Welding Tractors

The only serially manufactured welding tractor built to the last word in technology is the SR 712 BM, a joint development of the Liebherr and Maats companies. The tractor is a powerful all–terrain vehicle designed to perform welds on the right of way with a variety of power sources.

  • the engine is rated at 160 hp;
  • ground speed is 11 km per hour;
  • ground pressure is 0.45 kg/cm2

Welding tractors could be equipped for stick welding as well as
semi–automatic and automatic welding.

Welding tractors can also be built based on Liebherr pipe–layers.

welding tractor SR 712 BM

Advantages of the welding tractor SR 712 BM are:

1. A very advanced hydrostatic device

  • Excellent traction and manoeuvrability;
  • smooth ride;
  • constant torque on the track mechanisms regardless of travel speed

are achieved by a very advanced hydrostatic device
(Advantages of Hydrostatic Drive).


welding tractors SR 712 BM
on an automatic welding spread

  • Long tracks,
  • high ground clearance
  • and incredibly low ground pressure (0.45 kg/cm2)

enable the tractor to work in difficult soils along the edges of ditches, where most pipe–laying activity
is performed.

2. Unified Power Unit

The hydraulic system driven by the diesel engine of the tractor is the central power unit. All control and support systems of the tractor (transport drive, hydraulic HIAB crane, electrical generator, compressor etc.)
are driven by the central power source.

The system can be used to drive a pipe facing machine and a hydraulic line–up clamp as well. Thus the need
for additional equipment and systems is eliminated, achieving simplicity and lower cost in servicing of the welding tractor as a whole, and reducing noise and fuel consumption.

3. Stabilization of the electric welding power supply

The hydraulically driven electric generator develops power output matching customer's request (most popular, 125 KVA at 380/220V).

This generator with feedback supports up to six welders and stabilizes the welding cycles.

4 welding power sources

4. Ease of Control

Owing to the use of a hydrostatic drive, a single lever controls all travel movements of the machine.

Controls for the generator, loading crane as well as the compressor, are located next to the operator’s seat.
The operator can concentrate fully on the work area from their seat, and can guarantee safe handling
of the machine even at construction sites with little space for manoeuvring.

5. High–Torque Crane with Long Boom and Powerful Compressor

A fully hydraulic powered HIAB crane installed on the tractor can handle a working radius of 7.2 meters.

The crane’s torque is 70.6 kNm.

The crane’s boom can be fitted out with a console for a welding tent.

The air compressor with the hydraulic drive supplies compressed air for a pneumatic internal line–up clamp as well as for grinding machines.

welding tractor SR 712 BM,
with welding tent