There are two technical solutions that allow you to perform tensioning and clamping operations in different ways: the hydraulic tensioner and the mechanical tensioner.
The two products have different technical characteristics: the target is to know strengths and weaknesses of both in order to be able to correctly choose the most suitable solution for the specific application.
HYDRAULIC TENSIONER OR MECHANICAL TENSIONER?
If it is necessary to carry out tensioning operations in the Industrial, Oil & Gas, Energy and Metallurgical sectors, different technologies can be used.
FPT – Fluid Power Technology wants to analyse the technical characteristics of hydraulic tensioners and mechanical tensioner or super-nut, highlighting the information necessary to make the right choice for the specific application.
The peculiarities of hydraulic tensioners and mechanical tensioners are listed in the following table:
| CHARACTERISTICS | HYDRAULIC TENSIONERS | CHARACTERISTICS | MECHANICAL TENSIONERS | ||
| PLUS | MINUS | PLUS | MINUS | ||
| Hydraulic acting | High leverage effect. With the minimum effort for the operator, very high forces are obtained | Hydraulic pump and flexible hoses are necessary | Mechanical acting | Construction simplicity. Requires only a torque wrench. | Greater effort for the operator. Slow procedure due to the amount of screws to be tightened |
| Modular configuration | With its conversion kits it can be used on a wide range of threads | Encumbrance of the superior tool | Single-threaded architecture | Extremely compact dimensions similar to a conventional hexagonal nut | Poor versatility. Each nut is designed for a certain thread |
| Pure traction tightening | The studs are tensioned by pure traction. The operations is very precise and repeatable. | The required forces imply high pressures. 1500 bar typically | Tightening | L’utilizzo è molto semplice e non richiede attrezzature particolari | Tightening is by torsion: it is conditioned by the variability of the screw-nut screw friction |
| Contextuality of the operation | Using appropriate hydraulic connections it is possible to perform a simultaneous tensioning on several studs | The number of tensioners must be equal to the number of studs that must be tensioned contextually | Individuality of the operation | No plus. Moreover, being a nut, the necessary quantity is equal to the number of studs to be tensioned | It is necessary to provide an accurate tightening sequence to uniform the load |
| Removability | The tensioner is used only for tensioning operations and then it is removed | Tightening many bolts requires the same number of assembly and disassembly | Integration with machinery | It is designed as a nut becoming an integral part of the machine. The nut is mounted only once | The necessary quantity is often high and it is equal to the number of studs to be tightened |
| Heat sources | Appropriate design characteristics allow the realisation of tensioners for high temperature | Maximum temperatures are in function of the seals. 180/200°C is max. value | Heat sources | Heat resistance is high because they are only steel-made. Alloy solutions allow to reach more than 500°C | Long time of exposure at high temperature can cause corrosion |
For more information, contact the FPT technical department
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