In the process of using hydraulic torque wrench, there will always be some small problems that need to be known and solved. So what are the common problems with hydraulic torque wrenches? TorcStark summarizes some problems with hydraulic torque wrenches to help you use it better.

## How to calculate the torque output of a hydraulic wrench?

In the process of using the hydraulic wrench, it mainly relies on the power source provided by the working head to work, and the working head generally consists of three parts: frame, oil cylinder, and transmission parts. The three interact with each other and complete the work through coordination and cooperation.

Correct calculation of the output torque of a hydraulic wrench requires an understanding of the its working principle. The oil cylinder generally outputs force. The piston rod of the oil cylinder and the transmission part form a motion pair, and the reference for the distance of the hydraulic wrench to amplify the arm force is the distance from the center of the oil cylinder to the center of the transmission part. When calculating the actual output torque of the hydraulic wrench, you should be familiar with the basic formula, that is, the output torque of the hydraulic wrench = the output of the cylinder x the arm.

In addition, when calculating the actual output torque of the hydraulic wrench, it is necessary to pay attention to some influencing factors, such as frictional resistance, consumption force, etc. In the actual calculation, the actual output torque of the hydraulic wrench is less than the theoretical output torque.

You can also check the torque output table of the hydraulic wrench to quickly help you find the output torque value of the corresponding hydraulic wrench.

## How to use the pressure-torque comparison table of hydraulic wrench?

The specific method is as follows:

First of all, when using a hydraulic torque wrench, we need to convert the corresponding torque value first, so that the tightening or loosening of the bolt can be completed accurately and quickly. Unit conversion method of hydraulic wrench:

According to the design torque setting of the equipment, most equipment will give the specific torque value of the bolt in the product technical parameters, which is the set torque. If the design torque is not indicated in the technical parameters, it is often impossible to obtain the specific design torque during the renovation and maintenance of the old equipment. For the consideration of equipment and personal safety, it is recommended to refer to the hydraulic wrench torque and pressure comparison table to set the torque.

Set torque = (recommended table data) × (80% ~ 90%), for example: for grade 6.8 M100 bolts, the recommended pretightening force in the table is 20090N.M, then the set torque is 20090×80%=16072N. M. For recommendations, please refer to TorcStark’s “Recommended Table of Torque Values ​​for Bolts and Nuts”.

Next, according to the calculated torque value of 16072N.M, find the corresponding hydraulic wrench pressure in the pressure and torque comparison table. If you purchased a TorcStark hydraulic wrench and the torque value is 16377N.M, you can find the corresponding pressure in the TorcStark hydraulic wrench pressure and torque comparison table.

If the set torque is the imperial unit ft.lbs, you can check the imperial torque comparison table in the hydraulic wrench pressure comparison table. (Hint: 1MPa=145Psi; 1Psi=0.007Mpa; 1ft.lbs=1.3549N.M)

## What is the method of converting torque and pressure of hydraulic wrench?

nm is the torque unit, and psi is the pressure unit. There is no direct correspondence between the conversion of nm to psi in the hydraulic wrench, and a distance value is required for conversion. In the hydraulic wrench pump station, the output pressure is converted into torque output, which is accomplished by pushing the piston through the pressure action wrench cylinder. As for the specific nm conversion to psi, generally TorcStark will provide the “pressure-torque comparison table” of the hydraulic wrench to the user, and the user can find out the corresponding required psi value according to the torque value.

The method of torque and pressure conversion of hydraulic wrench:

1. Known conditions: bolt tension F, bolt diameter M

Calculate the torque value N.m required for the bolt: torque value Nm=F(KN)×M(mm)×factor 0.16

Assumption: The bolts require a pulling force of 70 tons, and the bolts are M52

2. Calculation:

(70×9.8)KN×52mm×0.16(coefficient)=5707.5Nm

## What should be paid attention to in the identification of hydraulic wrenches?

The importance of identifying hydraulic wrench torque:

Generally speaking, the nominal torque accuracy of a hydraulic wrench is ±3%, and if it is less than ±3%, the accuracy is not enough. If the deviation of torque accuracy is too large, the actual pretightening force acting on the bolt will be lower, and the pretightening effect will be worse. This is very likely to cause safety hazards to the operation of field equipment, especially in some industries with extremely high requirements. For example, when the wind power equipment is installed and pre-tightened, if the bolts are in a loose state, it may cause the blades, hubs, towers, etc. to fall and collapse due to the influence of gravity, wind force and mechanical rotation! In the petrochemical industry, there will be leakage accidents if serious, so it is very important to carry out the torque identification of the hydraulic wrench.

