A screw-pile comprises a circular hollow section of steel shaft with one or more helical plates welded near to the end of it. The size of the shaft (diameter, wall thickness and length), combined with the size and placement of the helical plate are Engineer designed to take full advantage of the available soil capacity. Screw-piles are screwed into the ground like a self-tapping screw using rotary hydraulics, namely DIGGA TORQUE HEADS which are attached to earthmoving equipment, and installed to a specified torque capacity and a depth as directed by a certified foundation engineer.

Digga's torque head is used to screw the screw anchor into the ground. As the screw anchor reaches the desired compression torque or depth, the operator stops. At this point the screw anchor is under load.

When the operator stops, the load is trying to spin the screw anchor backwards. While the screw anchor is only tensioned to say a ¼ or ½ a turn, when it releases, it does so in under 1/10 of a second. This motion can have dire effects on both the gearbox and the motor, as it sends reverse energy back up into the drive unit. This motion effectively turns the reduction gearbox into a multiplier, essentially turning the hydraulic motor into a pump.

The Energy Control Valve (ECV) was designed to relieve the kick/flick-back motion of the screw anchor on the drive-head. It does so by controlling the release of oil to the low-pressure side of the motor. The added benefit of the design is that it does not reduce the power available to the unit when the drive is installing the screw anchor. Its unofficial name comes from the sound it makes while working — A gentle 'swoooosshhh' as the oil is released.

An ECV is required for all drives used installing screw anchors; from PD4HF to PD50. This maintains a full gearbox and motor warranty (3 yr Gearbox and 2 yr Motor).

Should you be installing screw anchors with a torque requirement up to 16,000 Nm and do not have an ECV fitted, you will have limited warranty (2 yr Gearbox and 1 yr Motor).

Using torque heads without an ECV (effectively, an earth drill) for installing screw anchors with an installation torque requirement of greater than 16,000 Nm will have NO WARRANTY for its Gearbox or Motor.

This will be determined by the maximum torque requirement of the specific screw piles that will be installed at the site in question. This in turn will be specified by the foundation engineer who has designed and designated the exact dimension, installation and torque requirement for this job site.

This will be determined by the maximum torque requirement of the specific screw anchors that will be installed at the site in question. This in turn will be specified by the foundation engineer who has designed and designated the exact dimension, installation and torque requirement for this job site.

Dependent on the available flow and pressure available from the parent machine there will be a variation in the rpm speed of a smaller drive to a larger drive.

e.g. With the same parent machine with flow 200 lpm fitted with an SD45 would have 17 rpm at maximum torque, as opposed to same machine with same flow fitted with an SD95 would have 8 rpm at maximum torque. So, a definite flow decrease the larger the torque head.

It is worth noting, speed (rpm) is dependent on Flow (lpm). Power (Nm) depends on pressure (bar).

Every hydraulic motor fixed to a planetary gearbox has a listed maximum power (kW) rating. Exceeding this rating will cause motor damage and failure.

Power is created by combining pressure and flow. You may increase pressure while reducing flow, or increase flow while reducing pressure – maximise both simultaneously may exceed the motor's safe operating limits. The kW power can be calculated with the following formula (kW) = Flow (litres/minute) × Pressure (bar) ÷ 600.

Operating outside the rated kW will cause:

• Excessive heat buildup, degrading hydraulic fluid
• Internal seal and shaft damage
• Motor seizure and failure
• Costly downtime and replacement

Yes, all torque heads are capable of use in screw anchoring and also as an earth drill. Larger torque heads with higher torque capabilities will be limited by the rpm that will satisfy your drilling requirements.

Yes, but the size of the screw anchor would be limited by the amount of torque required, so that the machine is not compromised and is not at risk of boom failure or machine tipping. For safety factors, It is advised to confirm with the machine supplier for the machine in question.