Pressure compensation with application of perforated plate

Perforated metal is commonly used to enclose electrical equipments to attenuate the EMI/ RFI radiation they release and to ventilate them at the same time. Many questions occur about which perforated pattern is fit to meet the design requirements and shielding effectiveness of different perforated patterns and materials.

Shielding effectiveness of 40 dB offers 99% attenuation of the electromagnetic radiation while a shielding effectiveness of 92 dB, the maximum shielding effectiveness offered to provide 99.997% attenuation. A shielding effectiveness of 40 dB is minimum in common applications. Effective shielding was offered by most samples to frequencies of 7GHz. Beyond that frequency some samples reduced below 99% effective, however some samples remained easily above 75% effective even at the maximum frequency level of 10 GHz. The conclusion is that there are various perforated patterns to be chosen by designers to meet their design needs.

The major single source of leakage is contact surfaces between two components. If a tightly sealed electrical connection is not made, leakage through interface can be more than through structure.

Pressure loss through perforated plate

In various perforated plate applications, the estimated energy loss or pressure loss through plates is one of the design factors. A lab system maintain a non-swirling flow impacting perpendicularly on the sample. Different perforated gauge plates were inserted in a uniform velocity air flow stream. Pressure loss for ambient air flow was then measured at a range of velocities and counted as inches of water column loss for ever flow. It provides the best flow condition value of loss.

Pressureloss by decorative wire mesh can be measured depending on ratio of anticipated velocity of the highest tabulated velocity. This ratio squared multiplied by the tabulated pressure loss can be used to approximate the higher velocity loss. Pressure loss can be evaluated from the different gas density values by using the ratio of the expected gas density to the measured density as a multiplier of the measured loss. Distorted flow patterns with high velocity zones increase the plate loss, as direction flow will not perpendicular to the plate surface.

To punch that array of holes needs special cluster tooling that not just is costly even also takes time to develop. Additionally the tooling you make will be limited in its service on a  specific material and a limited range of thickness because of clearance requirements. If the type and thickness of a material for a component changes, new tools will be required.

Punching the holes with a cluster tool, simply as the name refers, allows punching only a small cluster of holes with every stroke of the press. The machine time needed will make the holes very costly.

Maintaining accuracy in the arrangement of holes and uniformity in their spacing will be tough due to the damage in the work piece that occurs with each press stroke.

When the component is prepared from the punching process, it will be deformed and require flattening. Without a roller leveler, you will require to send the component to retain the shape. It means even more time and money.