US1528400A successfully refreshed from Google Patents.
Patent US3810007A successfully refreshed from Google Patents.
US3810007A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Holiday detector and coating resistivity checker
Assignee: ConocoPhillips Co
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Filing: 1973-07-23
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Granted: 1974-05-07
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Expires: 1993-07-23
Abstract
Abstract A portable, accurate, non-destructive holiday detector and resistivity coating checker employing electronic resistance bridge means for comparing the resisitivity of non-conducting coatings to a standard resistance value either in the field or in plants where such coatings are applied to metallic vessels, pipes or the like and providing respective signal outputs proportional to the coating resistivity and the standard resistance. The apparatus employs comparator means for comparing the two outputs of the resistance bridge, and an alarm responsive to the output of the comparator means for indicating the presence of a holiday in the non-conducting coating under test where the coating resistivity is less than the standard resistance value. Probe means are also disclosed for providing electrical contact with the surface of the non-conducting coatings under test. Also disclosed is a method of checking coating resistivity for the detection of holidays therein.
Inventors
- 👤 M Wiseman
- 👤 R Schroeder
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 19:32
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/02; G01N27/04; G01N27/20; G01N27/205; G01R; G01R27/00; G01R27/02
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
252 words
An apparatus for automatically comparing the resistivity of a non-conducting coating on a metallic vessel or the like to a predetermined standard minimum resistance, and providing indication where the resistivity of the non-conducting coating falls below the predetermined standard minimum resistance, comprising: a voltage source; electronic resistance bridge circuit means having first and second legs electrically connected in parallel to said voltage source; variable resistance means in the first leg of said resistance bridge circuit means and electrically connected in series between said voltage source and the first side of said resistance bridge circuit means; probe means in the second leg of said resistance bridge circuit means and electrically connected in series between said voltage source and the second side of said resistance bridge circuit means, said probe means being adapted to connect the metallic vessel and the non-conducting coating in series between said voltage source and the second side of said resistance bridge circuit means; comparator means electrically connected to the first side and the second side of said resistance bridge circuit means for comparing the current flowing through the metallic vessel and the non-conducting coating with the current flowing through said variable resistance means, and providing a signal output when the current flowing through the metallic vessel and the non-conducting coating is greater than the current flowing through said variable resistance means; and indicator means electrically connected to said comparator means and responsive to the signal output therefrom for indicating the presence of the signal output from said comparator means.
Claim 2
Independent Claim
252 words
An apparatus for automatically comparing the resistivity of a non-conducting coating on a metallic vessel or the like to a predetermined standard minimum resistance, and providing indication where the resistivity of the non-conducting coating falls below the predetermined standard minimum resistance, comprising: a voltage source; electronic resistance bridge circuit means having first and second legs electrically connected in parallel to said voltage source; variable resistance means in the first leg of said resistance bridge circuit means and electrically connected in series between said voltage source and the first side of said resistance bridge circuit means; probe means in the second leg of said resistance bridge circuit means and electrically connected in series between said voltage source and the second side of said resistance bridge circuit means, said probe means being adapted to connect the metallic vessel and the non-conducting coating in series between said voltage source and the second side of said resistance bridge circuit means; comparator means electrically connected to the first side and the second side of said resistance bridge circuit means for comparing the current flowing through the metallic vessel and the non-conducting coating with the current flowing through said variable resistance means, and providing a signal output when the current flowing through the metallic vessel and the non-conducting coating is greater than the current flowing through said variable resistance means; and indicator means electrically connected to said comparator means and responsive to the signal output therefrom for indicating the presence of the signal output from said comparator means.
Claim 3
Dependent Claim
19 words
The apparatus as defined in claim 1 wherein said indicator means is characterized further to include visual indicator means.
Claim 4
Dependent Claim
19 words
The apparatus as defined in claim 1 wherein said indicator means is characterized further to include audible indicator means.
Claim 5
Dependent Claim
21 words
The apparatus as defined in claim 1 wherein said indicator means is characterized further to include visual and audible indicator means.
Claim 6
Dependent Claim
44 words
The apparatus as defined in claim 1 wherein said comparator means comprises: a unitary circuit comprising a plurality of semi-conductor devices and resistors; a positive d.c. voltage source applied to said unitary circuit; and a negative d.c. voltage source applied to said unitary circuit.
Claim 7
Dependent Claim
75 words
The apparatus as defined in claim 5 wherein said indicator means is characterized further to include: a transistor having the base thereof, electrically connected to the signal output of said comparator means, and having the emitter thereof grounded; resistor means connected in series between the base of said transistor and ground; audible indicator means connected in series with the collector of said transistor; and, a voltage source connected in series with said audible indicator means.
Claim 8
Dependent Claim
27 words
The apparatus as defined in claim 6 wherein said indicator means is characterized further to include: visual indicator means connected in parallel with said audible indicator means.
Claim 9
Dependent Claim
43 words
The apparatus as defined in claim 1 wherein said probe means is characterized further to include: electrical connector means for providing electrical connection to the metallic vessel; and, sponGe means, saturated with an electrolyte, for providing low-resistance electrical connection to the non-conducting coating.
Claim 10
Dependent Claim
46 words
The apparatus as defined in claim 8 wherein said metallic vessel is in the form of a metallic pipe and said sponge means is characterized further to include: an annular sponge sized to conform to the outer periphery of the non-conducting coating on the metallic pipe.
Claim 11
Dependent Claim
33 words
The apparatus as defined in claim 1 wherein said variable resistance means is characterized further to include: visual indicator means for displaying the resistance value to which said variable resistance means is set.
Claim 12
Independent Claim
115 words
A method of checking the resistivity of a non-conducting coating on a metallic vessel or the like and detecting holidays in said coating, comprising the steps of: applying a known d.c. voltage across a standard resistance and across the non-conducting coating and metallic vessel connected in parallel; comparing the current flowing through the standard resistance with the current flowing through the non-conducting coating and metallic vessel; detecting when the current flowing through the non-conducting coating and metallic vessel is greater than the current flowing through the standard resistance; and providing indication when the current flowing through the non-conducting coating and metallic vessel is detected to be greater than the current flowing through the standard resistance.
Claim 13
Independent Claim
115 words
A method of checking the resistivity of a non-conducting coating on a metallic vessel or the like and detecting holidays in said coating, comprising the steps of: applying a known d.c. voltage across a standard resistance and across the non-conducting coating and metallic vessel connected in parallel; comparing the current flowing through the standard resistance with the current flowing through the non-conducting coating and metallic vessel; detecting when the current flowing through the non-conducting coating and metallic vessel is greater than the current flowing through the standard resistance; and providing indication when the current flowing through the non-conducting coating and metallic vessel is detected to be greater than the current flowing through the standard resistance.
Claim 14
Dependent Claim
46 words
The method as defined in claim 11 wherein the step of providing indication is characterized further to include: providing an audible signal when the current flowing through the non-conducting coating and metallic vessel is detected to be greater than the current flowing through the standard resistance.
Claim 15
Dependent Claim
47 words
The method as defined in claim 11 wherein the step of providing indication is characterized further to include: providing audible and visible signals when the current flowing through the non-conducting coating and metallic vessel is detected to be greater than the current flowing through the standard resistance.
References Cited (Backward Citations)
US2440044A
Cited
US2460688A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-05-06 | 1977-11-05 | 1978-05-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-05-06 | 1981-11-05 | 1982-05-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-05-06 | 1985-11-05 | 1986-05-07 | $7700.00 | Window Closed / Lapsed |