SY/T 0088-1995 Technical Standard for Cathodic Protection of Bottom and External Wall of Steel Storage TanksSY/T0088-1995 Standard download decompression password: www.bzxz.net

Standard of the People's Republic of China for petroleum and natural gas industry Cathodic protection for bottom of steel storage tanks Technical standard Standard of external surface cathodic protection for bottom of steel storage tanks SY/ T 008895 Edited by: China National Petroleum Corporation Planning and Design Institute Approved by: China National Petroleum Corporation Petroleum Industry Press Beijing, 1996 General provisions Determination of the necessity of cathodic protection Criteria for cathodic protection and its measurement technology Design of cathodic protection system Installation of cathodic protection system Interference and protection Operation and maintenance of cathodic protection system Appendix A Explanation of terms used in this standard Additional instructions · Cathodic protection for bottom of steel storage tank Explanation of the provisions of the extreme protection technical standard
(22)
Document of China National Petroleum Corporation
(95) CNPC Technical Supervision No. 731
Notice on the approval and release of 26 oil and gas industry standards including the "Standard for Investigation Methods of Corrosion and Protection of Steel Pipelines and Storage Tanks"
To all relevant units:
The "Standard for Investigation Methods of Corrosion and Protection of Steel Pipelines and Storage Tanks" and other 26 oil and gas industry standards (draft) have been reviewed and approved and are now approved as oil and gas industry standards and are hereby released. The numbers and names of the issued standards are as follows: 1
SY/T 0087--95
SY / T 0545--1995
SY/ T 4013--95
SY /T 4041--95
Standard for investigation method of corrosion and protection of steel pipelines and storage tanks
Determination of thermal characteristic parameters of wax precipitation in crude oil
Scanning calorimetry
Technical standard for polyethylene anticorrosion layer of buried steel pipeline (replaces SYJ4013--87)
Installation and acceptance specification for wet steam generators for oil fields (replaces SYJ4041--89)
SY /T 4084-95
SY/T 4085-95
SY7T 4086-95
SY /T 4087-95
SY /T 4088 95
SY/T 4089-95
SY/T 4090-95
SY/I 409195
SY /T 4092-
SY /T 409395
SY/T 4094-95
SY/T 4095-95
SY/T 409695
SY/T 409795
SY/T 409895
SY /T 4099-95
SY/T 4100--95
SY/T 4101-95
SY7T 4102—95
SY/T41031995
SY4104—95
Technical specification for beach environmental conditions and loads
Technical specification for oil and gas gathering and transportation in beach oil fields
Beach structures 1. Technical specification for pipeline network design and construction
Technical specification for ventilation and air conditioning in beach oil projects Technical specification for water supply and drainage in beach oil projects Electrical specification for beach oil projects
Technical specification for power generation facilities in Weihai oil projects Technical specification for corrosion protection in beach oil projects
Technical specification for thermal insulation in beach oil projects
Technical specification for selection and installation of cranes on beach oil facilities
Shallow sea steel Technical specification for design and construction of fixed steel platform structure
Technical specification for design and construction of shallow sea steel mobile platform structure
Technical specification for wellhead protection device of beach oil field Technical specification for design and construction of beach slope sandstone artificial island structure
Technical specification for design and construction of beach ring wall steel formwork-concrete artificial island structure
Technical specification for design and construction of beach seawall
Technical specification for beach engineering survey
Technical specification for beach rock survey engineering
Specification for inspection and installation of valves
Welding and acceptance of steel pipelines
Quality inspection and assessment standard for petroleum construction projects Pipeline crossing and spanning projects
SYT 008895
Technical Standard for Cathodic Protection of Bottom and External Wall of Steel Storage Tanks
The above standards shall come into force on June 1996. China National Petroleum Corporation
December 18, 1995
1.0.1 In order to effectively implement the cathodic protection of the bottom and external wall of steel storage tanks (hereinafter referred to as storage tank cathodic protection), this standard is formulated.
