Making a PVC tank liner is a very specialized process. To make a great fitting liner requires trained personnel, specialized equipment, and a high commitment to standards.
The first step in making a PVC liner is to develop a fabrication drawing. Because liners are custom made each one requires its own layout drawing. Besides showing how each piece of the liner is to be cut, creased, and welded together, the layout drawing must also account for the most efficient yield of the material. It must also take into consideration how the pieces will interact with the welding equipment.
With the layout drawing completed the raw material can be laid out on the cutting table. Each piece is transferred to the material. Where the liner is to be creased or holes punched for Wittclips™ is also indicated. Then the individual pieces are cut from the raw material.
The first machining stage is the creasing machine. Flexible PVC has a very strong memory and wants to return to being a flat sheet. Wherever an angled bend is needed we place a dielectric crease in the material. Without this crease the liner will want to go back to being flat and would greatly affect the fit of the liner.
After creasing we then fabricate the bottom and top corners of the liner. We utilize a specially manufactured radio frequency welding machine that allows us to create a three sided corner piece. We never use a butt or joint weld on the corners as these welds are inferior to a dielectric weld.
With the corner pieces completed we then build in the rest of the liner using one of our many radio frequency welders. Unlike a hot air weld or chemical weld which only bonds a few mils of each surface layer to each other, an RF weld goes all the way through the material. The end result is that the welds on our liners maintain the same properties as any other place in the liner.
With the liner completed, it moves on to quality control. Quality control is a highly critical visual inspection of the liner ensuring that all welds are complete and any excess material flow is properly trimmed off. Final measurements of the liner are also completed to ensure that the liner is made to the proper specifications. Then the liner can be properly packaged and ready for shipping.
A short video on this process follows.