GB/T 47544-2026Marine LNG reliquefaction units (English PDF)

4.1 Type

4.1.1 Classification by cooling object.

a) Direct liquefaction type. directly cools and liquefies the BOG generated in the liquid cargo tank;

b) Indirect liquefaction type. BOG in the liquefied cargo tank is indirectly cooled by subcooled LNG.

4.1.2 Classification by refrigeration principle.

a) Throttling refrigeration type. generates a refrigeration effect through a throttling device, cooling and liquefying BOG;

b) Expansion refrigeration type. The refrigeration effect is generated through an expansion device to cool and liquefy BOG.

4.2 Specifications The specifications of the reliquefaction unit are shown in Table 1.

4.3 Model Identification The model designation method for reliquefaction units is shown in Figure 1.

5.1 Environmental adaptability

5.1.1 The reliquefaction unit shall be able to operate normally under the following conditions.

a) Lateral tilt ±15°, longitudinal tilt ±5°;

b) Roll ±22.5°, Pitch ±7.5°;

c) Operating ambient temperature. 0°C~45°C; absolute atmospheric pressure. 0.1MPa; relative humidity. 60%;

d) Seawater temperature. 0°C~32°C;

e) Vibrations and shocks generated during normal ship operation;

f) Humid air, salt spray, oil mist, and mold.

5.1.2 The refrigerants used in the reliquefaction unit, if multiple refrigerants are used and may come into contact with each other, shall be compatible with each other.

5.2 Materials

5.2.1 The selection of materials for reliquefaction units should take into account the corrosiveness of the contact medium and be compatible with its design pressure and temperature.

5.2.2 Materials in contact with cryogenic media shall meet the requirements of Chapter 6 of the Specification for Construction and Equipment of Ships Carrying Liquefied Gases in Bulk.

5.3 Safety

5.3.1 The explosion-proof rating of the electrical equipment of the reliquefaction unit shall comply with the provisions of GB/T 22189.

5.3.2 Safety valves shall be installed in the pressure vessels and other closed components of the reliquefaction unit that may accumulate pressure.

5.3.3 If the cold box or other areas of the reliquefaction unit have independent enclosed spaces, combustible gas detectors should be installed.

5.3.4 The design pressure of the reliquefaction circulation system should be greater than or equal to

1.25 times the working pressure.

5.3.5 The control system, safety system, and alarm system of the reliquefaction unit should be designed as independent systems. If one or more of these systems fail, the system will be disabled. When one system fails, it should not affect the normal operation of other systems.

5.4 Environmental Protection

5.4.1 The reliquefaction unit shall be equipped with exhaust gas containing methane during pressure-controlled operation and within the design conditions. interface.

5.4.2 The refrigerant should be an environmentally friendly medium with an ozone depletion potential (ODP) of 0, conforming to the International Convention for the Prevention of Pollution from Ships. Require.

5.5 Appearance The reliquefaction unit must meet at least the following appearance requirements.

a) The welded surfaces on the outer surface of the device should be clean, free of rust, scale, and welding slag;

b) The outer surface of the device shall be painted, and the surface shall be flat, smooth, and uniform in color;

c) The connections of the equipment should be neat and orderly, and the main pipelines should be marked with the medium and the direction of medium flow.

5.6 Main Components

5.6.1 General Requirements Pipeline welding should undergo welding procedure qualification, and non-destructive testing should be performed after welding in accordance with the requirements of the "Guidelines for Ship Welding Inspection". (For conveying flammable and explosive materials...) For pipeline connections involving explosive media, butt welding should be used, and the butt weld should be a full penetration weld. Additionally, sleeve welding and threaded connections are also acceptable. The specifications adopted should meet the requirements of the "Code for Construction and Equipment of Ships for Bulk Transport of Liquefied Gases".

5.6.2 Compressor The compressor should meet the following requirements.

a) Screw compressors shall comply with the provisions of GB/T 19410.

b) Piston compressors shall comply with the provisions of GB/T 20322.

c) Centrifugal compressors shall comply with the provisions of GB/T 45595.

5.6.3 Expander The expander shall comply with the provisions of JB/T 11847.

5.6.4 Compression and Expansion Integrated Machine

5.6.4.1 General Requirements The integrated compression expander shall comply with the provisions of JB/T 6443.Its press housing, rotor, and magnetic levitation bearings (if applicable) shall also comply with... Requirements

5.6.4.2 to 5.6.4.4.

