What are the requirements for railway transportation, loading and unloading of flammable liquids?

1. Requirements for crane pipes for railway loading and unloading of flammable liquids

Hanging pipe is the main equipment for loading and unloading liquid on the upper part of railway tank car, and its main body is made of steel pipe or aluminum pipe with a diameter of108 mm. The structural size and installation position of the hanging pipe must conform to the relevant provisions of the standard gauge railway approaching the gauge.

(1) When flammable liquid loading and unloading lines are combined with Class C and Class B liquid loading and unloading lines for simultaneous operation, the distance between the two crane pipes should not be less than 24m；; When not working at the same time, the distance between two crane pipes can be unlimited.

(2) The distance between the center line of large hanging pipes arranged on both sides of two special lines and the center line of railway special lines with a walking distance of 2m should be 2.6m, and the distance between adjacent hanging pipes should be 12m. The distance between the loading and unloading crane pipe and the fence and railway gate should not be less than 20m.

(3) In the flammable liquid railway loading and unloading area, the distance between the diesel locomotive and the crane pipeline of another stacking platform: the crane pipeline of Class A and Class B liquids should not be less than 12m, and the crane pipeline of Class C liquids should not be less than 8m. The distance between two adjacent hanging pipes shall not be less than 10m, but the distance between two adjacent hanging pipes for loading and unloading Class C liquid shall not be less than 7m. When flammable liquid is closed for loading and unloading, its fire protection distance can be reduced by 25%.

2. Requirements for flammable liquid railway loading and unloading trestle

Flammable liquid railway loading and unloading trestle is an operating platform for loading and unloading operations. Generally, it is built together with the crane pipeline. There is a lifting ladder (the inclination angle is not more than 60) between the trestle and the tanker, and the operator can operate the tanker from the ladder. The structure of flammable liquid railway loading and unloading trestle is shown in Figure 5-7.

(1) When arranging the railway receiving and dispatching trestle for flammable liquids, it should be located at the edge of the flammable liquid warehouse as far as possible to avoid crossing the roads in the warehouse, and should be arranged in the upwind direction of the auxiliary operation area, and can only be arranged on one side of the loading and unloading line, keeping a certain distance from other buildings and structures. Trestles should not be set on both sides of the production line to avoid the influence of simultaneous loading and unloading operations.

(2) The trestle for loading and unloading flammable liquids shall be made of incombustible materials, with a deck height of 3.5m and a width of 1.5 ~ 2m. Safety railings should be set on the bridge deck, and the spacing between the trestle columns should be as consistent as possible with the spacing between the crane pipes, generally 6m or 12m. At both ends of the trestle and along the trestle, 45 inclined ladders should be set up for getting up and down the trestle every 60 ~ 80m.

(3) The distance between the edge of the newly-built and expanded flammable liquid loading and unloading trestle and the center line of the liquid loading and unloading line should not be less than 2m, and the distance above 3m should not be less than1.85m..

Figure 5-7 Schematic Diagram of Railway Loading and Unloading Trestle

1- special railway line; 2- trestle; 3- liquid collection tube; 4- Loading and unloading oil crane pipe

3. Safety requirements for filling operation of railway liquid tank car

(1) cannot be filled according to the total capacity of the liquid tanker. Railway liquid tankers should be filled according to the filling height at the highest temperature along the way and at the terminal, but not according to the total capacity of liquid tankers. This is because it may be affected by temperature rise, liquid expansion or overflow due to vibration and bumps during transportation. In the case of liquid overflow, if the railway tanker "grinds the shaft" or Fei Huo, it may cause a fire. Therefore, it must be filled according to the safe capacity.

(2) The safe filling height should be calculated. The calculation method is as follows: firstly, check the liquid temperature in the storage tank of the starting station, and then subtract the difference between the highest liquid temperature and the liquid temperature of the starting station from the highest liquid temperature in the checkpoint and along the way in Table 5-8. From the place with high liquid temperature to the place with low liquid temperature, the loading height can be filled according to the remaining 5% ~ 7% empty capacity of the liquid tanker.

