This specification is applicable to the design of sacrificial anode protection systems for buried and underwater steel pipelines. This specification is not applicable to sacrificial anode cathodic protection in marine environments. SY/T 0019-1997 Design Specification for Sacrificial Anode Cathodic Protection of Buried Steel PipelinesSY/T0019-1997 Standard download decompression password: www.bzxz.net

1 General Provisions
Petroleum and Natural Gas Industry Standard of the People's Republic of China
Design Specification for Sacrificial Anode Cathodic Protection of Buried Steel Pipelines
Approval Department: China National Petroleum Corporation Approval Date: 1997-07-17
Implementation Date: 1998-01-01
SY/T 0019--1997
Replaced, SYJ19--1986
SYJ 20--1986
1.0.1 In order to effectively implement sacrificial anode cathodic protection technology, achieve advanced technology, economic rationality, safety and applicability, and ensure quality, this specification is specially formulated.
1.0.2 This specification is applicable to the design of sacrificial anode cathodic protection systems for buried and underwater steel pipelines. This specification is not applicable to sacrificial anode cathodic protection in marine environments. 1.0.3 In the design of sacrificial anode cathodic protection systems, in addition to implementing this specification, the uninvolved parts shall be implemented in accordance with the requirements of relevant standards (specifications).
1.0.4 Reference standards:
GB/T4948—1985 Aluminum-zinc-indium alloy anode SYJ23--1986 Cathodic protection parameter test method for buried steel pipeline 2 Terminology
2.0.1 Cathodic protection Electrochemical protection achieved by reducing the corrosion potential. 2.0.2 Sacrificial anode Metal or alloy that provides cathodic protection current by increasing its own corrosion rate. Sacrificial anodes usually include magnesium, zinc and aluminum. 2.0.3 Temporary cathodic protection Corrosion control measures taken for pipe sections in highly corrosive areas after the pipeline is buried underground and before the formal cathodic protection is put into operation. 2.0.4 Electrolytic grounding cell uses one or more pairs of sacrificial anodes separated by insulating pads, filled and wrapped with fillers, and coupled through the resistance of the fillers to eliminate strong electrical surge shocks.
2.0.5 Ground mat
ground mat
Exposed conductor installed on the ground or underground. They are connected to each other to provide an equipotential within the step distance. In order not to affect the cathodic protection of the pipeline, magnesium strips or zinc strips can usually be used. 2.0.6. Backfill
Conductive material filled around the anode to improve the working conditions of the ground anode. 2.0.7 Cold insulation
Step surface formed during the cooling process of metal casting. 2.0.8 Permanent reference cell Reference electrode in soil or water with a service life of more than 1 year. 689
SY/T 0019-~1997
3 General provisions
3.0.1 The design of the sacrificial anode system should ensure the effectiveness and reliability of cathodic protection of the anode within the design life. 3.0.2 The design life of the sacrificial anode should match the service life of the pipeline, generally 10 to 15 years. 3.0.3 The design life of the temporary cathodic protection sacrificial anode should meet the user's requirements, generally 2 years. 3.0.4 The protected pipeline should have a good quality cover. The cover resistance of the newly built pipeline shall not be less than 100002·m, otherwise it is not suitable to use sacrificial anodes. For old pipelines, it should be decided according to specific needs. 3.0.5 When the soil resistivity is greater than 100α·m, sacrificial anodes should not be used. 3.0.6 All protected buried steel pipelines should be equipped with insulating joints or insulating flanges as required. 3.0.7
Protection criteria:
The cathode polarization potential of the pipeline relative to the saturated copper/copper sulfate reference electrode is at least 850mV. 2 The cathode polarization potential difference between the pipeline surface and the stable saturated copper/copper sulfate reference electrode in contact with the electrolyte is at least 100mV. This parameter can be data during the establishment or decay of polarization. 4 Technical conditions
4.1 Magnesium alloy anode
4.1.1 The chemical composition of magnesium alloy anode (hereinafter referred to as magnesium anode) shall comply with the provisions of Table 4.1.1. Table 4.1.1 Chemical composition of magnesium anode
Anode model
High purity Mg
Mg-Al-Zn-Mn
10. 50 ~-1.30
5.3~~6.72.53.50.15~~0.60
Chemical content (%)
The electrochemical performance of magnesium anode must comply with the indicators in Table 4.1.2. 4.1.2
Electrochemical properties of magnesium anode
Open circuit potential
Theoretical generated electricity
In seawater
(3 mA/cm）
In soil
(0.03 mA/rm*)
Current efficiency
Generated electricity
Consumption rate
Current efficiency
Generated electricity
Consumption rate
--V(SCE)
A·h/g
kg/(A·a)
A·h/g
kg/(A·a)
Note: When testing with soil medium, filling material with a thickness of 5 to 10 mm should be used. 4.1.3
Mg, Mg-Mn
Mg-Al-Zn-Mn
Magnesium anodes are divided into two types according to their cross-sections: trapezoidal and D-shaped. Their specifications are shown in Table 4.1.3-1 and Table 4.1.3-2. When used in water, the anode can be made into a hemispherical or bracelet shape, and its weight should be able to meet the requirements of the anode's working life. 690
Specification No.
