Hydraulic Precision Power Wrench

Owing to its hydraulic components, ROWRENCH P4 Rec requires hardly any maintenance compared to mechanical power wrenches.

• Maintenance interval: 2 years or 200,000 wrenching cycles
• no wearing parts apart from oils and filters
• machine is always immediately ready for use

Calibration by a torque measuring adapter is repeated annually by the trained building contractor's personnel in their own workshop or at the manufacturer's. Calibration also serves as the functionality record to be submitted to the site supervisor.

The hydraulic precision power wrench's programmable logic controller (PLC) quickly guides you through the setup menu and its parameters even if you have not much wrenching experience:

• screwing pattern (field or track side)
• type of track (K, KS, W)
• line data (number of line/track, kilometrage, rail)
• mark at first screwed joint

Since the self-learning control unit of 30.73 PSM continuously compares planned to actual values and to the prevalent wrenching case and since it adapts the torque accordingly, the above settings are mainly intended to optimise the speed and result of work and to accurately document the wrenching process.

Comparison control loop:

1 – Within milliseconds, the force transducer checks by how much the screw has been tightened at any time of the wrenching process and

2 – transfers the reading to the PLC.

3 – The PLC recognises the wrenching case with reference to the gradients it stores.

4 – The spindle speed is accurately set to achieve the final torque.

• The machine stops automatically when the PLC detects the maximum torque of 250 Nm and that it has been applied within an acceptable time.
• To save time, it calculates the speed for the next wrenching process.
• Check the display to see whether wrenching has been completed correctly.
• All captured data is logged including the status of every wrenching completed and/or every screw skipped.
• In case a fault is displayed, the machine undoes the screwed joint and repeats the process.
• As opposed to mechanical machines, final steps such as checking and re-tightening the screws is not required.

When loosening screwed joints, the torque is dynamically and linearly increased to up to 880 Nm. This is not only preserving the machine mechanism but also applying a high loosening torque which reliably tears off rusty screws of older K-type track fastenings. A process stored in the PLC can be chosen from the menu to loosen screws seized in loose W-type track dowels.

Since the PLC controls the dynamic process of 30.73 PSM, it is now for the first time possible to check the torque of previously tightened screws without having to completely unscrew them as had to be done hitherto. Again, all torques measured in the process are logged. This method is mainly intended to quickly show that the hardware in older tracks is still tight in conformity with regulations.

Directive Ril. 824.5050 published by Deutsche Bahn on how to produce uninterrupted tracks and on the bracing of rail fastenings aims for a reliable connection between rails and sleepers while minimising damage to the sleepers.

Pursuant to the Directive, a rail is correctly fastened if the set-point geometric bracing (gap size ≤ 0.5 mm) is achieved without exceeding the maximum permissible torque of 250 Nm.

Every hundredth sleeper (if fastened by a hydraulic power wrench) or every twentieth sleeper (if fastened by a mechanical power wrench) is to be checked by using a torque spanner. Conformity with the Directive has to be shown in writing.

The Directive also provides supportive arguments in case of conflicts. If there is a conflict about the cause of sleeper damage, the logging of wrenching processes supports the building contractor in its position against the client because an excessive torque can be ruled out as the cause of a cracked sleeper.

ROWRENCH P4 Rec meets all standards set by DB Directive 824.5050. DB has therefore decided to exempt this power wrench type from the otherwise compulsory verification of every hundredth or twentieth screw.

• The Precision Power Wrench automatically logs and encodes all wrenching results.
• The digital log is output via a protected waterproof USB port.
• The vibration-proof and thermally resistant USB stick can be read by standard Office applications, i.e. without having to use extra software or readers.

Upon request, ROWRENCH P4 Rec is equipped with a GPS data logger. If so, the log line of a particular fastened joint then includes the exact GPS position. A fault in any track fitting can therefore be found and removed quickly and without doubt.