General - Frequently Asked Questions
1. What makes poly tanks a good choice for my chemical storage/application?
2. What chemicals can I store in your tanks?
3. What material does KEFCO use to manufacture it's poly tanks?
4. Which tank material is best?
5. How heavy a material can polyethylene tanks hold?
6. What is the wall thickness of your tanks?
7. Are your tanks FDA approved?
8. What is the maximum temperature that your tanks will withstand?
9. Can I store petroleum products in your tanks?
10. Can your tanks be pressurized?
11. Can your tanks be buried?
12. What is the warranty on your tanks?
13. How many years will my tank last?
14. Will freezing temperatures hurt my poly tank?
15. Is there some way to tell when my tank was made?
1. What makes poly tanks a good choice for my chemical storage/application?
- Poly tanks are lower cost than stainless steel or fiberglass
- Lightweight - less than one-half the weight of steel
- Seamless construction for easy cleaning and leak proof service
- Exceptional Impact resistance
- Broad range of chemical resistance
- Better weatherability
- Available in a variety of resins
- Translucent when molded of natural resin for visible liquid level
- Virtually maintenance free
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2.What chemicals can I store in your tanks?
Poly tanks have a broad range of chemical resistance to both Agricultural and Industrial chemicals. For Industrial Chemicals refer to the KEFCO Chemical Resistance Recommendation Chart (PDF Document) [click here for HTML version] on that site 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 KEFCO INCORPORATED 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.
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3.What material does KEFCO use to manufacture it's poly tanks?
KEFCO uses HDLPE (high density linear polyethylene) to manufacture our tank line. High density linear polyethylene has good structural rigidity and impact resistance. It is resistant to a broad range of chemicals including sulfuric acid, sodium hypochlorite, and sodium hydroxide.
We also offer, for specific applications XLPE (cross-linked polyethylene). Crosslinked polyethylene has excellent structural rigidity and impact resistance. It is used as an alternative to HDLPE for storing surfactants or solvent-based chemicals, or for higher service temperatures.
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4. Which tank material is best?
General guidelines of material selection are not advisable. It is always best to provide the tank manufacturer with specific application details (chemical, concentration, specific gravity, temperature, dimensions, mechanical loading) so a proper tank design recommendation can be made by the factory and/or your KEFCO distributor.
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5. How heavy a material can polyethylene tanks hold?
A tank with a specific gravity of 1.5 can hold a liquid up to 12.5 pounds per gallon at 100 degrees F. A tank with a specific gravity of 1.9 can hold a liquid up to 15.75 pounds per gallon at 73 degrees F. Please note that an increase in liquid temperature will 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 KEFCO Chemical Resistance Recommendation Chart (PDF Document) [click here for HTML version] or call KEFCO INCORPORATED to determine which tank design is best suited for the
chemical application.
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6. What is the wall thickness of your tanks?
Because KEFCO tanks have a stratiform wall thickness (varies 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 actual weight of the tank is also not a good comparison when shopping for tanks. Just because a competitor may use more material in the tank does not make it a better tank. That is determined by the resin, mold design and the steps taken during the rotomolding process. Lower grades of resins will require a thicker tank wall to compensate.
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7. Are your tanks FDA approved?
The resin used to manufacture our linear polyethylene tanks (HDLPE) meet specifications contained in FDA Regulations 21 CFR 177.1520, © 3.2 an 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. The HDLPE resin that KEFCO uses is also NSF 61 listed.
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8. What is the maximum temperature that your tanks will withstand?
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: The leading manufacturers in this industry design their tanks based upon 100 degrees F with ASTM D 1998 calling out 73 degrees F. It is important to contact the factory when your application will continuously be above 100 degrees (ambient). The tank can be designed specifically for your
elevated temperature application.
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9. Can I store petroleum products in your tanks?
We do not recommend storing petroleum products in our tanks because they will permeate (soften) the tank walls. Contact KEFCO with your specific application. You will find that aromatic hydrocarbons and halogenated hydrocarbons will not be recommended for polyethylene.
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10. Can your tanks be pressurized?
No, our tanks cannot be pressurized. They are all designed to atmospheric pressure.
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11. Can your tanks be buried?
Tanks specifically designed for above ground use cannot be put underground 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 cistern and septic tank line that is available that is designed for below ground use.
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12. What is the warranty on your tanks?
KEFCO warrants to the purchaser for any manufactured tank product proven to be defective in material or workmanship within 3 years from date of original invoice from factory. An extended tank warranty is available as a purchased option for an additional 5-year period (total of 8 years) on KEFCO Vertical Storage Tanks and Cone Bottom Tanks on some applications. KEFCO also offers chemical specific warranties on certain
chemicals including sulfuric acid, sodium hypochlorite and others. Contact KEFCO on questions regarding warranty for your specific application.
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13. 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 KEFCO's "Guidelines for Use & Installation". Having flexible connections that compensate for the expansion and contraction of the tank will extend the life of the tank.
View the Kefco Tank Use and Installation Guide (html format).
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 states 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.
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14. 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.
KEFCO utilizes a test called "Low Temperature Impact Resistance". This is a test utilized by both the ARM (Association of Rotational Molders) and ASTM D 1998. KEFCO's guidelines for this test actually exceed the
requirements of ARM and ASTM D 1998. They call out -20 degrees F for the test and Snyder does its' 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 any tank, especially with sharp items, at any temperature.
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15. Is there some way to tell when my tank was made?
KEFCO tanks are produced with a molded-in serial number (wheel-date/month format). In addition, the tank's bar code label has a 10-digit serial number and date of manufacture. Your KEFCO Sales or Customer Service person, can help you interpret the date of manufacture.
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