What are the consequences of incorrect use of hydraulic jacks?

What are the consequences of incorrect use of hydraulic jacks?
 The wrong way of using Jack will do great harm to jacks and even people. First of all, we will understand the working principle of hydraulic jack.           

 1.Pump suction process           

When the lever handle 1 is lifted by hand, the small piston is started up and the sealing capacity of pump body 2 increases. At this time, because the oil drain unidirectional valve 3 and the oil drain valve 8 say goodbye to shut down the oil pipeline at their respective locations, the increase of the working volume in pump body 2 caused a part of the vacuum successfully. Under the action of atmospheric pressure, the oil in the tank opens the oil suction one-way valve 4 through the tubing and flows into the pump body 2, thus completing the oil suction behavior once.          
 2.  Pump Pressure and Heavy Lifting Process           
 When the lever handle L is depressed, the small piston is driven down and the working volume of the small oil chamber in pump body 2 decreases. Then the oil in the small oil chamber is squeezed out, and the one-way oil draining valve 3 is pushed aside (at this time, the one-way oil suction valve 4 automatically closes the oil passage to the oil tank). The oil enters the hydraulic cylinder (oil chamber) 11 through the oil pipe, because the hydraulic cylinder (oil  chamber) 11 is also a seal. Because of the working volume, the hard work of the incoming oil due to extrusion will push the big piston up and lift the heavy load to do work. Repeated lifting and pressing lever handle can make the weight keep rising and reach the lifting target.           
 3.  The process of falling heavy objects           
 When the large piston is required to retreat downward, the release valve 8 is opened (rotated 90 degrees), and the oil in the hydraulic cylinder (oil chamber) 11 flows back to the tank 5 under the action of the weight of the heavy object, and the large piston falls to its original position.           
 Through the working process of hydraulic jack, we may summarize the working principle of hydraulic transmission: oil as working medium, through the change of sealing volume to convey activities, through the internal pressure of oil to convey power. Hydraulic transmission device is essentially an energy conversion device.           
 Accurate use of hydraulic jacks will require the car to stop, pull up the hand brake, manual gear into gear 1 or reverse, and automatic gear into gear P. After that, the jack must be used on the tough and flat road surface. If the jack is used on the soft ground, such as mud road or sand road, it is suggested to use wooden or stone pad under the jack before the jack is used to reduce the  pressure, so as to prevent the jack from falling into the soft ground.            
 The wrong maintenance point will damage the chassis. Many car owners have never used or personally changed spare tires, nor carefully read the vehicle footnotes on the use of jacks and maintenance points of the introduction.           
 According to reports, the bottom of the body has a special maintenance point to maintain the hydraulic jack. The maintenance point of the family car is usually in the  inside of the side skirt, like two fins on both sides of the chassis, which is controlled by 20 cm at the back of the front wheel and 20 cm at the front of  the rear wheel. This fin is protruded from the chassis steel plate, may wish to receive a large control pressure, if the jack is supported on the chassis steel  plate, it is likely to cause unnecessary damage to the chassis. In addition, it is imprecise to maintain on the hanging lower arm. If the hydraulic jack slips and the vehicle falls down, the chassis and the jack will all be damaged.           
 The Jack rocker arm of many household cars is of separate structure. It needs to rotate after connecting with the matching wrench and sleeve. Therefore, in the process of lifting the jack, it is necessary to exert equally, and avoid overexertion or overexertion.