Series SD 39
26
6. Problems: Causes and Remedies
1) Output low or no output at all
2) Excessive output
3) Motor overload and thermistor stops
4) Pressure surge or water hammer on shut down
7. Appendix
7.1
Permissible pump pressure
* The maximum permitted final pump pressure [bar] consists of the intake pressure and the pump delivery head at zero capacity.
1) 2) 3) 4) Problem
Remedy
Excessive draw-down in sump, excessive
suction lift or inadequate flooded suction
• Check the system design and pipe sizing
• Check the settings and operation of level controls
Pump not completely primed
• Vent the pump
• Check shaft sealing arrangements for air tightness
Air lock in suction pipe
• Prime the suction pipe
• Check suction pipework and valves for air tightness
Excessive delivery pressure
• Open up restricting valves
• Check system design for excessive pressure losses
• Modify pump (after consulting the manufacturer)
Insufficient delivery pressure
• Check the system design
• Restrict discharge valve
Wrong rotation
• Correct rotation
Pipework, fittings or pump clogged
• Remove deposits or obstructions
Pump internal worn
• Replace worn parts
Speed too low
• Check electrical installation
Speed too high
• Check electrical installation
Motor two phasing
• Check electrical installation
Set misaligned
• Check alignment
• Eliminate loads from pipework and realign set
Packed gland packing overtightened
• Slacken gland packing
Excessive viscosity/density of pumped medium
• Fit a more powerful motor (after consulting the manufacturer)
System design
• Examine system design
Table 3: Problems
Type
Maximum admissible final pump pressure* [bar]
pump media temperature up to +80°C
casing parts made of
EN-GJL-250
CuSn10-C
SD 200-250
7
5
SD 250-300
7
5
SD 300-310
5
4
SD 350-420
7
6
SD 400-460
5
4
SD 500-600
5
4
SD 510-630
5
4
Table 4: final pressure of pump
