Reasons for the noise in the fan check valve
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Is the noise from the fan check valve caused by too low airflow or fan surging?
Either the pressure in the pipeline is higher than your outlet pressure, or the fasteners inside your valve have loosened: lol
The air volume passing through must be too small
It is possible that the inlet filter is clogged, which reduces the flow rate and causes surging; this in turn leads to the outlet check valve cycling between low and high pressures, resulting in abnormal noises.
Could it be that the check valve was selected incorrectly? The pressure at the fan’s outlet is equal to or slightly less than the spring force of the check valve, which results in regular fluctuating knocking sounds
As a supplementary note, our small blowers are usually placed outdoors. When winter arrives and frost forms, or when the air humidity is high and temperatures drop suddenly, it is necessary to manually strike the inlet filter using pipes or hammers in order to dislodge any thin ice crystals. This prevents the fan’s filter from getting clogged by ice, which could otherwise reduce the flow area at the inlet and cause the fan to surge.
The pressure at the fan outlet is too low to fully open the check valve, or the flow rate is too low