LNG Storage Tank

LNG stands for Liquefied Natural Gas. Its primary component is methane. LNG is colorless, odorless, non-toxic, and non-corrosive, with a volume approximately 1/600th that of an equivalent volume of gaseous natural gas. Its weight is roughly 45% of the same volume of water, and its calorific value is about 52 MMBtu per ton (1 MMBtu = 2.52×10^8 calories).

Model:

CFL-5/0.8，CFL-10/0.8，CFL-15/0.8，CFL-20/0.8，CFL-30/0.8，CFL-50/0.8，CFL-60/0.8，CFL-100/0.8，CFL-150/0.8...

CFW-5/0.8，CFW-10/0.8，CFW-15/0.8，CFW-20/0.8，CFW-30/0.8，CFW-50/0.8，CFW-60/0.8，CFW-100/0.8，CFW-120/0.8，CFW-150/0.8…

Low-temperature storage tanks are designed and manufactured in strict accordance with national standards, widely used for the storage and use of deep cold liquids such as liquid oxygen, liquid nitrogen, liquid argon, liquid carbon dioxide, liquid natural gas, and liquid ethylene, featuring various working pressures and specifications. Utilizing unique high-vacuum insulation technology, they offer superior insulation properties, long-lasting vacuum retention, and extremely low operational costs. Modular piping systems and high-configured components enhance the equipment's performance and durability, reduce maintenance costs, and significantly boost your competitive edge.

Introduction:

Low-temperature insulation tanks are of vacuum powder insulation type, consisting of a double-container structure with an inner container and an outer container, which can be divided into vertical and horizontal types. The inner container, selected based on the medium it contains, is made of Austenitic stainless steel, specifically S30408. The material for the outer container varies according to the user's location, typically Q345R. The space between the inner and outer containers is filled with pearlite insulation material and then vacuumized.

Usage:

Store Liquid Oxygen (LO2), Liquid Nitrogen (LN2), Liquid Argon (LAr), Liquefied Natural Gas (LNG), Liquid Carbon Dioxide (LCO2)

Thermal Insulation Performance:

Insulation materials use pearlescent sand filling in the vacuum layer under high temperatures, and then vacuum extraction. After the sandwich is sealed, the standard vacuum degree is:

Sealing Vacuum Gauge

Design Parameters:

Design Pressure: 0.84 Mpa, 1.32 Mpa, 1.68 Mpa

Operating Pressure: 0.8 MPa, 1.2 MPa, 1.6 MPa

Design Temperature: -196°C

Operating Temperature: -196℃

Effective Volume: 2.5m³, 3.5m³, 5m³, 10m³, 15m³, 20m³, 30m³, 50m³, 60m³, 100m³

Definition:

LNG stands for Liquefied Natural Gas.

The primary component is methane. LNG is colorless, odorless, non-toxic, and non-corrosive, with a volume approximately 1/600th of the same amount of gaseous natural gas. Its weight is about 45% of the same volume of water, and its calorific value is around 52 MMBtu/ton (1 MMBtu = 2.52×10^8 calories).

Formed:

The natural gas produced from the gas field is first purified and then liquefied under ultra-low temperature (-162℃) and atmospheric pressure to form liquefied natural gas.

The critical temperature of LNG between gas and liquid phases at atmospheric pressure is -162℃.

The standard commonly used in LNG manufacturing is API 620.

Meaning:

Liquefied Natural Gas (LNG) storage tanks are specialized products for storing LNG, a type of special equipment.TwoCategory pressure vessels, made of 06Ni9DR material, completed with flaw detection, hydraulic and pneumatic testing, on-site inspection by the Technical Supervision Bureau, issuance of pressure vessel inspection certificate, and external rust removal and painting processes. The liquefied gas storage tank undergoes strict quality assessment for the material, dimensions, weld quality, operational quality, installation quality, internal equipment, and safety accessories of the pressure-bearing components.

Routine physical and chemical tests of the drum material, such as mechanical properties and chemical composition.

