When the delta belt of a Roots fan is abnormal, the following failure conditions may occur:

1. Loose Triangle Belt: If the triangle belt is not properly taut, the drive will not be in place and the fan will not operate properly. It may be necessary to readjust and tauten the triangular belt.
2. Worn or Broken V-belts: V-belts that have been in use for a long time or are aging may become worn, cracked or broken. This will result in reduced drive efficiency, weakened fan performance or even failure to operate properly, requiring a new V-belt.
3. Triangle belt deviation from the track: If the triangle belt of the Roots fan deviates from the original track, it may be caused by inaccurate positioning of the gears or pulleys. In this case, the position of the track needs to be readjusted to ensure the correct operation of the belt.
4. Triangle belt is too tight: too tight triangle belt will bring too high load to the transmission system of Roots fan, which may lead to bearing wear and failure. In this case, it is necessary to loosen the triangle belt appropriately, so that it is in the right state of tension.
5. Damaged delta pulley: The delta pulley of a Roots fan may be damaged, such as worn grooves, broken or deformed. This will result in the delta belt not being able to drive properly and the damaged delta pulley will need to be replaced or repaired.

If there is an abnormality with the Roots Blower's delta belt, it is recommended that it be stopped immediately and that the problem be inspected and repaired. Please note that it is important to disconnect the power supply before carrying out any repair and replacement work to ensure safe operation. It is best to solve the problem according to the Roots fan manual or consult a professional technician for advice.