What is Difference Between Hydraulic Jacks and Mechanical Jacks
(Last Updated On: March 3, 2022)
What is a mechanical jack?
Mechanical jack, also known as screw jack, is driven by manpower through a screw pair, and the screw or nut sleeve is used as the jacking member. Ordinary screw jacks support heavy objects by thread self-locking and have a simple structure, but low transmission efficiency and slow return. The thread of the self-lowering screw jack has no self-locking effect and is equipped with a brake. Release the brakes, and the heavy objects can descend quickly on their own, shortening the return time. But the structure of this jack is more complicated. The screw jack can support heavy objects for a long time, and the maximum lifting capacity has reached 100 tons, which is widely used. After the horizontal screw is installed on the lower part, it can also make the heavy objects traverse a small distance.
What is a hydraulic jack?
Hydraulic jack refers to a jack that uses a plunger or a hydraulic cylinder as a rigid jacking member. It has the characteristics of compact structure, stable operation, large top support, and self-locking. The hydraulic jack has a strong supporting capacity, and the supporting force of heavy hydraulic jacks exceeds 100t.
The difference between mechanical jacks and hydraulic jacks
Mechanical jacks and hydraulic jacks are two types of jacks that are widely used at present. The two types of jacks have different working principles and application areas. People often ask such a question, what is the difference between a mechanical jack and a hydraulic jack? Can they be used interchangeably? Let us discuss this issue in detail below.
We take the screw jack, the typical representative of the mechanical jack, as an example to compare it with the hydraulic jack. The screw jack is driven by manpower through the screw pair, and the screw or nut sleeve is used as the jacking member. Ordinary screw jacks support heavy objects by thread self-locking and have a simple structure, but low transmission efficiency and slow return.
The thread of the self-lowering screw jack has no self-locking effect and is equipped with a brake. Release the brakes and the weight will drop on its own, which shortens the return trip time. However, the structure of this jack is more complicated. The screw jack can support heavy objects for a long time, and the lifting capacity has reached 100 tons, which is widely used.
The hydraulic jack is driven by a hydraulic pump, which can be driven by manpower or electricity, driven by a hydraulic system, and uses a cylinder or a piston as a jacking member. Hydraulic jacks can be divided into integral and separate types. The integral type is that the pump is integrated with the hydraulic cylinder, and the separate type is that the pump is separated from the hydraulic cylinder but connected by a high-pressure hose. The hydraulic jack has a compact structure and can lift heavy objects smoothly. Its lifting capacity has reached 750 tons and the transmission efficiency is high, so it is widely used. However, it is easy to leak oil and is not suitable to support heavy objects for a long time.
In conclusion, mechanical jacks can be used to support heavy objects for a long time, but the transmission efficiency is relatively low. Hydraulic jacks cannot support heavy objects for a long time, but the transmission efficiency is relatively high.
Application scope of mechanical jack:
It can be used for railway vehicle maintenance, mine, construction engineering support, and general heavy lifting and lowering.
Application scope of hydraulic jack:
Electric power maintenance, bridge maintenance, lifting of heavy objects, static pressure piles, foundation settlement, bridge and transmission construction, especially in highway and railway construction, and mechanical adjustment, equipment dismantling, etc.
Example: Why do bridges swivel and buildings use hydraulic jacks instead of mechanical jacks?
Regarding the jacks used in engineering, anyone who has studied this area should know that mechanical jacks have a very good pressure holding capacity due to mechanical principles, and can be in a high load state for a long time without causing excessive losses. Therefore, it is often used for long-term jacking support during bridge maintenance.
Most hydraulic jacks work more efficiently and are more convenient to use. But there is one point, that is, it does not have a strong pressure-holding ability, and it is difficult to support heavy objects for a long time. But you should have paid attention to such a problem: most bridge swivels and building translations use hydraulic jacks instead of mechanical jacks. Why?
It is not difficult to understand this point. First of all, we need to know that the hydraulic jacks used in such large projects are special kinds of hydraulic jacks, that is, synchronous hydraulic jacks. The key point is “synchronization”. Because in projects such as building translation, it is absolutely impossible to use the jack alone, but multiple hydraulic jacks are used to lift the entire building.
The synchronous hydraulic jack adopts the design of the diverter valve, that is, multiple hydraulic jacks are controlled by one switch, so that the hydraulic oil flows to the hydraulic device of the jack synchronously, so as to realize synchronous lifting and ensure the stable lifting of the building. The fluid is easy to achieve synchronization effect, but to achieve the consistency of lifting through the screw drive, it needs to consume more hardware facilities. Obviously, mechanical jacks are inferior to hydraulic jacks in this regard.
Therefore, when it comes to the lifting and translation of the larger building as a whole, the hydraulic jack can play its own advantages, while the mechanical jack can play its own role in the long-term support.
The main difference between hydraulic and mechanical jacks is durability. TorcStark believes that screw jacks are the most suitable when long-term lifting is required, such as bridge maintenance. For building translation and synchronous jacking, hydraulic jacks are the first choice.