Eccentric Orifice Plate
Here the hole is located off-center to allow the undesired portions of the fluid to pass through the orifice rather than build up on the upstream face.
For gas flows, the hole should be offset downward, so any liquid droplets or solid particles may easily pass through. For liquid flows, the hole should be offset upward to allow gas bubbles to pass through and offset downward to allow heavy solids to pass through.
An alternative to offsetting or re-shaping the bore hole of an orifice plate is to simply drill a small hole near the edge of the plate, flush with the inside diameter of the pipe, allowing undesired substances to pass through the plate rather than collect on the upstream side.
If such a hole is oriented upward to pass vapor bubbles, it is called a vent hole. If the hole is oriented downward to pass liquid droplets or solids, it is called a drain hole.
- Used for measurement of flow for fluids containing solids and slurries.
- It is also used for vapors and gases where condensation is present.