Resin Materials (Taking a storage tank as an example)
Polyethylene resins can be hard to identify after a product has been installed.
Common misconceptions are LPE is the same as XLPE.
The following pictures will help you determine materials.
The picture on the right is a Linear LDPE tank: Notice the “White color”. Linear PE is a weldable, FDA approved material Used commonly for day tanks and small chemical feed applications.
On the left is a Crosslink HDXLPE tank: Notice the “off White / Yellow color”. Crosslink polyethylene is used for large industrial bulk storage applications.
Linear PE molecules when molded bond”end to end” sides& Crosslink PE molecules bond on all four forming an “X” type bondas shown below:
Crosslink has a stronger molecular structure than linear PE
LDPE: Two-dimensional structure
XLPE:Four-dimensional “X” crosslink structure
Ultra-Violet Exposure:
Over-exposure to Ultra-violet rays is pictured below. Quality polyethylene resins are compounded with Ultra-violet stabilizer prior to being distributed to the tank manufacturer’s facility.
Tanks that are installed in areas that have extreme amounts of UV exposure should be sheltered from the environment, insulated or colored for additional protection.
Common in the industry, tank manufacturers reduce wall thickness by using less resin in the upper sidewall and dome of the tank.
This makes the tank roof more susceptible to ultraviolet damage.
SUNSOAR polyethylene tanks are constructed with uniform-wall thickness from top to bottom.
This added thickness gives additional protection to Ultra-violet exposure and extends the service life of the tank.
A common test method to see if your tank has undergone Ultra-violet attack is to use water based stain or marker and color in a small area that has been exposed to sunlight.
This will fill any voids in the polyethylene material making cracks visible. Areas to check are the dome and lower sidewall of the tank .
Chemical Resistance:
This information is based on our experience, research and support from other published chemical resistance charts.
It is believed to be reliable; it is however, intended to be used only as a guide. SUNSOARTECH no responsibility in connection with it’s use.
Additional assistance should be requested if there is a doubt about compatibility, suitability, warranty, allowable
transportability, or storage in SUNSOAR products.
Tank Failure:
Polyethylene tanks are the most corrosion resistant method for storage of harsh chemicals.
Improper plumbing attachments, Chemical and UV attacks are the most common causes for failure.
Tanks can also fail due to age. Pictured below is a polyethylene tank that failed due to age.
As you can see in the picture this tank has cracked a few inches above the tank floor. Typically cracks will develop near the tank base where the tank expands and contracts under normal operating conditions.
When inspecting a tank always look near the tank’s knuckle radius.
This picture is a chemical stress crack in a Crosslink polyethylene tank. Stress cracks normally develop at or near tank sidewall connections. A Crosslink tank will typically develop a stress crack prior to complete tank
failure. This gives the end user warning to get the tank removed from service. Normally a Linear polyethylene tank will not give this type of warning before complete failure.
