Many customers do not know what size hydraulic wrench should be used for the working conditions of the project, and how to determine the size of the hydraulic wrench. Now, Torcstark will go into detail on the question of what size hydraulic torque wrench should I use. Hopefully, through this tutorial, our users can easily determine the size of the hydraulic wrench they need.

Determining what size hydraulic wrench to use is a total of three steps. For the construction, maintenance and emergency repair of hydraulic wrenches in wind power manufacturing and installation, ship engineering, petrochemical, construction, electric power, mining, metallurgy and other industries, various and complex applications, each situation will affect the choice of the hydraulic wrench. Therefore, when choosing a hydraulic wrench, the following three steps are necessary.

## Determine the size of bolts and nuts

First confirm the size of the required bolt, the size of the opposite side of the nut and the strength grade of the bolt. The bolt and nut specifications are 1, 2, 3, or large-size models, and the sleeve size can be determined according to the hexagonal specification and model range of the nut.

## Determine the torque value required for bolt tightening

The torque size of the hydraulic wrench is the main parameter for selecting the wrench. According to the different torque sizes, it can be divided into various specifications and models. The torque of the bolt is different, the torque of the same bolt material is different, the torque of the same material is different under different working conditions, and the bolt torque is different for rolling mill machinery and chemical machinery equipment. You can choose according to the ready-made torque value and space size. The torque required for the tightening of the bolts on the general equipment is provided by the equipment manufacturer. If there is no torque value, it can also be calculated and selected according to the bolt specification and strength grade, referring to the recommended value in the “Bolt Specification and Torque Comparison Table”. Also, refer to the following tabular data:

 Strength Grade 4.8 6.8 8.8 10.9 12.9 Minimum breaking strength 392MPa 588 MPa 784 MPa 941 MPa 1176 MPa Materials General structural steel Mechanical structural steel Chrome molybdenum alloy steel Nickel-chromium-molybdenum alloy steel Nickel-chromium-molybdenum alloy steel BoltM （mm） NutS (mm) Torque Torque Torque Torque Torque (KGM) (NM) (KGM) (NM) (KGM) (NM) (KGM) (NM) (KGM) (NM) 14 22 7 69 10 98 14 137 17 165 23 225 16 24 10 98 14 137 21 206 25 247 36 353 18 27 14 137 21 206 29 284 35 341 49 480 20 30 18 176 28 296 41 402 58 569 69 676 22 32 23 225 34 333 55 539 78 765 93 911 24 36 32 314 48 470 70 686 100 981 120 1176 27 41 45 441 65 637 105 1029 150 1472 180 1764 30 46 60 588 90 882 125 1225 200 1962 240 2352 33 50 75 735 115 1127 150 1470 210 2060 250 2450 36 55 100 980 150 1470 180 1764 250 2453 300 2940 39 60 120 1176 180 1764 220 2156 300 2943 370 3626 42 65 155 1519 240 2352 280 2744 390 3826 470 4606 45 70 180 1764 280 2744 320 3136 450 4415 550 5390 48 75 230 2254 350 3430 400 3920 570 5592 680 6664 52 80 280 2744 420 4116 480 4704 670 6573 850 8330 56 85 360 3528 530 5149 610 5978 860 8437 1050 10290 60 90 410 4018 610 5978 790 7742 1100 10791 1350 13230 64 95 510 4998 760 7448 900 8820 68 100 580 5684 870 8526 1100 10780 72 105 660 6468 1000 9800 1290 12642 76 110 750 7350 1100 10780 1500 14700 80 115 830 8134 1250 12250 1850 18130 85 120 900 8820 1400 13720 2250 22050 90 130 1080 10584 1650 16170 2500 24500 100 145 1400 13720 2050 20090 110 155 1670 16366 2550 24990 120 175 2030 19894 3050 29890

Note:
1. The above is the German industrial standard. The torque value in the table is measured when the bolt reaches 70% of the yield limit.
2. The recommended tightening torque value is: the data in table × 80%. For example: M48, 8.8 grade bolt, the locking torque is: 400×80%=320KGM.
3. The loosening torque is 1.5~2 times the locking torque. For example: the tightening torque in the above example is 320KGM, then the loosening torque is about 320×(1.5~2)=480~640KGM.

After the bolt tightening torque is determined, select the corresponding hydraulic wrench. Generally, the tightening torque of the bolt does not exceed 70% of the selected hydraulic wrench. For example, if the bolt tightening torque is 6000NM, choose a hydraulic wrench with a maximum output torque of more than 8600NM, because the required torque is lower than 70% of the maximum torque value of the selected hydraulic wrench. However, if this torque needs to be loosened, you need to choose a hydraulic wrench with a maximum torque value greater than 9000NM.

## Determine which type of hydraulic wrench to choose based on working conditions

Hydraulic wrenches are classified according to the power form: according to different power forms, they are divided into electric, pneumatic, etc. According to its appearance, it can be divided into drive and bell hollow. The specific choice should be based on the working environment of different industries.

For Example

The drive hydraulic wrench drives the sleeve to work through the rotation of the drive shaft. One type of wrench can work with multiple sleeves, which is relatively widely used. However, in some small spaces, there are also cases where the hydraulic wrench of the drive shaft cannot be put in to cause interference. At this time, a low-profile wrench is used. The low-profile hydraulic wrench is composed of a power head and a working head. Due to its flat structure and the feature of being used directly on the nut, it is suitable for narrower spaces. A low-profile hydraulic wrench may be required in the following situations:

Five situations in which a low-profile hydraulic wrench is required

Low-profile hydraulic wrenches also have limitations. For example, some user units want to use one working head to achieve nut work under various working conditions. At this time, they will choose a bushing to increase the scope of use. However, increasing the spacer will increase the thickness of the working head, that is, the C value in the following figure will become larger:

This way the hydraulic wrench cannot fit over the nut. Moreover, two adjacent nuts with bushings are easy to break when used because the bushings are too thin. Generally speaking, a working head can only add two bushings at most, and sometimes only one bushing can be added. For example: the working head of the opposite side 80 can turn 80 to 70, and 80 to 65. Therefore, when using a hollow hydraulic wrench to add a bushing, you must understand the data of the working conditions in detail.

In some working conditions such as flange surface connection, using two or four synchronizations to work at the same time greatly improves the work efficiency, and the flange surface is evenly stressed, and some chemical equipment is less likely to leak.

## In the end

How to choose a suitable hydraulic wrench and improve the use effect of the hydraulic wrench is to choose different hydraulic wrenches according to the size of the user’s on-site working conditions. If you do not know the relevant data yourself, you can directly provide the working condition information to our sales manager, and we will recommend the most suitable hydraulic wrench for you.