Solid particle erosion in the oil and natural gas industry can be detrimental to piping and plant equipment, which can lead to production shutdown and other economic losses. Therefore, it is important to be able to detect and quantify the amount of solids present in the piping and plant equipment. This paper presents experimental results obtained using acoustic sand detectors for a broad range of operating conditions at the Tulsa University Sand Management Projects (TUSMP). The effectiveness of sand monitoring in multiphase flow conditions is evaluated and presented. Experimental impingement measurements were performed with acoustic monitors while varying superficial gas and liquid velocities, sand size, and pipe flow orientation. The major focus was to determine the threshold limits for the acoustic sand monitor. Different tests with various velocity combinations to achieve annular, bubble, dispersed-bubble, mist, slug and stratified flow regimes were performed using pipe sizes of 2-inch and 4-inch diameters, and 20 µm, 150 µm and 300 µm sand sizes. The effects of sand size and flow regime on threshold sand rates as sand injection rates change were investigated. The threshold sand rate results for these multiphase flow regimes were determined experimentally and statistical analysis were performed to eliminate the effect of background noise generated when no sand is present in the system. Threshold limits observed for the stratified flow regime was similar and sometimes higher than the ones for annular and slug flows with the slug flow threshold limits being the lowest of all three regimes. Data for other flow regimes like liquid only, bubble and dispersed bubble flows were compared to annular, slug and stratified flow; the highest threshold limit was recorded for liquid only flows closely followed by the limits for bubble flow compared to the other flow types, the smallest threshold limit was recorded for dispersed bubble flow in the horizontal pipe orientation for the flow conditions tested.The threshold sand detection limits for 150 µm and 300 µm sand types are presented and discussed.