Learn How Hydraulic Jacks Work & A Buying Guide

In a?hydraulic jack, fluid pressure multiplies force in a cylinder in order to lift a heavy load. They use Pascal’s law to lift the heavy load, which requires a smaller input force to lift heavy objects. They have a broad range of applications: machine shops, automobile industry, material handling equipment, lifting platforms, railway, hydropower plants, etc. Hydraulic jacks can be automatic or manual. Unlike manual hydraulic jacks using hand power, automatic hydraulic jacks utilize air or electric power. However, the operating principle is the same.

Hydraulic jack operating principle

Hydraulic jacks are based on Pascal’s law. The law states that a pressure change at any point in an enclosed incompressible fluid transmits?throughout the fluid such that the same change occurs everywhere. This law also governs the hydraulic press and the braking system for most vehicles.

Bottle jacks:?

These?bottle jacks?are designed for lower clearance applications. They can operate in both vertical positions in lifting loads and horizontal positions in splitters and bearing/shaft removal with a large base area for strength and stability.

Hydraulic floor jack:

The?hydraulic floor jack, or trolley jack consists of a horizontal piston pushing the short end of a bell crank. The bell crank’s long arm connects to the lift pad providing vertical motion of the load. The long arm is connects to the castor and wheel to compensate for the arc motion. The horizontal cylinder and piston allow the floor jack to operate with a low profile and easy to maneuver under load, such as a vehicle.

Hydraulic bottle jack?vs floor jack

Hydraulic bottle jackHydraulic floor jackVertically positioned cylinder for higher liftHorizontally positioned cylinderPortability by being carriedPortable with casters for easy rollingSmall and be fitted into tight cornersBulky and requires more spaceProfile not as low as floor jackLower profileTypically shorter handlesLonger handles for easier operationNot as stable as floor jackHigh stability

Selection criteria

There are several specifications of a hydraulic jack to consider when deciding which is best for you and your application. Here are some guidelines that you may find useful:

1. Load capacity:The lifting load capacity is the most crucial parameter.
2. Clearance:Check to see that the hydraulic jack can fit under the load. The hydraulic floor jack offers the lowest profile of the two main types. If it is a side lift, you can also consider the toe type bottle jack.
3. Lift height:The telescoping bottle jack extends the lift height of a standard bottle jack, but with a lower lifting capacity.
4. Orientation:Consider if the hydraulic jack is for vertical lift, horizontal push, or both.
5. Automatic or manual:A heavy-duty hydraulic bottle jack operates with air or electric pumps.?An automatic hydraulic jack replaces the manual hand lever with a powered pump. The general principle remains as described in the article.

Things to be cautious of

The correct use of equipment such as hydraulic jacks is important. Consider the following in addition to the selection criteria:

• First, do not exceed the maximum lifting weight in tons. Overloading can damage the cylinder casing or cause leakage of the hydraulic fluid. However, the design of some hydraulic jacks has a fail-safe valve if maximum pressure is exceeded.
• Second, there must always be sufficient oil in the reservoir. Else, the maximum pressure of the hydraulic jack will not be reached.

A leakage in the cylinder during operation can lead to a fatal accident. Check the manufacturer’s instruction on preventive maintenance.