What Is a Hydraulic Torque Wrench?
A hydraulic torque wrench is a torque wrench that can apply large force powered by hydraulic pressure.
Hydraulic torque wrench is mainly used for fastening large bolts because it can generate large torque with a small force.
Hydraulic torque wrench consists of three major parts.
- Hydraulic Piston
Converts the pressure energy of the hydraulic fluid into kinetic energy - Ratchet
Restricts the direction of movement to one direction using a tooth stop - Casing
Discharges oil efficiently
The hydraulic pump can also be used in explosion-proof areas by using an air hydraulic pump.
Applications of Hydraulic Torque Wrenches
Hydraulic torque wrenches are used in the following situations where medium to large bolts and nuts need to be tightened or loosened.
- Electric power generation facilities
- Petrochemical
- Ironworks
- Shipyards
- Shield tunneling
- Construction Machinery
- Construction of large structures
Shield tunneling, among others, takes advantage of the benefits of hydraulics, which can be used even when the power source is far away. The use of long hydraulic hoses makes it possible to tighten bolts underwater and flange bolts of submarine cables.
Principle of Hydraulic Torque Wrenches
Hydraulic torque wrench uses “Pascal’s Principle” which can generate large torque with a small force using hydraulic pressure.
1. What Is Pascal’s Principle?
Pascal’s principle is a law that states that when a certain amount of force is applied to a sealed container of liquid, the pressure is equal in all directions without decreasing the volume.
For example, suppose the pressure and cross-sectional area applied to a container are as follows
- Pressure: 1.0 MPa
- Cross-sectional area at input: 10 cm2
- The cross-sectional area of the output side: 100 cm2
In this case, the following torque is required to maintain the same pressure.
- Force required for input: 100 kg
- Force that can be output: 1,000 kg
Thus, since a large output can be obtained with a small input, a hydraulic torque wrench is used for automobile brakes and hydraulic jacks, as well as a hydraulic torque wrench.
2. Principle of Tightening Bolts and Nuts
Hydraulic torque wrench makes it easy to tighten bolts and nuts.
- Pressure is increased by hydraulic oil in a pressure pump.
- The hydraulic piston is moved by hydraulic pressure.
- The hydraulic piston pushes the push pawl (ratchet ball) linked to the ratchet, changing the force into a rotational force.
- The rotational force moves the ratchet.
At this time, the ratchet does not rotate to the specified torque in a single stroke but rotates approximately 30 degrees in each stroke. In addition, the ratchet mechanism includes a reaction plate, which moves only in one direction. Therefore, the bolt does not reverse when the piston returns.
Other Information on Hydraulic Torque Wrenches
1. Advantages and Disadvantages of Using Hydraulic Torque Wrench
- Small and lightweight, therefore easy to carry
- High tightening accuracy (accuracy within ±3%)
- Less noise during operation compared to impact wrenches, etc.
These are the advantages of using a hydraulic torque wrench. In particular, the low noise level during operation is a unique advantage of the hydraulic torque wrench. For example, when you want to excavate a tunnel at night on the ground, you are less likely to disturb the neighbors.
However, the hydraulic torque wrench has the disadvantage of slow working speed. However, it is possible to reduce the working time by connecting two units.
2. How to Use a Hydraulic Torque Wrench
- Connect a socket and a hydraulic hose to the hydraulic torque wrench and the hydraulic pump.
- Check the set pressure from the torque conversion table.
- Set the pressure of the hydraulic pump.
- Set the hydraulic torque wrench on the bolt to be tightened.
- Turn on the hydraulic pump.
- Tighten the bolt until it stops rotating.
A torque conversion table is often enclosed with the hydraulic torque wrench. If you do not have it, there are websites where you can convert units on the web.
Tightening is complete when the pressure rises to the set value but the ratchet does not turn. Insufficient tightening can cause accidents or injuries, so be sure to check the tightening.