Nace CP 1, Course Manual

Page: 438 / 535

RP0196-2004
8
NACE International
reference electrode shall be used to take
readings at several locations in the tank.
7.3.2.4 Annual Inspections
7.3.2.4.1 All galvanic anode CP system
components should be completely inspected
annually. The inspection shall include
polarized potential measurements—corrected
for IR drop by either interruption of the anode
current or the coupon connection to the
tank—to ensure that the system is operating
properly. For tanks with handholes in the top,
this includes lowering a portable reference
electrode into the tank and taking instant-off
measurements along the tank wall to evaluate
whether all surfaces of the tank are protected.
When instant-off measurements are not
possible, the coupon data or some other
method shall be used to correct for IR drop.
The connection to the portable reference
electrode and all the metal components on
the electrode and the wire shall be completely
insulated.
7.4 Anode Replacement
7.4.1 All galvanic anodes that have ceased to function
properly should be replaced. Tank-to-water potentials,
current output, and/or visual inspections shall be used
to evaluate anode performance.
7.4.2 Damaged or deteriorated cables, anode lead
wires, and electrical connections shall be replaced or
repaired using specific system components compatible
with the original design.
7.4.3 In tanks subject to icing conditions, galvanic
anodes shall be inspected and/or tested after the
probability for freezing has passed. Damaged anodes
shall be replaced.
7.4.4 When the water storage tank is taken out of
service, the galvanic anodes should be examined and
broken or damaged anodes shall be replaced.
7.4.5 Galvanic anodes should also be examined to
determine consumption. When galvanic anode
remaining life is less than the time to the next
inspection, anodes should be scheduled for
replacement.
7.5 Records
7.5.1 Tank Information
7.5.1.1 Complete information and the history of
the tank itself should be recorded, including:
(a) Dimensions and capacity,
(b) Tank erection and CP contractor,
(c) Date of erection,
(d) Coupon type, configuration, and location,
(e) Original coating, including system, surface
preparation, and materials,
(f) Subsequent coatings and dates of coating,
(g) History of any structural repairs,
(h) Costs associated with maintenance of the
tank,
(i) Tank
location,
(j) Warranty dates on coatings and CP, and
(k) Water temperature range.
7.5.2 Water Information
7.5.2.1 Complete information about the water
stored in the tank should be recorded. This
information includes both the chemical and
electrical characteristics, as well as information
about the variations in these characteristics that
occur throughout the year. If different sources of
water that have substantially different resistances
are used, the frequency of maintenance testing
may need to be adjusted so that tests are
conducted at each time a change in water
chemistry occurs. Basic to determining the
changes in chemistry would be the resistivity of the
water, which can also be reflected by the total
dissolved solids in the water.
7.5.2.2 Operational information about frequency
of draining, cleaning, and filling should be
recorded.
7.5.3 CP
7.5.3.1
Complete information about the
installation and design of the galvanic anode CP
system should be documented, including:
(a) The number and configuration of galvanic
anodes,
(b) Galvanic anode dimensions and typical
composition,
(c) Stationary reference electrode type, model
number, and manufacturer,
(d) Wiring and anode suspension,
(e) Electrical
schematic diagrams,
(f) Individual galvanic anode circuits and shunt
resistances,