AMPP CP1 Tester flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Rectifier lockout and tagout

Before opening a rectifier cabinet, de-energize the AC supply and apply a lock and tag. Input line voltage is lethal and is separate from the DC output hazard.

Induced AC touch hazard

Pipelines running parallel to power lines can carry induced AC voltage, creating touch and step potential hazards. Measure AC voltage to remote earth before contacting the structure.

Confined space test stations

Test stations inside pits or vaults may accumulate oxygen-deficient air, hydrogen sulfide, or flammable gas. Test the atmosphere with a calibrated multi-gas meter before entry.

Copper sulfate electrolyte hazard

Saturated copper sulfate solution irritates skin and eyes and is toxic to aquatic life. Wear gloves and eye protection, contain spills, and dispose of waste per regulations.

Temporary bond polarity check

Reversed DC connections on temporary bonds can cause arcing, unexpected structure potentials, and shock. Verify polarity with a meter before energizing any temporary circuit.

Portable reference electrode comparison

Compare a copper/copper sulfate half-cell against a second portable reference in the same electrolyte. A difference above about 5 millivolts indicates contamination or a blocked junction.

Voltmeter input impedance requirement

Pipe-to-soil potential measurements require a voltmeter with at least 10 megohms input impedance. Lower impedance draws current through the soil and produces a biased reading.

Wenner soil resistivity formula

Soil resistivity equals two pi times pin spacing times measured resistance, rho = 2 pi a R. Use consistent units, such as centimeters and ohms to obtain ohm-centimeters.

Current interrupter timing verification

Verify interrupter on and off timing with a timing device or oscilloscope before a survey. GPS-synchronized units protecting one structure must start and stop together.

Copper sulfate to SCE conversion

A copper/copper sulfate reference reads about 76 millivolts more negative than saturated calomel for the same structure. Add roughly 76 millivolts to express a copper sulfate reading versus SCE.

Instant-off potential

An instant-off reading is taken immediately after interrupting cathodic protection current. It excludes the resistive IR voltage drop in soil, leaving the true polarized potential of the structure.

100 mV polarization criterion

A structure meets this criterion when its potential has shifted at least 100 millivolts in the cathodic direction from the native, depolarized potential, measured as an instant-off value.

Non-interruptible current sources

Galvanic anodes, solar panels, TEGs, and foreign rectifiers that cannot be interrupted contaminate instant-off readings. Identify and account for them before interpreting survey data.

Rectifier no-output troubleshooting

When a rectifier shows no DC output, check the AC supply voltage, fuse, tap setting, and diode or stack condition, then confirm with a clamp-on DC ammeter.

-850 mV CSE criterion

The minus 850 millivolt copper sulfate criterion applies to the polarized potential with IR drop removed. Applying it to an IR-included reading can leave the structure underprotected.

Stray DC interference detection

Structure-to-soil potentials that shift in step with another structure's current cycle indicate stray DC interference. Map potentials with the foreign source switched on and off.

Close interval survey spacing

Close interval surveys typically record structure-to-soil potentials at one to three meter intervals, with tighter spacing in congested areas and near coating defect indications.

DCVG percent IR

In direct current voltage gradient surveys, percent IR compares a defect's voltage gradient to the total pipe-to-soil voltage shift, ranking the relative severity of coating defects.

Native potential measurement

Native potential is measured after all cathodic protection current has been off long enough for the structure to depolarize, sometimes days. It is the baseline for polarization criteria.

Current requirement test

A temporary anode bed and power source apply current to the structure while potentials are recorded, showing how much current is needed to reach the protection criterion.

Half-cell placement

Place the reference electrode in undisturbed, moist soil as close to the structure as practical. Pavement, dry backfill, and gravel raise contact resistance and bias the reading.

Out-of-trend reading verification

Repeat any reading that differs sharply from adjacent data, and check lead continuity, electrode contact, and AC noise before accepting or rejecting the recorded value.

Field record required elements

Each reading is recorded with date, time, test point identification, structure, reference electrode type, instrument serial number, calibration date, and technician name.

Stating CP criterion

Reports must name the protection criterion applied, such as minus 850 millivolts instant-off or 100 millivolts polarization, and state whether IR drop was removed.

Rectifier operating log

Log the date, time, AC input voltage, tap or mode setting, DC output volts and amps, and any adjustment made during the rectifier inspection visit.

As-found and as-left

Record the rectifier or system condition before adjustment and after adjustment, so reviewers can see exactly what changed and who authorized it.

Data traceability and backup

Back up raw logger files before leaving site. Unsaved, unsigned, or uncorrected data cannot be defended as a record of the survey.

Pipe-to-soil lead connections

Connect the structure to the voltmeter positive terminal and the reference electrode to the negative or common terminal. A negative reading indicates cathodic polarity.

IR drop in readings

Current flowing through soil resistance between structure and reference adds an IR error that drives readings more negative. Interrupting the current and reading instant-off removes it.

AC voltage to remote earth

Measure AC voltage between the structure and a remote earth reference to assess induced AC exposure. Values near or above 15 volts are commonly treated as requiring mitigation review.

Shunt current calculation

Current through an anode or bond equals the measured millivolt drop divided by one thousand, then divided by the shunt resistance in ohms.

Telluric current effects

Naturally occurring earth currents from solar activity cause slow potential fluctuations that can mimic cathodic protection changes. Compare repeat readings taken minutes apart during quiet periods.