Specification No.
(kg）
(mm）
（mm）
Table 4. 1. 3-1
Table 4. 1. 3-2
Shape and size of trapezoidal stamped surface magnesium anode
Specification No.
Shape and size of D-section magnesium anode
Specification No.
SY/T0019-1997
Strip magnesium anode can be made of high-purity magnesium or Mg-Mn alloy. Its shape and properties are listed in Table 4.1.4. Table 4.1.4 Shape and performance of strip magnesium anode Section (AXB)
Steel core diameter
(5 000 n * cm)
(150000 *cm)
9.5 mmX19 mm
10mA/m
4.1.5 Cast magnesium anode should not be warped, and its surface should be free of burrs, cracks, pores, inclusions and attachments. The shrinkage cavity and cold shut depth should be less than 10% of the thickness of the magnesium anode.
4.1.6 The surface of the strip magnesium anode manufactured by extrusion should be smooth, free of cracks, inclusions and attachments. 691
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4.1.7 The surface of the magnesium anode steel core should be galvanized, and the contact resistance between the anode body and the steel core should be less than 0.001Q. 4.2 Zinc alloy anode
4.2.1 The chemical composition of zinc alloy anode (hereinafter referred to as zinc anode) shall comply with the provisions of Table 4.2.1. Table 4.2.1 Chemical composition of zinc anode
Anode model
High purity Zn
Zn-A-Cd
0. 3~~0. 6
0.05~0.12
Chemical composition (%)
The electrochemical properties of zinc anode shall comply with the provisions in Table 4.2.2. 4.2.2
Electrochemical properties of zinc anode
Table 4. 2, 2
Open circuit potential
Theoretical generated electricity
In seawater
(3 nA/cm2）
In soil
(0.03 mA/cm\)
Current efficiency
Generated electricity
Dissipation rate
Current efficiency
Generated electricity
Consumption rate
Note: When the soil medium is used for the anode performance test, the anode should be surrounded by filling material. Unit
V(SCE)
A·h/g
kg/(A· a)
kg/(A· a)
Zn, Zn alloy
≤17. 25
4.2.3 The zinc anode has a trapezoidal cross section. Its specifications are divided into seven types according to net weight: 6.3, 9, 12.5, 18, 25, 35.5 and 50kg, and its length is 600800 and 1000mm.
4.2.4 The specifications of the zinc anode used as a reference electrode are 50mm in diameter and 300mm in length. 4.2.5 The structure of the zinc anode used as a grounding electrode is shown in Figure 4.2.5. 4.2.6 The surface of the steel core used for zinc anodes shall be galvanized, and the contact resistance between the anode body and the steel core shall be less than 0.0010. 4.2.7 The cast zinc anode shall not be warped, and its surface shall be free of oxide slag, roughness, flash, cracks, and the shrinkage depth shall be less than 10% of the anode thickness. 4.3 Magnesium-zinc composite anode
4.3.1 The composite sacrificial anode consists of two parts, magnesium and zinc, with zinc in the core and magnesium on the outside. The composition of the magnesium part and the zinc part shall comply with the provisions in Table 4.1.1 and Table 4.2.1 respectively.
4.3.2 The specifications of the composite anode zinc core shall comply with the provisions of 4.2.3, and the thickness of the magnesium coating shall be based on the minimum thickness of the manufacturing process. 4.3.3 The surface of the composite anode is a casting surface, which shall be clean and smooth, without obvious casting defects such as inclusions, and the surface is allowed to be machined. The magnesium coating is allowed to have slight cracks and incomplete coating defects. 4.4 Anode quality assurance
4.4.1 All buried anodes must have a quality assurance certificate provided by the manufacturer. Each batch of products should be accompanied by a quality assurance certificate, which should be included in the technical file. The quality assurance certificate should indicate: 1 Supplier name,
2 Product name;
Brand, specification, batch number:
4 Weight or number;
5 Chemical analysis report;
Seal of the technical supervision department;
