Slurries are specialized compounds found in various processing industries, including sanitary sectors like mining, aggregates, mineral processing, dredging, tunneling, and water treatment, as well as other industries that involve slurry or sewage. Because slurries combine the properties of liquids and solids, special consideration must be given when determining the type and size of the slurry pump to use with them. Kingda Pump features several companies that specialize in slurry pumps capable of handling a wide range of loads, from light to heavy.
This article will concentrate on the following:
- Slurries are defined as
- Pumps that can be used to transport slurries
- Considerations when selecting a slurry pump for a specific application
SLURRY PUMPS ARE?
Slurries are solid-liquid mixtures, with the liquid acting as a transport mechanism for the solid. The size of particles in slurries can range from a micron to thousands of millimeters. The ability of a pump to move a slurry through a process line is greatly influenced by particle size.
A slurry pump is a centrifugal pump used to transport abrasive and frequently corrosive solid particles inside a carrier fluid. To minimize substantial particle velocity and thus wear rates, the slurry pump should have a low specific speed design that allows for slower operating speeds than ordinary water pumps. Depending on the application, wear-resistant metallic or elastomeric materials are used in slurry pump components that come into contact with the pumped medium.
All slurries share five essential characteristics:
- Abrasive when compared to pure liquids.
- Thicker in texture than pure liquids.
- Many solids may be present (determined by a percentage of total volume).
- When the slurry is not moving, the solid particles usually settle out of the residue relatively quickly (depending on the particle size).
- Moving slurries require more energy than moving pure liquids.
Slurries are further classified into four classes by industry based on their aggressiveness, with Class 1 being the least aggressive and Class 4 being the most aggressive. Pumping slurries can wear out pumps and pipeline components in the following ways:
- Gouging, high-stress grinding, and low-stress grinding are abrasions (applicable only with settling-type slurries).
- Surface material resulting from the actions of particles that make up the slurry that is pumped is known as erosion. Pumping settling-type slurries cause the most decay.
- Corrosion is caused by electrical galvanic action in the pumped fluid. Specific slurries (highly acidic or alkaline compounds) have a more significant impact on component corrosion than others.
SLURRY PUMP TYPES
Several types of pumps are suitable for pumping slurries, as described below. However, we must address a couple of critical issues before deciding which technology to use.
- The nature and size of the solids present in the liquid. The size and type of solids present in the fluid will influence physical wear and tear on parts of the pump and the extent to which the components can pass through the pump without getting damaged.
The pump’s speed and shear the pump can cause damage to solids or slurry, which is a concern for centrifugal pumps. Twin screw pumps, generally, because of the minor slurry’s solids.
- The more corrosive slurries make the pump components wear faster and can influence the materials from which the pump is constructed.
Because slurries weigh a lot and are hard to push, the pumps explicitly made for slurries will have heavier and more potent than pumps designed for liquids with less viscosity.
Slurry pumps tend to be larger than conventional pumps, have more horsepower, and are constructed with more robust bearings and shafts. The centrifugal pump can be described as the most popular kind of pump for slurry. These pumps employ an impeller rotating like water-like liquids flow through a centrifugal pump.
Pumps designed explicitly for slurry pumps will usually feature the following features compared to conventional centrifugal pumps. Centrifugal force can push it outward if something is spinning fast around a central point.
- Impellers that are bigger and prepared with more material. This is to compensate for abrasive slurries’ wear.
- The impeller has fewer, thicker vanes. This allows solids to pass through more easily — typically 2-5 vanes versus 5-9 vanes on a standard centrifugal pump.
These pumps may also be made of specialized high-wear alloys for pumping abrasive slurries. Hardening stainless steel is another popular option for abrasive slurries.
Helpful displacement pumps may be better than centrifugal pumps for certain slurry pumping conditions.
Among these conditions are the following:
- The slurry flow rate is low.
