Theoretical explanation of the pump characteristics curve, you may read the previous article. The pump characteristic curve is influenced by the size and design of the pump, the size of the impeller diameter, as well as the magnitude of the operating rotation. The characteristics of a pump are shown through a head vs flow pump. On this curve also included some information about the associated pump such as BHP, NPSHR, hydraulic efficiency point, and pump power characteristics.
Now lets talk about the system characteristic curve. The system characteristic curve is used to determine which centrifugal pumps will be installed on the system. A fluid flow system can generally be described in a characteristic curve called the system characteristic curve.
Like the pump characteristics curve, the system characteristic curve is also the head on vertical axis and the flow at horizontal axis. The head of the system curve is a function of the static head of the system, and its losses. This can be expressed through the following equation:
h = dh + hl
h = head system
dh = head elevation system / height difference between system inlet and outlet
hl = the head loss of the system
If the loss of the head is greater, such as if the discharge valve system is throttled, will result an increased of head loss. Thus shifted the system characteristic curve upwards. At the start point of this curve, the system head value is not equal to zero, so even if there is no flow in the system the head is equal to the value on the curve.
To determine the exact centrifugal pump used on a system, the pump characteristics curve and system characteristic curves are combined. The meeting point between the two curves is an operational point if the associated pump used on the system. The most optimal operational point is if the meeting point between the two curves is in the BEP (Best Efficiency Point) area.
The pump operating point shall be kept to the highest pump efficiency area as far as possible. Especially the operation of the pump is used on systems that require head variation and large fluid flow, so there will be a shift in the system curve.