Precautions for identifying torque of hydraulic wrench:

First of all, you must choose a reliable and authoritative measurement department to ensure the accuracy and validity of the identification results, but the cost is usually high. Second, you must choose a reliable identification instrument. The accuracy of the identification instrument itself is higher. For an identification device with an accuracy of 3%, the identification result must be more than 1% accurate to be reliable. If the accuracy of the identification instrument is less than or equal to the accuracy of the equipment being identified, the identification is invalid. Therefore, when choosing a hydraulic wrench torque testing instrument, you should pay attention to whether the accuracy of the selected equipment is appropriate. Due to the high cost of the third-party testing agency, if the hydraulic wrench you are currently using is frequently used and the internal wear is relatively serious, it is recommended that you pass the inspection of the manufacturer after maintenance, and then, if necessary, You can request a third-party review.

## How to Calibrate a Hydraulic Torque Wrench?

Notes on calibrating the torque of hydraulic wrenches:

Before using the torque calibration instrument, adjust the standard device and zero the hydraulic wrench pressure gauge. According to the size of the socket of the hydraulic wrench, select the adapter used for the connection. Connect the torque sensor, the machine adapter of the workbench and the hydraulic wrench, and fix them on the same axis, and determine the calibration direction of the hydraulic wrench and whether the reaction arm is stable and safe, so as to ensure that the three will not move relative to each other during the force application process. Then, start loading for verification.

The method of torque calibration of hydraulic wrench:

Select the correct torque sensor range according to the rated torque value of the hydraulic wrench. Apply to the rated torque value step by step according to the selected verification point, and record the torque value of each point. Carry out each procedure at least 3 times, remove the load after reaching the rated torque value each time, check the zeroing condition of the standard device and the hydraulic wrench indicator, and then continue after resetting to zero.

## What is the difference between the hydraulic wrench pressure-torque comparison table and the bolt pre-tightening force recommendation table?

[Hydraulic wrench pressure-torque comparison table]: Its main purpose is to find the corresponding pump station pressure value for the output torque value of the purchased hydraulic wrench. The premise is that the user knows the pretightening force of the required bolts, but does not know how much pressure the hydraulic wrench pump station should adjust. However, due to the different models of hydraulic wrenches of various brands, the [Hydraulic Wrench Torque Comparison Table] is also different, and the specifics should be determined according to the model of the purchased hydraulic wrench.

[Recommendation table of bolt pre-tightening force]: It is a comparison table of the recommended value of bolt pre-tightening force based on bolts of different materials, different strength levels and different specifications. Before comparing this table, the user needs to know the material, specification and strength of the bolt, and then check the table to find the required torque. Or when the bolt is unlocked on site, there is no exact torque requirement, and a reference value can be obtained according to this table for operation. After checking the [bolt pre-tightening force recommendation table] to determine the pre-tightening force, it is necessary to adjust the pressure of the pump station according to the [hydraulic wrench pressure-torque comparison table] for operation.

The difference between the two can be summed up in one sentence: if you don’t know the pretightening force, you can find the “bolt pretightening force recommendation table”, and if you don’t know the pressure, you can find the “hydraulic wrench pressure-torque comparison table”.

## What is the difference between a drive hydraulic wrench and a hollow hydraulic wrench?

The difference between the drive hydraulic wrench and the hollow hydraulic wrench: mainly lies in the difference in appearance, shape, working conditions and use. The drive hydraulic wrench has a large volume. As long as the height, space and operating radius are determined, the corresponding socket can be directly equipped according to the torque value and the specification of the bolt and nut, and its use range is relatively wide. The hollow hydraulic wrench is composed of a working head and a power head, and is equipped with a transition insert for use. It is generally used in the conditions of long screw extension, double nut, too small bolt spacing, too small nut and equipment wall, or in some specific industries. When you choose a hydraulic wrench, the specific hydraulic wrench you need depends on the working conditions on site.

