When it comes to plastic tank testing, we've developed the standard… literally. As one of the first companies using thermoplastic in large tanks, we developed a series of testing procedures to ensure the integrity of your tank and components.

Non-destructive testing of thermoplastic materials is difficult at best. Ultrasonic tests and X-rays are ineffective, as are most other conventional testing methods.

So how can we be assured of our stated material values? How can we be certain as to the strength of our welds?

There are no domestic 'standards' for our types of construction, not even through ASTM. And the only international benchmark available is DVS-2205; which are not standards or codes, but the German Guidelines for Thermoplastic Welding.

As calculations are based on certain assumptions regarding material and weld strengths, we felt that it was necessary that we develop reliable methods and procedures to validate them.

Methods and Procedures

1. The first step of validation is contributed by our material suppliers. With each incoming shipment, traceable values of tensile strength and other factors are supplied by our vendors. Those values are used in our load and stress calculations for each application.
2. Secondly, we follow rigid shop procedures throughout the fabrication process. Our Quality Control System includes standard procedures for Material inventory and traceability, material cutting and edge preparation, fitting procedures, weld profiles and the regular calibration of our equipment. This internal control method also takes advantage of one of our finest assets: the experience of our senior technicians. At every level, our younger fabricators are learning from senior technicians, gaining their own expertise to secure our collective future.
3. The third component of our validation strategy is contributed by outside agents performing destructive tests on our sample weld profiles. Butt-fusion, corner-fusion, and multiple extrusion and hand-bead weld samples are periodically submitted for tensile, torque, bending and other mechanical tests. The success of our welds through testing validates that our established fabrication methods and procedures consistently produce reliable results.
4. In some cases, other in-house testing methods are also used:
   • Thinner materials used build pit linings or trenches are spark-tested for weld integrity.
   • We also perform simple hydrostatic (ambient standing-water) tests; however, these are usually redundant, given our strict adherence to established fabrication policies and procedures.
   • With our in-house recirculating boiler, we perform hot tests at actual operating temperatures up to 200 deg F. During hot tests, we also verify accuracy of the dimensional changes we've estimated will occur at operation.
5. Our fusion-welding equipment (welds with no filler materials) regularly produces welds that are stronger than the parent material. A typical extrusion weld sample (a homogeneous one-pass weld of multiple-pass size) has upwards of 90% of the strength of the parent material. Hand beads, by their nature the weakest plastic welds, typically fail at 25-30% of the strength of the parent sheet. For this reason, hand beads are not used in areas with high structural demands.