Method for protecting the inner surface of large carbon steel and low alloy steel vessels

Abstract

Large carbon steel and low alloy steel container inner surface protection method. At present, the method of filling nitrogen and keeping micro positive pressure is mostly used for protection, and the pressure gauge is used for monitoring the pressure in the container in the protection period, which has many disadvantages. The present application comprises the following steps: after the container is manufactured and the generated rust on the inner surface is removed, the water-based rust inhibitor is sprayed / brushed on the inner surface for protection; after the water-based rust inhibitor protection of the inner surface of the container is completed, silica gel desiccant and gas phase rust inhibitor powder are placed at different positions in the container for protection; after the desiccant and gas phase rust inhibitor powder are placed in the container, the branches and manholes of the container are immediately sealed, the humidity monitoring equipment is installed at the installation hole, and the sealing of the installation hole is completed; nitrogen is filled to replace the air in the container to reduce the oxygen in the container, and after the nitrogen replacement is completed, the nitrogen filling replacement interface and the air outlet are sealed. The present application is used for the inner surface protection of large carbon steel and low alloy steel container.

Description

Technical Field

[0001] This invention relates to a method for protecting the inner surface of large carbon steel and low alloy steel containers. Background Technology

[0002] Carbon steel and low-alloy steel containers have been widely used in boilers, petrochemicals, nuclear power, and other fields, such as boiler drums, gasifiers, and deaerators in the conventional island of nuclear power plants. Due to their low price, excellent processing performance, and good performance, carbon steel and low-alloy steel have become the preferred materials for many container products. While using carbon steel and low-alloy steel to make containers offers significant advantages, it also has certain drawbacks. Among these, the poor atmospheric corrosion resistance of carbon steel and low-alloy steel has become a problem that plagues container manufacturers and users. During the production and manufacturing process of large carbon steel and low-alloy steel containers, including the procurement and storage of raw materials, processing and manufacturing, transportation, and storage, carbon steel and low-alloy steel materials will corrode significantly in a short time when exposed to water or humid air. Several stages are difficult or even impossible to protect against, such as machining, plate rolling, welding, and hydrostatic testing. To achieve good performance, users often require that the inner surface of the container be free of significant rust.

[0003] Rust generated during the manufacturing process is removed by pickling or mechanical grinding before final shipment to meet user requirements. However, transportation and on-site storage periods are generally long, ranging from several months to several years. Currently, nitrogen purging with a slight positive pressure is commonly used for protection during transportation and storage, with pressure gauges monitoring the pressure inside the container during the protection period. When operated correctly, this method offers excellent protection, effectively preventing significant rust on the inner surfaces of large carbon steel and low-alloy steel containers. However, it also has several drawbacks. Actual container products often have large volumes, numerous branches, and internal structural dead zones. Maintaining a slight positive pressure with nitrogen purging makes it difficult to achieve a tight seal, leading to nitrogen leakage and frequent nitrogen replenishment. Furthermore, in situations where a tight seal is not possible, diurnal temperature variations cause gas volume changes, allowing air to enter the container and reducing the effectiveness of nitrogen purging. Simultaneously, structural dead zones inside the container cannot be protected using nitrogen purging with a slight positive pressure because the existing air cannot be replaced by nitrogen. Summary of the Invention

[0004] The purpose of this invention is to solve the above-mentioned problems and provide a method for protecting the inner surface of large carbon steel and low alloy steel containers.

[0005] The above objectives are achieved through the following technical solutions:

[0006] A method for protecting the inner surface of large carbon steel and low alloy steel containers, the method comprising the following steps:

[0007] Step 1: During container manufacturing, a nitrogen purging port, an air vent, and a humidity monitoring device mounting hole are pre-drilled. The nitrogen purging port is located at the bottom of the container, the air vent at the top, and the humidity monitoring device mounting hole at a height of 1.5-1.8m or similar. The nitrogen purging port and air vent are used for nitrogen filling and air venting after container manufacturing. The mounting hole is used to install the humidity monitoring device. The humidity monitoring device's sensor is placed inside the container, and the measurement result display is on the outside of the container, allowing for real-time monitoring. The humidity monitoring device's measurement range is at least 30%-99%.

[0008] Step 2: After the container is manufactured and the rust on the inner surface is removed, spray / brush a water-based rust inhibitor onto the inner surface for protection.

