Unibloc-Pump UNIBLOC-PD 551 User Manual (English)

Questions and Answers:

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Patricia GuzmanAug 18, 2025
What to do if my Unibloc-Pump UNIBLOC-PD 551 Water Pump has no flow, but the pump turns and doesn't prime?
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  Cynthia StephensAug 18, 2025
  If your Unibloc-Pump Water Pump isn't priming despite turning, several factors could be at play. First, ensure the motor is turning in the correct direction; if not, reverse it. Check for air pockets in the pipe or pump and fill them with liquid, inspecting pipe fittings for leaks. Insufficient Net Positive Suction Head Available (NPSHA) can also cause this; try increasing the suction pipe diameter, shortening its length, decreasing pump speed, or raising the feed tank level. Verify the pump speed is adequate and increase it if necessary. High viscosity can also be a culprit; lower it if possible. Finally, check for obstructions in the discharge piping or closed valves, removing any obstructions and opening any closed valves.
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Eduardo PhillipsAug 21, 2025
Why is my Unibloc-Pump UNIBLOC-PD 551 Water Pump motor overheating?
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  David WilsonAug 21, 2025
  If the motor of your Unibloc-Pump Water Pump is overheating, several factors could be responsible. The motor might be too small, in which case you should consider increasing its size. High discharge pressure can also cause overheating; try lowering the pump speed and pressure, and check the suction and discharge piping for any closed valves or obstructions. If the viscosity is higher than expected, decrease the pump speed and increase the pipe size or shorten the discharge pipe length. Lastly, ensure that the motor and pump are properly aligned and correct any misalignment.
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Mr. Matthew MontgomeryAug 23, 2025
Why is my Unibloc-Pump Water Pump noisy and cavitating?
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  Kara WoodAug 23, 2025
  If your Unibloc-Pump Water Pump is making excessive noise and cavitating, several issues could be the cause. A collapsed suction hose might be the problem; replace it with a reinforced hose or rigid piping. If the liquid temperature is too high, reduce the speed and increase the NPSHA. Excessive speed can also lead to cavitation, so decrease the speed. If the viscosity is higher than expected, decrease the speed and increase the pump size. Low NPSHA can also cause this issue. Ensure the suction side valve is open and check the suction side piping for any obstructions.
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riosannAug 26, 2025
What to do if my Unibloc-Pump UNIBLOC-PD 551 shaft seals leak?
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  ryanrossAug 26, 2025
  If the shaft seals of your Unibloc-Pump Water Pump are leaking, there are several potential causes. If you're using single mechanical seals, check for loose drive collars and reset them. Worn parts can also lead to leaks, so replace the seals and/or o-rings. Make sure the pump isn't operated without liquid coming into contact with the seals or without flushing liquid; always operate the pump with liquids present and replace any worn seal parts. Finally, the seal might be incompatible with the liquid being pumped. Contact the factory for proper seal selection and operation, and replace the seal if necessary.
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Paul LevyAug 28, 2025
Why is the capacity of my Unibloc-Pump UNIBLOC-PD 551 Water Pump too low, even though the pump turns?
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  Jessica GreeneAug 28, 2025
  If your Unibloc-Pump Water Pump's capacity is lower than expected despite the pump turning, several factors could be the cause. Insufficient NPSHA might be the issue. The pump might be running too slowly, so increase the speed. Increased slip in the pump could also be a factor; check rotor clearances and replace worn parts if necessary. If the discharge pressure is higher than expected, check the discharge piping for closed valves or obstructions, increase the pump speed (but do not exceed pressure limits), increase the discharge pipe size, or increase the pump size. Also, ensure the front cover is tight by tightening the cover nuts to the specified torques. Finally, an o-ring installed in the front cover that is too thick can cause this; replace it with the correct size.
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Wendy CruzAug 30, 2025
Why is my Unibloc-Pump UNIBLOC-PD 551 Water Pump noisy?
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  Jason WebbAug 30, 2025
  If your Unibloc-Pump Water Pump is generating excessive noise, several factors could be responsible. Cavitation is a common cause. If the liquid contains air, check the pump shaft seals and suction side pipe fittings for leaks and increase NPSHA. High discharge pressure can also lead to noise; check the suction and discharge piping for closed valves or obstructions and consider increasing the pump size.
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tramosSep 2, 2025
What causes rotors to gall and a Unibloc-Pump UNIBLOC-PD 551 to seize?
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  Andrea SmithSep 2, 2025
  If the rotors in your Unibloc-Pump Water Pump are galling and the pump is seizing, several issues could be the cause. High liquid temperature can lead to this; lower the temperature or increase rotor clearances. Incorrect rotor clearances can also cause galling; adjust them to the factory-recommended settings. Check for loose rotor bolts or housing studs and tighten or replace them if necessary. Worn bearings or gears should be replaced. Foreign particles in the pump can cause seizing, so install a suction side filter. If the particles in the product are too large, increase rotor clearances, use plastic rotors, or increase the pump size. Lastly, high discharge pressure can contribute to this problem.
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Marcus TapiaSep 7, 2025
Why is the capacity of my Unibloc-Pump UNIBLOC-PD 551 too low, but the pump turns?
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  wilsonryanSep 7, 2025
  If the capacity of your Unibloc-Pump Water Pump is too low despite the pump turning, several factors could be responsible. Insufficient Net Positive Suction Head Available (NPSHA) is a potential cause. The pump might be running too slowly, so increase its speed and check the hydraulic pressure and filter. Increased slip within the pump can also reduce capacity; inspect rotor clearances and replace worn parts if necessary. High discharge pressure can also limit capacity, so check the discharge piping for closed valves or obstructions, and consider increasing the pump speed, but do not exceed the pump's pressure limits; you might also increase the discharge pipe size or the pump size itself. Finally, ensure the front cover is tightened to the torque specified.
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Michelle WilliamsSep 10, 2025
Why is my Unibloc-Pump UNIBLOC-PD 551 so noisy?
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  Brendan CrosbySep 10, 2025
  If your Unibloc-Pump Water Pump is noisy, several factors could be at play. Cavitation can cause noise. The liquid might contain air; check the pump shaft seals and suction side pipe fittings for leaks, and increase the NPSHA. High discharge pressure can also contribute to noise; check the suction and discharge piping for closed valves or obstructions, and consider increasing the pump size.
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Jonathan WilliamsSep 12, 2025
What to do if Rotors gall and Unibloc-Pump UNIBLOC-PD 551 Water Pump seizes?
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  John CrossSep 12, 2025
  If the rotors gall and the Unibloc-Pump Water Pump seizes, several issues could be responsible. High liquid temperature can cause this; lower the temperature or increase rotor clearances. Incorrect rotor clearances can also lead to galling; adjust them to the factory recommended settings. Loose rotor bolts or housing studs can be a factor; tighten or replace them if necessary. Worn bearings or gears can cause seizing; replace the bearings or gears. Foreign particles in the pump can also lead to this issue; install a suction side filter. If the particles in the product are too large, increase rotor clearances, use plastic rotors, or increase the pump size. Lastly, high discharge pressure can contribute to rotor galling.