Engineering Data : Frequently Asked Questions


WHAT’S THE DIFFERENCE BETWEEN Commercial & Industrial Tanks?
Our Industrial Grade Tank list is for engineered tanks. These tanks have a thicker wall based on a 600 hoops stress calculation to determine the specific gravity rating. These tanks are also designed based on the criteria developed by the American Society for Testing and Materials (ASTM). Multiple fittings at many locations can be added to tanks listed in the Industrial Tank List.

Our Commercial Grade Tank List is for tanks in less chemically severe applications. These tanks are thinner walled based on lower hoop stress calculation to determine the specific gravity rating. This industry has a definite distinction between manufacturers that build ASTM tanks and commodity tanks. These tanks come with either no fittings (other than a Manway) or a predetermined fitting package outlined in the price list.

To determine which tanks you need (Industrial or Commercial) will depend on the application. Our published Chemical Resistance Recommendations chart outlines the design information (specific gravity and hoop stress) for several chemical applications. Another determining factor is fittings required on the tank. If the fittings required are other than the predetermined fitting package offered, then the Industrial (ASTM) Tank line should be used.

Since there is no one type of resin that is best suited for every application, We offer tanks manufactured using both cross-linked polyethylene (XLPE) and linear polyethylene (HDLPE) resins. While XLPE tanks are preferred in some applications such as surfactants, field experience and laboratory testing demonstrate that in many applications HDLPE tanks are equivalent to or superior to XLPE tanks. Please refer to the Chemical Resistance Recommendation Chart to determine which resin is best suited for your application. Or call us for assistance.

The resins used to manufacture our linear polyethylene tanks meet specifications contained in FDA Regulations 21 CFR 177.1520, 9 (c) 3.2 and so may be used as an article or component of articles intended for use in contact with food, subject to any limitations in the regulation. Cross-linked polyethylene (XLPE) tanks do not meet FDA regulations. Note: The HDLPE tank that we offer is also NSF 61 listed. This resin is also NSF 61 listed by Exxon. Contact us for further details.

Linear polyethylene (HDLPE) storage tanks have a maximum storage temperature of 120 degrees F. Cross-Linked polyethylene (XLPE) storage tanks have a maximum storage temperature of 130 degrees F. Note: Standard tanks are designed based upon ambient conditions or 100 degrees F. Contact us for application.

A tank with a specific gravity of 1.5 can hold a liquid up to 12.5 pounds per gallon at 73 degrees F. A tank with a specific gravity of 1.9 can hold up to 15.83 pounds per gallon at 73 degrees F. Please note that an increase in liquid temperature can substantially decrease the specific gravity rating. Also, certain chemicals have environmental stress cracking agents in them so higher specific gravity tanks are needed to compensate even though the weight of the chemical may be lower. Please refer to the Chemical Resistance Recommendation Chart or call us to determine which tank design is best suited for the chemical application.

Because our tanks have a stratiform wall thickness (tapers from top to bottom on a tank), wall thickness is not the best gauge for determining the quality of a tank. The very bottom of the tank is the thinnest part of the tank and is made that way to flex when the tank is empty or full. The lower sidewall is the heaviest or thickest part of the tank. As the head pressure is reduced going up the wall of the tank the thickness of the tank is also reduced based upon the Barlow formula and ASTM D 1998-13.

The actual weight of the tank is also not a good comparison when shopping for tanks. Lower density resins and lower grades of resins require heavier walls to compensate for the lower physicals of the resins. Just because a competitor may use more material in the tank does not make it a better tank. You will find that the equipment used by some manufacturers also restricts their ability to put the resin where it needs to be. The quality of the tank design is determined by the resin, mold design and the steps taken during the rotational molding process to properly cure the resin.

Refer to the Chemical Resistance Recommendation Chart or contact the chemical supplier to see if their product is compatible with high-density linear polyethylene (HDLPE) or cross-linked polyethylene (XLPE). If they cannot answer your question, call us and we will be happy to research it for you. Try to have as much information available as possible such as the temperature of the product, the percent concentration of product (Ex: Sodium Hypochlorite, 15%) etc. You will often find that the chemical manufacturer can make the best recommendation. Their actual experience is often the best source. The manufacturer will be listed on the MSDS sheet.

We do not recommend storing certain petroleum products in our tanks because they will permeate (soften) the tank walls. Contact us in regards to specific applications.

No, our tanks cannot be pressurized. They are all designed to atmospheric pressure.

