QUESTION
Could you explain to me what the definitions are, according to the current fight-fighting standards, for SUCTION LIFT and POSITIVE HEAD?
ANSWER
The standard to refer to, is of course UNI EN 12845:2020 in particular point 10.6.1, where it talks about the suction conditions
And point 10.6.2, to be precise, points 10.6.2.2. (suction lift) and 10.6.2.3. (positive head)
In addition, chapter 8 of UNI/TR 11438:2016 is also dedicated to the issue.
Starting from the basic condition shown in the figure below, where the reference plane is the horizontal one that passes through the centre of the pump’s suction mouth, the SUCTION LIFT and POSITIVE HEAD hydraulic conditions are easily identifiable.
Therefore, the standard requires that the condition of SUCTION LIFT be preferably used, with the following limits:
Therefore, in the case of SUCTION LIFT, the foot valve is not only required, but the limit distance between the pump axis and the free water is 3.2 m.
Learn more