1.0.2 This standard is applicable to the cathodic protection of existing and newly built storage tanks. 1.0.3 In addition to implementing this standard, the cathodic protection of storage tanks shall also comply with the provisions of the relevant current national standards (specifications).
1.0.4 Reference standards:
GB5005794 Code for design of lightning protection for buildings
SY/T0017-96 Technical standard for DC discharge protection of buried steel pipelines SYJ23-6 Test method for parameters of cathodic protection of buried steel pipelines SYJ3288 Test method for AC interference of power lines on buried steel pipelines
SYI3689 Design specification for forced current cathodic protection of buried steel pipelines 2.0,1
2 General provisions
In the design of the cathodic protection system of storage tanks, a margin of 0 should be left for the total amount of cathodic protection current according to the process calculation.
2.0.2 The design life of the anode at the bottom of the tank in the cathodic protection system should be the same as the service life of the tank
2.03 When using forced current cathodic protection, pay attention to the possible interference with other external metal structures, and take corresponding protective measures. 2. The rated power of the DC power supply equipment should have a margin: its output impedance should match the loop resistance
2. The core 5 trap electrode can also serve as the lightning protection and anti-static grounding electrode of the storage tank. When renovating the lightning protection and anti-static grounding electrode of the existing storage tank: it is recommended to use a rod-type zinc grounding electrode: its grounding resistance should comply with the provisions of the current national standard "Building Lightning Protection Design Code". 2.0.6 The electrical insulation device of the cathodic protection system shall include insulation flanges, prefabricated insulation joints or connectors to facilitate corrosion control. 3. Determination of the necessity of cathodic protection 3.0.1 Before determining the necessity of cathodic protection for tanks, the following items shall be investigated in detail: 11. The foundation materials for the design and manufacture of the tanks shall include: (1) the surface of the site and tank area, and the soil properties and resistivity of the soil; (2) the groundwater level; (3) the design of the tank foundation; (4) the start and end dates of construction; (5) whether the tank has any Covering layer and its type: (7) The existing cathodic protection status of nearby structures; [8] Maintenance and inspection records of storage tanks: 3.0.1.2 Basic information of the medium in the tank includes: (1) Type of medium, (2) Temperature of the medium; (3) Whether there is water bottom and its depth; (4) The number of medium atmosphere transmitters and receivers. 3.0.1.3 Bottom condition investigation includes (1) Corrosion rate detection record (the moment of corrosion status of the storage tank); (3) Stray current status of the tank area, |(4) Distribution of ground potential of storage tanks.
3.0.2 For existing storage tanks, when investigation and analysis prove that corrosion will endanger the safe operation of the storage tanks, cathodic protection measures shall be taken. 3 For the outer wall of the tank bottom of a newly built storage tank, when it is confirmed that cathodic protection is required, cathodic protection shall be used in the design to control corrosion and ensure that the tank is continuously protected during its entire service life.
4 Criteria for cathodic protection and its measurement technology
4.1 Criteria for cathodic protection
4.1.1 The cathodic protection of the outer wall of the tank bottom shall meet the following specified indicators 4.1.1.1- Generally speaking, the minimum protection potential of the tank bottom to the ground should reach -0.85V relative to the saturated sulfur copper reference electrode. When the soil contains sulfate-reducing bacteria and the sulfate content is greater than 0.5%, the protection potential should reach -0.95V or more negative; 4.1.1.2 The cathode polarization potential difference measured between the tank bottom and the reference electrode in contact with the soil is not less than 100mV: This criterion can be used for the polarization establishment process or the polarization decay process.
