The Application And Operation Skills of Hydraulic Torque Wrench
(Last Updated On: December 24, 2021)
In the oil, natural gas, petrochemical, nuclear power, and processing industries, pressure vessels, thermal pipeline joints, valves, pumps, and machinery will face the problem of how to control the tightness of bolts. It is required that the gap between the flanges should be uniform, the sealing surface should be installed tightly, the connection points should not leak, and the use of media and gaskets should be good. Therefore, users need to master the knowledge of bolt pre-tightening force, hydraulic torque wrench operating performance, safety precautions, maintenance and maintenance knowledge, and how to use hydraulic wrenches safely and reasonably to save time and effort to uniformly apply a constant torque to the bolts. Finally, the task will be completed quickly and accurately.
Over the past few decades, even with the use of high-quality and high-precision tools, it has been impossible to stop the occurrence of leaks. Traditional methods such as sledgehammer percussion and manual trigger are completely judged by human feelings, and there is no precision at all. There are two unknown factors whether the nut is turned to the proper position: for torque, the friction coefficient between the rotating surface and the thread; for tension, the estimated value of over-tension and manual tightening of the nut. In addition, various application factors, working conditions, fitting tolerances, perpendicularity, and friction coefficient of the bolts and nuts used affect the bolt fastening factors, making the accuracy of bolt fastening difficult to control. In the heavy industry, the economic loss caused by the leakage due to the sealing problem and the failure due to the loose bolt is very huge. If the remaining tensile force of each bolt is the same, the flange can obtain a uniform load. If the load is uniform, the flanges will be closed in parallel and there is no leakage. Correctly tightening the bolts and accurately controlling the pre-tightening force of the bolts is the only way to reduce leakage and bolt looseness.
Bolt pre-tightening force: It is the pre-tightening force of the bolt in the direction of the bolt axis line generated between the bolt and the connected part under the action of the tightening torque during the bolt tightening process. For a particular bolt, the magnitude of its pre-tightening force is related to the tightening torque of the bolt, the friction between the bolt and the nut, and the friction between the nut and the connected part. For an uncertain bolt, the maximum pre-tightening force that a bolt can use is related to the type of bolt material, the heat treatment of the bolt material, and the size of the bolt diameter. Suppose that the bolts play a pre-tightening effect on the pressure vessel sealing end cover, and there are several bolts of the same specification evenly distributed on this end cover. Then, the sum of the minimum pre-tightening force that these bolts can withstand must be greater than the reaction force generated by the highest pressure in the sealed container. Otherwise, the seal between the end cap of the pressure vessel and the body cannot be guaranteed.
Pre-tightening can improve the reliability of the bolt connection, the anti-loosening ability and the fatigue degree of the bolt, and enhance the tightness and rigidity of the connection. In fact, a large number of tests and experience have proved that a higher pre-tightening force is beneficial to the reliability of the connection and the life of the connection, and it is especially necessary for the connection that requires sealing. Of course, as the saying goes, “things must be reversed.” Excessive pre-tightening force, if improperly controlled or accidentally overloaded, will often lead to failure of the connection. Therefore, it is very important to accurately determine the pre-tightening force of the bolt.
Definition and use of hydraulic torque wrench:
Hydraulic torque wrench: It is a hydraulic tool for fixed value tightening and disassembly of bolt connections. It is composed of a body wrench, an electric hydraulic wrench pump, a double high-pressure oil pipe, and a high-strength socket. After the hydraulic torque wrench pump is started, pressure is generated by the motor, and the internal hydraulic oil is transmitted to the hydraulic torque wrench through the hose. The piston rod of the hydraulic torque wrench is pushed, and then the piston rod drives the ratchet at the front of the wrench, and the ratchet drives the drive shaft, so as to complete the pre-tightening and loosening of the bolts.
Introduction and operation of square drive wrench:
Judging the direction: For the “square shaft + socket type” hydraulic torque wrench (that is, the square drive type), first determine whether to loosen or tighten (face the head of the wrench, observe the direction of the square drive shaft, left is loose, right is tight). By pressing the positioning button of the drive square shaft, the retaining cap can be removed and the square head drive shaft can be taken out. Take out the drive shaft to change the direction of left and right.
Quick release lever: 360-degree plug-in type, which can support the reaction arm in multiple positions. The unique quick-release lever design makes it easy to remove the wrench head. When the wrench head is stuck, the wrench cannot be removed. At this time, press and hold the hydraulic pump start switch, apply pressure to it, then pull down the quick release lever and keep it still, then release the switch to release the pressure. In this way, the wrench can be easily removed. It should be noted that each time before the wrench works, check whether the quick release lever stays in the release position. If not, dial to the corresponding location to work. Pay attention to the position of your hands during operation and do not get caught.
Electric hydraulic pump: There is an automatic pressure relief device. Before unloading the pressure of the hydraulic system, do not connect or disassemble oil pipes and connection joints. There is a pressure gauge on the hydraulic pump, first confirm that the pressure has been completely unloaded before operating. When connecting the quick-release joint, make sure that the installation is correct, and that the connection is firm and leak-free. Before using the hydraulic pump, check the following points:
①Is the fuel tank full of oil?
② Where is the power interface closest to the work site?
③ Is the surface of the tubing intact, and is there any bulge? (A bulge will cause pinhole leakage under high pressure, and the injection of hydraulic oil may cause injury to the operator) Power supply: Before operating the hydraulic pump, check the nameplate of the hydraulic pump.
Power requirements: Correctly choose the generator or power supply.
(1) The power of the power source should be more than three times the nominal power of the pump station before the hydraulic pump can start and work normally. which is:
① If a three-phase generator is used, the generator power should be more than 9 times the nominal power of the pump station: a generator with a power of 15KVA or above should be used;
② If a single-phase generator is used, the generator power should be more than 3 times the nominal power of the pump station: a generator with a power of 5KVA or above should be used;
(2) The 230V single-phase voltage output terminal should use a voltage stabilizer to avoid frequent voltage fluctuations from adversely affecting the hydraulic pump.
(3) Ensure that the power supply is normal, and that the current, voltage, and power are within the requirements of the hydraulic pump. Ensure that the power supply is well grounded.
Debug the pump station: Before using the hydraulic pump, it must be debugged. Press and hold the start switch, turn the pressure regulating valve clockwise to adjust the pressure from zero to the highest, and observe whether the pressure is stable and there is no obvious oil leakage. If it is working properly, you are ready to start working. Before adjusting the pressure, the pressure regulating valve must be adjusted to zero (counterclockwise), and the pressure must be adjusted from low to high when testing the pressure.
Debugging wrench: Connect the hydraulic wrench to the pump station through the oil pipe, and operate it under no-load conditions. Observe whether the wrench is working properly and whether there is oil leakage. If everything is normal, you can start working. It is required that the joint must be tightened and no gaps should be left, otherwise the shut-off valve (steel ball) of the oil pipe joint will be stuck, making the oil path blocked and the wrench not working properly.
The above is an introduction to the application and use skills of hydraulic torque wrenches. TorcStark is an internationally renowned hydraulic wrench manufacturer. It has very rich experience in the manufacture of hydraulic wrenches and can provide 12 months of free after-sales service. With the competitive price and high quality, TorcStark hydraulic wrench will be the best choice!