## How to choose a hydraulic wrench?

1. According to bolt specifications: there are generally several specifications, such as M36, M42, M48. If you don’t say what’s the size of the nut, it is the opposite side of the matching socket of the metric bolt and nut pair. The hexagon opposite side of the nut is 55 for M36, 65 for M42, and 75 for M48. If the bolt size span is too large and the torque span is large, then two types of wrenches must be used to pretighten these bolts.

2. According to the bolt torque, bolt and nut space position: if there is no space limit, any type of wrench can be used: it is more economical to choose a drive hydraulic wrench. If the thread exposed after the bolt is screwed is long or the space above the bolt is limited, it is best to use a hollow hydraulic wrench. If the distance between the nuts is narrow, a hollow hydraulic wrench can be used.

3. Other precautions: One type of hydraulic wrench can only solve several similar bolts, generally with 1-10 sockets. For manufacturers who are not sensitive to cost, it is best to use one electric pump with two wrench heads, which can be used diagonally, which can improve the efficiency and make the torque more accurate. The hydraulic wrench must be used and kept by a special person, and it must be maintained regularly, such as oil change, cleaning, etc. The bolt torque standard shall be subject to the national standard.

## How to solve the problem that the hydraulic wrench cannot reach the predetermined torque value?

1. Use the exclusion method first. Remove the oil pipe and start the hydraulic wrench pump. Press and hold the work button of the handle, adjust the overflow valve clockwise to see if the working pressure of the pump station can be adjusted to 70Mpa, and observe whether the pointer of the pressure gauge vibrates. If everything is normal, the problem with the pumping station can be ruled out. If the pressure cannot be adjusted up, or the pointer of the pressure gauge vibrates severely, it is initially determined that it is either a problem with the overflow valve or the plunger is worn.

2. If there is no problem with the pump station, check whether the hydraulic wrench has oil leakage. If there is no oil leakage, disassemble the hydraulic wrench to see if the internal piston has internal leakage. If leaks are found, replace the seals. If not, the problem of the hydraulic wrench can be ruled out.

3. Next, check whether the male and female connectors on the hydraulic wrench or hydraulic pump station are reversed. If the connectors are reversed, even if the pressure of the pump station is increased, because the oil pipe is reversed, the oil inlet is connected to the oil return port, so the hydraulic wrench always works under the low pressure working pressure. Therefore, the hydraulic wrench rotates when it is not loaded, but once it is on the bolt, it will either not rotate or the torque value will not be reached.

## What are the advantages of hydraulic wrenches?

1. Large output torque. Compared with traditional wrenches, the output torque of hydraulic wrenches is several times or even hundreds of times, which can meet the pre-tightening and loosening of most specifications of bolts on the market;

2. The torque accuracy is guaranteed. Some industries have requirements for torque accuracy, and hydraulic wrenches can ensure torque accuracy;

3. Replace manual work. With the continuous increase of labor costs, a hydraulic wrench can now replace the workload of the previous few people;

4. Safety is guaranteed. In the past, people either used a sledgehammer, a crane, or a forklift when bolting, which brought great safety hazards to the on-site operation;

4. It can meet the working conditions of narrow space. For some bolts with limited space, ordinary wrenches cannot be put in, but hydraulic wrenches are competent enough, which not only saves time and effort, but also improves efficiency and ensures torque.

## How to use a hydraulic torque wrench?

### I. Inspection before operation:

1. Electric hydraulic pumps shall not be used in flammable and explosive environments, but pneumatic hydraulic pumps shall be used;

2. Check that the operating voltage of the electric pump should meet 220V;

3. Check the pressure adjustment, filtering and fuel injection triple device of the hydraulic wrench pump. Carry out drainage, add 46# anti-wear hydraulic oil, and adjust the intake pressure;

4. Check that the oil level of the oil indicator of the hydraulic pump is above the 0 line, and the hydraulic oil is clear and transparent. Special hydraulic oil should be added, and it is strictly forbidden to mix other oils;

5. Check whether the ultra-high pressure hose has any damage such as bending. When connecting, straighten out the hose and do not get tangled. Wipe the plug and socket clean of dirt, and insert the quick connector to the end to ensure reliable connection. And lock the threaded sleeve by hand, otherwise the one-way valve in the quick-release joint will not be able to supply oil normally if the one-way valve is not opened.

### II. The correct operation steps of the hydraulic wrench:

1. Wire-controlled switch button function: Press the RUN button to advance the cylinder. Release the button, the cylinder will reset automatically. Press the STOP button to stop the oil pump.