7 Implementation standard number;
8 Manufacturing date and factory time.
Beng Han hardware
Connecting hardware
Grounding electrode
Head hardware 2~10
-60-60-
Assembly diagram
Single use
Combination of 2
Figure 4.2.5 Structure diagram of zinc grounding electrode
Punching hardware
SY/T 0019-1997
4.4.2 When accepting sacrificial anodes, the appearance and quality should be inspected. The contact resistance, chemical composition and electrochemical properties of the steel core and the anode should be sampled and inspected in batches, with a sampling rate of 3%, but at least not less than 3 pieces. If it is unqualified, double the sampling, and if one of them is still unqualified, the batch is judged to be unqualified. When the chemical composition is unqualified, but the contact resistance and electrochemical properties are qualified, it can be used. The contact resistance test method is shown in Appendix B of "Sacrificial Anodes of Aluminum-Zinc-Indium Alloys". The chemical composition analysis method is carried out according to the standards adopted by the supplier. The electrochemical performance refers to Appendix C of "Sacrificial Anodes of Aluminum-Zinc-Steel Alloys" (the test medium is changed to local soil and saturated with local groundwater. There should be 5-10mm thick packing material around the tested anode). The composition and electrochemical performance of the composite anode can be tested separately according to the magnesium and zinc parts. 4.4.3 Sacrificial anodes should be stored in indoor warehouses. It is strictly forbidden to be contaminated with oil, paint, and contact with acids, alkalis, and salts. 5 Process Calculation
The grounding resistance of a single anode is calculated according to the following formula. R
In the formula: R
Horizontal anode grounding resistance (Q)
Vertical anode grounding resistance (Q);
Soil resistivity (α·m);
Resistivity of packing material (Q·m);
.Anode length (m);
Anode packing layer length (m):
++Pln）
(5.0.1-1)
(5.0.1-2)
SY/T 0019--1997
d-Anode equivalent diameter [d=-—
D—-packing layer diameter (m);
, C is the side length (m)];
t-the distance from the center of the anode to the ground (m). 5.0.2 The combined anode grounding resistance is calculated according to the following formula. Ry
Rtotal k
Where: Rtotal—total grounding resistance of anode group (Q), N—number of anodes (pieces),
k——-correction coefficient, refer to Figure 5.0.2.
(w country)
Anode length (m)
Time)
Figure 5.0.2 Anode grounding resistance correction coefficient k5.0.3 Anode output current is calculated according to the following formula. I=
Where: I,—---Anode output current (A); E cathode open circuit potential (V);
E. Anode open circuit potential (V):
e—Cathode polarization potential (V)
t.-Anode polarization potential (V),
R. -——Anode grounding resistance (Q);
(Ee)-(E+e)
Anode length (m)
Anode length (m)
R. --—Cathode transition resistance ();
Rw———National line conductor resistance (2),
△E--Anode effective potential difference (V),
R---Total loop resistance (Q).
5.0.4 The required number of anodes is calculated according to the following formula. In the formula: N--Number of anodes (branch);
I~—Required protection current (A);
I.--Single anode output current (A);
f----Reserve coefficient, take 2 to 3 times.
5.0.5 The working life of the anode is calculated according to the following formula. Where: T--anode working life (a);
W---anode net mass (kg);
ar-anode consumption rate [kg/(A·a)]; I-anode average output current (A).
6 Engineering design
6.1 Selection of pole type
T= 0. 85 W
SY/T0019-1997
(5.0.4)
(5.0.5)
6.1.1 The type of sacrificial anode is usually selected according to the soil resistivity, and the specifications of the anode are selected according to the size of the protective current. The recommended types of sacrificial anodes in water and soil are shown in Table 6.1.1. Table 6.1.1 Application of anode types in soil Optional anode types
Strip magnesium anode
Magnesium (—1.7 V)
Magnesium (-1.5 V)
Magnesium (-1.5 V), zinc
Note: ① In the case of moist soil, the use range of zinc anode can be expanded to 30 α·m# ② The potentials in the table are relative to Cu/CuSO, electrode. Soil resistivity (a·m)
60~100
6.1.2 If used as a reference electrode in a soil environment, high-purity zinc should be used. Its dimensions are shown in 4.2.4. 6.1.3 The grounding electrode for lightning protection and anti-static should be zinc alloy, and its dimensions should meet the requirements of 4.2.5. 6.1.4 Under the conditions of zinc anode use, composite anodes can be used. In order to prevent electrical shock to insulating parts, a pair of zinc anodes can usually be used to form a grounding battery. 6.1.5
6.1.6 Strip anodes are used in high resistivity environments, temporary cathodic protection, protection of conveying pipes in casings, and grounding pads to prevent AC interference. 6.2 Anode bed
6.2.1 Buried sacrificial anodes must use chemical packing materials, the formula of which is shown in Table 6.2.1. 695
SY/T 0019—1997
Anode type
Magnesium anode
Zinc anode
Gypsum powder
(CaS04 2H20)
6.3 Anode distribution
Table 6.2.2 Formula of sacrificial anode packing
Filling material formula [%(m/m)]
Industrial sodium sulfate
Industrial magnesium sulfate
Bentonite
Applicable conditions
(resistivity)
≤20Qm
≤200·m
>202·m
>20α·m
>202·m
6.3.1 The distribution of sacrificial anodes on the pipeline should be single or concentrated in groups. The same batch number or anodes with similar open circuit potential should be selected in the same group.
