APPENDIX A (continued)
IR drop (get at least one on every structure).
Correct readings if necessary.
Be sure to indicate polarity of all readings.
Voltage between structures. Test voltage between all metallic
structures. (Be sure to indicate polarity of each reading.)
Insulating joint - Test resistance of all known joints and look for
others. Use four connections (two on each side of joint) with DC
For mechanical pipe joints:
Test each piping system to find out if mechanical joints exist.
Test representative number of mechanical joints to determine
quantitative resistance per joint.
Be sure to use the four point contact method with direct current.
All electrical tests at each manhole:
As in b, e, and f above.
Be sure to test voltage between all cables in multiple run
Visually inspect all hardware in each manhole:
Condition of cables
Note material of each component and its condition
Note fastening methods and insulation between components
Investigate stray current:
Stray currents must be indicated by abnormal structure-to-soil
voltages or IR drop. (Either steady or fluctuating.)
If stray current is suspected, investigate:
a) Any possible source of direct current in the area.
b) Operating cathodic protection.
Have suspected source turned off and on to establish its affect
on any structure.