5.6.4.2 Pressure Vessel Housing The pressure compressor housing should undergo strength analysis. For pressure compressor housings that meet one or more of the following conditions for high-speed compressors, strength analysis should also be performed according to operating conditions. An inclusion analysis was performed at 120% of the rotational speed, and the analysis results should not show any non-inclusion failures.

a) The maximum linear velocity of the impeller exceeds 500 m/s.

b) The pressure vessel housing is made of a material with an elongation of less than 5%.

c) The thickness of the pressure vessel casing is less than 15mm.

5.6.4.3 Rotor The rotor shall conform to the requirements of GB/T 9239.11.

5.6.4.4 Magnetic levitation bearings Magnetic levitation bearings shall meet the following requirements.

a) The insulation class of the stator winding shall not be lower than Class H (180°C), and the overall bearing assembly shall not be lower than Class F (155°C);

b) Each magnetic levitation bearing should be equipped with a temperature sensor for over-temperature protection;

c) Equipment using magnetic levitation bearings is equipped with protective bearings;

d) Design measures to maintain levitation in the event of power failure, such as equipping with a backup power source;

e) Axis trajectory monitoring should be set, and early warning values and interlocking shutdown values should be set.

5.6.5 Heat Exchanger The heat exchanger shall comply with the provisions of GB/T 151 and NB/T 47006.

5.7.1.1 Under

1.25 times the design pressure, the working medium pipeline and natural gas pipeline of the reliquefaction unit shall be free from deformation, leakage and abnormality.

5.7.1.2 Under

1.50 times the design pressure, the cooling water pipeline of the reliquefaction unit shall be free from deformation, leakage and abnormality.

5.7.2 Air tightness The reliquefaction unit should be leak-free under design pressure.

5.7.3 Pipeline dew point and oxygen content The dew point of the working medium pipeline and natural gas pipeline of the reliquefaction unit should not be higher than -40°C, and the oxygen content should not exceed 2% (by volume).

5.7.4 Insulation Resistance The cold and hot insulation resistance of the reliquefaction unit should be greater than 1 MOmega.

5.7.5 Monitoring, Alarm and Shutdown The reliquefaction unit should be equipped with monitoring, alarm, and shutdown functions as per Table 2.

5.7.6 Operating Mode The reliquefaction unit should operate in at least the following modes. pre-cooling mode, cooling mode, and warm-up mode (if applicable). Pre-cooling temperature, cooling capacity, and power consumption should be specified. Parameters such as energy consumption and expander inlet temperature (if applicable) should meet the design requirements.

5.7.7 Load performance The load performance of the reliquefaction unit should be tested for its cooling capacity and power consumption. The load performance test should comply with the provisions of Appendix A, and the test results should meet the requirements. The following requirements are sufficient.

a) A cooling capacity curve or table should be drawn based on the test results, showing the measured cooling capacity at 100%, 75%, 50%, and 25% load. It should not be less than its rated value;

b) Power consumption curves or tables should be plotted based on the test results. The measured power consumption at 100% load should not exceed its rated value. 110% of;

c) It should have variable operating condition capability to meet the cooling capacity requirements from 0% to 100%.

5.7.8 Mechanical Operation During the mechanical operation test, the system should be fault-free. After the test, the equipment and components in the system should be checked and found to be without abnormalities.

6.1 General Requirements

6.1.1 A visual inspection shall be conducted on the integrity, dimensions, quality, equipment and piping installation, paint, and electrical insulation of the reliquefaction unit. The investigation includes electrical bridging of gasketed connections in natural gas pipelines.

6.1.2 Purge and replace the natural gas pipeline of the reliquefaction unit.

6.1.3 The working medium in the pipeline of the reliquefaction unit shall be filled according to the filling pressure and medium ratio specified in the design documents.

6.1.4 The temperature, pressure, working medium, and electrical system of the inlet natural gas shall meet the design requirements and meet the conditions required for operation.

6.1.5 The production environment at the testing site should meet the design requirements, and all auxiliary systems should meet the conditions required for operation.

6.2 Visual Inspection

6.2.1 Visually inspect the appearance quality of the reliquefaction unit.

6.2.2 Inspect the surface shape and appearance of the weld using visual inspection and weld inspection ruler.

6.3 Inspection of major components

6.3.1 Visually inspect the main components of the reliquefaction unit.

6.3.2 Verify that the main components of the reliquefaction unit are consistent with their quality certification documents.

6.4 Strength Test A pressure test was conducted on the working medium pipeline and natural gas pipeline of the unit. The test pressure was

1.25 times the design pressure and lasted for 30 minutes. above. A water pressure strength test was conducted on the cooling water pipeline of the device. The test pressure was

1.50 times the design pressure and lasted for more than 30 minutes.

