What diameters have the freeze pipes?
Casing steal pipes closed at the bottom with around 5 inch outside diameter are often used in freeze shaft constructions. API grade of J55 or even higher is favoured. API coupled connection, integral or omega are usual; an important point when up to kilometres of pipes have to be combined water-tight. The steel pipes are closed at their ends. A special rotary drilling is necessary before, because only a few percentage of vertical deviation is allowed. The inner concentric down pipes with lets say 3 inch diameter are normally of polyethylene.
