Liquefied Natural Gas Storage Tank

Low-temperature Liquefied Natural Gas (LNG) Storage Tanks, Manufacturer of LNG Storage Tanks:Huzhou Boiler Factory Co., Ltd., Manager Yu。

LNG above-ground storage tanks are available in five forms: the single-container type is commonly used, which includes single-walled and double-walled tanks. For safety and insulation reasons, single-walled tanks are not used for LNG storage. The outer shell of the double-walled single-container tank is made of ordinary carbon steel, unable to withstand the low temperatures of LNG or the low-temperature gases; it primarily serves to secure and protect the insulation layer. Single-container tanks are generally suitable for locations far from densely populated areas and prone to catastrophic damage, requiring a larger safety distance and land area due to their structural characteristics. The design pressure of single-container tanks is typically kPa, with an operating pressure of 12.5kPa. For large-diameter single-container tanks, the design pressure is correspondingly lower; according to BS7777 standards, this type of storage tank has a design pressure less than 14kPa, which is challenging to achieve when the tank diameter is 70-80m, with the maximum operating pressure around 12kPa. Due to the lower operating pressure of the equipment, during the unloading process, the evaporated gas cannot be returned to the LNG ship's cargo hold, necessitating an additional return gas fan. The lower design pressure requires a larger power for the evaporated gas recovery and compression system, thereby increasing investment and operating costs. While the investment in single-container tanks is relatively low and the construction period is shorter, the risk of leakage is a significant issue. According to regulations, the safety distance between single-container tanks is larger, and firebreaks must be set up, thereby increasing land and firebreak investment. No other critical equipment should be present nearby. Therefore, there is a higher requirement for safety inspections and operations.

LNG Storage Tanks, Low-Temperature LNG Storage Tanks, Manufacturer of LNG Storage Tanks:

Heze Boiler Factory Co., Ltd., Manager Yu。

(1) A trench with a base of 1.5 em, length of 20,000 cubic meters, and width of 2 meters is filled with clay for backfill. Figure 3 shows the electrolytic ion grounding electrode, and Figure 4 illustrates the installation of the electrolytic ion grounding electrode at a depth of 330 cm. (2) Clean the grounding electrode with a dry cloth, ensuring no oil residue; inject clean water into the ion release holes at the top, middle, and bottom of the electrode. (3) Mix GAF powdered grounding modifier with water, and place it at the bottom of the trench. (4) Position the grounding electrode at a certain angle on the trench bottom, covering the top with the modifier. (5) Wrap the grounding electrode leads with insulating tape and connect them to the grounding main with a heat-fused welding method. 5 Static Grounding Setup When LPG is injected into the storage tank, the liquid flow causes charge separation, and when the charges accumulate to a certain level, static discharge occurs. Since static discharge is completed in nanoseconds, the peak current can reach dozens of amperes, making the instantaneous power immense and the static discharge highly destructive. To avoid static hazards: 1) Limit the speed of flammable liquid flow to greatly reduce the generation and accumulation of static electricity; 2) Ensure proper static grounding. Static grounding provides a path for the release of static charges by grounding. The grounding circuit must be reliable to prevent spark discharges at points of poor contact. Specifically, grounding bolts are welded to the inner wall of the tank, connected to the outer metal body through a 70 mm² insulated copper core wire to release static electricity. The static grounding connection is shown in Figure 5. Figure 5 Static Grounding Connection Wall 6 Grounding Test Results According to GB 50057-2010 Section 4.3.10, the冲击 grounding resistance value at each grounding point should not exceed 30 Ω. According to GB 12158-2006 "General Guidelines for Preventing Static Electricity Accidents" Section 6.1.2, to dissipate static charges quickly in static hazard areas, all objects that are static conductors must be grounded. The grounding resistance value of each dedicated static grounding body should generally not exceed 100 Ω in areas with high soil resistivity, such as high-resistance soil areas, and should not exceed 1000 Ω. After the lightning protection grounding project is completed, the measured grounding resistance value is 0.8 Ω, and all grounding leads are well connected to the grounding main, meeting the lightning protection grounding requirements.

Liquefied Natural Gas (LNG) Storage Tanks, Low-Temperature LNG Storage Tanks, Manufacturer of LNG Storage Tanks:

Heze Boiler Factory Co., Ltd., Manager, Mr. Yu。

Current Transformer Secondary Circuit Open-Circuit Differential Protection. By selecting the control word, the differential protection output can be locked or not when the secondary circuit of the current transformer is open-circuited. When the secondary circuit of the current transformer is open-circuited and the differential current is not significant, the differential protection device emits an alarm signal, notifying the dispatch personnel to shut down the transformer for maintenance by reversing the load. This prevents the main transformer from tripping due to the secondary circuit open-circuit of the current transformer. If the differential current increases to the open-circuit differential protection set value (usually the rated current of the transformer, P), the open-circuit differential protection is activated. This ensures that the transformer differential protection operates, the main transformer trips, and the protective device can correctly disconnect the fault current, preventing the accident from escalating. This can be considered a compromise solution that balances the advantages and disadvantages of the first two methods, achieving good results. For the No. 1 110 kV substation's No. 3 main transformer (capacity 63 MVA, voltage ratio 110 kV/10.5 kV, connection type YNdll, primary current transformer ratio 600 A, secondary current transformer ratio 4000 A, the differential protection set values are as follows: differential quick-break current set value, ... = 4.4 (A), differential protection start-up set value, ... = 0.28 (A), ratio制动 coefficient set value K = 0.5, second harmonic braking coefficient 0.15, open-circuit differential protection set value 0.8. On a certain day at 06:42, an alarm was reported at the No. 1 substation back-end, indicating that the secondary circuit of the No. 3 main transformer's differential protection current transformer was open-circuited, with a sudden change in current of 0.08 A and a phase difference differential current of 0.056 A. After contacting the dispatch personnel to reverse the load and shut down the power, the equipment was inspected and found to be loose terminals on the SF6 enclosed switchgear busbar. After tightening the busbar terminals, the fault was eliminated.