[0009] Step 3: After the inner surface of the container is protected with water-based rust inhibitor, place silica gel desiccant and vapor phase rust inhibitor in different locations inside for protection;

[0010] Step 4: After placing the desiccant and vapor phase rust inhibitor inside the container, immediately seal all branch pipes and manholes of the container, install humidity monitoring equipment at the mounting holes, and ensure the mounting holes are sealed.

[0011] Step 5: Fill the container with nitrogen to replace the air inside, thereby reducing the oxygen inside the container. The nitrogen filling volume should be at least 1.5 times the container volume.

[0012] Step Six: After nitrogen purging is completed, seal the nitrogen purging port and air vent to complete the protection work;

[0013] Step 7: When the humidity monitoring equipment shows that the humidity inside the container is higher than 60%, it is considered that the protective measures have failed and the desiccant and vapor phase rust inhibitor need to be replaced in time, and nitrogen should be refilled.

[0014] The specific steps of step two in the method for protecting the inner surface of large carbon steel and low alloy steel containers are as follows:

[0015] (1) Prepare the working solution by mixing the water-based rust inhibitor according to the proportions and preparation method in the product instructions;

[0016] (2) Spray the prepared rust inhibitor working solution onto all parts inside the container, including the surface of the internal parts, leaving no dead corners. Spray repeatedly at least 3 times, and finally clean up the dripping rust inhibitor in time.

[0017] (3) After the final spraying is completed, use an axial flow fan or convection hot air fan with heating function to dry the surface of the sprayed rust inhibitor with 80°C hot air.

[0018] (4) Subsequent internal wall protection operations can only be carried out after the water-based rust inhibitor has completely dried.

[0019] The specific steps of step three in the method for protecting the inner surface of large carbon steel and low alloy steel containers are as follows:

[0020] (1) The desiccant should not be placed directly inside the equipment. It should be packaged in non-woven bags, with each bag containing 1 kg of desiccant. Before being packaged in non-woven bags, the desiccant should not be exposed to the air directly. Keep the original packaging. The packaging process should be completed as soon as possible.

[0021] (2) After the desiccant is dispensed, the vapor phase rust inhibitor is immediately placed in a non-woven bag and placed on top of the desiccant. Each vapor phase rust inhibitor is individually packaged in 50g bags. Four bags of vapor phase rust inhibitor are placed in each non-woven bag. Then the non-woven bag is tied tightly. The dispensing process should be completed as soon as possible. After dispensing, it is necessary to temporarily seal it with plastic sheeting, wooden bucket or wooden box until it is placed inside the equipment.

[0022] (3) The desiccant should be placed evenly along both sides of the equipment. Before placing it, use a marker pen that meets the requirements of auxiliary materials to number the non-woven bag in sequence. The number should be clearly visible so that on-site personnel can check it when taking it out. Then fix it inside the equipment with rope or wire.

[0023] In the method for protecting the inner surface of large carbon steel and low alloy steel containers, the amount of water-based rust inhibitor used in step two is 0.1~0.2 kg / m2.

[0024] The method for protecting the inner surface of large carbon steel and low alloy steel containers, wherein the water-based rust inhibitor in step two comprises 5.0–30.0% of C8–C10 carboxylates, 5.0–15.0% of ethanolamine, 3.0–8.0% of boric acids, and 0.0–5.0% of polyethylene glycol.

[0025] In the method for protecting the inner surface of large carbon steel and low alloy steel containers, in step three, the desiccant content is not less than 1 kg / m³, and the vapor phase rust inhibitor content is not less than 0.2 kg / m³.

[0026] The method for protecting the inner surface of large carbon steel and low alloy steel containers, wherein the silica gel desiccant in step three comprises 99.6% SiO2, 0.17% Na2O, 0.02% Fe2O3, 0.01% MgO, 0.04% CaO and 0.16% Al2O3.

[0027] The method for protecting the inner surface of large carbon steel and low alloy steel containers, wherein the vapor phase rust inhibitor in step three comprises 50-60% base oil, 4-8% barium petroleum sulfonate, 2-5% barium dinonylnaphthalene sulfonate, 10-15% lanolin, 8-12% aluminum stearate, 3-5% lanolin metal soap, 1-2% lead nonanoate, and 6-10% calcium stearate. Beneficial effects

[0028] 1. This invention employs a combined protection method of "nitrogen replacement + metal rust inhibitor + vapor phase rust inhibitor + desiccant + humidity monitoring" to effectively protect the surfaces of all components inside the container and has the ability to monitor the protection effect in real time.