Table 5-8 Maximum Liquid Temperature of Railway Tank Cars in Different Areas of China

4. Handling method of flammable liquid railway tank car

The loading and unloading method of flammable liquid railway tank car mainly depends on the terrain conditions of flammable liquid warehouse and the structure of tank car.

(1) Gravity loading and pumping loading mainly use the height difference of terrain to carry out gravity loading. This loading method not only saves investment and reduces cost, but also is safe and reliable, and is not affected by power supply. It also needs terrain conditions for self-flow loading. Pumping loading is a method used when the terrain conditions of gravity loading are not available, as shown in Figure 5-8. At present, many reserve oil depots in China are built in mountainous areas, and the storage areas are mostly arranged in mountainous areas or deep canyons, and the altitude is mostly higher than the working area. Therefore, most oil depots use pump unloading and gravity loading.

Figure 5-8 Schematic Diagram of Railway Pumping Loading

(2) Loading and unloading is mainly to insert the rubber hose or movable aluminum pipe at the end of the hanging pipe into the car from the tank cover at the upper part of the liquid tanker, and then unload the car with a pump or siphon. When the liquid railway tank car is filled with armor and Class B liquid from the top, the crane pipe inserted into the bottom of the tank car should be adopted. The flow velocity of liquid in the crane pipe should not be greater than 4.5m/s. When the pump is used to unload the liquid (Figure 5-9), it must be ensured that the pump suction system is full of liquid, and there will be no phenomenon of gas blocking the flow at the top of the crane pipe and any part of the suction system, so a vacuum pump must be equipped to meet the requirements of filling the pump and sucking the liquid oil at the bottom. Its characteristic is that the liquid discharged from the bottom of the tank car can be directly pumped into the liquid storage tank without passing through the zero tank, which reduces the evaporation of flammable liquid, but it needs to be equipped with a tall hanging pipe, trestle and vacuum system. There are many equipments, complicated operation, and great fire risk, which forms air resistance and affects normal oil unloading.

When the tank car level is higher than the zero tank level and there is enough liquid level difference, siphon gravity flow can be used to discharge the liquid (Figure 5- 10). However, there must be a vacuum pump or liquid filling equipment to fill the crane siphon. The advantages of this unloading method are mainly less equipment and simple operation; The disadvantage is that the zero fuel tank is added, and it is transported once more, which increases the evaporation of combustible liquid. Submersible pump is also used to unload the upper oil (Figure 5- 1 1). The submersible pump is installed at the hose end of the pipeline of the oil unloading crane. The pump is driven by a motor, both of which are installed in a sealed casing, and the motor is cooled by the delivered oil. This oil unloading method is flexible and effective, and is mainly suitable for field operation, but the motor must meet the requirements of explosion-proof grade.

Figure 5-9 Schematic Diagram of Pump Unloading

Figure 5- 10 Schematic Diagram of Siphon Gravity Unloading

Figure 5- 1 1 Unloading oil by using the upper part of submersible pump

(3) Bottom unloading is a widely used method for receiving and unloading oil and other liquids in railway liquid tankers at present (Figure 5- 12). It is mainly composed of a liquid storage tank truck unloader and an infusion pipeline. The connection between the tank car unloader and the liquid collecting pipe is mainly completed by rubber pipe or aluminum drain arm. The use of lower drainage overcomes the shortcomings of upper drainage, and there are few buildings on the ground, which is beneficial to air concealment and operation. However, due to the frequent opening and closing of the ship unloader and the vibration during driving, it is easy to leak flammable liquid, which increases the fire risk along the way and during storage. However, when the unloading system of railway liquid tanker adopts the way of receiving and unloading from the lower part, the closed pipeline system should be adopted.

Fig. 5- 12 schematic diagram of oil unloading at the lower part of railway tank car