Don’t get hung-up on pump selection ever again! We are going to get over this problem right now, once for all, and you will never feel scared or confused about pump selection again.
We’ve all come across the popular saying ‘Less (Information) Is More’. While that may be true in some cases, it certainly doesn’t apply here. When it comes to pump selection, the more informed you have, the more likely you are to select the right pump for your system and application.
There are several factors that play a significantly role in the pump’s performance, efficiency, maintenance costs and life expectancy. All information and conditions that will affect the selection of a pump should be analyzed before selecting a pump for a job. Below are a few tips to guile you in selecting the right pump for your application.
Fluid Properties
It is important to understand the type of fluid you are pumping. The properties to consider are:
· Chemical Composition & pH: The primary cause of damage to pumps is corrosion and the entry of solid debris or liquid into the pumping chamber. Corrosive and acidic fluids can degrade pumps. Refer to the Chemical Resistance Chart that will aid you in selecting suitable seals for your pump.
· Viscosity: Viscosity of a liquid is a measure of its resistance to flow. High viscosity fluids result in reduced pump performance and increased power requirements.
· Specific gravity: The specific gravity of a fluid is the ratio of the fluid density to the density of water under at a specified temperature. Specific gravity affects the force required to lift & move the fluid, and must be considered in determining pump power requirements.
· Operating Temperature: Pump material, seals, and other packing materials are to be taken into consideration when pumping fluids that are hotter than 80°C. The pump should always be operated within its range of designed temperature ratings.
· Vapor pressure: Vapor pressure is the force exerted by the fluid in an effort to change phase from a liquid to a vapor. The amount of force depends on the fluid’s chemical and physical properties. Proper vapor pressure consideration of the fluid will help minimize cavitation.
· Solids present and concentration: When abrasive liquids are pumped such as sludge and slurry, select a pump based on particle size, volumetric percentage of solids and hardness to prevent the pump from service failure or clogging.
Pump Types
There are several types of pumps available for various purposes based on several methods of classification. Each type of pump is best suited for a certain application. Some of the commonly used pumps are:
Rotary Vane Pumps – A rotary vane pump is a positive-displacement pump that consists of vanes mounted to a rotor and moves fluid by rotating inside a cavity that creates a vacuum to capture and draw in the fluid. These pumps unlike centrifugal pumps, produce the same flow at a given speed / RPM regardless of the discharge pressure. The sliding vane design combines low cost with high reliability and easy maintenance. While rotary vane pumps can handle moderate viscosities, they are great at handling low viscosity fluids such as solvents, LPG (butane / propane), ammonia, fuel oils, diesel, petrol, refrigerants and alcohol.
Centrifugal pump – Centrifugal pumps are used to induce flow or raise a fluid from a low level to a high level. It is the most popular type of pump for capacities up to 15 cumec and heads of up to 34m. These pumps are often used on construction sites. It is popular because the pump is self-priming, resists abrasion and can handle liquids containing solids.
Turbine pump – Turbine pumps utilize fluid momentum and speed to build pump pressure. This pump is a continuous duty pump designed for low flow applications with moderate to high differential pressures. The free-floating impeller minimizes wear and delivers years of trouble-free service. Applications include LPG transfer, cylinder filling, vaporizer feed, aerosol propellant/filling
Gear pump – A gear pump is a type of. Gear pumps are a type of positive displacement (PD) pump where the fluid is pushed between two gears. It delivers a smooth pulse-free flow proportional to the rotational speed of its gears. Gear pumps are commonly used for pumping highly viscous fluids such as crude oil, paints, foodstuff and soaps.
Side Channel pump – Side Channel Pumps are self-priming pumps used for low flow and high head applications involving low viscosity, clean fluids. A side channel pump consists of one or more stages (impellers). The stages are similar to those used in centrifugal pumps but the close tolerances between the impellers and casting has more in common with PD pump designs. Typical applications include seawater transfer, LPG pumping, refrigerants, reverse osmosis, hot water circulation, boiler feeder, heating / air conditioning and more.
Diaphragm pump – The diaphragm pump is also a positive displacement pump having a central portion of the flexible diaphragm, which is raised and lowered by a pump rod. This action draws fluid into and discharges it from the pump. This pump can handle fluid containing large quantities of mud, sludge, sand, and trash and is resistant to corrosion.
Submersible pump – Submersible pumps are mostly centrifugal pumps powered by electric motors close-coupled to the impellers in one housing. The pump is largely submerged in the fluid to be pumped. Typical applications include gas stations (underground tanks), drainage, sewage treatment plants, seawater handling, slurry pumping, firefighting, offshore drilling rigs and irrigation systems.
