GMW GMW15586 PDF

Note: Nothing in this standard supersedes applicable laws and regulations.

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

Purpose. This procedure describes the standard equipment configuration and test method for line purge and bell cup cleaning of waterborne basecoat using low Volatile Organic Compounds (VOC) and low Hazardous Air Pollutants (HAP) purge solvent solutions.

The procedure can also be applied, on an as needed basis, for the cleaning capability testing of solventborne basecoats using higher VOC purge materials.

Foreword. The purpose of a line purge and bell cup wash cycle is to clean out the paint line and the fluid tip and to remove any paint overspray which has collected on the exterior surfaces of the bell cup during the normal paint application process.

This test procedure should be performed during the development of new purge materials prior to submission of proposals to GM.

Note: It should be noted that this test procedure does not represent actual production conditions, but rather represents a screening method that provides a relative comparison of the cleaning effectiveness between a known and/or verified baseline purge material and one or more test materials by comparing the build-up left on an applicator after a given number of test cycles.

Applicability. Dependent upon the objective of the testing, the baseline purge material can be a solution of butyl cello solve/amine, as indicated in the Test Equipment section of this test procedure, a solution of a specified concentration of a current production material, or a solution of a given concentration of a material specified by the responsible engineer at GM Paint & Polymers Center.

All proposed purge materials for the cleaning of waterborne basecoat should first be tested by the supplier using the solution of butyl cellosolve/amine as a baseline test to verify that the proposed purge material is at least as effective as a butyl cellosolve/amine solution.

After verification with butyl cellosolve/amine, contact the responsible engineer at GM Paint & Polymers for the baseline purge material that has demonstrated process stability for a specific plant for further testing.

More build-up on the applicator after completion of the specified number of spray/purge cycles for the test purge vs. the build-up achieved for the baseline material after the completion of a given number of cycles would indicate that the test purge is not as effective as the baseline purge, while less build-up on the applicator vs. the baseline purge after the completion of a specified number of cycles would indicate that the test purge is more effective than the baseline purge.

The standard equipment configuration is composed of a stationary rotary atomizer mounted vertically within a downdraft or side-draft spray booth. Because the procedure does not incorporate the use of a bell wash station, cleaning of the bell cup interior and exterior surfaces is accomplished through direct contact of the purge solvent solution with any paint overspray or build-up.

This equipment configuration is required for the evaluation of the cleaning capabilities of new or proposed purge materials relative to a standard baseline solution when tested with approved waterborne or solventborne basecoat technologies specified by GM Paint & Polymers Center.

The test procedure can be applied in determining the cleaning capabilities of purge materials relative to a standard baseline solution for both bell and gun cleaning applications.

A proposed change in purge formulation or purge supplier at a given facility will require that the current production purge be compared with the proposed test purge according to this test method or that the change be approved by the responsible engineer at GM Paint & Polymers Center.

A change in basecoat at a given facility will require that the current production purge be evaluated according to this test method or that the change be approved by the responsible engineer at GM Paint & Polymers Center.

A change in applicator at a given facility will require that the current production basecoat and purge system be evaluated under plant specific parameters to verify adequate cleaning capabilities or that the change be approved by the responsible engineer at GM Paint & Polymers Center.