2. Before starting the hydraulic pump, first open the loosening and pressure regulating valve, and then turn on the power “ON”. Check whether the hydraulic pump is running normally. Then press the wire control button several times to make it run for a few minutes, and adjust the pressure to the desired value. The rated pressure is 70Mpa.

3. When adjusting the pressure, press and hold the remote control button. When the wrench “clicks” is heard, the quick release lever jumps down, the wrench stops turning as it is in place, and the pressure gauge rises rapidly from 0. Use the other hand to slowly adjust the pressure regulating valve upward and lock it with the lock nut.

4. When idling, put the hydraulic wrench on the ground, press the RUN button, and the wrench starts to rotate. When you hear a “click” sound of the wrench, the wrench is in place and stops turning. At this time, release the button, and the wrench will automatically reset. When you hear a “click” sound of the wrench again, the reset is complete. Repeat several working cycles, and if the wrench rotates without abnormality, put the wrench on the nut for work.

5. Loosen the nut: adjust the pressure of the hydraulic pump to a maximum of 70Mpa, confirm that the wrench is turned in the direction of loosening, find the reaction fulcrum and hold it firmly, and repeat the working cycle of the cylinder forward and backward. If the nut cannot be removed, take rust removal measures. If it still cannot be removed, use a larger hydraulic wrench.

6. Tighten the nut: check the pressure-torque comparison table to determine the pressure setting of the hydraulic pump, confirm that the wrench is turned in the tightening direction, find the reaction fulcrum and hold it firmly, and repeat the working cycle of the cylinder forward and backward until the nut does not move.

7. When the hydraulic torque wrench is stopped, turn off the power in time.

8. After the work is completed, disconnect the power supply, press the pressure relief valve to remove the residual pressure of the system, fully open the pressure regulating valve, and then disassemble the oil pipe;

When carrying the wrench, the oil pipe must be removed.

## What are the models and configuration schemes of hydraulic wrenches for petrochemical maintenance?

Model of hydraulic wrench for petrochemical maintenance: Generally speaking, the specifications of the bolts used in petrochemical maintenance are basically M24 to M80, the pretightening torque is from several hundred Nm to tens of thousands of Nm, and the disassembly torque may require a maximum of tens of thousands of Nm, so both drive hydraulic wrenches and hollow hydraulic wrenches are used. However, the specific type of hydraulic wrench to be used should be determined according to the actual working conditions on site.

Configuration scheme of hydraulic wrench for petrochemical maintenance: At the construction site, considering the construction progress and construction period, some small-sized and non-critical flange bolts will be pre-tightened with a manual torque wrench or an electric torque wrench. Those larger and more important flange bolts are pre-tightened with hydraulic wrenches. In the hydraulic wrench configuration scheme, considering a large number of flange bolts on site and the ease of operation, the hollow hydraulic wrench is generally configured as the main, and the large torque driving hydraulic wrench is supplemented. Usually it is a two-synchronized configuration, and some also require a four-synchronized hydraulic wrench configuration.

## What are the materials of hydraulic wrench sockets?

The function of the hydraulic wrench socket: The hydraulic wrench socket is mainly used to drive the hydraulic wrench. As long as the torque range of the drive hydraulic torque wrench allows, the corresponding sockets can be replaced to complete the pre-tightening or loosening of bolts of different specifications. Its range of use is relatively broad.

Hydraulic wrench socket material: There are three commonly used materials, mainly chrome-molybdenum steel, chrome-vanadium steel, and 45-gauge steel. Chromium-vanadium steel is an alloy tool steel with chromium-vanadium alloying elements, mainly used for hand tools. No. 45 steel is mainly used in machinery manufacturing, although its mechanical properties are better, but its hardness is poor. Chromium-molybdenum steel, also known as temperature-resistant hydrogen-resistant steel, is an alloy of chromium, molybdenum, iron, and carbon. With its special high-quality properties, it is often used to manufacture high-temperature and high-pressure-resistant valves and pressure vessels.

## What are the factors that affect the service life of hydraulic wrenches?

1. Hydraulic wrenches are used frequently and for a long time.

2. The hydraulic oil is not changed frequently or wiped frequently, so that the surface is covered with dust or oil.

3. The working environment used. The surrounding environment should be kept as clean and tidy as possible to prevent fine oil fume, dirt and dust from entering the hydraulic wrench.

