Silicon Pressure Cell Fill Oil Volume Verification Methods
Confirm fill oil volume using pre- and post-injection micro-gravimetric mass checks combined with non-contact laser interferometric diaphragm dome profiling.
Micro-Cavitation
Fluid Phenomenon
Localized boiling occurs when the local static pressure of a fluid drops below its vapour pressure at a microscopic scale. Rapid vaporisation and subsequent collapse of tiny bubbles during micro-cavitation generate intense acoustic emissions and localized shock waves. This event occurs primarily in high-velocity shear layers or near restrictor orifices.
It differs from macro-scale cavitation by its restricted spatial extent and high frequency.
Material Erosion
Physical damage occurs when these microscopic vapour bubbles collapse adjacent to solid boundaries. Over time, micro-cavitation causes pitting on the surface of control valves, sensor diaphragms, and pump impellers. This wear degrades the dimensional tolerance of the component and leads to premature mechanical failure.
Materials such as hardened stainless steel are selected to withstand this localized stress.
Signal Interference
Measurement distortion rises as the collapsing bubbles create high-frequency noise that masks the true pressure signals. In dynamic pressure sensors, micro-cavitation introduces spurious spikes that confuse the electronic transmitters and cause incorrect feedback loop actions. These signals can be filtered using digital low-pass algorithms, but this increases the response time of the loop.
Engineers must position sensors upstream of the restriction to avoid the cavitation zone.
Control Measure
Prevention strategies involve maintaining the process pressure above the vaporisation threshold. Installing a downstream flow restrictor raises the backpressure, which effectively prevents micro-cavitation from occurring.