The weld joints, welds, tank end caps, and the geometric positions of all pressure elements are rigorously inspected through X-ray non-destructive testing and magnetic particle inspection. Tests are conducted on the product's sealing, pressure resistance, and all technical indicators that could affect the safe operation of the product.

1. Natural Gas Storage Tank LNG Storage System: The LNG storage system consists of low-temperature storage tanks, auxiliary pipelines, and control instruments.

2. By capacity classification:

Small natural gas storage tanks, 5-50 cubic meters, commonly used in residential gas liquefaction stations, LNG refueling stations, etc.

Medium-sized natural gas storage tanks, 50-100 cubic meters, commonly used in satellite liquefaction units, industrial gas vaporization stations, etc.

3. Natural gas storage tanks, typically use austenitic stainless steel pipes for LNG pipelines. Austenitic stainless steel pipes offer excellent low-temperature properties.

4. Vertical natural gas storage tanks (LNG tanks) with vacuum powder insulation technology. The inner cylinder and pipeline materials are made of OCr18Ni austenitic stainless steel, while the outer cylinder is made from high-quality carbon steel Q345R pressure vessel steel plate. Our company offers a variety of specifications ranging from 50 to 100 cubic meters for liquefied natural gas storage tanks.

5. Uses of Natural Gas Storage Tanks: Chemical fuel, residential fuel, automotive fuel, combined power generation, heat pumps, fuel cells, etc.

6. Natural Gas Storage Tank Liquefaction Process: Cascade Liquefaction Process, Mixed Refrigerant Liquefaction Process, Liquefaction Process with Expander.

7. The natural gas storage tank liquefaction unit consists of a natural gas pretreatment process, liquefaction process, storage system, control system, and fire protection system, etc.

Maintain and repair

Routine Maintenance

The housing must not be subjected to any impact, and operations must be carried out according to regulations. The valves and pipe fittings should be kept clean and intact, with valves able to open and close smoothly, and regular inspections should be conducted as per regulations. Under normal operation, a comprehensive check and maintenance of all valves, pipe fittings, and instruments should be performed annually. Replacement of wear parts (such as valve seals) should be done promptly.

2. Insulation Performance Maintenance

One of the key requirements for low-temperature liquid storage tanks is excellent insulation performance, with the quality of vacuum being crucial to this insulation.

Once the tank's vacuum is compromised, it can no longer store low-temperature liquids. Therefore, special attention must be paid to protecting the tank's vacuum integrity. The explosion-proof device and the exhaust valve on the tank shell are directly connected to the vacuum jacket. The device must not be tampered with when the jacket vacuum is not damaged or when there is no need to replenish and re-evacuate with mica sand. The exhaust valve is sealed with lead at the factory and must not be moved at will; otherwise, it will damage the tank's vacuum.

The tank shell is an external pressure vessel, subjected to atmospheric pressure. It is strictly prohibited to敲打和磕撞 to prevent damage to the shell, which may affect the vacuum degree.

3. Inspect

(1) Routine inspection

1) Is the valve in the correct open/close position?

2) Accuracy and reliability of pressure gauge and differential pressure (level) meter measurements.

3) Check for any leaks or blockages in pipes and valves.

4) If the container pressure reaches the set pressure of the safety valve and the valve does not activate, the safety valve set pressure should be immediately adjusted to ensure the safety of the storage tank.

5) Check if the turbocharger flange bolts are loose and if there is any deformation in the pipes.

(2) Regular maintenance

1) The pressure gauge is calibrated annually.

2) The safety valve is calibrated annually.

3) Measure vacuum level annually.

4) Thermocouple vacuum gauge (purchased by the user, not within the supply scope) should be calibrated according to the instructions before each measurement.

5) Inspect the storage tank grounding resistance annually; a resistance below 10Ω is considered acceptable. If it exceeds 10Ω, the connection status should be checked promptly.

(3) Vacuum Level Inspection and Re-evacuation

The tank's vacuum level is measured once a year. To measure, simply unscrew the protective cover of the metal thermocouple tube and insert the plug of the thermocouple vacuum gauge, then you can know the interlayer vacuum level.