- A considerable head (i.e., the altitude to which the pump can transport liquid)
- A desire for greater efficiency than centrifugal pumps provide
- Enhanced flow control
CHOOSING AND USING A SLURRY PUMP
Follow these four simple steps to determine what type of slurry pump is the best for your particular need or application.
STEP 1 IDENTIFY THE TYPE OF MATERIALS BEING PUMPED
Think about the following:
- Particle size, shape, and hardness (influences the likelihood of abrasion and corrosion of pump components)
- The slurry solution’s corrosiveness
- If the product’s exact in-pump viscosity is unknown, CSI can assist.
STEP 2 CONSIDER THE PUMP’S PARTS
Are the design and material used to construct the impeller of a centrifugal pump suitable for pumping slurries?
- What kind of materials was utilized to construct the pump? Pumping highly abrasive slurries requires higher alloys.
- Are the discharge components of the pump suitable for the slurry to be pumped?
- What is the best sealing configuration for this application?
- Will the solid size be able to pass through the pump?
- How much solid damage is the customer willing to accept?
It is also critical to consider the slurry’s chemical compatibility with any elastomers in the pump. Once the nature of the slurry and the components of various types of pumps have been addressed, we can choose a potential candidate slurry pump for the application.
STEP 3 WORK OUT WHAT SIZE THE PUMP SHOULD BE
The most crucial part of this equation is determining the required pump horsepower to supply a certain quantity of liquid at the needed differential pressure. Think about the following:
- Solids concentration in the slurry — expressed as a percentage of total volume.
- The pipeline’s length. The longer the channel, the more slurry-induced friction the pump will have to overcome.
- The size of the slurry pipe.
- The static head is the height to which the must lift the slurry in the piping system.
STEP 4 DETERMINE THE OPERATING PARAMETERS OF THE PUMP
Most centrifugal slurry pumps operate at low speeds to reduce component wear — typically less than 1200 rpm. Find the ideal spot where the pump can run at a minimum speed without allowing solids to settle into the slurry and clog the lines.
Then, to reduce wear even further, reduce the pump’s discharge pressure to the lowest setting possible. Also, use proper piping layout and design principles to ensure consistent and uniform slurry delivery to the pump.
What distinguishes slurry pumps?
Thanks to features such as the large diameter of the impeller, shafts, bearings, and internal passageways, and their heavy-duty construction, Slurry pumps can withstand massive wear. Slurry pumps have more upfront operating costs than water pumps in the industrial industry. But, only slurry pumps are efficient in hydro-transporting solid materials. The longer-term advantages outweigh the initial cost.
The production of centrifugal force that causes the material to move outwards from the center of the pump is crucial for the efficiency of slurry pumps. However, the power of centripetal force pulls the material toward the center. Since the energies that impart the speed of the slurry increase, the process of transport of Slurry pumps works on the principle of centrifugal force. A centrifugal pump, however, is ineffective since the solids in the slurry would build up rather than flow freely.
Installation of slurry pumps
Knowing the exact conditions required for each pump is crucial for anyone planning to set up a slurry pump.
There are three kinds of Slurry installations:
Wet – the drive and slurry pump are entirely submerged in this setup. Certain types of slurry pumping, like underwater operations, will require this.
Dry — the setup protects the bearings and the pump’s drive free of the slurry. The wet part is freestanding and free of any liquid that surrounds it, comprised of the impeller, shell and suction liner, hub and shaft sleeve, and the stuffing box. The slurry pump technician puts most horizontal pumps in place using this method.
Semi-dry — this particular arrangement is used in horizontal pump dredging. The wet side and the bearings are flooded; however, the drive is dry. In this situation, bearings require a sealing arrangement.
This guide gives a brief overview of slurry pump types and their installation; however, there is more to be learned. Kingda will be there to help those looking to comprehend slurry pumps and applications or require help deciding what type of pump and installation is best for their needs.
Kingda Pump can help you choose the proper Slurry Pump installation that will fulfill and exceed your requirements for slurry transportation. Go to the Kingda Pump website to see an overview of all our services and how they can aid you.