Slurry Pump Basics ǀ What is a Slurry Pump ǀ Slurry Pump Components

Slurry Pump – Dredging Pump – Sand Pump Basics

In this section you will find what a submersible slurry pump is and the factors to consider when selecting a submersible slurry pump.

Slurry is a mixture of liquid and particles of solid matter, some of them incapable of being dissolved. This mixture could be pumped, which is the procedure often used as a convenient way of handling solids.

There are two types of slurries: non-settling and settling. Non-settling slurries are composed by very fine particles of low specific gravity.  Settling slurries are usually composed by high specific gravity particles.  Both slurries have different abrasion impact on the elements of the pump according to their hardness or shape.

Industry sectors like mining, dredging, sand and gravel extraction, and other industries use slurry pumps as a cost effective solution for transporting solids.  

What is a Slurry Pump?

A Slurry pump is a special type of pump able to handle slurry.  Unlike water pumps, are slurry pumps are subject to wear and are more robust and heavy duty. 

Slurry Pumps Types

There are several types of slurry pumps, the most common: centrifugal pumps and positive displacement pumps.

Centrifugal slurry pumps which can deliver high capacity with limited head are mostly used in pumping slurry through pipelines at concentrations below 70% solids by weight. Centrifugal slurry pumps could be vertical, horizontal or submersible.

Positive displacement slurry pumps which can deliver high heads with limited capacity are used in pumping slurry through pipelines with very high concentration of solids.

Let’s focus on submersible centrifugal slurry pumps. 

Submersible Centrifugal Slurry Pump Description

A Submersible Centrifugal slurry pump is a continuous flow type of pump that works submerged and is capable of handling abrasive slurries.  It has an inlet at the suction of the pump that increases the speed of the slurry through the vanes of a rotating impeller, producing centrifugal force which sends the slurry through the casing to the discharge.  The casing is a horn-shaped element that transfers speed into pressure.

The pump performance is defined by the design of the casing and the impeller. The efficiency is related to the number and design of vanes in the impeller. Handling slurries, efficiencies are usually compromised by clearances and the need to build abrasion resistant heavy duty components, taking in consideration materials, thickness, etc.

A submersible Slurry pump could be electrically or hydraulically driven.  If it is an electric pump, the motor shaft carries the impeller. If it is a hydraulic pump the motor is directly coupled to the main shaft of the pump.

 

 

 

Slurry Pump Components

MOTOR: Could be electric or hydraulic. The cooling of the electric submersible slurry pump is important. If the slurry pump works semi-submerged or if it is going to work dry for extended periods of time, it should include a cooling jacket. For Heavy Duty Electric slurry submersible pumps is recommended to have a motor with Class H insulation. They could include also high temperature and /or moisture sensors. 

IMPELLER: The impeller is the rotating component of the slurry pump. It transfers the centrifugal force to the slurry. Usually made of High-chrome spheroidal cast iron that is very abrasion resistant. The impeller could be closed, semi-open, open or recessed.

CASING: The casing shape is generally of semi-volute or concentric. It is normally made of cast iron, but depending of the application could come with protective anti-corrosion coating, or could be made in special alloys for abrasive applications.

SHAFT AND BEARING ASSEMBLY: The shaft is used to transmit the rotatory movement from the motor to the impeller. The shaft has Heavy-duty roller bearings that prevent its displacement in other directions and reduce vibration.

SHAFT SLEEVE:  Its function is to protect the shaft. The shaft sleeve is made of corrosion and abrasion resistant material.

SEALS PACKAGE: The seals package prevents leakage of slurry into the motor and bearings. The seal package could be composed of lip seals, mechanical seals or hybrid seals.

 

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UPPER AND LOWER WEAR PLATES: These plates are located over and below the impeller. They are subject to wearing. The calibration of their clearances maximizes the efficiency of the pump.

STRAINER: the strainer prevents the entry of  large particles that could get stuck inside the impeller zone causing damage to the pump.

AGITATOR: Allows the pump to pick up sediments, putting solids on suspension.  The way it works, due to the design of the vanes, forces a continuous high pressure flow of liquid towards the sediments, this flow following the shape of a cone; transport the solids to the eye of the impeller achieving a high concentration of solids. The agitator also prevents solids from blocking the holes of the strainer.

 

 

Slurry Pump Curve

Pump performance curves provide the necessary information to select a pump according to specific needs. Manufacturers provide the results of the factory testing of their pumps. The main elements of a slurry pump performance curve are the Total Head and pump Capacity related to the absorbed Power and Efficiency at any specific point of the curve.

The head is shown on the y-axis. This number, measured in feet or meters, represents the total pressure a pump can overcome to achieve a specific flow. It should match the system curve at its total dynamic Head which includes the head due to friction loses in the system (pipes, valves, elbows, etc.), the head due to submergence, the static head and corrections due to viscosity, particle size, etc.

The pump flow capacity is shown on the x-axis. This number represents the gallons or liters per minute (US gpm or L/min) or M3/h of pumped slurry at any given operating point.

