(1) Motor
reversal
Due to wiring reasons, the direction of rotation of the motor may be
opposite to the actual requirement of the sewage pump. Therefore, when starting,
it is generally necessary to observe the direction of rotation of the sewage
pump. If the direction of rotation is reversed, any two wires on the motor
terminal should be exchanged.
(2) Impeller channel blockage
If the flow
channel of the impeller is partially blocked, it will affect the work of the
impeller and cause a decrease in outlet pressure. Therefore, it is necessary to
disassemble the pump for inspection and removal of foreign objects. To prevent
the problem from recurring, a filtering device can be installed before the inlet
of the sewage pump if necessary.
(3) Internal leakage occurs
When the gap
between the rotating and stationary parts of the sewage pump exceeds the design
range, it will cause internal leakage, which is reflected in a decrease in the
discharge pressure of the pump, such as the clearance between the impeller mouth
ring and the interstage gap of the multi-stage pump. At this point,
corresponding disassembly and inspection should be carried out to repair or
replace the components that cause excessive clearance.
(4) Cavitation occurs
at the inlet
If the suction pressure of the sewage pump is too low, lower
than the saturated vapor pressure of the pumped medium, cavitation will form. At
this time, check whether the inlet Plumbing is blocked or whether the opening of
the inlet valve is too small, or increase the liquid level of the suction
pool.
(5) Speed decrease
The important factors affecting the head of
sewage pump are the outer diameter of the impeller and the speed of the pump.
When Ceteris paribus, the head of the pump is in direct proportion to the second
power of the speed. It can be seen that the speed has a great impact on the
head. Sometimes the speed of the pump decreases for some external reason, which
will reduce the head of the pump accordingly. At this point, the pump speed
should be checked. If the speed is indeed insufficient, the cause should be
checked and a reasonable solution should be found.
(6) The operating point
shifts towards high flow and low head
In general, centrifugal pumps have a
continuous downward performance curve, and the flow rate gradually increases
with the decrease of head. During the operation process, due to some reason, the
back pressure of the pump decreases, and the working point of the pump passively
shifts towards the low head and high flow point with the device curve, which
will cause the head to decrease. In fact, this is caused by external factors
such as changes in the device, and has no special relationship with the pump
itself. At this point, simply increasing the pump back pressure, such as closing
the outlet valve a little, can solve the problem.
7/11/2023
What factors can cause a decrease in the head of the sewage pump
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