[0029] 2. This invention retains the advantages of conventional nitrogen-filled protection while avoiding the disadvantages of difficulty in maintaining a slight positive pressure and the inability to protect structural dead zones. It can better protect the inside of the container and effectively ensure that the inner surface of large carbon steel and low alloy steel containers does not rust during transportation and storage. Detailed Implementation

[0030] During container manufacturing, a nitrogen purging port, an air vent, and a humidity monitoring device mounting hole are pre-installed. The nitrogen purging port is located at the bottom of the container, the air vent at the top, and the humidity monitoring device mounting hole at a height of 1.5-1.8m or similar. The nitrogen purging port and air vent are used for nitrogen filling and air venting after container manufacturing. The mounting hole is for installing the humidity monitoring device. The humidity sensor is located inside the container, and the measurement result display is on the outside, allowing for real-time monitoring. The humidity monitoring device has a measurement range of at least 30% to 99%.

[0031] After the container is manufactured and the rust on the inner surface is removed, a water-based rust inhibitor is sprayed / brushed onto the inner surface for protection. Specific requirements are as follows:

[0032] The water-based rust inhibitor is composed of: C8-C10 carboxylates (sodium, potassium or ammonium salts, 5.0-30.0%), ethanolamines (mono-, di- or triethanolamines, 5.0-15.0%), boric acids (boric acid or ammonium borate, 3.0-8.0%), and polyethylene glycol (8-10 degrees of polymerization of ethylene glycol, 0.0-5.0%).

[0033] Construction dosage: 0.1~0.2Kg / m2, calculated based on the surface area of ​​the container equipment.

[0034] The operation steps are as follows:

[0035] Prepare a working solution of a certain proportion according to the ratio and preparation method in the product instructions.

[0036] Spray the prepared rust inhibitor solution onto all parts of the container (including the surfaces of internal components), leaving no blind spots. Repeat the spraying at least three times, and promptly clean up any spilled rust inhibitor. Spraying is recommended; however, brushing may be used if spraying is not feasible.

[0037] After the final coat of spraying, use an axial flow fan or convection hot air blower with heating function to dry the surface sprayed with 80℃ hot air. If the on-site ventilation conditions are good, it can also be air-dried naturally.

[0038] Subsequent internal wall protection operations can only be carried out after the water-based rust inhibitor has completely dried.

[0039] After the inner surface of the container is protected with a water-based rust inhibitor, appropriate amounts of silica gel desiccant and vapor phase rust inhibitor are placed in different locations inside for further protection. Specific requirements are as follows:

[0040] Components of silica gel desiccant and vapor phase rust inhibitor

[0041] Silica gel desiccant: SiO2: 99.6%, Na2O: 0.17%, Fe2O3: 0.02%, MgO: 0.01%, CaO: 0.04%, Al2O3: 0.16%.

[0042] Vapor phase rust inhibitor: Base oil: 50-60%, barium petroleum sulfonate: 4-8%, barium dinonylnaphthalene sulfonate: 2-5%, lanolin: 10-15%, aluminum stearate: 8-12%, lanolin metal soap: 3-5%, lead nonanoate: 1-2%, calcium stearate: 6-10%.

[0043] Construction dosage: The quantity to be placed is calculated based on the equipment volume, with a minimum of 1 kg / m3 for desiccant and a minimum of 0.2 kg / m3 for vapor phase rust inhibitor.

[0044] The operation steps are as follows:

[0045] Desiccant should not be placed directly inside the equipment. It should be packaged in non-woven bags, with each bag containing 1 kg of desiccant. To prevent the desiccant from becoming ineffective due to prolonged storage in a humid environment, it should not be exposed to air directly before being packaged in non-woven bags; the original packaging should be kept intact. The packaging process should be completed as quickly as possible.

