Nace CP 1, Course Manual

Page: 463 / 535

RP0200-2000
6 NACE International
This method works best with the four-wire method.
Using fewer than four wires introduces a lead-
resistance problem into the circuit.
6.2.7 Pipe/Cable Locator: The presence and location
of a pipe-to-casing metallic contact may also be
approximated by following a low-power audio or
radio signal (pipe locator trace) set between the pipe
and the casing. The signal returns at the point of
metallic contact, which should be verified from the
opposite end.
6.3 Instrumented (“Smart”) Pigs
6.3.1 If feasible and practical, in-line inspection of a
pipeline may be used to determine the presence or
absence of pitting-corrosion damage on carrier pipe
inside a casing. In-line inspection techniques are
capable of detecting many types of corrosion
damage with a high degree of accuracy. However,
they may not detect metal-to-metal contact between
the casing and carrier pipe.
6.4 Leakage Survey
6.4.1 Visual Inspection: The casing vent and the
area in the vicinity of the casing end may be
observed for evidence of product leakage such as
product, product odor, or dead and dying vegetation.
6.4.2 Instrumented Surveys for Pipe Carrying
Combustible Hydrocarbons: Appropriate leak-
detection instruments, such as combustible gas
indicators, may be used to analyze the atmosphere
within a casing for the presence of combustible
hydrocarbons. Pressure tests or other leak-detection
devices are used on other systems. These surveys
should be done at the frequency required by the
applicable code or in accordance with the operating
company’s practice.
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References
1. NACE Standard RP0169 (latest revision), “Control of
External Corrosion on Underground or Submerged
Metallic Piping Systems” (Houston, TX: NACE).
2. NACE Standard RP0286 (latest revision), “The
Electrical Isolation of Cathodically Protected Pipelines”
(Houston, TX: NACE).
3. NACE Standard RP0274 (latest revision), “High-
Voltage Electrical Inspection of Pipeline Coatings Prior to
Installation” (Houston, TX: NACE).
4. NACE Standard RP0490 (latest revision), “Holiday
Detection of Fusion-Bonded Epoxy External Pipeline
Coatings of 250 to 760
µ
m (10 to 30 mils)” (Houston, TX:
NACE).
5. ASTM D 938 (latest revision), “Standard Test Method
for Congealing Point of Petroleum Waxes, Including
Petrolatum” (West Conshohocken, PA: American Society
for Testing and Materials [ASTM]
(1)
).
6. ASTM D 937 (latest revision), “Standard Test Method
for Cone Penetration of Petrolatum” (West
Conshohocken, PA: ASTM).
_______________________________________________________________________
Bibliography
Johnston, V.
Road Casing Electrical Contact
Characterization. American Gas Association
Distribution Conference, 1983
. Cleveland, OH:
American Gas Association (AGA),
(2)
1983.
NACE Publication 10A192 (latest revision), “State-of-the-
Art Report on Steel Cased Pipeline Practices.”
Houston, TX: NACE.
Peabody, A.W. Control of Pipeline Corrosion. Houston,
TX: NACE, 1967.
____________________________
(1)
ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428.
(2)
American Gas Association (AGA), 1515 Wilson Blvd., Arlington, VA 22209.