Calculation of the effective net positive suction head for pumps; please help, experts
Thread Content
Recently, I came across a note in HG20570 regarding the calculation of the pump’s effective net positive suction head: \"The operating pressure in the suction side vessel is the lowest pressure that occurs under normal conditions.\" Since the pump’s effective net positive suction head is calculated based on the most unfavorable conditions, can this be interpreted as meaning that at the time of startup, the pressure on the suction side is almost equal to the saturated vapor pressure of the liquid, with only the effects of vapor columns and losses taken into account during the calculation? Thank you
That’s the case, but it’s not necessarily only when starting to drive; in many situations this happens even with normal operation
The minimum pressure that occurs under normal conditions; using this value ensures safety
You mean that this method of calculation allows for sufficient design margin in actual operation, but it increases the production requirements for the pump manufacturers
It’s not exactly that; in many operating conditions the fluid is in a saturated state, so it’s necessary to act accordingly. If your design isn’t based on this principle, then there’s no need to be so strict about it. Why is the fluid only saturated while the machine is in operation? Have you considered this too much?
I was thinking in too narrow a way just now; I overlooked the fact that normal operation also involves saturated liquid. Thank you