6.5 Air tightness test The airtightness of the working medium pipeline and natural gas pipeline of the reliquefaction unit was tested at a pressure of

1.0 times the design pressure, continuously. For pipelines where the working medium contains helium, helium gas spectrometry leak detection should also be performed according to GB/T 15823.

6.6 Pipeline dew point and oxygen content test The natural gas pipeline and the working medium pipeline are purged with nitrogen or inert gas, and the outlet gas dew point and oxygen content are detected by instruments.

6.7 Insulation Resistance Test

6.7.1 Perform cold and hot insulation resistance tests on the reliquefaction unit.

6.7.2 After confirming that the reliquefaction unit is de-energized, select a suitable insulation resistance meter according to Table 3 and measure the insulation resistance between live parts and easily accessible metal surfaces. Insulation resistance between components.

6.8 Monitoring, Alarm and Shutdown Test Perform monitoring, alarm, and shutdown tests according to Table

2.The tests can be conducted through simulation.

6.9 Operation Mode Test

6.9.1 Pre-cooling mode Start the reliquefaction unit, switch it to pre-cooling mode, and record the pre-cooling temperature.

6.9.2 Cooling Mode

6.9.2.1 Rated operating condition test The operation of the reliquefaction unit under rated operating conditions was tested. The system was adjusted to the rated operating point and maintained in a stable operating state. The system status records parameters such as cooling capacity and power consumption.

6.9.2.2 Variable operating condition test The operation of the reliquefaction unit under varying operating conditions was tested. At this time, the unit speed can be adjusted according to the cooling capacity requirement to achieve variable operating conditions. The system operates under conditions and records parameters such as cooling capacity and power consumption.

6.9.3 Warm-up Mode Switch the reliquefaction unit to warm-up mode (if applicable) and record the expander inlet temperature.

6.10 Load Performance Test

6.10.1 Adjust the reliquefaction unit to its rated speed, run it for 1 hour or until it reaches steady-state operation, and record the cooling capacity of the reliquefaction unit under rated operating conditions. Parameters such as power consumption.

6.10.2 During the test, tests shall be conducted under no-load, 25%, 50%, 75%, and 100% load conditions, and the stable operating time under each condition shall be at least 30 minutes.

6.11 Mechanical Operation Test Conduct pre-cooling, cooling, and warm-up (if applicable) operation tests in sequence, with the rated operating time in cooling mode not less than 4 hours.

7.2 Type Testing

7.2.1 Type testing shall be conducted for trial-produced products, products transferred for production, products with significant design improvements, or products required by the ordering party. See below for testing items. Table 4.

7.2.2 The number of type test samples is one.

7.2.3 If all items in the type test meet the requirements, the type test is deemed (qualified). If any item fails to meet the requirements, the test results may be doubled. The sample will be retested. If the retest meets the requirements, the type test is still deemed (qualified); if there are still items that do not meet the requirements during the retest, the type test is deemed (qualified). The test failed.

7.3 Factory Inspection

7.3.1 Each reliquefaction unit shall undergo factory inspection. The inspection items are shown in Table 4.

7.3.2 If all inspection items meet the requirements, the factory inspection is deemed (qualified). If any item fails to meet the requirements, corrective measures are permitted. A re-inspection will be conducted after application. If the re-inspection meets the requirements, the product is still deemed to have passed the factory inspection. If the re-inspection still fails to meet the requirements, the product is deemed to have passed the factory inspection. The test failed.

8.2 Packaging

8.2.1 The packaging of the reliquefaction unit shall comply with the provisions of GB/T 13384.

8.2.2 Before packaging, all accumulated oil and water in the product parts should be thoroughly cleaned. Exposed and unpainted machined surfaces of the product parts should also be cleaned. It needs to be coated with an anti-rust layer or properly protected.

8.2.3 The packaging shall ensure that accessories, documents, etc., are not damaged or lost during transportation. The packaging shall be marked with markings indicating rainproof, moisture-proof, shockproof, and do not... Inverted markings and other markings shall comply with the provisions of GB/T 191.

8.2.4 The following documents shall be included with the reliquefaction unit when it leaves the factory and sealed in a waterproof document bag.

a) Certificate of Conformity.

b) Random files, including.

---User and maintenance manual;

---Installation diagram;

---General layout and main component drawings;

---Spare parts list;

---List of specialized tools (if applicable).

8.3 Transportation and Storage

8.3.1 Transportation should avoid causing damage to the product.

8.3.2 The product should be stored in a dry, ventilated warehouse or a covered place, and rust prevention and damage prevention checks should be carried out during storage.