This presentation discusses the use of linear flexible anodes in deep vertical groundbeds for cathodic protection. It describes the product specifications and design options for the anodes. A case study is presented where the anodes were installed in a 61m deep vertical well in Italy. Monitoring data showed the groundbed resistance and cell voltage stabilized at low levels, demonstrating the effectiveness of the flexible anodes in deep well applications. The anodes can provide installation cost savings through reduced borehole diameters and shorter active zones.

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SPECIALTIES & NEW APPLICATIONSPOOLS & ELECTROCHLORINATIONELECTRONICS & SURFACE FINISHINGCHLORINE & CAUSTIC INDUSTRY
APPLICATION IN DEEP
VERTICAL GROUNDBEDS OF
LINEAR FLEXIBLE ANODES
Simone Tremolada

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What is linear
flexible anode?
Technical
specifications of
the product
Product Design
Options
Case History:
Installation in
deep well
groundbed.
Installation Cost
Savings
Conclusions
Presentation Outlook

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This system is considered the ideal
solution when the anode has to be
installed very close to the structure to
protect in confined spaces.
Linear Flexible anode
Linear flexible anodes were designed
for the cathodic protection of
pipelines, tanks (AST or Mounded LPG
Storage Bullets) in soil or sand and
reinforced concrete structures.
Linear flexible anode designed for
close by Cathodic Protection in HDD
applications.

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Linear Flexible anode
The anode is assembled inside a
protective sock that prevents accidental
contacts with the cathode and is
surrounded by calcinated petroleum
coke. A protective braid is increasing
mechanical resistance.
The product core is a pure titanium
wire Grade 1 according to ASTM B
863 thermally coated with mixed
metal oxides of group VIII.
This design allows to optimize the
current distribution and to reduce the
resistance at the anode-soil interface
of the groundbed, either horizontal or
vertical.

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Linear Flexible Anode
easy and
timesaving
installation
procedure
accurate QC on the
factory-made
conductive
connections
optimization of
the current
distribution
green product: zero
discharge of
pollutants and energy
saving
Advantages for the installators of impressed current cathodic
protection groundbeds:

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Max current density 100 A/m2
Anodic titanium wire diameter 1,5mm Ø 3mm Ø
Current output at the Max current
density
470 mA/m 940 mA/m
Expected design life 25-30 years
Technical specifications.
Flexible product in current output and expected design life.

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Mixed metal
oxide titanium
diameter:
1.5mm, 3mm
Feeding cable
cross section:
10mm2 or
16mm2
Feeding cable
insulation:
XLPE/PVC or
Kynar/HMWPE
Anode to cable
splicing interval:
at every interval of:
10 metres or
as required by the
design
Anode backfill
composition:
Calcined
Petroleum Coke
Breeze; Fixed
Carbon 98 % -
99%
Coating load can
be optimized for
the required
design life up to
25-30 years.
Product design options.
The product is flexible even in design. It is possible to select
several parameters:

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Mixed metal
oxide titanium
diameter:
1.5mm, 3mm
Feeding cable
cross section:
10mm2 or
16mm2
Feeding cable
insulation:
XLPE/PVC or
Kynar/HMWPE
Anode to cable
splicing interval:
at every interval
of: 10 metres
or
as required by
the design
Anode backfill
composition:
Calcined
Petroleum Coke
Breeze; Fixed
Carbon 98 %-
99.4%
Coating load can
be optimized for
the required
design life up to
25- 30 years.
Product design options.
Optimization for impressed current vertical groundbed, in deep
vertical well in Italy:

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Case History
In 2015 this product was introduced
for the first time in Italy, optimized for
an impressed current vertical
groundbed, in a 61m deep vertical
well, where a traditional anode was
replaced.
The installation was performed on
March, 3rd 2015 in Northern Italy in a
vertical well.

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Length of the groundbed 61 m
Active part of the groundbed length 15m
Depth of the groundbed active zone 46m
Well Casing plastic pipe with holes in
the active part
Water table depth 6 m
Hydrochloric acid and gaseous
chlorine could be present
Deep well groundbed design.

