O.M.A.C. s.r.l.
Via Giovanni Falcone, 8 42048 Rubiera (RE) - Italy Tel.0522/629371 - 629923 Fax 0522/628980
Rev.4 del 01/2011 O.M.A.C. s.r.l.
FAILURE: UNPRIMED OF THE PUMP (follow)
POSSIBLE CAUSES: REMEDIES:
Excessive medium viscosity Decrease the speed of the pump, increase the temperature of the medium
Too loose packing gland Tighten the packing gland rightly (see instructions)
Excessive pump speed Decrease the speed of the pump
FAILURE: SEIZURE OF THE PUMP
POSSIBLE CAUSES: REMEDIES:
Excessive medium temperature Decrease the temperature of the medium, cool the pumping case
Presence of suspended particles in the medium
Clean suction piping and install a fi lter on it
Excessive back-pressure
Remove possible obstructions in the outlet piping, increase the piping diameter, reduce its lenght and the number of the
bends
Too tight packing gland Loosen the packing gland and tighten it rightly (see instructions)
Piping press on pumping case Check the piping alignement, if necessary fi t fl exible expansion joints, and fi x the piping on the plant structure
Worn out bearings Replace the bearings by the manufacturer
Worn out or untimed gears Replace the gears or time them according to the instructions
Wrong quantity / quality of gears oil Act according to the manufacturer’s instructions
Parts in contact in the pumping case Check the design pressure coincides with the operating pressure
FAILURE: NO FLOW-RATE
POSSIBLE CAUSES: REMEDIES:
Wrong rotation direction Invert the rotation direction
Unprimed pump Fill pumping case and feeding piping with liquid, expelling air
Insuffi cient N.P.S.H (Net Positive Suction Head)
Increase the head, the piping inlet diameter, reduce the suction piping lenght and the number of the bends, decrea-
se the speed of the pump and the temperature of the medium, check that the increase (caused by the decreasing
temperature) is suitable to the motor power
Presence of air in the suction Increase medium level, lower suction opening position
Dirty or blocked valve or suction fi lter Clean fi lters
The relief valve leaks Check the relief valve setting, clean sealing parts, substitute worn parts
FAILURE: LDPU LOW FLOW-RATE
POSSIBLE CAUSES: REMEDIES:
Insuffi cient N.P.S.H (Net Positive Suction Head)
Increase the head, the piping inlet diameter, reduce the suction piping lenght and the number of the bends, decrea-
se the speed of the pump and the temperature of the medium, check that the increase (caused by the decreasing
temperature) is suitable to the motor power
Medium evaporates in inlet
Increase the head, the piping inlet diameter, reduce the suction piping lenght and the number of the bends, decrea-
se the speed of the pump and the temperature of the medium, check that the increase (caused by the decreasing
temperature) is suitable to the motor power
Air enters in inlet Check and tighten suction piping connections, tighten the packing glands and, if necessary, replace them
Presence of air in the suction Fill pumping case and feeding piping with liquid, expelling air
Not enough liquid level in the tank in the suction Increase medium level, lower suction opening position
Dirty or blocked valve or suction fi lter Clean fi lters
Insuffi cient medium viscosity Increase pump speed, decrease the temperature of the medium
Excessive medium temperature Decrease the temperature of the medium, cool the pumping case
Excessive back-pressure
Remove possible obstructions in the outlet piping, increase the piping diameter, reduce its lenght and the number of the
bends
Too loose packing gland Tighten the packing gland rightly (see instructions)
Insuffi cient pump speed Increase pump speed
Transmission belt slips Stretch the belt
Worn out rotors Replace rotors
The relief valve leaks Check the relief valve setting, clean sealing parts, substitute worn parts
The relief valve is wrongly set
Check the relief valve setting and the spring compression in the way that the spring will open at a 10% more of the
operating pressure
The relief valve vibrates Check the relief valve setting, check and clean the valve
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