Hydraulic screwdrivers
Hydraulic screwdrivers or hydraulic ratchet screwdrivers are used for torque tightening or for unscrewing mainly large screw connections above M24. They are therefore machine-operated torque wrenches .
The principle is that of a side at a lever arm mounted hydraulic - cylinder which executes when pressure is applied to the lever arm a pivoting movement. The lever arm then acts like an open-end or ring spanner on a nut or screw and tightens or loosens it. The direction of rotation is reversed by repositioning the output square or by turning the screwdriver. According to this principle, a compact mechanical system can be integrated in a housing and, depending on the lever arm length and hydraulic operating pressure, large screw tightening torques can be applied in a very small space. Modern hydraulic screwdrivers with a total weight of 4 kg and an operating pressure of 700 bar can deliver a torque of up to 4,500 Newton meters to the screw connection. In addition, the hydraulic screwdriver works relatively slowly, but very precisely with an accuracy of +/- 3%. The size of such a 1 "square screwdriver is then comparable to that of a 1/2" pneumatic impact screwdriver , which is far below that in terms of performance and accuracy .
Hydraulic screwdrivers are available in two different designs. The cassette screwdrivers and the hydraulic screwdrivers with square drive.
Hydraulic screwdrivers with square drive usually start with 3/4 "drives and thus at about SW 27. They also have 1", 1 1/2 "or 2 1/2" square holders and are therefore for torques up to 100,000 Nm and very large wrench sizes in use. The procurement costs start below € 10,000 but can be significantly more depending on the size. Hydraulic torque wrenches are therefore usually only found in industry , e.g. B. in power plant construction, in the assembly of large systems and components. A very typical area of application is the assembly and maintenance of large wind turbines.
Cassette screwdrivers consist of two basic components. The drive head with the hydraulic connections and the exchangeable cassette. The interchangeable cassette defines the wrench size with the hexagon drive integrated in it. A separate interchangeable cassette is usually used for each wrench size. Sometimes reducing adapters or in / out sockets are also used, which can expand the spectrum of the cassette. The advantage of this design is the low height of the screwdriver, which also allows it to be used in confined spaces.
Due to the high hydraulic pressures, the very high torques and the resulting reaction forces, particular attention must be paid to occupational safety. The use of safety goggles and appropriate work clothing is mandatory. The hydraulic screwdrivers used can also promote the worker's safety at work. Built-in backstops in modern hydraulic screwdrivers and safety handles ensure that the operator does not have his fingers in the danger area when working with the devices and that there is no risk of crushing.
See also
Individual evidence
- ↑ Dirk Westrup, Business Manager Bolting, Atlas Copco and http://www.aaw-montagetechnik.de/hydraulikschrauber.htm