Più di una spinta
Il 125Plus è stato utilizzato di recente da Balfour Beatty Utilities (BBUL) in Darlington spingere 332 metri di diametro di 75mm PE in una principale in ghisa 4” nel corso di un progetto live del gas di rete inserimento. Ruotando la macchina intorno dopo il primo impulso, BBUL was able to insert the PE in two directions from one excavation; the first push was 182m in length and took 25 minutes and the second 150m.
This was the first time that the Live Mains Insertion technique, together with pipe pushing machines, had been used in the area and BBUL’s Paul Bolton said that he was so pleased with the results that more of the mains insertion programme would be carried out ‘live’ using a pushing machine.
A much larger pushing machine, il 355, was used recently in Reading to live insert 255mm PE into a 16” cast iron main.
Designed principally for inserting or sliplining old gas, water and sewer pipes during renewal operations, pipe pushing machines can also be used to push cable into ducting and have been used successfully to pull kilometres of unwanted high tensile cable from steel ducting before replacing it with fibre optic cable.
The machines work on the principle of grasping the pipe in a set of jaws, thrusting it forward and holding it in that position whilst the jaws return to the start position ready to push again. Pushing pipe rather than winching it has several advantages. Firstly it can speed the operation by eliminating the need to feed a winch cable through the host pipe. It also means that only one excavation need be opened during insertion, reducing disruption to traffic and pedestrians and easing traffic management liabilities.
Pushing also avoids the risk of stretching or exerting excessive tension on the pipe, an important consideration prior to jointing the PE. Another benefit is that the pushing action can be reversed to pull the pipe back if an obstruction is met.
Long sections can be inserted with a pushing machine; 100 a 150 metres are typical whilst 1000 metres is possible given the right conditions.
The 125Plus handles pipe diameters from 40mm to 125mm and is pneumatically operated. With a top pushing speed of 15 metri al minuto, the machine has a maximum pushing force of half a tonne. An optional back clamp can be fitted to help grip the pipe between pushes on longer insertions.
Steve Vick International manufactures a range of pipe pushing machines to handle pipe from 40mm diameter up to 630mm, although larger machines can be supplied to special order. The smallest machine is manually operated; the 125Plus operates from a standard compressor whilst the larger machines are hydraulically operated. Each model can be fitted with shells to accommodate different pipe diameters.
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