Title of Invention

AN IMPROVED DEVICE USEFUL FOR CATHODIC PROTECTION OF STEEL STURCTURES

Abstract An improved device useful for cathodic protection of steel structures which comprises a linear D.C. power supply (1) and an isolated D.C. power supply (2) , characterised in that both the power supplies (1 ,2) being connected to a function generator (3) capable of generating constant current driven steady state ramp, output of the said function generator(S) being connected to the input of a pulse width modulation (PWM) controller (4), the said PWM controller (4) being also connected to the output of steel structure (10) through soil potential difference sensor (11) , output control signal of the said PWM controller being connected to the input of a fast switching power circuit (5), the negative terminal of the power circuit (5) being connected to the said steel structure (10) and the positive terminal being connected through an auto/manual switch (8) to an anode bed (9), means (LED indicator 6 & LCD meters 7) being provided for monitoring parameter such as input / output voltage, current
Full Text This invention relates to an improved device useful for cathodic protection of steel structures. The device of the present invention is used with sintered insoluble magnetite anodes. This invention is related to those industries who are having underground pipeline and under water/sea structures such as Oil & Natural Gas Commission (ONGC), Indian Oil Corpn Ltd. (IOC), Oil India, Gas Authority of India Ltd. (GAIL) etc. The use of present invention will take care of corrosion of the steel pipelines and prevent from corrosion by cathodic protection. Beneficiaries of cathodic protection device could be Iron & Steel Indust- ries,Fertilizer and Chemical Factories, Municipal Corporation, Petrochemical Industries, e.g. IPCL, BPCL, HPCL, NTPC, National Hydro Power Corp. (NHPC).
With the scope as mentioned above the following types-of metal¬lic structures may be protected by cathodic protection:
Buried under ground pipeline, Tanks, Sewage and water pumping installation, Piling and structural foundations, Submerge structures, Off-shore metallic structures, Ship and barge hulls, Lock gates and shutter gates, Piers and piling.
In the hitherto known process the anode used is either sacrifi¬cial anodes e.g,aluminium alloys, zinc or magnesium alloys or applying impressed current (manual control) for protection using insoluble anodes e.g. platinum or platinum titanium alloy.
The conventional device is shown in Fig. 1 of the drawings accompanying this specification wherein the transformer (1) is connected to diodes (3,4,5,and 6) through a switch (2) at dif-

ferent tappings Inductor 7 and capacitor bank 8 and 9 filter the raw D.C which is coming from diode bridge (3,4,5,& 6). In this device the control is manually done by changing of tap in the transformer (secondary side) by a switch (2). After fil¬tering D.C is fed to anode bed (10) and pipeline (11). In this
device using half cell (12) (Cu/CuSO4 ) pipeline to soil poten-
tial is measured manually and for desired level of pipeline protection. Voltage is adjusted by tap changing only. The device has got no automatic control and thus un-manned operation cannot be achieved. Limitations of Known Device are :
1. It is only a rugged device for cathodic protection for
small power handling device becomes bulky because compactness is
not possible. The device is bulky and not suitable for transpor¬
tation and handling
2. Efficiency of the de vice is about 65 % only
3 Device used is obsolete as on today for precision power control
4. In the long run the device is not cost effective due to
manual operation for fluctuation control land the device being
bulky etc
5. Because of power fluctuations in AC mains, there is enough
fluctuations reflected in the current and rectifier scheme which
are uncontrolled in operation as shown in Fig. 1 of the draw¬
ings.

The main object of the present invention is to provide and improved device useful for cathodic protection which overcomes the above mentioned drawbacks.
The device of the present invention controls the current re¬quired for full protection of the structures/pipelines/installa¬tions efficiently. Irrespective of power fluctuations, the control system of the device takes care of entire performance of the device and will not allow any fluctuation in current or potential across the structures. Protection is maintained all the time and depends on current and voltage requirement i.e. desired protection level automatically.
At present thousands kms of pipelines for transportation petro¬leum products need protection, the auto-controlled Cathodic protection (CP) device used by the present invention will be an ideal choice.
In the present invention, we have not any conventional uncon¬trolled rectifier. we have used the fast power switching device for power handling. Pulse width modulation (PWM) is scheme in power control which prevents the power fluctuations in the output although there is a fluctuation in the input. Noth¬ing is reflected in the output side. In our power control strategy we have used the technique of PWM scheme which prevents any fluctuations.
The device of present invention consists of power transformer charging regulator, battery banks, control power and indication circuits. Puls width modulation (PWM) technique adopted in power circuit controls the voltage across.anode bed and pipe-