[0046] Immediately after the desiccant is dispensed, place the vapor phase corrosion inhibitor powder in a non-woven bag, on top of the desiccant. Each 50g package of vapor phase corrosion inhibitor powder should contain 4 bags of powder in each non-woven bag (if the powder is in a different specification, ensure each bag contains 200g). Then tighten the non-woven bag. The dispensing process should be completed as quickly as possible. After dispensing, the bag should be temporarily sealed with plastic sheeting, a wooden bucket, or a wooden box until it is placed inside the equipment.

[0047] The desiccant should be evenly placed along both sides of the equipment. Before placement, use a marker that meets the requirements for auxiliary materials to number the non-woven bags sequentially, for example, 1, 2, 3… The numbers should be clearly visible for easy verification by on-site personnel when removing them. Then, secure them inside the equipment with rope or wire. It is recommended not to place them at the lowest point of the equipment, and the placement location should be easily accessible for on-site personnel. The operator must record the placement process of the non-woven bags in detail, including at least the number and location of the non-woven bags, the start time of the operation, the completion time of the operation, the operator's name, and the signatures of the inspector. The placement of the non-woven bags should be recorded using a combination of paper records and photographs / video footage to facilitate later inspection and removal of the non-woven bags.

[0048] After placing the desiccant and vapor phase rust inhibitor inside the container, immediately seal all branch pipes and manholes. Install humidity monitoring equipment at the mounting holes and ensure the mounting holes are sealed.

[0049] Nitrogen gas is introduced to replace the air inside the container, thereby reducing the oxygen level inside. The nitrogen filling volume is at least 1.5 times the container's volume.

[0050] After nitrogen purging is completed, the nitrogen purging interface and air outlet are sealed to complete the protection work.

[0051] When the humidity monitoring equipment shows that the humidity inside the container is higher than 60%, it is considered that the protective measures have failed and the desiccant and vapor phase rust inhibitor need to be replaced in time, and nitrogen should be refilled.

[0052] The invention employs a combined protection method of "nitrogen replacement + water-based rust inhibitor + vapor phase rust inhibitor + desiccant + humidity monitoring" to effectively protect the surfaces of all components inside the container, including structural dead zones, and can monitor the protection capability in real time. Even if the container is not tightly sealed, it can maintain the protection capability for a certain period of time, and can effectively ensure that the inner surfaces of large carbon steel and low alloy steel containers do not rust during transportation and storage.

[0053] Taking a cylindrical carbon steel container with a diameter of 4m and a volume of 100m³ (surface area of ​​100m²) as an example, the manufacturing process involves pre-reserving a nitrogen purging port at the bottom, an air vent at the top, and a mounting hole for a humidity monitoring device at a height of 1.5m above the ground. After manufacturing and rust removal from the inside of the container, 15kg of water-based rust inhibitor, diluted according to the instructions, is sprayed onto the inner surface of the container at least three times. Then, an axial flow fan or convection hot air blower with heating function is used to dry the sprayed rust inhibitor surface at 80℃. Finally, 100kg of silica gel desiccant and 20kg of vapor phase rust inhibitor for ferrous metals are partially placed inside the container using drawstring canvas bags. After placement, all branch pipes and manholes are sealed, and the humidity monitoring device is installed. The sensor of the humidity monitoring device is placed inside the container, while the display screen is placed outside for easy observation. After installation, fill the nitrogen purging port with 150m³ of nitrogen gas. Then seal the nitrogen purging port and air vent to complete the protection. Regularly check the humidity monitoring equipment. When the humidity reading exceeds 60%, replace the desiccant and vapor phase rust inhibitor, and refill with nitrogen gas.

Claims

1. A method for protecting the inner surface of large carbon steel and low alloy steel containers, characterized by: The method includes the following steps: Step 1: During container manufacturing, a nitrogen purging port, an air vent, and a humidity monitoring device mounting hole are pre-drilled. The nitrogen purging port is located at the bottom of the container, the air vent at the top, and the humidity monitoring device mounting hole at a height of 1.5-1.8m or similar. The nitrogen purging port and air vent are used for nitrogen filling and air venting after container manufacturing. The mounting hole is used to install the humidity monitoring device. The humidity monitoring device's sensor is placed inside the container, and the measurement result display is on the outside of the container, allowing for real-time monitoring. The humidity monitoring device's measurement range is at least 30%-99%. Step 2: After the container is manufactured and the rust on the inner surface is removed, spray / brush a water-based rust inhibitor onto the inner surface for protection; Step 3: After the water-based rust inhibitor has been applied to the inner surface of the container, place silica gel desiccant and vapor phase rust inhibitor in different locations inside for protection; Step 4: After placing the desiccant and vapor phase rust inhibitor inside the container, immediately seal all branch pipes and manholes of the container, install humidity monitoring equipment at the mounting holes, and ensure the mounting holes are sealed. Step 5: Fill the container with nitrogen to replace the air inside, thereby reducing the oxygen inside the container. The nitrogen filling volume should be at least 1.5 times the container volume. Step Six: After nitrogen purging is completed, seal the nitrogen purging port and air vent to complete the protection work; Step 7: When the humidity monitoring equipment shows that the humidity inside the container is higher than 60%, it is considered that the protective measures have failed and the desiccant and vapor phase rust inhibitor need to be replaced in time, and nitrogen should be refilled.

