... equipment ,environmental protection equipment ,refrigeration equipment and other machines.3.How to know the cooling fans grade?1.When we choose the ... FG signal(Detect fan speed value), water proof and so on.4.CEETIFICATE:CE: have been got the certificate.UL: About ... ,hundred percent guarantee non-oil and gas.Low vibration: after a high-precision balance design, testing, calibration, fan's vibration ...