How Do You Know If Your Chemical Storage Tank Is Compatible?
When you’re storing hazardous fluids such as corrosive acids, bases, or aggressively oxidizing chemicals, you need to be confident that your chemical storage tank can meet your expectations for years. You can’t afford to invest in chemical tanks, only to discover a year later that your chemical storage tank isn’t compatible with the chemicals you’re using. That’s a loss of product, time, and money—and it could put your people, equipment, and environment at risk, as well.
Sometimes customers come to us seeking proof that our storage tanks are compatible with the specific chemicals they’re using. Usually, it’s due to one of these scenarios:
- They want to know if their current tank can handle a new kind of chemical
- They’re ordering a new tank and want to ensure it will perform to expectations
- They see something about their current tank that concerns them, such as discoloration of the tank wall
Designing and Testing Your Chemical Storage Tanks
At Poly Processing, your tank’s safety and longevity is our top priority. We partner with you throughout the design and manufacturing process to ensure that your crosslinked polyethylene chemical tank will meet the demands of your specific application for years. Whether you need a SAFE-Tank double wall tank, full discharge IMFO tank, or an industry leading vertical plastic tank, our technical team asks you key questions about every factor that could have an impact on the life and performance of the XLPE tank—and it starts with chemical compatibility. We want to make sure that the chemical(s) you're storing are the basis of our tank design. It might be sulfuric acid, acetic acid, or other hazardous or non-hazardous chemicals. We want to make sure to get it right the first time, every time.
Poly Processing Company measures tanks we manufacture to ensure that they pass the testing protocols in the ASTM D-1998 standard set up by the American Society for Testing and Materials. In rare cases as needed, we leverage relationships with third-party labs to perform rigorous, independent testing on the tank wall. Typically, we supply XLPE samples from our facility, or you can supply a sample from a tank you already have at your site. In either case, the sample is sent to the third-party testing facility and the test results are delivered to you.
Let’s look at two of the most common tests that are performed to determine long-term structural integrity.
Polymer Chemical Resistance Tests
Polymer chemical resistance tests ensure that the corrosive acid, base, or oxidizer you’re storing won’t interact with the polymer tank wall which might result in premature tank failure or malfunction. A sample of our crosslinked polyethylene is tested across several properties that could be affected, including mechanical strength, chemical deterioration, and material swelling.
Chemical resistance testing helps determine if the crosslinked polyethylene that we produce our tanks with will perform reliably throughout its service life.
Simulated Stress Testing
The ASTM D543 evaluates plastic materials for resistance to harsh chemicals. Chemical reagents can include cleaning agents, acids, bases, oxidizers, or anything else that the test material may come into contact with. ASTM D543 simulates the tank material’s performance and the environment the tank will be used in. The test accommodates changes in weight, dimensions, appearance, and strength properties. Provisions are made for various exposure times, strain conditions and elevated temperatures.
Before the test, samples of the tank wall are weighed and measured. The samples are then placed in contact with the chemical reagent to simulate the real-world stress on the tank. After testing, the specimens are removed and re-evaluated for changes in weight, appearance, and strength properties.
ASTM D-1998 Standards and Testing
Not all tank manufacturers follow ASTM D-1998 standards. The ASTM D-1998 standard is set up by the American Society for Testing and Materials to ensure that tanks are built and tested to a recognized standard.
ASTM standards require that many polyethylene tanks and tank materials go through three tests to measure:
- The consistency in the tank’s walls
- The amount of impact the tank can withstand
- The structural integrity of the tank as a whole
There’s also an additional test for cross-linked polyethylene (XLPE) tanks to measure the chemical makeup of the tank materials.
Let’s take a look at each of the tests and what they mean for your chemical storage tank. As you’ll see, Poly Processing doesn’t simply meet ASTM standards, in some cases we exceed them.
Ultrasonic test: wall thickness
The ultrasonic test is performed to ensure a consistent wall thickness around the entirety of the polyethylene chemical storage tank. Variations in thickness are potential weak spots for tank failure.
This test incorporates an ultrasonic instrument that sends out measurable sound waves. By measuring the time it takes for the waves to travel back, we can calculate the wall depth and verify if it is consistent throughout the tank. We can do this test at various points around the diameter of the chemical storage tank, all the way up the tank wall if it is required.
Impact test: structural integrity
A sample of the tank’s material is taken, usually from holes where fittings will be placed, and tested for structural integrity. The sample material is frozen overnight at -20 degrees Fahrenheit, then placed into a machine where a “dart” is dropped at a certain foot-pound to create the appropriate impact for testing. There are various calculations to determine the required impact. The thicker the tank material, the higher the impact.
This test is administered to verify the tank material can withstand mechanical stress and other challenges associated with long-term industrial or municipal chemical storage.
Hydrostatic test: internal pressure
In this test, the storage tanks are filled to the dome with water. ASTM requires that it sits for 30 minutes to verify that there are no leaks and the tank can withstand the hydrostatic weight of the water. Poly Processing’s internal standard is to let the tank sit for at least an hour, but it is common for some of our customers to request a 4-hour or 24-hour hydro test.
This test is performed on the tank as a whole, not just a sample. It not only measures the tank’s ability to withstand hydrostatic pressure, but it tests the fittings and gaskets as well.
Gel test: cross-linking
Performed only on cross-linked polyethylene tanks, the gel test measures the percentage of cross-linking in the wall itself. A sample of the tank material is weighed, then placed in boiling xylene, which breaks down the linear polyethylene, the base material of the resin. All that is left is the cross-linked materials. The sample is weighed again and the difference is calculated to determine the percentage of cross-linking.
To meet ASTM standards, a tank must be at least 60% crosslinked polyethylene. If the gel percentage is too high though, it creates a brittle material. Since some chemicals can only be stored in cross-linked polyethylene tanks, it is critical that the tank’s crosslink percentage hits that sweet spot of 60% to 70%.
At Poly Processing, we manufacture all of our industry leading tanks that are required to meet ASTM D-1998 standards to those standards and test to make sure they do. In fact, we strive to exceed expectations to ensure that all of our tanks provide the best chemical storage applications in the industry.
Reliable Tank Performance
Poly Processing understands how important it is to have peace of mind about your crosslinked polyethylene chemical tanks. You can count on our technical team to work with you until you’re confident that your XLPE poly tank will meet or exceed your performance expectations. Our track record under the harshest chemicals is proof of that commitment.
Ready to design your chemical storage tank? Get started now!
- April 3, 2023
- Topics: Value Added
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