Screw Pile Capacities and Installation Equipment

  60Rrangeb 76RRangeb 89R-39336b
Screw Pile Range 60R 76R 89R
Torque Head Model 400H 500X 650H 1600X 2500X
  400H 500X_XG 650H 1800X 2500XGb
Max Torque 4kNm 5kNm 6.5kNm 16kNm 25kNm
Machine Type Hand-held Excavator Hand-held Excavator Excavator
Ultimate Pile capacity
(un-factored) torque
120kN 150kN 180kN 450kN 625kN
Safe Working Load
(2.5 FOS)
48kN 60kN 73kN 180kN 250kN
Specification Sheet
(PDF)

Un-factored Load - A Maximum load that the Pile will take before deflection exceeds standard limits.

FOS - Factor of Safety - is the ratio between the un-factored load and the working load

Safe Working Load -The actual load the pile is taking when the building is in place

All machines offer torque read outs, allowing the pile capacity to be calculated instantly.

Screw Pile Specifications

SPECIFICATION DEFINITION 60R 76R 89R
Wall Thickness Thickness of the screw pile tube wall 6.35mm 9.5mm 9.5mm
Torque Limited The ability of the pile to transmit torque is always the limiting factor. This is therefore the ultimate practical pile install torque capacity. 4kNm 16kNm 25kNm
Ultimate Strength Single Helix This figure shows the load which can be supported by a single helix- most piles use multiple helixes, but if a single one has to support more load, although non standard, this can be accommodated. 90kN 160kN 220kN
Empirical torque factor KtKt m-1 This is the “Empirical Torque Factor” expressed in metric units when torque is measured in kNm and force in kN. Its value decreases as pile diameter and helix plate thickness increases. This is due to a combination of skin friction and the energy needed to displace the soil. 30m-1 28m-1 25m-1
Tube Specification   S355 HFS DIN1629 ST52 or Equal S355 HFS
Helix Specification   BS4360 43A BS4360 43A HRMS BS4360 43A
Fasteners Specification   Metric M16 GR8.8 ISOM20GR8.8 Metric M22 GR 8.8

Pile Life/Corrosion

In most conditions, provided the top 2 metres are galvanised the pile life will be in excess of 100years. Where the soil resistivity is less than 10 Ohm– further steps must be taken. This means salt water, wet peat and where soils are subject to saturation. For more information please download the soil corrosion chart.

The estimated life is based on the assumption that a loss of 40% in thickness is acceptable without adverse effect on structural integrity. The atmospheric exposed areas of the piles are coated with high build zinc rich coating system or galvanised. There is a safety factor of x2 included for the anode design to take account of variances in corrosion conditions and ground resistivity.

Ground Resistivity(Ohm-m) Corrosion rate based on Uhlig data mm/yr Estimates life with corrosion protection (years) Corrosion protection methods, required for top 2m section of Pile. (Min 9.35mm wall thickness) Estimated life with additional corrosion protection* (years)
Less than 5 0.1-0.2 18-37 Zinc rich coating
4 x 20kg galvanic zinc bracelet
100
5-10 0.033 80+ Zinc rich coating
4 x 20kg galvanic zinc bracelet
100+
10-50 0.025 100 Zinc rich coating 100+
50-100 0.018 100+ n/a 100+
Greater than 100 0.014 100+ n/a 100+