Judging the Performance of a Polyethylene Tank

While, at a glance, it’s impossible to gauge the life of your polyethylene chemical storage tank, there are many things to know and consider that will help you extend the life of your tank to its fullest potential. It is important to know that from the production of the tank, through installation, it is expertly manufactured with all of the right gaskets and fittings. After tank installation, it is important to have it inspected regularly to look for problems that could cause tank failure.

Let’s walk through each phase and take a look at what you should consider to appropriately judge the performance of your polyethylene tank.

The Production Stage of Polyethylene

First and foremost, it is critical that you specify the chemical you’ll be storing when you order your tank. The tank is designed and manufactured based on the chemical, so it’s important to know if your chemical will require an antioxidant layer or thicker tank walls based on the specific gravity of the chemical. Additionally, the chemical you are storing will dictate the types of gaskets and fittings used on the tank system.

Thinking ahead in this way makes for a longer tank life. It is also important that the material of your tank be tested prior to use. Poly Processing performs all ASTM D 1998 testing in-house to ensure your tank is built to last.

The Installation Stage of Polyethylene

Upon installation, it’s very important for it to have a smooth and clean landing place. One rogue screw or bolt can impact the life of the tank significantly, because it can damage the tank wall or prevent it from expanding and contracting naturally. Because of that expansion and contraction, having flexible connectors on the lower sidewall is equally important to the lifespan and performance of your polyethylene tank. If the connectors are not flexible, they cannot move with the tank, creating a hinge point that can cause premature tank failure.

Finally, it is very important to make sure that the tank is vented properly. Whether the tank is mechanically or pneumatically filled, there are venting guidelines that state the minimum venting requirements for different tanks and fill methods. If the tank is under-vented it could lead to mechanical failure from over-pressurization.

It goes without saying that reading the installation guide and appropriate checklists contained within will be well worth the time.

The Inspection Stage of Polyethylene

It is important to note that you must exercise safety when inspecting a tank. If you must do any sort of inspection inside the tank, you must neutralize and clean the inside, especially when you have a confined space entry situation.  Any and all confined space regulations/procedures should be followed when entering the tank. When inspecting the inside of the tank, also check where it is wetted with chemical, and where it is exposed to fumes (also called the vapor space). Fumes can be more corrosive on a tank than the chemical itself.

On the outside of the tank, look for cracks and crazing (hairline cracks in plastic). In outdoor tanks, UV degradation will often be more evident on the dome because of more direct sun exposure. Although Poly Processing’s polyethylene resins have built-in UV stabilizers, over time there could be UV degradation. It’s important to also check for leaks around fittings, to check to see if there are signs of corrosion or wear in the gaskets, and to check all vent lines to make sure there are no restrictions, including bird nests and beehives. Restrictions can lead to over-pressurization.

One strong suggestion is to not change the chemical you’re storing in the tank before talking to a chemical storage expert. Since the tank was specifically designed for your original application, you may need different connectors, manways, or a different tank altogether. Poly Processing offers an inspection checklist, but we also have Field Service Technicians that can perform tank inspections for you. These skilled experts can even take a sample of your tank back to the shop for an ASTM D 1998 Gel and Impact Test to make sure your cross linked polyethylene tank is still up to the task.

Get in touch with one of our Field Service Technicians today

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