From the aerospace field, aircraft design to mining, seabed oil field exploitation, the application range of hydraulic pressure is really wide and deep. The use of hydraulic pressure in construction machinery such as roller and excavator can complete the "vigorous work" which is beyond human power in high rescue and fast. Although machine tools and controllers at the Atomic Energy Research Institute can perform a certain level of power work, they still use hydraulic pressure to control work similar to the human nervous system. Although at present compared with mechanical, electrical and pneumatic machinery, hydraulic mechanism is expensive. However, more and more high power, special structure and cheap hydraulic mechanism. Generally speaking, the price of hydraulic mechanism is higher, but it has the advantages of easy use, low maintenance cost, good safety and so on. Large hatches are provided on the decks of cargo ships for easy loading and unloading. The hatch must be sealed by watertight, airtight doors in navigation. The closed device, the hatch cover, is usually 20t or 30t. Before the Second World War, it was time-consuming and difficult to lift and close hatchcovers by crane. Cargo ships now use hydraulic cylinders, hydraulic motors and hydraulic torque hinges to fully open and close the hatch doors.

Equipped with hydraulic hatchcovers, ships need to be built 5% or 6% more expensive. However, given the savings in port and cargo costs, the extra cost of construction could be offset in a few years, and the crew's labor would be significantly reduced. So if equipped with a huge hatch cover, the first thing to consider is whether to use hydraulic lifting instead of a crane. This is an instance where hydraulic pressure has to be used. There are many similar applications on land and in mine-related enterprises. The higher the degree of need for hydraulic device, the faster and wider its application. If only "ease of use" is considered without in-depth consideration of equipment costs and maintenance costs, the hydraulic device used in this case is contrary to the example of hatch cover, which is difficult to popularize this kind of machinery and equipment.