A Beginner’s Guide to Pumping Slurry

Slurry pump selection for each unique pumping medium is the vital first step to maintaining the long-term performance of pumping equipment. Here is an overview of the different types of pumps for slurry:

Centrifugal Slurry Pump

A centrifugal pump is designed to handle corrosive or highly abrasive fluids and consists of the following primary components:

• Impeller: A rotating impeller generates flow by conveying velocity to the slurry. Open impellers are typically used instead of closed impellers since they are less likely to clog. Slurry impellers must be thick and sturdy to sustain operation in harsh slurry mixtures.
• Shaft: Supported by rugged bearings, the impeller usually gets mounted onto a rigid shaft.
• Stationary Casing: The casing helps direct and contain the flow. Constructed using high-chrome alloys, steel, or other heavy-duty materials, it can withstand corrosive and abrasive wear caused by the slurry and is often coated and/or lined with rubber or metal for added protection.

This style of slurry pump relies heavily on the centrifugal force created by the rotating impeller to impart kinetic energy and move the slurry through the pump.

Positive Displacement Slurry Pump

Positive displacement pumps operate with a piston or plunger that moves up and down to force the slurry through the pump. This style of slurry pump is beneficial in applications requiring a low flow rate and high head, providing increased efficiency and flow control.

The common positive displacement pumps used for pumping sludge include:

• Rotary Lobe Pumps
• Twin-Screw Pumps
• Diaphragm Pumps

As the impeller on a centrifugal slurry pump rotates in a circular motion, the slurry enters via the eye of the impeller, and centrifugal force moves it outwards between the impeller blades. The slurry reaches a high speed at the edge of the impeller. Inside the casing, the slurry’s high-speed energy is converted into pressure. The slurry pump increases the pressure of the solid particles and liquid, turning electrical energy into kinetic energy for pumping the slurry.

When a slurry pump is matched to the right industrial application, companies enjoy many benefits:

• Low, easier maintenance
• Durable, long-lasting machinery
• Simple mechanisms with few components
• Low life cycle cost of capital investment

The optimal slurry pump selection for a specific application depends on the following slurry properties:

• Desired flow rate
• Pressure requirements
• Particle size
• Particle type
• Concentration
• Viscosity

Slurry pump performance depends on design and speed of the rotating impeller and its ability to handle these factors. Larger particle sizes and higher viscosity can increase flow resistance, and higher slurry concentrations can potentially increase abrasion on pump components, wearing them down and making the pump less efficient over time.

It is essential to choose a slurry pump that can handle the specific properties of the slurry and to operate the pump within its design capabilities to ensure efficient and reliable performance.

There are several factors to consider when purchasing a slurry pump:

1. Compatibility: It is important to ensure compatibility between the pump and the chemical and physical properties of the slurry, including abrasiveness, pH, and density.
2. Size: Select the appropriate size to ensure the total head and required flow rate are achievable.
3. Power Source: Consider power source needs, such as direct diesel drive, hydraulic or electric.
4. Construction Materials: The slurry pump construction materials should be selected carefully to ensure the casing has the necessary abrasion and corrosion resistance properties. Stainless steel construction is a common solution for reducing wear and tear of pump components.
5. Maintenance & Repair: Consider the repair and maintenance needs of the slurry pump to ensure it can be easily kept in proper working condition.

It can be a significant challenge to get sludge, mud, or guck to flow through a slurry pump, especially if the mixture is prone to clogging. There are several techniques for improving the flow of slurry, which can include:

• Adding flow-enhancing additives to the mixture
• Breaking up large clumps by agitating and stirring the slurry
• Reducing viscosity by heating the substance

For stubborn clogs, use a scraper or rake for an immediate solution. Monitoring a sludge pump for clogs or blockages—and taking the necessary steps to remove them if and when they occur—can go a long way in extending the lifespan of pumping equipment and components.

Leaks, spills, and other dangerous conditions can occur when pumping corrosive material through a sludge pump. It is essential to take the necessary precautions to prevent these serious safety and environmental consequences.

Some sludge chemistry is so corrosive that other materials are used to build specialized slurry pumps with plastic or stainless steel corrosion-resistant properties. Lined pipes can also add an extra layer of protection to ancillary equipment.

All employees need to be aware of potential health hazards associated with handling corrosive materials. To minimize the risk of accidents and protect workers from harmful exposure, take the following precautions:

• Provide personal protection equipment (goggles, gloves, etc.)
• Reduce the risk of toxic fume inhalation by providing adequate ventilation
• Implement proper storage and handling procedures