4.1.2 The above criteria can be used in one or all of them according to the specific situation. 4.2 Determination technology
4.2.1 The determination method of cathodic protection potential and cathodic polarization shall be carried out in accordance with the provisions of the current national standard "Test Method for Cathodic Protection Parameters of Steel Pipelines". 4.2.2 The number and distribution of monitoring points shall ensure that the corrosion control of any part of the tank bottom can meet the requirements of 4.1.1, and the potential distribution of the tank bottom shall be as uniform as possible. It shall meet the following requirements
4.2.2.1 The number of monitoring points distributed around the tank shall generally not be less than four. When the diameter of the tank bottom is large: it should be appropriately increased
4.2.2.2 Monitoring points shall be set at the important parts of the tank bottom plate, and other parts shall be appropriately increased according to the size of the tank bottom plate area:
When monitoring is idle at the center of the tank, according to the on-site experience, it is recommended that the protective potential around the tank bottom be maintained at -1.1～-1.15V (relative to CuCuS0, electrode).
The measurement results should be verified by IR reduction in the soil. 4.2.3
5 Design of cathodic protection system
5.1 Information to be mastered before design
Information to be collected before designing cathodic protection system 5.1.1
(1) Site and tank area layout and system layout (2) Construction start and end dates
(3) Tank design information
(4) Electrical insulation and electrical bridging of facilities in the site: (5) Cable path: (6) Boundary of explosion hazard zone.
5.1.2 Data related to the site during cathodic protection design (1) Existing and planned cathodic protection systems, (2) Special environmental conditions
(3) Depth of bedrock and frost layer
(4) Adjacent underground metal structures and their proximity; (5) Feasibility of electrical insulation from external structures 5.1.3 Obtain the following data through on-site investigation and corrosion testing (1) The required amount of protection current to meet the criteria; (2) Soil resistivity;
(3) The electrical insulation required by the system;
(4) The electrical continuity of the system;
(5) The strength of the covering layer Integrity:
(6) Leakage history of similar tanks in the same area: (7) Existing stray current:
(8) Other maintenance and operation data,
5.2 Selection of protection method
5.2.1 According to the corrosion environment and conditions, the state of the protected tank and technical requirements, selective anodic protection or forced current cathodic protection method 5.2.2 Anodic protection is generally suitable for environments with low soil resistivity, small tank diameter and complex layout of surrounding underground metal structures. 5.2.3 Forced current protection is generally suitable for environments with high soil resistivity and large tank diameter.
5.3 Forced current system
5.3.1 Forced current system The calculation content is as follows: 5.3.1.1 Required protection current - obtained by estimating or testing the current requirement on site. Combined with the specific situation of our country's storage tank, the recommended tank protection current density is 5-10mAm, and the total required protection current is: L=ia-s
Total required cathode protection current, A:
Cathode protection current density, mA/m:
Total protected area, 1n. The rated output voltage of the DC power supply is calculated as follows: V=IR.+R+R.)+
-cathode grounding resistance,
R.Wire resistance Q;
Rtank bottom ground-to-ground transition resistance
(5.3.1— J)
(5.3.1- 2)
V-anode ground-to-ground back electromotive force (coke material can take 2V), V: protection current of the protection system (take 1.1 points), A. P=iW/n
(5.3.1— 3)
Power factor, wbzxz.net
1—Power rectifier efficiency, can be taken as 0.7.
Auxiliary stage required quantity is calculated according to the trial training:
.G-TgK
Anode induction weight stack, kg:
Anode effective life, a
Cathode consumption rate. kA·a
—"Anode working current, A:
K—Anode utilization coefficient, take 0.70.85. [5.3.1— 4
The auxiliary anode grounding resistance shall be calculated in accordance with the relevant provisions of the current national standard "Design Specifications for Forced Current Cathodic Protection of Steel Pipelines". 5.3.2 Auxiliary anode materials can be selected from high-silicon cast iron, graphite and steel, etc., and should generally be installed in locations with low resistivity: chromium-containing high-silicon electrodes should be used in saline and coastal soils: steel electrodes should be used in locations with high resistivity. 5.3.3 The layout of auxiliary anodes can usually be selected from the upright type around the tank (as shown in Figure 5.3.3-1), the deep well type beside the tank (as shown in Figure 5.3.3-2), the angled type at the bottom of the tank (as shown in Figure 5.3.3-3) and The tank bottom is horizontal (as shown in Figure 5.3.3-4). When the object of protection is a tank, several tanks can be protected as a joint unit, and the auxiliary anode layout is shown in Figure 5.3.3-5.