line as per requirement which is sensed by Cu-CuSO4 half cell. The Cu-CuSO4 half cell is used as a measure of the value of pipeline to soil potential (PSP) as well as feed back parameter for power controller, control pulse is generated using steady ramp, feed back signal from half cell and control voltage.
The device of the present invention is shown in Fig. 2 of the drawings accompanying this specification. The device of the present invention consists of a linear power supply, isolated power supply, function generator, pulse width modulation (PWM) 4, controller (1) fast switching power supply (5) LED indicator (6) LCD meters (7) Manual switch / auto - switch (8), Anode bed (9) pipeline (10) soil to pipeline sensor (11).
Accordingly, the present invention provides an improved device useful for cathodic protection of steel structures which comprises a linear D.C. power supply (1) and an isolated D.C. power supply (2), characterised in that both the power supplies (1 ,2) being connected to a function generator (3) capable of generating constant current driven steady state ramp, output of the said function generator(S) being connected to the input of a pulse width modulation (PWM) controller (4), the said PWM controller (4) being also connected to the output of steel structure (10) through soil potential difference sensor (11) , output control signal of the said PWM controller being connected to the input of a fast switching power circuit (5), the negative terminal of the power circuit (5) being connected to the said steel structure (10) and the positive terminal being connected through an auto/manual switch (8) to an anode

bed(9), means (6&7) being provided for monitoring parameters such as input/output voltage current.
An embodiment of the device of the present invention for cathod-ic protection of steel structures using sintered insoluble magnetite anode consists of linear power supply (1) which gener¬ates 12 volt DC for integrated circuit and is connected to function generator (3) which is used to generate constant cur¬rent driven steady state ramp for controlled circuit, isolated power supply (2) generate 12 volts DC voltage for isolation of ground in power circuit and is also connected to function gener¬ator (3) and is connected to PWM controller (4) which is used to generate the required control signal for fast switching power circuit with the help of ramp signal and the feed back signal connected to fast switching power circuit (5) which- comprises of latest power switching device along with inductor and capaci¬tor filter which handle the desired power for protection of pipeline steel structures (10) and is connected with anode bed (9) which comprises of sintered magnetite anode (insoluble) which acts as positive terminal of power output through manu¬al/auto-switch (8). The steel structure is connected to nega¬tive terminal whose protection is required . LED indications (6) are provided for showing under and overvoltage of supply source conditions and is connected to in between terminals of PWM controller (4) and fast switching power control (5),LCD meters (7) are provided for monitoring the parameters like input volt¬age input current output voltage output current and pipeline to soil potential. Manual/Auto-switch (8) indicates the

manual/automode of operation of the device and is connected in between the terminals of fast switching power circuit (5) and anode bed (9). Soil to pipeline sensor (11) is one sort of sensoring and monitoring pipe soil potential (PSP) value (pro¬tection value) and which is used as the feed back to the PWM controller(4).
Anode bed and pipeline are buried under soil in the test set-up. By the device of present invention there is no fluctuation in the voltage and current and thereby the whole pipeline structure will be protected throughout without any failure. The following examples are given by way of illustration and should not be construedS to limit the scope of the device of the present invention.
Examples 1,2 & 3 are the test results of the performance of our proposed prototype device. Test set-up comprises of device along with 24 V D.C insoluble sintered magnetite as anode bed
buried under soil and Cu-CuSO half cell. Buried earth was
4
made artificially with the help of soil back fill and anode bed. All these examples are the test results at different output conditions of the device i.e at 30 % ,50 %, 80% of the output of the device. Voltages, currents are the input and output of the device. Pipeline to soil potential is measured from the
output of Cu-CuSO4 half cell as used in the test set-up.
Example-1
Duty cycle - 30 % i.e on ( time/Off time 100}
Input voltage - - 24 V D.C
Input current - 0.45 amps D.C
Out put voltage - 7V D.C. (filtered)
Out put current - 1 amps D.C
Pipeline to soil potential -1.0V D.C