Tanks specifically designed for above ground use cannot be buried because the weight of the ground around the tank can cause the wall to collapse. If you have an application for a below ground tank we do have a few tank lines available that are designed for below ground use.

Dedicated Plastic Tanks Inc. warrants to the purchaser that if any molded tank proven to be defective in material or workmanship within 3 years from date of original invoice from the factory then Dedicated Plastic Tanks will (at company option) either repair or replace said tank. The Dedicated Plastic Tanks Standard Limited Warranty does not apply to damage resulting from misuse, improper application, neglect, shipment damage, material wear, accident or improper installation.

Dedicated Plastic Tanks Inc. also warrants to the purchaser that if any tank fitting or attachment product is proven to be defective in material or workmanship within 1 year from the date of original invoice and that Dedicated Plastic Tanks Inc. is notified within 15 days after such defect is discovered, Dedicated Plastic Tanks Inc. will (at company option) either replace or repair said part. The Dedicated Plastic Tanks Inc. Standard Limited Warranty does not apply to damage resulting from misuse, improper application or recommendation of material, neglect, shipment damage, material wear, accident or improper installation or maintenance.

We also offer chemical specific warranties on certain chemicals including sulfuric acid, sodium hypochlorite and others. Contact us on questions regarding warranty for your specific application.

How many years will my tank last?
There are many variables that can have an effect on the life of a polyethylene tank.

The type of material being stored in the tank, it's concentration, and temperature. The temperature of the application can be a factor, especially if the tank design is not based upon the temperature of the application. Some applications may permeate the polyethylene at elevated temperatures. Special considerations - some chemicals will have long term affects on the polyethylene and may require special considerations. As an example, sodium hypochlorite will degrade from UV exposure and elevated temperature. As it degrades it can build up sediment in the bottom of the tank. If this sediment is periodically flushed from the tank it will extend the life of the tank.

Installation and PIPING! - The number one reason for tank failures is due to improper installation. It is important to follow our "Guidelines for Use & Installation". Having flexible connections that compensate for the expansion and contraction of the tank will extend the life of the tank.

Is the tank used indoors or outdoors? The amount of U.V. exposure will be based upon the time of exposure and the closeness of the installation to the sun (elevation). What part of the country are you in? Tanks used outdoors in areas subjected to more intense sunshine will be more affected by the sun. UV rays will have a detrimental effect on the life span of all poly tanks.

Storage or process - Is the tank a holding tank or a processing tank? A tank that is continuously cycled will see more stress then a tank that remains at one level or close to one level for extended periods of time. Tanks with excessive agitation may also be exposed to undo stress. Stationary tanks will also not see the stress of a tank that is being transported.

Will freezing temperatures hurt my poly tank?
Freezing temperatures will not have an affect on a polyethylene tank, however if there is liquid in the tank, make sure the freezing liquid has enough head room to expand.

Manufacturers utilize a test called "Low Temperature Impact Resistance". This is a test utilized by both the ARM (Association of Rotational Molders) and ASTM D 1998. Our testing capabilities exceed the requirements of ARM and ASTM D 1998. They call out -20 degrees F for the test, but our manufacturer has conducted testing at -40 degrees F. This test is critical to determine if the resin has been properly processed and it will give you an idea as to the temperatures that the resins can see. It is important that efforts be made to avoid impacting the tank, especially with sharp items, at any temperature.

Can I store BIODIESEL in your tanks?
Biodiesel is the name of a clean burning alternative fuel, produced from domestic, renewable resources. Biodiesel contains no petroleum, but it can be blended at any level with petroleum diesel fuel to create a biodiesel blend. Biodiesel or B100 (100%) refers to the pure fuel. Biodiesel blends or BXX refers to a fuel that is composed of a % of biodiesel blended into a conventional fuel (example B20 = 20% Biodiesel blended with 80% conventional fuel).

Our manufacturers have conducted chemical compatibility testing on B100. Our chemical compatibility testing showed that uniquely processed HDLPE and XLPE resins are compatible with B100. From chemical compatibility testing, we recommend ONLY above ground 1.9 specific gravity Industrial (ASTM) designed tanks (600 psi hoop stress) for B100 applications. Not recommended are below ground, agricultural or other non-ASTM designed tanks to be used in this application.

The manufacturers warranty for biodiesel B100 applications is one year (1) against defects in material and workmanship.
Chemical compatibility testing does not include any biodiesel blends so we have no recommendation for biodiesel blends at this time.

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