Ships and marine technology - Performance test procedures for LNG fuel gas supply systems (FGSS) for ships
1 Scope
This document specifies evaluation methods of characteristics such as pressure, flow rate, temperature and system stability of fuel gas supply systems (FGSS), which are manufactured to use vaporized liquefied natural gas (LNG) or boil-off gas (BOG) as fuel gas supply to the vessel's gas consumers.
It is applicable to evaluate the performance of the LNG FGSS: (1) prior to delivery or after installation on board a ship, and (2) to assure the system characteristics are taken into account for the entire gas consumers during ship's gas trial or sea trial.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
IGC Code International Code for the Construction and Equipment of Ships carrying Liquefied Gases in Bulk (IGC code)
IGC Code International Code of Safety for Ships using Gases or other Low-flashpoint Fuels (IGF code)
3 Terms and definitions
For the purpose of this document, the following terms and definitions apply.
3.1
LNG fuel gas supply system
LNG FGSS
system that supplies gas fuel at the temperature, pressure and flow conditions required by the gas consumer, from the fuel tank(s) to the gas consumer, excluding the fuel tank(s), in-tank pump(s), tank ESD valve(s) and the master gas fuel valve(s) used to control the gas supply
3.2
maximum pressure
maximum operating pressure(MPa) measured during the test period
3.3
minimum pressure
minimum operating pressure (MPa) measured during the test period
3.4
pressure pulsation
pressure variation (MPa) during the test period, defined as the difference between the maximum pressure (3.2) and the minimum pressure (3.3)
3.5
flow rate
arithmetic mean of the mass flow rate (kg/h) measured during the test period
3.6
average temperature
arithmetic mean of the temperature (°C) measured during the test period
3.7
test temperature
temperature (°C) of the fluid during the test, designated by the client
3.8
test pressure
pressure (MPa) of the fluid during the test, designated by the client
3.9
test flow rate
flow rate (kg/h) of the fluid during the test, designated by the client
3.10
emergency shutdown system; ESD system
system that safely and effectively stops the flow of LNG and vapour in LNG operations
4 Test arrangement
4.1 Test preparation
The LNG FGSS under test shall be designed in accordance with the IGC and/or IGF Codes established by the International Maritime Organization (IMO) for the safety of systems.
The test arrangement used for the performance test shall supply a test fluid to the inlet of the system and related devices at the required test pressure, test temperature and test flow rate designated by the client, without disruption.
Before any test run is carried out, all relevant arrangements for the safety of attending personnel shall be available and operational, and their correct functioning shall be ensured.
For safety, the air shall be properly replaced with inert gas or a suitable medium in the test arrangement. The system and the test arrangement shall be maintained at cryogenic temperatures prior to the test.
Provisions, to the maximum extent possible, shall be made to minimize the methane emission.
Figure 1 shows a typical test arrangement.
Typical examples of LNG FGSS within the scope of the test are shown in Annex B.
Other systems such as EDS valve(s), blow down valve(s), etc., shall be installed in appropriate locations.
Note: Bunkering piping is excluded from the scope of the test.
4.2 Test fluid
As a principle, LNG shall be used as the medium to verify the performance of the FGSS.
A medium other than LNG, such as liquefied nitrogen or other fluids colder than the liquefied temperature of LNG, maybe used to conduct the test as a reference to the performance of the FGSS, in this case, the temperature designed shall be corresponding to the temperature of the medium.
If a fluid other than LNG is used, correction values should be applied as set forth in ISO 6976 (or equivalent standard) based on the actual testing result.
4.3 Test parameters
The test parameters listed in the example report of Annex A, items 3 and 4, shall be measured and recorded during the test that shall be performed according to Clause 5.
The data of pressure, flow rate and temperature of LNG FGSS shall be recorded in accordance with the FGSS clients' requirements, but in any case, no less frequently than once in every 5 s.
Ambient temperature and humidity shall be recorded before and during the test.
The measuring instruments used in the test shall be appropriately calibrated.
5 Test procedure
5.1 Safety test
5.1.1 Test of e.g. alarm and safety devices
It shall be confirmed that the alarm and safety devices, such as the ESD system, operation of valve(s), etc., are properly operative at ambient temperature and at the minimum working temperature.
The FGSS control system shall be connected and fully operative during the test.
5.1.2 Cryogenic function tests
The cryogenic function tests shall be carried out at the design temperature or lower before pressurizing the FGSS to the design pressure.
The cryogenic function tests shall include following:
a) cryogenic mechanical operation test (e. g. valve operation, leakage verification, etc.) ;
b) electrical integration test (control system) in cryogenic conditions.
5.1.3 ESD and blow down test
The normal operation of the ESD system shall be confirmed prior to the test set up. The test control system shall be able to shut down the ESD valves in the test setup and safely depressurize the piping system and return it to atmospheric pressure conditions by activating the blow down system. The piping system shall be pressurized with nitrogen prior to this test. This test shall confirm the test arrangement's capability to shut down (ESD system) and depressurize the FGSS to atmospheric pressure (blow down system) in case of emergency.