5.3.4 When designing a new tank, it is advisable to bury a permanent reference electrode at an appropriate position on the bottom of the tank (as shown in Figure 5.3.4-1). The potential distribution around the tank wall can be monitored by burying reference electrodes around the tank (as shown in Figure 5.3.4-2). 5.3.5 Forced current system DC power supply equipment can choose rectifiers and constant potentiostats. When the local potential or loop resistance often changes greatly, a constant potentiostat should be used.1— 3)
Power factor, w
1—Power rectifier efficiency, can be taken as 0.7.
Auxiliary stage required quantity is calculated according to the following test:
.G-TgK
Anode inductor weight, kg:
Anode effective life, a
Cathode consumption rate. kA·a
—"Anode working current, A:
K—Anode utilization coefficient, take 0.70.85. [5.3.1— 4
The auxiliary anode grounding resistance shall be calculated in accordance with the relevant provisions of the current national standard "Design Specifications for Forced Current Cathodic Protection of Steel Pipelines". 5.3.2 Auxiliary anode materials can be selected from high-silicon cast iron, graphite and steel, etc., and should generally be installed in locations with low resistivity: chromium-containing high-silicon electrodes should be used in saline and coastal soils: steel electrodes should be used in locations with high resistivity. 5.3.3 The layout of auxiliary anodes can usually be selected from the upright type around the tank (as shown in Figure 5.3.3-1), the deep well type beside the tank (as shown in Figure 5.3.3-2), the angled type at the bottom of the tank (as shown in Figure 5.3.3-3) and The tank bottom is horizontal (as shown in Figure 5.3.3-4). When the object of protection is a tank, several tanks can be protected as a joint unit, and the auxiliary anode layout is shown in Figure 5.3.3-5.
5.3.4 When designing a new tank, it is advisable to bury a permanent reference electrode at an appropriate position on the bottom of the tank (as shown in Figure 5.3.4-1). The potential distribution around the tank wall can be monitored by burying reference electrodes around the tank (as shown in Figure 5.3.4-2). 5.3.5 Forced current system DC power supply equipment can choose rectifiers and constant potentiostats. When the local potential or loop resistance often changes greatly, a constant potentiostat should be used.1— 3)
Power factor, w
1—Power rectifier efficiency, can be taken as 0.7.
Auxiliary stage required quantity is calculated according to the following test:
.G-TgK
Anode inductor weight, kg:
Anode effective life, a
Cathode consumption rate. kA·a
—"Anode working current, A:
K—Anode utilization coefficient, take 0.70.85. [5.3.1— 4
The auxiliary anode grounding resistance shall be calculated in accordance with the relevant provisions of the current national standard "Design Specifications for Forced Current Cathodic Protection of Steel Pipelines". 5.3.2 Auxiliary anode materials can be selected from high-silicon cast iron, graphite and steel, etc., and should generally be installed in locations with low resistivity: chromium-containing high-silicon electrodes should be used in saline and coastal soils: steel electrodes should be used in locations with high resistivity. 5.3.3 The layout of auxiliary anodes can usually be selected from the upright type around the tank (as shown in Figure 5.3.3-1), the deep well type beside the tank (as shown in Figure 5.3.3-2), the angled type at the bottom of the tank (as shown in Figure 5.3.3-3) and The tank bottom is horizontal (as shown in Figure 5.3.3-4). When the object of protection is a tank, several tanks can be protected as a joint unit, and the auxiliary anode layout is shown in Figure 5.3.3-5.
5.3.4 When designing a new tank, it is advisable to bury a permanent reference electrode at an appropriate position on the bottom of the tank (as shown in Figure 5.3.4-1). The potential distribution around the tank wall can be monitored by burying reference electrodes around the tank (as shown in Figure 5.3.4-2). 5.3.5 Forced current system DC power supply equipment can choose rectifiers and constant potentiostats. When the local potential or loop resistance often changes greatly, a constant potentiostat should be used.
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