How do you know by looking at a chemical storage tank how well it’s constructed? There’s a big difference between a well-designed, properly constructed tank and an inexpensive one that doesn’t meet structural requirements. But it takes more than the naked eye to spot critical flaws.
That’s why we submit our cross-linked polyethylene tanks to five rigorous quality assurance tests. Our specialized inspections and tests meet and exceed the ASTM D-1998 standards. The ASTM D-1998 standard is designed to give end users a margin of safety and peace of mind. But it’s a voluntary standard, and not all tank manufacturers follow it.
When you receive your cross-linked polyethylene tank from Poly Processing, you can rest assured that the tank has been thoroughly inspected and tested.
The first and most basic line of testing is the eye test. We visually inspect every tank for defects or imperfections right after it’s molded to ensure that the tank meets our rigorous quality standards.
The impact test is designed to test a tank’s structural integrity. A sample of the tank is frozen overnight to -20 degrees Fahrenheit, then placed into a machine where a 20-pound “dart” is dropped from a specified height. This test is designed to verify that the tank material can withstand mechanical stress and other challenges associated with long-term chemical storage.
Performed only on cross-linked polyethylene tanks, the gel test measures the percentage of cross-linking in the tank wall itself. A sample of the tank material is weighed, then placed in boiling xylene, which dissolves the linear polyethylene. The remaining sample is cross-linked polyethylene (XLPE). The sample is dried, measured, and compared to the original sample to determine the crosslink percentage. To meet ASTM standards, the tank must be at least 60% crosslinked.
The ultrasonic test ensures a consistent wall thickness around the entirety of the polyethylene chemical storage tank, and ensures that the tank meets the standard for its designed use. This test incorporates an ultrasound instrument to measure the wall thickness. Various points around the diameter of the tank are tested, along the entire height of the tank wall. Standard wall thickness readings are done at 0 degrees, 90 degrees, and 270 degrees at 1-foot, 2-foot, and 3-foot elevations.
The hydrostatic test is performed on the tank as a whole, not just a sample of the materials. It not only measures the tank’s ability to withstand hydrostatic pressure, but it measures the fittings and accessories as well.
For the hydro test, the tank is filled to the dome with water. ASTM requires that it sits for 30 minutes, but Poly Processing requires that it sits for at least 60 minutes to verify that there are no leaks in the tank or installed fittings, and that the tank can withstand the hydrostatic weight of the water. It’s common for a customer to request anything from a 4-hour to a 48-hour water test.
A Warranty That Stands By Our Testing
Poly Processing offers a five-year warranty for tanks in most chemical applications. However, our customers report that crosslinked polyethylene tanks provide 15 to 20+ years of service in many applications. In the end, though, the life of your chemical storage tank depends on several factors and variables.