What problems should be paid attention to when installing the pipeline in the air separation tower?

When the air separation Tower turns from normal temperature to low temperature, the phenomena such as pipe crack and valve jam often appear. The main reason is that the installation prestress is too large and the cold compensation is not good. In order to reduce installation prestress and cold deformation stress, the installation should do:
1) generally, when piping, it should be big first and then small, difficult first and then easy, small pipe should be big pipe, and heat pipe should be cold pipe;
2) after the containers and valves are located, make pipes according to the actual situation. When the valve and the welded joint of the pipeline are out of place, do not install it reluctantly;
3) according to the on-site experience, generally, each weld joint will shrink about 1.5mm after cooling. Therefore, all the installation joints of the flange connecting with the valve and the container can be seen according to the specific situation. Before welding, tighten the flange bolt without Shim, and then add the Shim after welding, in this way, the pretightening force of bolts and the stress of pipelines can be reduced;
4) changing the valve hanger into a rigid bracket can prevent the valve stem from deformation caused by the displacement of the valve when the pipeline shrinks;
5) during installation and leak checking, the small tube and valve stem should be avoided as scaffold;
6) the temperature of the air separation Tower varies greatly from normal temperature to-190 ℃. The change of temperature will cause the thermal expansion or cold contraction of the pipeline, so the compensation of cold and heat should be considered in the design of the pipeline. In the actual installation, pipe elbow or expansion joint should be added to compensate for the parts which are not considered well in the design.