I. Preface At present, the loading and unloading of domestic rail light tanker trucks adopt the method of loading and unloading at the upper part. The unloading process is summarized as follows: one is the vacuum unloading process; the other is the auxiliary pump with centrifugal pump ; Third submersible pump unloading process. This paper introduces a new technology for unloading oil with a rotary piston pump for future use in new and modified oil depots. Second, the existing unloading process introduced 1, the vacuum unloading process Vacuum system using oil filling pump, cleaning warehouse and pumping emptying tank oil operations. The system requires more equipment, such as water ring vacuum pump, vacuum tank, vacuum lines, etc., and the vacuum pump water also consider winter frost problems. In addition, vacuum pump work, the exhaust pipe often have a lot of oil and gas discharge, it is not safe, so the current process has been rarely used in the depot. 2, the volume pump auxiliary centrifugal pump unloading process uses a positive displacement pump to replace the vacuum system, to achieve the centrifugal pump oil and sweep warehouse. The system is currently used more, especially for diesel and aviation oil products. The volumetric pump used is usually a vane pump or a swinging rotor pump. The application of the system should be noted that, in the sweep process, due to the presence of oil and gas mixed transmission case, the pressure of the pump outlet will be far lower than the pump rated value, so you must set the sweep tank or low empty tank, Otherwise it will not work properly. 3, submersible pump unloading process Submersible pump unloading process has two programs: First, low-lift submersible pump and the main oil pump work in tandem with the unloading process. Second, high-lift submersible pump directly into the tank unloading process. The advantages of the process scheme are the high unloading reliability, short working time, no need to worry about the problem of gas tube resistance and pump cavitation, and is particularly effective for high temperature unloading of gasoline in the plateau area. The disadvantage is the higher operating costs of investment, due to crane mouth equipped with submersible pump, the operation is not convenient. In addition, the program can not be omitted warehouse cleaning system, the setting method with centrifugal pump unloading process. Third, unloading new technology Rotary piston pump unloading process: Rotary piston pump is a positive displacement pump, with low speed (400 r / min), suction capacity (maximum vacuum of 0.085MPa), high efficiency (0.7 ~ 0.85), can be two-phase gas-liquid transport, low impurity characteristics of the filter. Because of its super self-priming capability, there is no need to set up another pump for its oil filling pump when unloading the truck. Because of the liquid that can transport the solid particles, the impurities in the cleaning operation have little effect on it. In the unloading process, just set a rotary piston pump to complete unloading, cleaning warehouse, pipeline venting, emptying cans and other oil pumping operations. As a result, the equipment and facilities such as the cleaning canister, the cleaning pump and the cleaning line are omitted, which not only saves the investment but also facilitates the operation and management. It is an ideal and economical new unloading technology. The unloading process has two options to choose from: First, all crane share a large flow rotary piston pump; the advantages of this program is investment in the province, less equipment, easy management. The disadvantage is that if the flow of the selected pump larger, then unloading the last one or two cars, due to lack of flow of the pump, may produce vibration and greater noise, mainly imported air into the pipeline to open the air to solve this problem . The program is suitable for unloading traffic between 100 to 200 m3 / h, unloading more time than the situation. Second, the pump is located under the trestle, according to a group of three crane, each with a small flow (60 ~ 80m3 / h) rotary piston pump. Unloading oil, all pumps can work simultaneously, which not only meet the requirements of large flow, fast unloading, unloading a train can be completed within three hours; and to avoid the unloading to the end, due to insufficient flow pump vibration problems. Suitable for unloading a short time, large flow and lift is not high.
