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NT 1008-C00 07 18 P BA series e
11. TROUBLESHOOTING
ZERO OR INSUFFICIENT FLOW RATE
1
PRELIMINARY CHECKS
1-1
Make sure that the plastic plugs have been taken away from the ports of the pump and that the pump is run-
ning (defective drive, damaged motor, etc., faulty transmission : broken coupling, worn or poorly coupled
clutch, etc.).
1-2
Make sure that the pump rotates in the correct direction corresponding to the direction in which the liquid
circulates in the installation (cf. the pump plate). If necessary, change the electric motor connections or
adjust the piping as necessary (Diesel engines drive).
1-3
Make sure that there is liquid in the tank from which the pump draws and that the end of the inlet piping is
constantly submerged.
1-4
Make sure that the pump rotation speed is sufficient. Determine this by checking the speed of the pump
motor (see motor plate) and the speed reduction ratio (see reduction gearbox plate) or use a rev. counter.
If these checks do not highlight the problem :
2
MEASURE THE DISCHARGE PRESSURE
(as close to the outlet of the pump as possible, with a minimum
distance of 5 pipe diameters).
2-1
If the pressure is lower than the figures given for the material, or null, this could be due to :
2-1-1
A poorly adjusted bypass, the valve setting is lower than the discharge pressure (tighten the set screw or
replace the spring after checking that the electric motor is suitably protected).
2-1-2 The bypass valve is not closed : check whether the seat is contaminated.
2-1-3 The pump is worn, this will also affect the suction capacity of the pump (cf 3-2-2 c).
2-2
If the pressure complies with the equipment data (pump speed and motor output) it is possible that :
2-2-1
The pressure required for the given installation to obtain the required flow rate is too high and the flow is
partially or totally circulating via the bypass, or :
a. the height of the discharge is too great (reduce it by bringing the discharge tank to the level where the
pump is. The opposite could also be effective if the intake situation allows it.)
b. that head losses are too high because :
- the piping is unsuitable (too many “bends”, too long or the diameter is too narrow) for the process
conditions : flow rate, specific gravity and viscosity which could change with temperature (reduce the
loss by simplifying the circuit : reducing the number of accessories, the bends, etc., changing the
height of the discharge or inlet reservoir if the inlet conditions allow, increasing the diameter of the
pipes, reducing the viscosity by heating, reducing the flow rate, etc.
- partially blocked piping (valve partially closed, tap partially shut, cloth obscuring flow, etc.).
2-2-2
The discharge piping is completely blocked (valve fully closed, tap completely closed, cloth plugging flow,
full protection seal left by carelessness, etc.), in this case, all the liquid passes via the bypass.