6.3.2 There are two types of sacrificial anodes buried vertically and horizontally, and the buried positions are divided into axial and radial directions. The buried position of the anode is generally 3~5m away from the outer wall of the pipeline, and should not be less than 0.3m. The buried depth should be no less than 1m from the top of the anode to the ground. When arranged in groups, the distance between the anodes should be 2~3m.
6.3.3 Sacrificial anodes must be buried below the freezing line. In dry areas where the groundwater level is less than 3m, the anodes should be buried deeper; in rivers, the anodes should be buried in a safe part of the riverbed to prevent damage during flood erosion and dredging. 6.3.4 When arranging sacrificial anodes, pay attention to the fact that there should be no metal structures between the anode and the pipeline. 6.3.5 The distribution of zinc anodes used for grounding should comply with relevant technical standards for power grounding. The grounding electrode can be single, or two or three connected in series. The number of grounding electrodes used should meet the requirements of grounding resistance. 6.4 Test system
6.4.1 The test system of sacrificial anode cathodic protection should be able to provide the functions of natural potential, anode performance and protection potential of the protected body. 6.4.2 Test piles should usually be set in the middle of two adjacent groups of sacrificial anode pipe sections, and the distance between the piles should not exceed 500m. 6.4.3 Auxiliary test pieces and long-term reference electrodes should be provided at the sacrificial anode test piles, and the auxiliary test pieces should be the same as the protected material. 6.4.4 Copper core cables are usually used for the connection cables of sacrificial anodes. The recommended model is: VV-1kV/1×10mm7 Construction requirements
7.0.1 Select an economically reasonable anode construction method according to the construction conditions. Vertical anodes should be constructed by drilling method, and horizontal anodes should be constructed by slotting method.
7.0.2 Before using the sacrificial anode, the surface should be treated to remove the oxide film and oil stains on the surface to make it metallic. 7.0.3 The buried depth of the anode connection cable should not be less than 0.7m, and there should be 5-10cm thick fine sand on all sides. The upper part of the sand should be covered with cement protective plates or red bricks. When laying, a certain margin should be left for the cable length. 7.0.4 The anode cable can be directly welded to the protected pipeline, or it can be connected through the connecting piece in the test pile. The cable connected to the steel pipeline should be connected by aluminum thermite welding technology. The welding point should be re-treated with anti-corrosion insulation, and the anti-corrosion material and grade should be consistent with the original covering layer.
7.0.5 The cable and the anode steel core should be connected by welding, and the length of the double-sided weld should not be less than 50mm. After the cable and the anode steel core are welded, necessary protective measures should be taken to prevent the connection part from breaking during construction. 7.0.6 The anode end surface, the cable connection part and the steel core should all be anti-corrosion and insulated. 7.0.7 The filling material can be packed indoors or on site, and its thickness should not be less than 50mm. No matter what method is used, the thickness of the filling material around the anode should be consistent and dense. Indoor pre-packed bags must be made of natural fiber (cotton or sack) fabrics, and artificial fiber fabrics are strictly prohibited.
7.0.8 The filling material should be mixed evenly and must not be mixed with stones, soil, weeds, etc. After the anode is buried, it should be fully watered and saturated. 8 Operation and management
8.0.1 The measurement items of the habitable anode after it is put into operation are generally: 1 Potential
1) Anode open circuit potential;
2) Anode closed circuit potential;
3) Pipeline open circuit potential (natural potential before commissioning) 4) Pipeline protection potential;
5) Test piece natural potential.
2 Current
1) Single anode output current;
2) Combined anode joint output current.
3 Resistance
1) Single anode grounding resistance;www.bzxz.net
2) Combined anode joint grounding resistance.
4 Soil resistivity at the buried point.
The measurement of all parameters shall comply with the provisions of the "Test Method for Cathodic Protection Parameters of Buried Steel Pipelines". 8.0.2 The commissioning test of sacrificial anode protection parameters must be carried out 10 days after the anode is buried underground and the filling material is watered. The test items shall be carried out in accordance with the provisions of 8.0.1.
8.0.3 After the sacrificial anode is put into operation, it shall be monitored and maintained regularly, at least once every six months. 697
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