BLACKMER SNP1.25, Installation, Operation And Maintenance Instructions

104-A00    Page 13/16 

TROUBLESHOOTING 

NOTICE: 

Maintenance shall be performed by qualified technicians only,  

following the appropriate procedures and warnings as presented in this manual. 

LEAKAGE 

Location 

Probable Cause/Corrective Action 

Between the head & casing 

Damaged head O-ring: Inspect and replace if necessary.  
Burrs/dirt in head O-ring groove or cylinder: File and clean as 
necessary. 

Around the shaft 

Packing: Adjust the packing. If this does not solve the problem, replace 
the packing with a complete new set.  
NOTE: On pumps equipped with packing, some leakage is necessary, 
and in some cases is desirable, depending on the application. 
Damaged shaft surface: Check the surface of the shaft in the seal area 
for damage. File any small burrs or ridges. If damage is severe, replace 
rotor & shaft. 
New Mechanical Seals: New seals may leak slightly at start up, but 
should seal up shortly thereafter. 
Damaged mechanical seals: Check for damaged O-rings or cracked, 
scratched or worn seal faces 
 

SHAFT BINDING 

Probable Cause 

Corrective Action 

Burrs, dirt or foreign particles on the heads or discs. 

During assembly, both heads and discs must be clean and smooth. File 
any burrs or rough spots, and wipe the discs with a clean cloth and 
alcohol to remove any dirt or foreign particles.  

Excessively tight packing. 

Refer to "Packing Adjustment". 

Contaminated mechanical seal faces. 

Any trace of grease or dirt on the seal faces will prevent the faces from 
mating properly, causing the rotor and shaft to bind or turn hard. Use a 
tissue paper & alcohol to clean the seal faces. NOTE: Apply a light oil 
or suitable lubricant to bronze seal faces only. 

Other possible causes of shaft binding  --------------------------------------------------------------------------------------------------  

• Foreign particles on rotor, liner or vanes. 
• Damaged vanes or rotor.  
 

• Bent push rods. 
• Liquids that "set up" when inactive. 

OVERHEATING 

Location 

Probable Cause/Corrective Action 

Pump equipped with internal relief valve. 

Continual, full bypassing of the liquid:

  Properly adjust the relief 

valve so that the pump will not bypass during normal operation.  

WARNING: Internal bypassing of liquid elevates the liquid 
temperature. Only use the internal bypass valve for brief periods 
and at differential pressures below 125 psi. 
For extended periods of higher pressures, the internal bypass 
port must be plugged and the liquid returned back to the source.

Pumps with packing. 

Packing:  NEVER tighten the packing without checking afterward for 
overheating.  If packing is old or worn, it will overheat and should be 
replaced. 

Other possible causes of overheating  ----------------------------------------------------------------------------------------------------  

• Improper relief valve adjustment  
   (See "Relief Valve"). 
 

• Plugged discharge line. 
• Closed valve. 

LOW DELIVERY RATE 

Probable Cause 

Corrective Action 

Relief valve setting too low, causing the liquid to bypass.  Set the relief valve 20 psi (1.4 bar) higher than the differential pressure.

Other possible causes of a low delivery rate   ------------------------------------------------------------------------------------------

•

Restriction in the suction line. 

•

Resistance in the discharge line. 

•

Air leaks in the suction line.  

•

Damaged or worn pump parts. 

•

Pump speed too low or too high. 

•

Relief valve leaking.  

•

Relief valve sticking open, or not properly seating. 

•

 Dirty 

strainer.