Grommets

The design of grommets is critical to the acoustic performance of any partition such as engine bay bulkhead.

Design Guidelines

• Grommets should be of soft material (natural rubber recommended by a supplier though may not be suitable for high temperature areas) to ensure consistent fit.
• Maximise grommet thickness.
• High contact area to hose/harness, usually involves a sleeve.
• High contact area to panel.
• Grommet should be bonded to hose/harness to ensure good contact.
• Hose/harness should be stress-free in area of grommet (i.e., is not at an angle or forced to one side of the grommet).
• Overlaps acoustic treatment ensuring that no metal is visible.
• For large areas, e.g., heater gaskets, do not use open cell foam, closed cell material provides a much better barrier.
• Minimise size of hole in panel.
• Put form in the panel around the grommet (i.e., a recess) to ensure a flat panel condition.
• Ensure that the holes in the panel are remote from seam sealer, underseal and spot welds.
• Harnesses - Wires bonded together under the grommet