Views: 266 Author: Site Editor Publish Time: 2021-06-17 Origin: Site
The sealing device is the most basic and most important device to ensure the normal operation of hydrostatic drive systems, and is mainly used to prevent the leakage of liquid or gas. A good seal is the guarantee that the hydraulic transmission system can transmit power and work normally. If the seal is not good, it will cause the leakage of the system and components, reduce the system efficiency, and cause energy loss. In severe cases, it will cause the oil of the hydraulic system to leak and pollute the environment. Therefore, the right design of the sealing form of connecting pipe joints of automatic transmission hydraulic system is very important.
The hydraulic power transmission system sealing device should have good sealing properties, that is, have suitable elasticity, can compensate for the manufacturing errors of the sealed surface and wear during work, and automatically improve the sealing degree as the pressure increases.
In addition, the hydrostatic drive transmission system sealing device should have good stability, that is, the effect of oil immersion on its shape and size changes should be small, and the effect of temperature on its elasticity and hardness should be small.
What's more, the hydraulic mechanical transmission system sealing device should be with low friction, flexible movement and long working life. And it should also have features of simple structure and easy to manufacture, use and maintain.
2 Main Materials of Seals
Commonly used hydraulic system sealing materials are as nitrile butadiene rubber, fuorine rubber and silicone rubber.
In the hydraulic power transmission system of the main engineering machinery product, the common oil ports that match the pipe joints have the following types.
1) 15° Internal Chamfered Oil Port
The 15° internal chamfered oil port type is commonly used in the design of the pump and motor oil inlet and outlet ports in the hydraulic pipeline. The thread form is determined by the pump and motor manufacturers according to different standards, including ISO 6149-1 , ISO 11926-1 and JIS B2351 standard, and the sealing form is O-ring sealing.
2) Flat Oil Port Structure
This kind of oil port is commonly used in the design of statically sealed oil inlet and outlet ports such as valves, confluence blocks, hydraulic adapter and pumps in hydraulic pipe fittings. The machining process is relatively simple compared to the 15° internal chamfering of the oil port. Only after the internal thread is processed, the oil port is flattened with a shallow sink to ensure the verticality requirements between the pipe joint and the oil port sealing surface.
3) Tapered Pipe Threaded Seal Port Structure
The imperial 55° threaded angle cone pipe threaded oil port structure is also called the oil port sealed with threads. The limit size and tolerance of this thread meets the requirements of GB/T 7306. When connecting with pipe joints, no packing or sealing medium is required to prevent leakage.
The limit dimensions and tolerances of the American-made 60°conical pipe threaded NPT seal oil port structure comply with GB/T 12716. It is mainly used for oil and lubricating oil pipeline joints. It is also suitable for high temperature and high pressure hydraulic mechanical transmission systems.