2. The method for protecting the inner surface of large carbon steel and low alloy steel containers according to claim 1, characterized in that: The specific steps of step two are as follows: (1) Prepare the working solution by mixing the water-based rust inhibitor according to the proportions and preparation method in the product instructions; (2) Spray the prepared rust inhibitor working solution onto all parts inside the container, including the surface of the internal parts, leaving no dead corners. Spray repeatedly at least 3 times, and finally clean up the dripping rust inhibitor in time. (3) After the final spraying is completed, use an axial flow fan or convection hot air fan with heating function to dry the surface of the sprayed rust inhibitor with 80°C hot air. (4) Subsequent internal wall protection operations can only be carried out after the water-based rust inhibitor has completely dried.

3. The method for protecting the inner surface of large carbon steel and low alloy steel containers according to claim 1, characterized in that: The specific steps of step three are as follows: (1) The desiccant should not be placed directly inside the equipment. It should be packaged in non-woven bags, with each bag containing 1 kg of desiccant. Before being packaged in non-woven bags, the desiccant should not be exposed to the air directly. Keep the original packaging. The packaging process should be completed as soon as possible. (2) After the desiccant is dispensed, the vapor phase rust inhibitor is immediately placed in a non-woven bag and placed on top of the desiccant. Each vapor phase rust inhibitor is individually packaged in 50g bags. Four bags of vapor phase rust inhibitor are placed in each non-woven bag. Then the non-woven bag is tied tightly. The dispensing process should be completed as soon as possible. After dispensing, it is necessary to temporarily seal it with plastic sheeting, wooden bucket or wooden box until it is placed inside the equipment. (3) The desiccant should be placed evenly along both sides of the equipment. Before placing it, use a marker pen that meets the requirements of auxiliary materials to number the non-woven bag in sequence. The number should be clearly visible so that on-site personnel can check it when taking it out. Then fix it inside the equipment with rope or wire.

4. The method for protecting the inner surface of large carbon steel and low alloy steel containers according to claim 1 or 2, characterized in that: The application rate of the water-based rust inhibitor in step two is 0.1~0.2 kg / m². 2 .

5. The method for protecting the inner surface of large carbon steel and low alloy steel containers according to claim 4, characterized in that: The water-based rust inhibitor in step two includes 5.0–30.0% of C8–C10 carboxylates, 5.0–15.0% of ethanolamine, 3.0–8.0% of boric acids, and 0.0–5.0% of polyethylene glycol.

6. The method for protecting the inner surface of large carbon steel and low alloy steel containers according to claim 1 or 3, characterized in that: In step three, the amount of desiccant is no less than 1 kg / m³. 3 The vapor phase rust inhibitor should be no less than 0.2 kg / m³. 3 .

7. The method for protecting the inner surface of large carbon steel and low alloy steel containers according to claim 6, characterized in that: The silica gel desiccant in step three comprises 99.6% SiO2, 0.17% Na2O, 0.02% Fe2O3, 0.01% MgO, 0.04% CaO, and 0.16% Al2O3.

8. The method for protecting the inner surface of large carbon steel and low alloy steel containers according to claim 7, characterized in that: The vapor phase rust inhibitor in step three includes 50-60% base oil, 4-8% barium petroleum sulfonate, 2-5% barium dinonylnaphthalene sulfonate, 10-15% lanolin, 8-12% aluminum stearate, 3-5% lanolin metal soap, 1-2% lead nonanoate, and 6-10% calcium stearate.