Industrial pumps are an essential piece of equipment to a wide range of businesses and industries worldwide. They help accomplish many different tasks, and manufacturers design different pumps with specific applications in mind. For you or your operators to use the pumps correctly and safely, you first need to understand the basics of industrial pumps.
The American National Standard Institute (ANSI) is a private, non-profit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States.
A common misconception is that the ANSI creates the standards that products, such as industrial pumps, need to follow. However, in actuality, they simply oversee the development of such standards.
The ANSI states, “it is the intent of this standard that pumps of all sources of supply shall be dimensionally interchangeable with respect to mounting dimensions, size, and location of suction and discharge nozzles, input shafts, baseplates, and foundation bolts.”
ANSI process pumps are typically preferred because their parts are functionally and dimensionally interchangeable. In other words, you can swap one pump out with another (even if it’s a different brand) because all of the parts should be dimensionally the same.
Pumps make up roughly 68 percent of all rotating equipment globally (this includes generators, engines, etc.). There are essentially two different classifications of pumps: centrifugal pumps and positive displacement pumps. Approximately 86 percent of all industrial pumps are centrifugal pumps.
Centrifugal pumps are pressure-creating devices that convert velocity energy to kinetic energy by accelerating liquid to the outer rim of a revolving device known as an impeller. The faster you turn the device, the more pressure you are going to get.
It’s important to note that a centrifugal pump does not create pressure; it only creates flow. Pressure is a measurement of the resistance to flow, and flow depends on the pump system’s characteristics. Centrifugal pumps are perfect if you require high flow rates for low-viscosity liquids.
Positive displacement pumps are designed to create flow by trapping a fixed amount of fluid and forcing (or “displacing”) that trapped fluid into the discharge pipe. Unlike centrifugal pumps, positive displacement pumps are “constant flow machines” and will produce the same flow at a given speed (RPM) no matter the discharge pressure.
A positive displacement pump operating against a closed discharge valve will continue to produce flow until the pressure in the discharge line increases to the point where the line bursts, the pump becomes damaged, or both.
Aside from centrifugal pumps and positive displacement pumps, several other less-common types of pumps serve specific purposes.
Industrial pumps transport various materials, including oils, fertilizers, chemicals, fats, and water. To avoid unnecessary damage to your equipment and harm to you or the pump’s operators, it’s crucial that you clearly understand the buildup and breakdown points of pumping these materials.
Specific gravity is the ratio of a fluid’s density to that of water. Water has a specific gravity of 1. A fluid with a specific gravity of 0.5 weighs half as much as water. Of course, the volume of the liquid has to be taken into account as well.
Oil, fat, and crude oil are examples of fluids with specific gravity values less than water. Just remember, if it floats, it’s lighter!
Vapor pressure, also known as the boiling point, is the pressure below which a liquid at a given temperature will become a gas. With water, this occurs when temperatures reach 212 degrees F at 14.7 psi at sea level. Vapor pressure varies depending on the fluid in question.
Pressure is the force exerted per unit area, typically measured per square inch (psi). When pressure exerts on a liquid, that pressure is transmitted equally in all directions. There are three different types of pressure.
Atmospheric Pressure is the force exerted by the atmosphere (pressure at sea level is 14.7 psi). Atmospheric Pressure = Absolute Pressure – Gage Pressure.
Gage Pressure is the pressure contained in a vessel not acted upon by the atmosphere (units/psig). Gage Pressure = Absolute Pressure – Atmospheric Pressure.
Absolute Pressure is the sum of Gage Pressure and Atmospheric Pressure (units/psia). Absolute Pressure = Gage Pressure + Atmospheric Pressure.
Head is a standard measure of pressure. Measured in “feet of liquid,” head is indicated by the height and weight of a column of liquid discharged by a centrifugal pump. Keep in mind, a pump with a given impeller diameter and speed will raise a liquid to a certain height regardless of the weight of the liquid.
Industrial pump operators must understand shaft dynamics and know how to solve problems as they arise.
Shaft whip occurs when the shaft shifts 180 degrees from its centerline in every rotation creating a cone shape. An unbalanced impeller is usually the cause of this rotation.
Shaft deflection occurs when a radial load or mechanical imbalance causes the pump shaft to bend down when it is in one position. When the shaft rotates 180 degrees, it still bends downward in a similar way.
Shaft Deflection is a function of four factors.
The following scenarios are common problems that industrial pump operators face.
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