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The anode, hanged to a dead
weight, was very easily
installed without the use of
special tools. It was
connected to a transformer
rectifier equipped with a
remote monitoring system.
The anode was very easily installed
without the use of special tools
Flexible anode installation in deep vertical groundbed.

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This system allows the daily reading
of minimum, medium and
maximum current output and DC
voltage values to monitor the
groundbed resistance evolution.
This data collection is aimed to
assess the presence of seasonal
effects on the anode
performance.
Any seasonal effect on the
anode perfromance ?
Remote monitoring system.

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Parameter
unit Deep well Water
main
pH pH 1.35 7.2
Conducibility
at 20°C
µS/cm 15.580 1055
Chlorides mg/l 394 104
Sulphates mg/l 254 179
Nitrates mg/l 57 29
Sodium mg/l 290 76
Potassium mg/l 15.7 2.4
Magnesium mg/l 120 24
Calcium mg/l 247 147
Hardness °F 111 46
Ammonia mg/l 7.2 <0.05
Nitrites mg/l 3.9 <0.05
The chemical analysis of the
water flooding the well allows
to check other parameters
that can influence the anodic
system durability like pH,
chloride content, and the
concentration of potential
pollutants like ammonia,
sulphates and nitrites.
Any chemical may influence anode
system performance?
Chemical analysis of the water.

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Reduced diameter of this anodic
system (38mm) will enable to
design new wells with consistently
reduced borehole diameter. Further
cost optimization can be reached
concentrating the length of the
active part of the anodic system,
this resulting in a reduced
perforation depth.
Reduced borehole diameter, Concentrated active part of
the anodic system for minimum perforation depth
Installation Cost Savings

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Design life (DL):25 years
Groundbed design current (IGB):12 A
Soil resistivity, r: 20 ohm.m.
Transformer rectifier rating: 15 V /15 A
The maximum linear anode current output is 940 mA/m at
100 A/m2 current density. Therefore the minimum required
length of the anode is 12/0.940= 12.8 m. Conservatively
this minimum length is rounded to 15m.
Deep Vertical Groundbed calculation
Anode material:
- Mixed metal oxide coated
titanium wire anode type
suitable for installation in soil
- length, l: 15 m;
- diameter, d: 3 mm;
- anode current output, ia: 15 A

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Based on maximum transformer DC output voltage (15 V)
and max. Groundbed design current (12 A), groundbed
resistance, RGB shall be not greater than 1.25 ohm
(15V/12A). Based on the above groundbed resistance, the
groundbed active length – anodes + backfill – was
calculated solving numerically the Dwight formula:
RGB = rsoil / (2πL)x(ln (8L/D-1))
where:
- rsoil: soil resistivity (ohm.m);
- L: minimum groundbed active length (m);
- D: groundbed diameter (m)
The calculated minimum groundbed active length is 12 m,
conservatively groundbed active length is increased to 15 m.
Groundbed active length

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Ω Av.
V Av.
A Av.
Installation: reduction of groundbed resistance from 0.95 to 0.91 Ω.
Average cell voltage decreased from 6.25V to 5.9V.
Results

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After over 2 months : average cell voltage increase: 5,9 V to 6,1 V
Resistance value stabilized at 0,94 Ohm.
Results

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Conclusions
Linear flexible anode
properly designed can
be an effective solution
in deep well groundbed
Installation is fast and
easy without the use
of special tools
Design of new
groundbeds with
reduced borehole
diameter and depth.
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Average cell voltage
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Thanks for your time.
Any question?

21. ELECTROCHEMISTRY AT YOUR SERVICETM
SPECIALTIES & NEW APPLICATIONSPOOLS & ELECTROCHLORINATIONELECTRONICS & SURFACE FINISHINGCHLORINE & CAUSTIC INDUSTRY
APPLICATION IN DEEP
VERTICAL GROUNDBEDS OF
LINEAR FLEXIBLE ANODES
Simone Tremolada