4. The operation method is unreasonable, resulting in the failure of the hydraulic wrench.

5. Hydraulic wrench maintenance is not guaranteed. In the case of using hydraulic wrenches, the experienced operators will generally carry out a simple inspection to find out if there is any problem with the hydraulic wrench, but many people do not care about the maintenance or ignore the maintenance. This can lead to the destruction of the hydraulic wrench during the entire application process.

5. The daily maintenance and periodic maintenance are not timely. Failure to solve the fault on time, or replace the damaged components in time, lead to the re-failure of the hydraulic wrench application.

## Three stages of hydraulic wrench wear

1. Initial wear: During the production process of hydraulic wrench parts, the surface of some parts will be uneven. When the metal surface moves relative to each other, the hydraulic wrench parts move at a relatively high speed. At this time, subtle conflicts will occur, resulting in initial wear;

2. Normal wear: When the hydraulic wrench is connected to the hydraulic wrench pump for a period of running-in work, it will enter a relatively long stable operation stage, which is called the normal wear stage;

3. Abnormal wear stage: At this time, each component has reached its service life. Under the environment of high temperature and high pressure, the metal surface will fall off in granular form. The longer the wear time, the failure of the component will occur.

## What should we do if the hydraulic wrench does not turn?

### I. Reasons why the hydraulic wrench does not turn:

1. The drive frame of the hydraulic wrench and the ratchet are stuck;

2. The ratchet and pawl are stuck;

3. The drive frame spring does not return.

### II. Analyze the cause of the failure:

When the operator presses and holds the right button of the remote control, the oil enters the wrench and the drive shaft starts to rotate. When the wrench shaft stops turning, release the button and you will hear a “tick” sound. When the sound stops, the wrench reset is complete. The normal operation is to repeat the above actions to start the work cycle. If you release the button without hearing a “tick” sound during the operation, it is easy to get stuck when you repeat the cycle. In addition, it may get stuck due to normal wear.

### III. How to deal with the hydraulic wrench not turning:

Use a fine-toothed triangular file to grind the ratchet and pawl, and adjust the position of the drive frame spring. When the drive frame is cracked and the ratchet and pawl is chipped, it can only be solved by replacing the spare parts. Try to check the hydraulic wrench system regularly. Once it is found that the hydraulic system is not working, the hydraulic wrench should be stopped in time. If the situation is unclear, contact professional personnel to help solve the problem.

### What should we pay attention to when loosening the bolts with a hydraulic wrench?

When using a hydraulic wrench, first determine the loosening or tightening action, and carefully use the power of the wrench torque to loosen or re-tighten the nut. Be careful not to injure your hands and wrists with the wrench. The reaction force and inertia of the force must be used well and flexibly during the operation. If you feel that it is a little laborious to turn the hydraulic wrench, you can also install a drive shaft locator at the front of the turning head, which can save effort to a certain extent.

## How to repair a hydraulic wrench?

1. When using a hydraulic wrench, if there is only a simple oil leakage or oil seepage, the hydraulic wrench can be repaired by replacing the internal seal. Usually in this case, the maintenance cost is lower and the speed is faster, and the hydraulic wrench can continue to be used for a long time after maintenance;

2. If the hydraulic wrench is connected to the pump station and cannot rotate, it is necessary to consider whether the oil circuit is blocked. The failure of the oil circuit is generally caused by the wear of the one-way valve of the quick connector. At this time, the quick connector of the hydraulic wrench needs to be replaced. Usually in this case, the maintenance cost is low and the maintenance speed is fast;

3. There is another kind of damage to the hardware inside the wrench, mainly including the wear and tear of the ratchet and the pawl, the deformation of the spring or the deformation or rupture of the oil cylinder grapple. If this happens, the cost of hydraulic wrench maintenance will be slightly higher, but maintenance is still more cost-effective than buying a new one;

4. The last situation is that the body of the hydraulic wrench is damaged or broken. In this case, the maintenance cost of the hydraulic wrench is relatively high, plus labor hours, accessories, etc., it is almost equal to buy a new hydraulic wrench. In this case, maintenance is not recommended.

## Summarize

The above is a summary of some problems with hydraulic wrenches from Torcstark, many of which will appear in the process of using hydraulic wrenches. We hope this summary will be helpful to users. If you have other questions about hydraulic wrenches, please leave a comment or contact us.