ASTM D 1998 Standard:
The ASTM D 1998 Standard defines a set of rules with respect to the material of construction, manufacturing process, product application, and product size.
The ASTM D 1998 Standard was established for rotationally molded upright, cylindrical, flat tanks 500 gallons and greater, molded in one-piece seamless construction. The tanks are designed for above-ground, vertical installation and are capable of containing chemicals at atmospheric pressure. This standard does not cover the design of vessels intended for use at pressures above or below atmospheric conditions. It is also not for vessels intended for use with liquids heated above their flash points, temperatures above 140 degrees Fahrenheit for Type I materials (cross-linkable polyethylene), or temperatures above 130 degrees Fahrenheit for Type II materials (non-cross-linkable polyethylene).
To ensure ongoing compliance to ASTM D 1998 Snyder Industries Inc. conducts various types test methods on our ASTM manufactured Industrial tanks.
Wall Thickness Test:
Ultrasonic testing is performed to ensure that our ASTM manufactured tanks meet design thickness requirements and tolerances. Ultrasonic testing is an instantaneous, reliable, repeatable and accurate method of measurement that is achieved by placing a probe on one side of the tank wall and transmitting a sound wave into the material.
The sound wave travels through the material to the inner surface. The wave is reflected off of the inner surface and back to the probe. The ultrasonic gauge measures the time it takes for the sound wave to travel through the material and then calculates the thickness based on the velocity of the sound wave.
Hydrostatic Water Test:
The hydrostatic water test shall consist of filling the tank to brim full capacity for a minimum of four hours and
conducting a visual inspection for leaks.
Low Temperature Impact Test:
ASTM D 1998 requires that test samples cut from the tank be conditioned at a temperature of -29 degrees Celsius (-20 degrees Fahrenheit) prior to performing the impact test. Snyder Industries Inc. has implemented a more stringent requirement of conditioning test samples to -40 Fahrenheit to ensure that only the highest quality molding conditions are achieved. After conditioning to -40 degrees Fahrenheit the test sample is impacted with a weighted dart that is dropped from a specified height onto the sample and impacted in accordance with the standard testing methods found in ASTM D 1998. Snyder Industries Inc. requires that test specimens < ½ inch thickness shall be tested at 100 foot pounds. Test specimens > ½ inch thickness shall be tested at 200 foot pounds. All Industrial ASTM D 1998 tanks require an impact test unless it is a tank with no holes and no fittings.
O – Xylene - Insoluble Fraction (Gel Test):
This test method is for determination of the ortho-xylene insoluble fraction (gel) of crosslinked polyethylene. This test is conducted in accordance with the standard testing methods found in ASTM D 1998. Crosslinked materials can provide improved low temperature impact strength, better heat and chemical resistance and is often preferred for many types of chemical storage and fuel tank applications. Crosslinking material is formed by connecting polyethylene molecules with a chemical link. A method for measuring the amount of crosslinking can be achieved by dissolving test samples from molded tanks in xylene and measuring the amount of remaining material called gel. ASTM D 1998 requires that the percent of gel level for Type I tanks on the inside 1/8th inch of the wall shall be a minimum of 60%. Snyder Industries Inc. has implemented a more stringent requirement that the percent of gel level for Type I tanks on the inside 1/8th inch of the wall shall be a minimum of 65%.