A 30 year old steel reinforced concrete pipe had, through the years, been severely damaged by tree roots and cracks caused by erosion. The existing steel reinforced concrete pipeline had an ID 1,200 mm and OD 1,700 mm.

A 500 metre section of sewer pipeline was replaced with HDPE OD 1200 mm SDR26 at a depth of five metres. The ground conditions onsite consisted of sand and clay. The T400 Hydrostatic Pipeburster was selected as ideal to meet the project specifications and conditions.

A bypass system was set up to re-route the sewage water during the project. The by-pass system was made from three parallel 315 mm diameter HDPE pipes. Specialised butt-fusion equipment was brought onsite in order to weld the 12 metre lengths of 1,200 mm diameter HDPE sections together into two 250metre sections.

Two pits were dug and the existing concrete pipe was removed. The pits were drained and levelled. One pit was for the T400 pulling unit and one for the installation of the new HDPE pipe, both measured approximately seven metres in length and three metres in width.

The T400 pipeburster operates with round threaded solid steel rods; weighing in at 127 kilograms with a 1.5 metre rod. An electrical hoist system is built onto the pulling rig to lift the steel rods in and out of the machine. A hydraulic driven rod spinner is attached to the back of the machine, to screw the steel rods on and off, for easier rod handling.

The flexible steel rods were pushed through the existing concrete pipe with a special guide cone in front, to avoid getting stuck on displaced flanges or other obstacles inside the old pipe. On arrival at the installation pit, the bursting head and HDPE pulling head were attached to the steel rod system.

The bursting head used, is a unique and simple cutting head design from the Scandinavian No-Dig Centre, which enabled the pulling power to be concentrated at one specific point. This made it easier to actually split the steel inside the concrete pipe, which resulted in the need for less pullback power. The cutting head was designed with a larger rear end dimension than the nominal size of the new HDPE pipe. This was to avoid potential damage to the new pipe caused by fragments of the old pipe during the pull-in phase.

The first section of the project was 260 metres and the elapsed time pulling back was just short of six hours. The pull back power needed for this project ranged from 250 up to 350 tonnes.

The new HDPE pipe was installed according to plan with the exact gravity line and depth. The completion of the 500 metres was carried out within five working days, all-inclusive. The equipment

The existing range of hydrostatic pipebursters has until now been limited to mid-range machines able to replace most pipes up to approximately 800 mm diameter. However the introduction of the T400 Hydrostatic Pipeburster has opened a new market. The T400 has a pull back capacity of 400 metric tonnes, equivalent to 440 short tonnes (US) or 880,000 pounds.

Scandinavian No-Dig Centres says that this makes it by far the most power full pull back unit ever build for pipe replacement purposes. Having a footprint as small as 3.50 x 1.40 metres yet able to replace existing pipes of diameters up to 1.5 metres, the T400 creates a new standard in professional pipe rehabilitation.

The T400 unit is fitted with many of the same features as the rest of the T-series pipeburster program. The machine is built on electric hoist system for easy rod handling, has automatic high pressure water cleaning of the steel rods during pull back and positive hydraulic jaw-gripping systems to prevent fly-back of the steel rods in case of breakage during. The T-series is the only machine-brand with the positive grip system.

As an addition to producing and selling the machines, the company has set up a new rental branch for the new T400 pipebursting machines. It is now possible to rent the T400 units, including a supervisor and consultant, for short and long term projects. All T-series pipebursters are also covered by a full 24 month warranty, terms apply.