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Modular hydraulic tensioners

Advantages of hydraulic bolt tensioning

Hydraulic tensioning is the modern way of manufacturing threaded connections. It is more precise and allows higher bolt forces than conventional methods. It allows multiple bolts to be tensioned at the same time, and flanges can be tensioned more evenly and tightly. 

The importance of setting losses

There are many ways to tighten a screw, the most popular is using a torque wrench.  The overall efficiency of a threaded connection is determined by:


· Accuracy of load

E.g., using a torque wrench is always somewhat inaccurate: the actually applied torque deviates from the presetted value due to rotation speed and evenness, torque wrench tolerance and other factors.


· Ratio of applied load to axial bolt force

When using a rotational method for bolt tightening, e.g. a wrench, the actual axial bolt force depends very much on the friction in the thread itself and in the contact area of bolt head. The effective friction is very difficult to predict and depends on many parameters as method of thread production (cutting vs. forming vs. rolling), kind of lubrication, lubrication distribution in thread and under the bolt head, nut material, bolt material etc.


· Setting losses

Only relevant with some kinds of hydraulic tensioning. It defines the amount of axial bolt force that remains after the tensioning process and the mechanical locking due to the change of force flow. With smart tensioner setting losses are very low.


Taking all factors into account, there is no better way to tighten a bolt than using hydraulic tools. Using wrenches, the axial force is highly unpredictable. This often means either overdimensioned bolts, unsafe connections or unevenly tensioned flanges. Further on, hydraulic tensioning means pure axial bolt stressing nearly without shear stress. Instead to rotational methods, where the bearable bolt force is significantly reduced because of the applied torque it fully uses the load bearing capacity of the bolt material.


Hydraulic bolt tensioning is MORE PRECISE and allows HIGHER BOLT FORCES.

Advantages of smartTensioner hydraulics

The stud is only elongated - no nut turning is needed. Therefore the full load bearing capacity of the stud material can be used to withstand the axial stud forces. There is no shear stress because external torque applies.

Multiple studs can be tensioned at the same time using our electronically synchronized pumps (HP). For example, with our HTU system, no setting losses appear and the targeted bolt force can be exactly determined, measured and guaranteed.

smartTensioner devices operate with very high hydraulic pressure, which allows the use of small, lightweight tensioning systems. The application of very high bolt forces even in very tight environments is possible.

Very small hydraulic volumes ensure overall operational safety.

smartTensioner technology reduces the duration of the tensioning process: no hoses need to be connected, no high-pressure connectors need to be operated, no heavy pumps need to be transported. The combined weight of the devices that need to be transported to the installation site is significantly lower.

Our tensioning devices operate at pressures of up to 300 MPa. This demands thicker cylinder walls but reduces the hydraulic space required. Since area reduction is the more relevant effect, our tensioning devices are smaller and lighter.

Conventional bolt tensioning requires one big and heavy hydraulic pump because all tensioning devices are hydraulically connected to each other and supplied by one pump. Our technology operates differently: our pumps are very small and light (1.5kg / 2.6kg). They are mounted directly on the tensioning devices. Instead of hydraulic connection, our pumps and tensioning devices are synchronized electronically via cable or wirelessly. Precisely defined bolting forces, even on flanges using different bolt sizes in parallel (e.g. turbine flanges), are ensured. The amount of pressurized volume is small, and no elastic components are needed. The risk of bursting hoses, leaking connectors or pistons that have moved too far is eliminated.

smartTensioner tensioning devices
  • are faster to mount and dismount
  • weigh less
  • consist of fewer components that cost less than commercially available solutions

The video shows the principles of operation of a bolt tensioner. An external hydraulic pump delivers the hydraulic pressure. Multiple bolt tensioners can be combined to tension many bolts at the same time.

Three ways to tension bolts with smartTensioner technology:


Hydraulic Nuts (HTU)

Replaces original nut. High forces, small diameters, very small thread diameters, high precision


Hydraulic Mechanic Nuts (HMTU)

Replaces original nut. High forces, mechanically locking, wide range in operating temperature


Bolt tensioners (BT, CFBT, IBT)

The original bolts and screws remain on the flange. No changes to established and approved procedures.