What is a Hydraulic Jack?

A hydraulic jack is a jack that uses a plunger or a hydraulic cylinder as a rigid jack. It has the characteristics of compact structure, stable work, large support force and self-locking. The hydraulic jack has a strong supporting ability, and the heavy hydraulic jack has a supporting force of more than 100t.

The working principle of the hydraulic jack is shown in Figure 1.

1. Pump suction process

When the lever handle 1 is lifted by hand, the small piston is driven upward, and the sealed working volume in the pump body 2 is increased. At this time, since the oil discharge check valve 3 and the oil discharge valve 8 respectively close their respective oil passages, the working volume in the pump body 2 increases to form a partial vacuum. Under the action of atmospheric pressure, the oil in the oil tank opens the oil suction check valve 4 through the oil pipe and flows into the pump body 2 to complete an oil suction action.

Hydraulic jacks are divided into: general hydraulic jacks, special hydraulic jacks.

Universal hydraulic jack is suitable for various lifting operations with small lifting height. It consists of oil chamber, oil pump, oil storage chamber, piston, rocker, oil valve and other main parts. During work, as long as the crank is reciprocated, the manual oil pump continuously presses the oil into the oil cylinder. As the oil pressure in the oil cylinder increases continuously, the piston and the weight on the piston are forced to move upward together. Open the oil return valve, and the high-pressure oil in the oil cylinder flows back to the oil storage chamber, so the weight and the piston also fall together.

The special hydraulic jack is a special tensioning tool, which is used to make prestress

1) Before use, you must check whether each part is normal, mainly check whether the piston, joints, high-pressure hoses are leaking.

2) When using it, you must strictly abide by the provisions in the main parameters, and avoid excessively high overload. Otherwise, when the lifting height or lifting tonnage exceeds the regulations, serious oil leakage will occur on the top of the hydraulic cylinder.

3) If the amount of oil in the manual hydraulic pump is insufficient, the hydraulic oil that has been sufficiently filtered must be added to the pump before it can work.

4) The center of gravity should be selected properly. The jacking point of the jack should be selected reasonably. The bottom surface should be leveled. At the same time, the soft and hard conditions of the ground should be considered. The tough wood should be lined up.

5) After the jack lifts the weight, the support should be used to support the weight firmly.

6) If several jacks are required to lift at the same time, in addition to properly placing the jacks, it should also be noted that the load of each jack should be balanced and that the lifting speed should be synchronized to prevent the lifted object from tilting and causing danger.

7) When using a jack, place the hydraulic cylinder first, and then tighten the drain screw on the hydraulic pump to work. To lower the piston rod, loosen the handwheel of the manual hydraulic pump slightly in the counterclockwise direction, unload the hydraulic cylinder, and the piston rod will gradually descend. Otherwise, the descending speed will be dangerous.

8) The split jack adopts a spring return structure. After lifting, it can be quickly removed, but the connected hose cannot be used to pull the jack.

9) Because the lifting stroke of the jack is small, it must not exceed the rated stroke during use, so as not to damage the jack.

10) Avoid severe vibration of the jack during use (such as hitting the workpiece with a hammer when the jack is under load). ^[2]

1) If runaway occurs during use, first loosen the oil drain screw on the pump body, blow the vertical head of the pump body down a few times, and then tighten the oil drain screw to continue using.

2) When using, do not add eccentric load or overload to avoid the danger of jack damage. When there is a load, do not remove the quick connector to avoid accidents and damage to the parts.

3) The hydraulic jack uses oil as the medium, so the maintenance of oil and equipment must be done well to avoid clogging or oil leakage, which will affect the use effect.

4) For new or long-time hydraulic jacks, because there is more air in the hydraulic cylinder, the piston rod may have a slight jump phenomenon when it is used. The hydraulic jack can be reciprocated 2 to 3 times without load. Exhaust air from the cavity. The hydraulic jack that has been idle for a long time is hardened because the seals are not working for a long time, which affects the service life of the hydraulic jack. Therefore, when the hydraulic jack is not in use, it must be reciprocated 2 to 3 times a month without load. ^[2]

(1) The bottom of the hydraulic jack should be flat and tough when in use. Non-oil stained wooden boards to increase the pressure bearing surface and ensure safety. Do not use iron plates instead of wooden boards to prevent sliding.

(2) It is required to be stable during lifting. After the heavy weight is lifted, check for abnormal conditions. If there is no abnormal condition, continue to lift. Do not lengthen the handle arbitrarily or operate too aggressively.

(3) Not overloaded or super high. When a red line appears on the sleeve, it indicates that the rated height has been reached and the lifting should be stopped.

(4) When several hydraulic jacks work at the same time, they must be instructed by someone to make the lifting or lowering synchronous. Support wooden blocks between two adjacent hydraulic jacks to ensure space to prevent sliding.

(5) When using a hydraulic jack, always pay attention to the sealing part and the pipe joint part, and ensure that it is safe and reliable.

(6) Hydraulic jacks are not suitable for places with acids, alkalis or corrosive gases.