Unibloc-Pump UNIBLOC-PD 350 User Manual

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Operation & Service Manual

UNIBLOC-PD

®

Models: 200-576

Original Instructions

MANUAL NO.: PD200-576 REVISION: 09/2019

Table of Contents

Questions and Answers:

S
Shelia MendozaAug 5, 2025
What to do if my Unibloc-Pump UNIBLOC-PD 350 has no flow, but the pump turns and doesn't prime?
- C
  Christina ColeAug 5, 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.
M
Melissa FinleyAug 10, 2025
Why is my Unibloc-Pump Water Pump motor overheating?
- L
  lopezericaAug 10, 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.
N
nicolebryantAug 14, 2025
Why is my Unibloc-Pump Water Pump noisy and cavitating?
- P
  Pamela FletcherAug 14, 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.
D
Dennis PriceAug 18, 2025
What to do if my Unibloc-Pump UNIBLOC-PD 350 shaft seals leak?
- M
  Monique WilsonAug 18, 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.
M
Mark ThomasAug 22, 2025
Why is the capacity of my Unibloc-Pump UNIBLOC-PD 350 Water Pump too low, even though the pump turns?
- D
  donald65Aug 22, 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.
A
amyperezAug 27, 2025
Why is my Unibloc-Pump UNIBLOC-PD 350 Water Pump noisy?
- S
  Sheryl HernandezAug 27, 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.
L
Leslie MatthewsAug 31, 2025
What causes rotors to gall and a Unibloc-Pump Water Pump to seize?
- M
  Matthew ReeseAug 31, 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.

Unibloc-Pump UNIBLOC-PD 350 Specifications

General

Category	Water Pump
Series	UNIBLOC-PD
Maximum Operating Temperature	120 °C
Shaft Material	Stainless Steel
Seal Type	Mechanical Seal

Summary

Safety

General Safety Precautions

General safety precautions for installation, operation, and servicing.

Specific Safety Instructions

Specific instructions to prevent injury and equipment damage during operation.

Operational Safety and Precautions

Alignment, hot surfaces, power disconnection, and system checks for safe operation.

Installation

System Design Considerations

Flushed Seal Arrangement

Mechanical Seal Flushing/Cooling

Pre-Start Checklist

A checklist of essential checks before starting the pump for the first time.

Maintenance

Maintenance Schedule and Spare Parts

Shaft Seal Service

Procedures for servicing the various types of shaft seals used in the pump.

Single Mechanical Seal Service

Covers removal and installation for single mechanical seals on different models.

Flushed Single Mechanical Seal Service

Covers removal and installation for flushed single mechanical seals.

Double Mechanical Seal Service

Covers removal and installation for double mechanical seals.

Double O-Lip Seal Service

Covers removal and installation for Double O-Lip seals.

Single O-Ring Seal Service

Covers removal and installation for Single O-Ring seals.

Double O-Ring Seal Service

Covers removal and installation for Double O-Ring seals.

Final Seal Installation Steps

Pump Bearing Housing Service

Bearing Housing Disassembly

Bearing Housing Assembly

Stainless Steel Rotor Assembly

QuickStrip Rotor Assembly

Troubleshooting Guide

Common problems, their causes, and solutions for the UNIBLOC-PD pump.

Technical Data

General Dimensions and Weights

Lubricant and Oil Specifications

Tools and Torque Requirements

Rotor Clearances

Pump Identification and Spare Parts

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