Vacuum pump – Vacuum pumps are devices used to remove air or gas particles from a sealed container by creating a vacuum. The main application for these pumps is to move dangerous fluids easily and safely, without spillage to protect the environment from waste and toxic substances.
Material of Construction
Again, it is important to understand material compatibility with the product (liquid) or any other fluid that could come in contact with the pump. Refer to our Chemical Resistance Chart that will aid you in selecting a suitable material for the pump.
Flow Rate and Head
Flow rate is the volume of fluid that is passing through a cross sectional area per unit time. Head is the height at which a pump can raise fluids up. The required flow rate in liters per minute (lpm) and total head is needed to accurately size the piping system, determine friction head losses and select the appropriate pump and motor drive.
Net Positive Suction Head (NPSH)
Don’t keep it hungry! The Net Positive Suction Head (NPSH) is identified by measuring the pressure experienced by a fluid on the suction side of a pump. It technically measures how close the fluid is to flashing or cavitation, at a given level. A rule of thumb is to ensure the suction head available exceeds that required by the pump by at least 25% over the range of expected flow rates.
Differential Pressure
Differential pressure is the difference of pressure at the suction vs. the discharge. Differential pressure of the pump can be determined by calculating friction losses in piping, static lifts, and other mechanical equipment (fittings, filters, valves, etc.).
Drives
Pumps can be driven using various modes of power depending on the performance & dimensions of the pump, torque & power requirements, pipelines through which the fluid travels as well as other environmental factors. Pumps should not be stressed past their operating limits, as it would result in eventual failure. Common drive options include:
Electric Motor Drive: Three-phase AC motors are the most commonly used drives for pumps because electricity is much easier to distribute and control as a power source and because the standard rotative speeds (1,750 and 3,500 RPM) are well suited to drive a variety of pumps. The pump may be direct driven through a coupling by an electric motor or belt driven by an electric motor.
PTO (Power take-off) Drive: PTO pumps work through transfer of power from remote engines, such as those found in trucks. PTOs are commonly used in commercial vehicles, trucks and farming equipment where electricity is not easily available. Once a PTO connection has been established with a vehicle’s engine, a PTO pump is ready to go. It is low cost to buy and run. Typical applications include loading and unloading fuel tankers, running a water pump on a fire engine
Hydraulic Drive: Pumps driven by hydraulic systems consist of an adaptor, motor, pump, cooler, and connecting hoses. The sizing of the hydraulic motor, hydraulic pump and hydraulic oil cooler must be done using the operational requirements of the pump (e.g. flow rate, speed, differential pressure, and torque and power requirements). One hydraulic pump can drive several hydraulic motors. The added strength and increased adaptability of a hydraulic system gives it an advantage over electrical drives.
Engine Drive: Engine drives are used in remote areas when there is no electricity to run the pump. The engines are powered by diesel or petrol and are popular in the domains of dewatering, mining, marine, agriculture, and more.
Battery Operated Drive: Direct current produced from 12V and 24V truck batteries are typically used for variable speed pumps, emergency pumps, drum pumps and portable fuel transfer pumps. Battery driven pumps are often used on farms, construction sites, fleet service facilities, mines or in sites where only the only available power source is from the truck or tractor’s battery or where the mobility of the pump is an issue.
Compressed Air – Pumps using compressed air to operate are called pneumatic pumps. Though their efficiency is low, they have low maintenance costs, and can handle large amounts of suspended solids. Compressed air drives are also preferred in environments where there is a risk of electric shock such as in tunnel dewatering.
Environmental Conditions
Our pumps & meters are designed and manufactured for outdoor duty. However, for applications where the pump will be subjected to extreme conditions for extended periods such as corrosive environments, explosive vapors, dust, arctic conditions, etc., special motor characteristics may need to be put in place. Consult an AYTC Application Engineer. Check local safety regulations and building codes to assure installation will meet local safety standards.
Price & Criticality
For critical applications, where a breakdown would prove catastrophic, you should consider reliable heavy-duty pumps or duplex pump sets equipped with distinctive features that enable them to function under the most demanding conditions. On the other hand, in an application where pumps can be withdrawn from the operation, affordable alternatives can be taken into consideration.
In Conclusion
By understanding the factors above, you’re arming yourself with the information needed to pick the right pump. Whatever the application may be, by now you should feel confident in selecting the right pump. However, Ali Yaqoob Trading Co. L.L.C. is always here for you if you need help. We have available for you a tremendous variety of pumps and related flow equipment. Our application engineers are factory trained to select the right pump for your application or system. Get in touch or come by for a cup of coffee and we’ll be glad to assist you!
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