Pre-setting device PST
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Product description
Product description
Bolt Tensioning Cylinders for Precise, Torsion-Free Pre-tensioning
The hydraulic bolt tensioning cylinders of the PST series – also known as bolt tensioners – generate the required bolt pre-tensioning force through controlled axial elongation of the bolt. In contrast to torque-controlled tightening, the pre-tensioning force is not built up by rotating the loaded nut.
This method is particularly suitable for highly stressed and critical bolted connections where reproducible pre-tensioning, low torsional stress, and the most uniform load distribution possible are required.
Features and Technical Characteristics
Four Components Form the Tensioning System
How does a hydraulic bolt tensioning cylinder work?
During hydraulic bolt tensioning, the bolt is first stretched in a controlled manner. Only during this elongation is the nut turned down against the contact surface. After pressure release, a defined portion of the generated tensile force is transmitted as a pre-tensioning force to the bolted connection.
The rotation sleeve, bridge, and load cell are positioned over the nut and bolt. Then the puller is screwed onto the free thread.
The high-pressure pump pressurizes the load cell. The piston pulls on the puller and elongates the bolt in a controlled axial direction.
While the bolt is stretched, the nut is turned down to the contact surface via the rotation sleeve. Only a small torque is required for this.
After the hydraulic pressure is released, the bolt retracts elastically. This creates the pre-tensioning force in the bolted connection.
Bolt tensioning instead of torque-controlled tightening
With classic torque-controlled tightening, a large part of the applied torque is needed to overcome friction in the thread and under the nut. Changes in lubrication, surface, or friction coefficient can therefore lead to significant differences in the actual pre-tensioning force achieved. With hydraulic tensioning, the required tensile force is applied directly axially to the bolt.
| Feature | Hydraulic bolt tensioning | Torque-controlled tightening |
|---|---|---|
| Force generation | Direct axial tensile force | Torque is indirectly converted into pre-tensioning force |
| Torsional stress | No additional torsion from the tensioning process | Bolt is additionally twisted during tightening |
| Influence of friction | Significantly lower during force build-up | Strong influence of thread and contact friction |
| Multiple bolts simultaneously | Possible with several coupled tensioning cylinders | Usually sequentially or according to tightening scheme |
| Nut load when turning down | Low, as the bolt is hydraulically stretched | Nut is turned under high load |
| Typical application | Critical flanges and highly stressed bolted connections | Universal bolted connections |
Less influence from friction
When tightening with torque control, a large part of the applied torque is needed to overcome friction in the thread and under the nut. Changes in lubrication, surface, or friction coefficient can therefore lead to significant differences in the actual pre-tensioning force achieved.
With hydraulic bolt tensioning, the tensile force is generated directly via the hydraulic pressure. The nut is only turned down during the axial elongation of the bolt. As a result, the resulting pre-tensioning is much less dependent on the friction coefficient during the actual force build-up.
Pre-tensioning several bolts simultaneously
Each PST load cell has two hydraulic connections. This allows several bolt tensioning cylinders to be coupled together via high-pressure connecting hoses and supplied by a common pressure source.
- simultaneous pressure build-up on multiple bolts
- more uniform loading of flange and gasket
- fewer individual tensioning operations
- particularly suitable for critical flange connections
Technical Data
A load cell can be combined with different adapter sets, depending on the model. This allows several metric and imperial bolt sizes to be covered with the same load cell.
| Load cell | Adapter set | Thread inch | Thread mm | max. load t | max. load kN | Outer Ø mm | min. pitch mm | C mm | A mm | B mm | Weight kg |
|---|---|---|---|---|---|---|---|---|---|---|---|
| PST-01 | A1-0.12 | 3/4" | – | 34.5 | 339 | 84 | 46 | 30 | 86 | 160 | 3.5* |
| A1-M20 | – | M20 | 47 | 30 | 86 | 160 | 1.3 | ||||
| A1-0.14 | 7/8" | – | 53 | 32 | 94 | 168 | 1.4 | ||||
| A1-M24 | – | M24 | 54 | 32 | 94 | 168 | 1.4 | ||||
| A1-1.00 | 1" | – | 55 | 32 | 94 | 168 | 1.4 | ||||
| PST-02 | A2-M27 | – | M27 | 40.6 | 397 | 98 | 56 | 34 | 96 | 170 | 4.5* |
| A2-1.02 | 1 1/8" | – | 59 | 37 | 98 | 172 | 1.8 | ||||
| A2-M30 | – | M30 | 62 | 37 | 97 | 173 | 1.9 | ||||
| A2-1.04 | 1 1/4" | – | 67 | 40 | 99 | 180 | 2.0 | ||||
