Several Common Sealing Methods of Loading Arms
Regarding the sealing of loading arms, let's first take a look at the regulations on loading arm sealing. For example, in the "Design Code for Oil and Gas Recovery Facilities in Oil Product Loading Systems" (GB50759 - 2012), Article 3.0.1 states that "Loading systems for gasoline, naphtha, aviation kerosene, solvent oil, or oils with similar properties shall be equipped with oil and gas recovery facilities." Article 5.1.4 states that "The connection between the loading arm and the tank truck shall be tight, and no oil and gas leakage shall occur." In the "Emission Standard of Air Pollutants for Oil Storage Depots" (GB20950 - 2007), Article 4.1 requires that "The oil and gas generated during oil loading shall be sealed, collected, and recycled." Article 4.2 states that "The volume fraction of oil and gas emitted from any leakage point in the oil and gas closed - collection system shall not exceed 0.05%... (The probe is 25 mm away from the leakage point and moves at a speed of 4 cm/s)." These regulations require us to ensure that the loading arm is sealed without leakage when using it, which is also for the safety of workers, the safety of equipment, and environmental requirements. Now, let's learn about several common sealing methods of loading arms.
I. Mechanical Sealing
Mechanical sealing is a relatively common sealing method for loading arms. It uses two relatively moving sealing surfaces (a rotating ring and a stationary ring) that fit tightly together, and an extremely thin liquid film is formed on their joint surface to achieve the purpose of sealing. There are mainly five leakage points in mechanical sealing, including the seal between the shaft sleeve and the shaft, the seal between the rotating or stationary ring and the shaft sleeve, the seal between the rotating and stationary rings, the seal between the stationary ring and the stationary ring seat, and the seal between the sealing end cover and the pump body. These sealing points mainly use sealing elements such as PTFE gaskets, O - rings, or bellows to achieve sealing.
II. Plate - Type Sealing Cap Sealing
For the closed - loading loading arms of railway tank cars, plate - type sealing cap sealing is a commonly used sealing method. The plate - type sealing cap is pressed tightly by the power of a cylinder to fit closely with the tank car opening, meeting the requirements of closed - loading. There are various forms of pressing power structures. For example, the axial pressing force can be provided by the self - weight of the sealing cap, the axial stress can be directly applied by the cylinder on the top of the sealing cap, or the axial tension can be provided by the cylinder - driven three - jaw hooks using the inner wall of the tank car. However, the closed - loading loading arms with three - jaw hook structures have a relatively high failure rate during daily use. Therefore, in practical applications, it may be necessary to consider other more reliable sealing methods.
III. Air - Bag Expansion Sealing
In response to the problems existing in the three - jaw hook - type loading arm sealing device, an improvement plan proposes to transform the sealing device into a system with a small alignment device, which uses an air source to inflate the air - bag for expansion and seals at the straight - pipe section of the tank car opening. This method can reduce the use of transmission systems such as three - jaw hooks, simplify the operation procedure, and enhance the flexibility and tightness of the sealing system through internal sealing, achieving the purpose of preventing oil splashing and the formation of explosive combustible gases.
IV. Other Sealing Methods
In addition to the above - mentioned common sealing methods, loading arms may also use other sealing methods, such as magnetic sealing and packing sealing. These sealing methods each have their own characteristics and are suitable for different usage scenarios and medium properties.
In conclusion, there are various sealing methods for loading arms. The specific choice of which method needs to be comprehensively considered based on factors such as the design of the loading arm, the usage scenario, and the properties of the medium. In practical applications, the effectiveness and reliability of the sealing method should be ensured to guarantee production safety and environmental protection.