After several years of use, the vacuum level of the tank may drop to 65Pa, requiring a re-evacuation to improve insulation performance. Prior to re-evacuation, the liquid inside the tank should be drained, and then heated and blown out with dry, oil-free air or nitrogen at 80-100℃ until it returns to normal temperature. Connect the vacuum pipeline, start the pump to remove the moist air from the pipes, then open the vacuum valve to evacuate the tank.

To shorten the vacuuming time, the container can be heated with dry, oil-free air at temperatures below 100°C. The vacuum degree of the jacketed seal should be ≤3Pa. If necessary, the user may contact the manufacturer regarding vacuuming matters, and both parties can agree on the specific process for re-vacuuming.

4. Fault Handling

(1) Safety valve troubleshooting

1) Safety valve leak

The valve disc and seat sealing surface may experience leakage beyond the allowable limit under operating pressure, and the possible reasons are:

There are debris on the sealed surface.

If the installation is not fully cleaned with compressed air prior to use, or if solid impurities are mixed with the fluid during trial operation, or if it is necessary to perform an action, debris can become trapped between the valve seat and the sealing surface. If it's easy to remove the debris, do so manually. However, if there is still leakage after removal, consider the following causes: it may be damage to the valve seat and its sealing surface; or, debris may be embedded between the valve seat and the sealing surface. If this situation is difficult for the user to handle, return it to the manufacturer for repair.

② Internal Pipeline Force

a) Human Factors

During the process of installing the safety valve on the pipeline, if it is forcibly rotated, the valve seat may rotate, which could cause the position of the safety valve adjustment ring to change or the sealing surface to be forcibly worn away, potentially leading to reduced operational performance. Depending on the situation, this can be handled on-site by the user or returned to the factory for repair; however, it is necessary to fully grasp the situation and make a quick judgment.

b) Internal Force Factors

The adverse effect of welding residue's force inside the pipeline on the safety valve. The issue occurring at this moment is almost completely consistent with the aforementioned situation. Therefore, it is crucial to fully consider the absorption of the force inside the pipeline during pipeline installation. This point is of great importance.

c) The setting pressure of the safety valve is too close to the normal operating pressure of the equipment, resulting in a low sealing pressure on the sealing surface. This makes it more prone to leakage when the safety valve is subjected to vibration or fluctuations in the medium pressure. Under conditions of meeting the strength requirements, the setting pressure of the safety valve should be appropriately increased during design.

③ Spring relaxation reduces the set pressure, causing the safety valve to leak.

The primary cause of spring relaxation may be that after the safety valve has been calibrated, the adjustment screw of the safety valve was not securely tightened, causing it to loosen during equipment operation. This leads to spring relaxation and a decrease in preload, resulting in the premature opening of the safety valve. The safety valve should be recalibrated.

2) Inflexible safety valve operation

The reason may be:

Improper adjustment of the safety valve's regulating ring can lead to an extended opening process or delayed seating, which should be re-adjusted. By adjusting the lower regulating ring, increase the seating pressure.

②The exhaust pipe of the safety valve has excessive resistance, causing significant back pressure during discharge and insufficient opening height for the safety valve. To normalize the safety valve's operation, the exhaust pipe should be modified to a straight-through design, removing the intermediate bend.

3) Safety valve frequent chatter or vibration

The reason may be:

The discharge of the safety valve is excessive. The rated discharge of the selected safety valve should be as close as possible to the required discharge of the equipment.

② The imported pipeline diameter is too small or the resistance is too great.

③ Excessive resistance in the exhaust pipeline causes excessive back pressure during emission. The resistance of the exhaust pipeline should be reduced.

④Improper adjustment of the regulating ring causes excessive return seat pressure. The position of the regulating ring should be realigned.

4) Operation of three-way valve A-5 during replacement of the safety valve

① Two safety valves operate simultaneously during normal operation, with both side channels open at the same time, handle position as shown in Figure 1.

②When replacing the safety valve, rotate the handle 90 degrees (as shown in Figures 2 and 3), close the side channel to be replaced, and empty the residual medium inside the channel before replacing the safety valve.