Efficiency of Slurry Pumps

The efficiency of a Slurry Pump is the ratio of energy delivered by the pump and energy supplied to the pump shaft.  Pump efficiency varies based on total head (vertical axis) and the flow (horizontal axis). When selecting a pump its operating range should fall around its best efficiency range. Pump efficiency directly proportional to the impeller size and the pump size.

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Selection of Slurry Pumps

When selecting a slurry pump we have to analyze several pump curves to identify the most efficient option.

The slurry pump has to run as slow as possible to reduce wear, but fast enough to keep solids from settling and clogging the lines.

The selection method consists in calculate the Total Dynamic Head for the particular application:

Total Dynamic Head = Static Head + Head due to friction loses - Head due to submergence

If you need help selecting a slurry pump for your needs, please contact us through info@dragflow.us. We will be glad to help you with the slurry pump selection at no cost.

You have to send us the following information:

  • Submergence: Working depth from the water surface to the bottom   ( ft.)
  • Level difference between the water surface and the discharge point (ft.)
  • Total length of discharge pipe from the pump to the point of discharge: (ft.)
  • Kind of water (ocean water or fresh water, PH)
  • Kind of solids and a description of Particle Size Distribution
  • Specific gravity of solids
  • Specific gravity of the slurry
  • Quantity of solids that need to be moved (Tons)
  • Working hours available to do the job (hrs)
  • Total quantity of solids to be pumped per hour (Tons/hr)
  • Quantity of slurry that needs to be pumped per hour (ds3/h)
  • And any other relevant information regarding clay content, viscosity, temperature, etc.

Heavy Duty Submersible Slurry Pumps from  Dragflow

Dragflow manufactures electric and hydraulic Submersible Slurry Pumps.

All Dragflow slurry pumps, Electric and hydraulic, has the following characteristics:

Standard high efficiency agitator to lift settled solids

High abrasion resistance with high chrome wearing parts

Low rotation speed to reduce wearing effect

Able to handle up to 70% of solids by weight

Electric pumps are available in 60Hz and 50Hz versions. Pumps are CE certified. UL/CSA certification available.

We have pumps from 5 HP to 400 HP with capacities up to 6000 US gpm.

In the products section of this website you can find our pumps and their specifications.

In the documents section you can download our products catalogues and the data sheets of our products as well.

We also provide Electric Control Boxes for our Electric slurry pumps and Hydraulic Power Packs (based on diesel engines or electric motors) specifically designed to drive our hydraulic slurry pumps.

The hydraulic slurry pumps could be retrofitted in the boom of a hydraulic excavator.

Slurry Pump accessories

Cutter heads:

Hydraulic or electric cutter heads could be attached directly to the pump for compacted materials.

 

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Water Jets Ring System:

A High pressure water jets ring system could be used for dry materials. It consists of a jet rings frame mounted on the pumps strainer and a high pressure water pump.

Mechanical seal:

Dragflow standard sealing system is its superb lip seals combination. A double silicon carbide mechanical seal in combination with a front deflector is available as an option for very abrasive applications.

Cooling Jacket:

Dragflow pumps from 3.7 to 18 kW come with top discharge that creates a natural cooling jacket for the pump. This allows the pump to work even if not completely submerged. An external cooling jacket can be available also for pumps bigger than 26kW and up to 110 kW thus allowing all the range to work also in semi-submerged conditions.

Anti-corrosion package:

 In cases of high or low pH pump strainer and lifting plates can be supplied in stainless steel (316SS). This choice together with Teflon layers in the seal zone makes Dragflow pumps suitable for environments with pH from 2 to 10."

Automatic greasing system:

Pumps installed can be equipped with an automatic greasing system that provides fresh grease to the seals on a regular basis.

This operation not only increases the overall sealing system life but also allows the operators to dramatically reduce maintenance and checks on the pump.

Anti-abrasion package:

The quality and type of casting used in Dragflow pumps are designed to face the most difficult and abrasive applications. For some specific applications an extra hardened coating layer can be applied inside the pump casing.

Hardened casing:

Pumps can be supplied with a hardened casing to ensure long life to this part. Beside our standard cast iron casing, we have available casings in S6 and High Chrome.

Lower Membrane protection:

Often the bottom of mine ponds is covered with a water-proof plastic lining.

Action of the pump during dredging operation could damage this lining. With Dragflow you have the option to add a protective ring to the pump strainer in order to prevent any damage.

Weed cutter-knife:

When the slurry is covered by a layer of vegetation, grass or seaweed, Dragflow cutter knife will help the pump to perform the task without clogging

Temperature and Moisture Sensors:

Temperature sensor, embedded in the motor; and Moisture sensor, in the oil chamber, are available to protect the pump in the most demanding applications.

Pump frames:

Dragflow pumps are used in several sectors. Custom frames can be supplied to for specific applications.

Flow rate dividers:

Dragflow have available Flow Rate Dividers to divide the oil flow (delivered by the hydraulic power pack) between the pump and the cutter heads, depending of the required configuration

Hoses and Pipes:

We have available flexible dredging hoses, HDPE Pipes and floaters in different diameters. Our commercial staff will be glad to support you in the selection of the discharge pipe line.