Example -2
Duty cycle - 50 %
Input voltage - 24 V D.C
Input current - 0.3 Amps D.C
Output voltage - 11.8 V D.C (filtered)
Output current - 0.6 Amps D.C
Pipeline to soil potenial-1.0 V D.C
Example -3
Duty cycle - 80 % Input voltage - 24 V D.C Input current - 0.32 Amps D.C Output voltage - 19 V D. C (filtered) Output current - 0.38 Amps D.C Pipeline to soil potential-1.0 V D.C
The main advantages of the device of present invention are:
1 The device of present invention controls and maintains the current across the structures so that pipeline to soil potential (PSP) always remain above protective potential of the system. Thus it ensures complete protection at all times whereas it is not possible in known device..
2. It automatically controls the fluctuation of current/volt¬
age in the power circuit whereas there is no such provision
with the hitherto known device
3. It gives an alarm if there is any failure in the auto-
control circuit and manually control can be set during auto-
circuit failure whereas such provision is not there in the
hitherto known device

4. In the long run, the system becomes cheap.
5. The control in the present device is very precise due to
adopting a new methodology in the electronic circuit
6. The present device consumes less power and the cathodic
protection system becomes compact than the known device.
7. The cathodic protection system designed in the present
device is effective for 100 kms on either side of the insoluble
anode whereas in the hitherto known device it is hardly 50
kms on both the sides of the anode.




We claim :
t.An improved device useful for cathodic protection of steel structures which comprises a linear D.C. power supply (1) and an isolated D.C. power supply (2) , characterised in that both the power supplies (1 ,2) being connected to a function generator (3) capable of generating constant current driven steady state ramp, output of the said function generator(S) being connected to the input of a pulse width modulation (PWM) controller (4) , the said PWM controller (4) being also connected to the output of steel structure (10) through soil potential difference sensor (11) , output control signal of the said PWM controller being connected to the input of a fast switching power circuit (5), the negative terminal of the power circuit (5) being connected to the said steel structure (10) and the positive terminal being connected through an auto/manual switch (8) to an anode bed (9), means (LED indicator 6 & LCD meters 7) being provided for monitoring parameter such as input / output voltage, current.
2. An improved device useful for cathodic protection of steel structure substantially as herein described with reference to the examples and Fig.2 of the drawings accompanying this specification.


Documents:

802-del-1997-abstract.pdf

802-del-1997-claims.pdf

802-del-1997-correspondence-others.pdf

802-del-1997-correspondence-po.pdf

802-del-1997-description (complete).pdf

802-del-1997-drawings.pdf

802-del-1997-form-1.pdf

802-del-1997-form-19.pdf

802-del-1997-form-2.pdf

abstract.jpg


Patent Number 217911
Indian Patent Application Number 802/DEL/1997
PG Journal Number 17/2008
Publication Date 25-Apr-2008
Grant Date 29-Mar-2008
Date of Filing 27-Mar-1997
Name of Patentee COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH
Applicant Address RAFI MARG, NEW DELHI-110001.
Inventors:
# Inventor's Name Inventor's Address
1 SUSHIL KUMAR MONDAL NATIONAL METLLURGICAL LAB. JAMSHEDPUR, INDIA.
2 ARABINDA NATH MUKHERJEE NATIONAL METLLURGICAL LAB. JAMSHEDPUR, INDIA.
3 SRI KRISHNA NARANG NATIONAL METLLURGICAL LAB. JAMSHEDPUR, INDIA.
4 MAHESH NANDAN SINGH NATIONAL METLLURGICAL LAB. JAMSHEDPUR, INDIA.
5 TRIPURI LAL SHARMA NATIONAL METLLURGICAL LAB. JAMSHEDPUR, INDIA.
6 INDER SINGH NATIONAL METLLURGICAL LAB. JAMSHEDPUR, INDIA.
PCT International Classification Number C23F 13/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA