Analysis of the causes of centrifugal pump failures and recommendations for pen-type vibration meters?

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The workshop has been in operation for many years. Some time ago, an issue arose: a multi-stage centrifugal pump that had been in use for 8 years was functioning normally most of the time, with only its mechanical seal being replaced from time to time; no special maintenance was carried out. Suddenly, it was unable to produce the required flow rate. Previously, the current and noise levels were normal. The opening degree of the control valve was increased by 10%, but still the pump couldn’t generate enough flow. As a result, the current rose from 90A to 140A, while the pressure dropped from 29KG to 25KG. After disassembling the pump, it was found that the impeller was experiencing friction, the mouth ring was severely corroded, the middle section was in good condition, but the shaft sleeves and shaft showed signs of erosion. Our analysis shows that this pump has not been maintained for years, resulting in severe cavitation, which is what caused the above issues. However, cavitation usually presents certain signs – so why were there no signs at all before? The current and pressure are both normal – why did it suddenly stop working? Model: 80Y50*5; flow rate: 45 m3, head: 280 m. Medium: MDEA decarboxylation solution, alkaline; temperature: ≤100°C. The company attaches considerable importance to this, and it urges the workshop to strengthen equipment inspections; vibration levels of the pumps also need to be measured. For convenience, the workshop plans to use pen-type vibration meters. After searching on forums, two brands were found on Taobao: Beijing Time TV200 TIME7120 pen-type vibration meter, and TECMAN pocket pen-type digital vibration meter TM63C for detecting vibrations in bearings and motors. Are there any other recommendations besides these two brands? The price should be around 2000, with accurate numerical measurement.