Note: Nothing in this standard supersedes applicable laws and regulations unless specific exemption has been obtained.

Note: In the event of conflict between the English and domestic language, the English language shall take precedence.

Purpose.

To evaluate the drop test capabilities of non-metallic fuel tanks.

Foreword.

This procedure is used by tank suppliers to develop tank designs and for quality control during production. It is included as part of the following specification listed on the part drawing (related to performance):

• GM Engineering Standard GM7473M, "Coextruded Multi-layer Plastic Fuel Tank"

This procedure specifies two methods that may be used:

Long Method:

This method takes a tank with a 60/40 glycol/water mixture inside (both at ambient temperature) and cools them together in a cold chamber to -40 ± 2°C (-40 ± 4°F). This method would be used if resources were not available to precool the glycol/water mixture (i.e., larger chamber, separate chamber for precooled glycol/water mixture, energy required to sustain pre-cooled glycol/water mixture).

Short Method:

This method takes a tank (at ambient temperature) and cools it to -40 ± 2°C (-40 ± 4°F). Then a glycol/water mixture pre-cooled to -40 ± 2°C (-40 ± 4°F) is added. The time it takes to cool the tank is much less than that required to cool the glycol/water mixture, thus saving time. This method, however, required resources to precool the glycol/water mixture (i.e., larger chamber, extra chamber to cool glycol/water mixture, dedicated test chamber, energy). An advantage of the short method when used in quality control is that if a test sample tank does not meet the requirement, then a fewer number of tanks will have been produced since the last test. This will result in less scrap.

Applicability.

Non-metallic fuel tanks.