CP 2 Practical Exercises Set #1 12 Practical Exercise Station 5 Current Span Sludents are to bacome competent in conducting tests fo calibrate pipeline current spans: Calibrating the current span is similar to establishing the shunt value or shunt factor in a current shunt. Once calibrated, the calibration factor can be used to determine the residual current flowing from CP current sources andlor stray current influences in the pipe span. PROCEDURE Part A. Test Span Calibration 1. Calibrate the current spans #1 and #2 by impressing the provided current from the CS-10 power source through the outside wires (top terminals) of the respective test station and measuring the voltage drop across the inside wires (bottom terminals) at each tests station, ‘TEST CONNECTIONS: PIPE Note: There are two identical test heads. Test Station #1 represents Current Span #1. Test Station #2 represents Current Span #2. Span #1 and Span #2 are spaced along @ segment of pipe and may be a mile or more apart from each other The test circuit is essen! schematic drawing. ly a series electrical circuit as shown in the following NACE © NACE International, 2008 72011CP 2 Practical Exercises Set #1 13 Controlled Power Supply Current interrupter hresr ie cso mv Vrest Tresioun. — “Torth) Resistor (Rseax) ————+ 2. Test Station #1 Measurements (Note polarity and thus direction) Irestt on (CS-10 ON) 1K oma esrior (CS-OOFF) O17 _ ma > ears = esr cater ore 12 Smal Vresrt on (CS-10 ON) 12D© my Vrestt orr (CS-10 OFF) [RO mv 3. Test Station #2 Measurements (Note polarity and thus direction) hrestzon (CS-10 ON) 1S mA restaore (CS-10 OFF) = _O __ma hresz = lrestz on ~Irestzorr 2 sa mA Vresrzon (CS-10 ON) 290 mw : Vresraore (CS-100FF) SIO mv *NACE © NACE International, 2006 72011CP 2 Practical Exercises Set #4 : 14 4, Pipe Span Resistance and Calibration Factor Calculate the current span resistance [Q] and the calibration factor (A/mV) for each: current span. Note: potentials must be in Volts to calculate resistance and mV to calculate CF. Vrrsrow —Vaesrorr) Cres) = Cresr) (AV resto — ™Vrestore ) Av Test Station #1 Ragan = {38% 2 CF agen = O°S2aImv Tost Station #2 R2ipn= O*Y 0 CFepan = 2290 amv 5. Residual Current Was there a residual current on the pipe section; that is, was there @ Vresr reading with no Test Cone 99 CS-107 Yes? No? If so calculate the current. Ts = Vresvore) 5 RESIDUAL (Ree J resist = Vor CF span Fest strton et Revise canes TOO Reo Test Station #2 Residual Current = A mA NACE © NACE International, 2008 72011CP 2 Practical Exercises Set #1 18 Practical Exercise Station 6 Coating Conductance. Students are to become competent in completing tests to measure and calculate the pipe coating resistance and conductance. The instructor will connect the station such that the pipe is receiving an interrupted supply of current from an anode. The instructor will give the following information: Repavt=_6°02. © OR CFspant =_0OS Paimv Repan 2= 00% 9 OR CF sean2= 009% Almv iameter D:-201F m __ Pipe Length PSS im Student © Confirm that the power supply is on and interrupting 1 Confirm that the switch behind Test Station #1 is in the “on” position as it controls the pipe-to-electrolyte potentials Pipe 4. Test Connections Ss The test is intended to determine the pipe to earth resistance’through the coating (R.) between the test stations as represented by the darker colored pipe, This can be represented by an electrical circuit as shown below. NACE © NACE International, 2008 72011CP 2 Practical Exercises Set #1 The objective is to calculate Re by 2. Test Station #1 Measurements Me? mw OX mV Eo 1B mv 197 mw MV pt on Vp oFF Erorr 3. Test Station #2 Measurements mVp20n sb mv mVpzore 02 mv Exon WL mv Ene L086 mv NACE » NACE International, 2008, 2011 (Pipe Span with current ON) (Pipe Span with Current OFF) © (OFF Pipe-to-electrolyte Potential) (ON Pipe-to-electrolyte Potenti (Pipe Span with current ON) (Pipe Span with Current OFF) (ON Pipe-to-electrolyte Potential) (OFF Pipe-to-clectrolyte Potential)) CP 2 Practical Exercises Set #1 4, Calculate Current in Each Pipe Span Equation Summary 7 TBs ron = Vevon 1 Ree Tron = Veron x OF, 3 Vezon 1Rez OR sow «Vesa x CF : Verore Res lesorr + Verorr x CF, Vesore_1 Ree losore = mVesoee_X CFs Vin Vatis)= mv/ 1000 mv=Vx 1900 Test Station #1 Ales Test Station #2 Iezon Ete s lnaorF ‘066 a Ales AY An 5. Current Pick Up in Coating Section (Ic) Je = Alps - Alp2 6. Average Potential Across Coating Due to Current Applied AEs = Eron— Erorr- AE = Exon — Ezore- ace IF mv ag=_20__mv Caloulate the average AE [AE ave =(AE: + AE: )/ 2] Average AEy, 2° _ mv NACE © NACE International, 2006 72011CP 2 Practical Exercises Set #1 18 7. Pipe Coating Resistance Calculate the total resistance of the pipe section to earth between test stations oO Io 108 Total pipe coating resistance (R. ry Yb 8. Pipe Surface Area Calculate surface area of pipe based on diameter and length of pipe given by A=a7dL Where A - Surface area of pipe D - Outside Pipe Diameter L- Lenath of coated pipe section 13.1416 Pipe Diameter = 0? 2©¢% _ m (given) Pipetengtn= 7595" mm given) surface aroa=_2/A-41_ mi? © 9. Specific Coating Resistance Calculate the specific unit coating resistance (re Jin Q-m? % =Re*A Specific unit coating roststance (x) =!” Vie oe 40. Specific Coating Conductance = (2 b5rke Calculate the specific unit coating conductance (ge ) in Sim? 1 : Ec = 1 Specific unit coating conductance (g.) =_2*70/0 ‘sim? Sace G © NACE International, 2006 72011