Multiple coupon apparatus for cathodic protection testing
A test coupon package suitable for a cathodic protection system includes a native test coupon and first and second active coupons. The active coupons may be biased with respect to the soil or other electrolytic medium in which a pipeline protected by the system resides. The first active coupon may have a surface area that will contact an electrolytic medium that is approximately equal to a surface area of the native test coupon that will contact the electrolytic medium. The surface area of the first active coupon may be substantially greater than a surface area of the second active coupon that will contact the electrolytic medium. The test coupon package may include an electrochemically stable reference electrode positioned between the first active coupon and the native coupon. The test coupon package may be substantially cylindrical and, in at least one embodiment, may include a conical nose connected to a first end of the test coupon package with the second active coupon attached to a narrow end of the conical nose.
1. A test coupon package for a cathodic protection system including a pipeline buried in an electrolytic medium, the test coupon package comprising:
a reference electrode connected to a reference probe input;
a first active coupon connected to a first probe input;
a second active coupon connected to a second probe input; and
a native coupon connected to a third probe input;
wherein a surface area of the second active coupon that will contact the electrolytic medium is substantially less than a surface area of the first active coupon that will contact the electrolytic medium.
2. The test coupon package of claim 1 , wherein the first active coupon is electrically connected to the pipeline during at least a portion of operation of the cathodic protection system and the second active coupon is electrically connected to the pipeline during at least a portion of testing.
3. The test coupon package of claim 1 , wherein the surface area of the first active coupon and a surface area of the native coupon that will contact the electrolytic medium are approximately the same.
4. The test coupon package of claim 1 , wherein the surface area of the first active coupon exceeds the surface area of the second active coupon by a factor equal to or exceeding 100 and further wherein the surface area of the second active coupon is approximately 1 cm2.
5. The test coupon package of claim 1 , wherein the test coupon package comprises a cylindrical housing and wherein the first active coupon and the native coupon comprise steel rings circumventing the cylindrical housing.
6. The test coupon package of claim 5 , wherein the reference electrode is positioned between the first active coupon and the native coupon and wherein electrically non-conductive spacers separate the reference electrode from the first active coupon and the native coupon.
7. The test coupon package of claim 5 , wherein the first active coupon and the native coupon are positioned between the second active coupon and the reference electrode and wherein electrically non-conductive spacers separate each of the reference electrode, the first active coupon, the native coupon, and the second active coupon from one another.
8. The test coupon package of claim 5 , wherein a surface area of the reference electrode exceeds the surface area of the first active coupon.
9. The test coupon package of claim 5 , further comprising:
a conical nose piece connected to the cylindrical housing, wherein the second active coupon is attached to the test coupon package at a narrow end of the conical nose piece, wherein only one surface of the second active coupon is configured to contact the electrolytic medium.
10. The test coupon package of claim 1 , wherein the reference electrode comprises a copper-copper sulfate electrode.
11. A test block for testing a cathodic protection system, the test block comprising:
a reference probe input configured to connect to a reference electrode of a test coupon package;
a first coupon input configured to connect to a first active coupon of the test coupon package;
a second coupon input configured to connect to a second active coupon of the test coupon package, wherein a surface area of the second active coupon that will contact an electrolytic medium is substantially less than a surface area of the first active coupon that will contact the electrolytic medium;
a third coupon input configured to connect to a native coupon of the test coupon package; and
a first auxiliary input, configured to connect to a first point of a pipeline and to a second contact of a switch configured, when closed, to connect the pipeline and the first active coupon.
12. The test block of claim 11 , further comprising:
a second auxiliary input connected to a second point of the pipeline, different than the first point of the pipeline.
13. The test block of claim 11 , further comprising:
an anode input connected to the second contact of the switch and further configured to connect to an anode.
14. The test block of claim 11 , wherein the first coupon input is connected to a first contact of the switch and wherein the switch is configured, when closed, to connect the first contact and the second contact.
15. The test block of claim 14 , further comprising, wherein the switch is manually controlled and wherein the test block further comprises a manually operated switch controller.