| A2-M33 | – | M33 | 68 | 40 | 99 | 181 | 2.1 | ||||
| A2-1.06 | 1 3/8" | – | 72 | 43 | 101 | 186 | 2.3 | ||||
| A2-M36 | – | M36 | 73 | 43 | 101 | 187 | 2.3 | ||||
| PST-03 | A3-1.04 | 1 1/4" | – | 65.2 | 639 | 115 | 69 | 40 | 99 | 185 | 5.9* |
| A3-M33 | – | M33 | 70 | 40 | 99 | 174 | 2.4 | ||||
| A3-1.06 | 1 3/8" | – | 74 | 43 | 101 | 177 | 2.9 | ||||
| A3-M36 | – | M36 | 75 | 43 | 101 | 178 | 2.9 | ||||
| A3-1.08 | 1 1/2" | – | 80 | 45 | 105 | 187 | 3.0 | ||||
| A3-M39 | – | M39 | 80 | 43 | 105 | 186 | 3.0 | ||||
| PST-04 | A4-1.06 | 1 3/8" | – | 73.6 | 721 | 128 | 75 | 43 | 101 | 183 | 7.7* |
| A4-M36 | – | M36 | 76 | 43 | 101 | 183 | 3.4 | ||||
| A4-1.08 | 1 1/2" | – | 81 | 45 | 105 | 183 | 3.6 | ||||
| A4-M39 | – | M39 | 81 | 45 | 105 | 183 | 3.6 | ||||
| A4-1.10 | 1 5/8" | – | 86 | 48 | 107 | 187 | 3.9 | ||||
| A4-M42 | – | M42 | 86 | 48 | 107 | 188 | 3.9 | ||||
| A4-1.12 | 1 3/4" | – | 91 | 51 | 108 | 192 | 4.0 | ||||
| PST-05 | A5-1.10 | 1 5/8" | – | 96.1 | 942 | 145 | 87 | 48 | 113 | 198 | 11.4* |
| A5-M42 | – | M42 | 87 | 48 | 113 | 200 | 5.2 | ||||
| A5-1.12 | 1 3/4" | – | 92 | 51 | 117 | 205 | 5.4 | ||||
| A5-M45 | – | M45 | 93 | 51 | 117 | 206 | 5.4 | ||||
| A5-1.14 | 1 7/8" | – | 98 | 54 | 120 | 212 | 5.6 | ||||
| A5-M48 | – | M48 | 98 | 54 | 120 | 212 | 5.6 | ||||
| A5-2.00 | 2" | – | 104 | 57 | 120 | 217 | 6.3 | ||||
| A5-M52 | – | M52 | 105 | 57 | 120 | 217 | 5.9 | ||||
| PST-06 | A6-1.14 | 1 7/8" | – | 138.2 | 1,354 | 165 | 99 | 54 | 120 | 209 | 14.8* |
| A6-M48 | – | M48 | 99 | 54 | 120 | 210 | 7.1 | ||||
| A6-2.00 | 2" | – | 105 | 57 | 123 | 215 | 7.6 | ||||
| A6-M52 | – | M52 | 106 | 57 | 123 | 215 | 7.6 | ||||
| A6-M56 | – | M56 | 113 | 62 | 126 | 223 | 7.8 | ||||
| A6-2.04 | 2 1/4" | – | 114 | 62 | 126 | 224 | 7.8 |
* Weight of load cell and adapter set for the indicated size. Dimensions according to manufacturer's data sheet. The required adapter depends on the thread size and the load cell used.
Typical applications for PST bolt tensioners
Which PST bolt tensioner is suitable for your bolted connection?
For selection, we need the thread size, desired preload force, available radial clearance, free thread length above the nut, and – for flanges – the bolt spacing. Based on this, the appropriate load cell with adapter set can be chosen.
Frequently Asked Questions about Bolt Tensioners
What is a hydraulic bolt tensioner?
A hydraulic bolt tensioner is a tool for axially preloading bolts and studs. The bolt is stretched hydraulically, then the nut is tightened, and the hydraulic pressure is released.
What is the difference between bolt tensioning and torque tightening?
In the torque-controlled method, the nut is turned under load, and the preload force is indirectly generated via the tightening torque. In hydraulic tensioning, the tensile force is applied directly axially to the bolt.
Why is hydraulic bolt tensioning less friction-dependent?
When building up tensile force, the loaded nut does not have to be turned against thread and seating friction. The preload force is first generated hydraulically, and the nut is only tightened when stretched.
Can multiple PST bolt tensioners be used simultaneously?
Yes. PST load cells have two hydraulic connections and can be connected to each other via suitable high-pressure connection hoses. This allows several bolts to be tensioned hydraulically at the same time.
Can one PST load cell be used for multiple bolt sizes?
Yes. Within the intended size range, the same load cell can be combined with different adapter sets. The adapter set includes the components matching the respective bolt size.
What information is required for the selection of a bolt tensioner?
Specifically, the thread size, desired preload force, available free thread length above the nut, radial space, bolt spacing, and the geometry of the contact surface are required.
Hydraulic Bolt Tensioners for Industrial Bolted Connections
Hydraulic bolt tensioners are used for the controlled preloading of heavily loaded bolts and studs. Typical applications include flange connections on pipelines, heat exchangers, pressure vessels, pumps, compressors, and other machine and plant components.
The PST series enables direct axial tensioning of the bolt. This means that the desired bolt load is not generated exclusively by a tightening torque and the associated friction conditions. For flange connections, multiple bolt tensioners can be hydraulically coupled and actuated simultaneously.
The selection of the appropriate bolt tensioner depends on the bolt thread, necessary tensile force, available installation space, free thread length, and bolt spacing. With interchangeable adapter sets, different bolt sizes can be tensioned with a suitable PST load cell.
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The hyTool Quality Promise
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