QC/T 755-2020Technical requirements for fuel gas systems of LNG vehicles (English PDF)

3.1 Fuel-gas system for LNG vehicles

A complete system that consists of LNG gas storage components, gas supply components, refuelling components and safety components installed on LNG vehicles.

3.2 Vehicular tank

It is a pressure vessel (hereinafter referred to as a gas cylinder) that is used by LNG vehicles to store and supply LNG fuel.

3.3 Accessories

In the gas storage parts, the liquid level sensor, liquid level transmitter, economic regulating valve, one-way valve, pressure gauge, relief valve (primary relief valve, auxiliary relief valve), pressure relief pipeline and other devices other than gas cylinders.

3.3.1 Liquid level sensor

A device that is installed in the gas cylinder, used to reflect the real-time liquid level of LNG, and can send out liquid level signal.

3.3.2 Liquid level transmitter

A device that converts the input signal of the liquid level sensor into a signal that can be received by the liquid level indicator.

3.3.3 Liquid level indicator

An instrument that is installed on the operating panel of the cab to display the remaining amount of LNG in the gas cylinder.

5.1 General requirements

5.1.1 The fuel gas system shall be manufactured in accordance with the product drawings and other technical documents approved by the prescribed procedures; and shall comply with the provisions of GB/T 36883.

5.1.2 All components in the fuel gas system shall have operating conditions and quality inspection certificates provided by the manufacturer; and the explosion-proof performance of electrical components shall comply with the provisions of GB 3836.1.

5.1.3 The installation of the fuel gas system shall comply with the provisions of GB/T 20734 and GB 19239.

5.1.4 When one of the following situations occurs, the fuel gas system shall be able to automatically cut off the LNG supply:

a) The ignition switch is not turned on;

b) The engine is not running;

c) The LNG gas supply pipeline is broken, falling off, etc.

5.1.5 The gas cylinders in the fuel gas system shall be able to adapt to the working environment temperature requirements specified in GB/T 34510-2017. Other parts and components shall be able to adapt to the respective working environment temperature.

6.1 Gas cylinder

6.1.1 Bursting discs shall not be installed in gas cylinders. The gas cylinder shall comply with the provisions of GB/T 34510 or GB/T 24159.

6.1.2 The gas cylinder shall be provided with a permanent nameplate identification; which shall comply with the relevant provisions of GB/T 34510. When installing the gas cylinder on the vehicle, it must not cover the nameplate mark.

6.1.3 The pipelines of LNG entering and exiting cylinders need to have indication marks to indicate the function of the pipeline and the direction of fluid flow. The marks should not be blurred due to "frosting".

6.1.4 If the gas cylinder is equipped with an LNG pump with compulsory liquid supply function, there shall be an LNG pump working pressure mark on it.

6.2 Accessories

6.2.2 Liquid level device 6.2.2.1 The liquid level transmitter shall meet the following requirements:

6.2.3.6 The instruction manual of relief valve product shall clearly explain the periodic calibration of the relief valve.

6.2.1 General requirements

6.2.1.1 The working pressure of all accessories of the gas cylinder shall be no less than the nominal working pressure of the gas cylinder and the working pressure of this part.

6.2.1.2 During the inspection period of gas cylinders, the performance of all seals shall comply with the provisions of 5.1.6.

--- the function of fault diagnosis, the sensor short circuit, open circuit and abnormal data sent by the transmitter shall be displayed on the instrument.

--- If the protection level reaches IP67, the explosion-proof performance meets the intrinsic safety requirements in GB 3836.1 and GB 3836.4, and the electromagnetic compatibility meets the relevant requirements of 4.5, 4.6, 4.7, 4.8 in GB 34660-2017, and GB/T 19951.

6.2.4 Pressure relief pipeline

6.2.4.1 The fuel gas system shall be equipped with a pressure relief pipeline; and the latter shall be able to withstand the pressure and temperature of LNG, and be able to withstand the pressure shock when the relief valve is fully opened.

6.2.4.2 The pressure relief pipeline shall be directly connected to the gas phase space of the gas cylinder; and the pipeline diameter shall meet the requirements for safe discharge. At the same time, a venting globe valve shall be set in the pressure relief pipeline; and the relief valve pipeline shall be connected in parallel with the venting globe valve.

6.2.4.3 The pressure relief pipeline shall have automatic pressure relief (relief valve starts pressure relief) and manual pressure relief functions.

6.2.4.4 When the gas cylinder is installed on the vehicle, the outlet of the pressure relief pipeline shall be connected to a safe location for discharge.

6.2.4.5 When the pressure relief pipeline is arranged in the protective cover of the M3 category vehicle, the mark of "pressure relief pipeline" shall be provided. The pressure relief pipeline below the roof and above the floor shall not be equipped with joints. The pressure relief pipeline shall not be arranged in the door axle box; and the end shall be set on the roof of the vehicle; and waterproof joints and rain caps shall be installed.

6.2.5 Pressure gauge

6.2.5.1 The pressure gauge shall comply with the provisions of GB/T 1226; the minimum burst pressure shall be no lower than 4 times the nominal working pressure of the gas cylinder; the range shall be 1.5 times ~ 3 times the working pressure; and the accuracy shall be no lower than Level-2.5; the vibration conditions in the normal operation environmental shall not exceed the Level-V.H.4 specified in GB/T 17214.3-2000.

6.2.5.2 The product instruction manual of the pressure gauge shall have clear instructions for the periodic calibration of the pressure gauge.

8.1 General requirements for LNG filling device

8.1.1 The LNG filling device shall meet the requirements of GB/T 25986.

8.1.2 There shall be a one-way valve between the fuel filling port and the connecting pipeline of the gas cylinder to ensure that the liquid does not flow back after the filling is completed.

8.1.3 If a multi-cylinder system shares a common structure with a single filling port, a stop valve shall be installed in each cylinder pipeline.

8.1.4 The filling device for M3 category vehicles is not allowed to be arranged in the door axle box.

8.2 Requirements for filling opening and return gas inlet

The filling opening and the air return inlet shall have good sealing performance; and there shall be no leakage under any circumstances. It shall be equipped with a dust cover to prevent dust from entering the interface and affecting the automatic sealing of the interface.

9.1 Gas cylinder protection

9.1.1 General requirements

Corresponding protective measures can be taken according to the arrangement of the gas cylinders. The protective mechanism of the car itself can be used, and protective fences, bumpers, partitions and protective covers can also be installed to prevent direct mechanical collisions or damage from the road gravels. Focus on protection for the cylinder valve and pipeline. If the protective material is non-metallic, the flame retardant performance of the material shall comply with the provisions of GB 8410-2006.