Given time, every component of the rotating machinery will eventually fail, even when operating in a perfect environment. For instance, rotation of the shaft subjects it to alternating load, changing from tension to compression with each shaft revolution.
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When a component of a large circulating water pump fails in a power plant, the power plant must often spend hundreds of thousands of dollars to remove the pump from service, replace the failed component, rebuild the pump and return it to service. In addition, circulating water pumps can require work on a massive scale-they can measure 30 ft or more in length and pump an average of 165,000 gpm. Rotating shafts for these pumps can measure 8 to 10 in. in diameter.
Progressive maintenance practices are vital to maximize pump life, minimize downtime and avoid costly repairs and lost production. It is good practice to plan the detailed groundwork of maintenance programs, along with contingencies for various maintenance events to minimize downtime.
Pump manufacturers in a variety of industries are increasingly asked to deliver more with less; they need to handle increased loads with improved system efficiency but reduce envelope, environmental impact and total system cost.
Knowing the basics of pump repair can simplify preventive maintenance.
It has been 54 years since Tracy Hall invented the first manmade diamond at the General Electric (GE) laboratories in Schenectady, New York. Since then, synthetic polycrystalline diamond (PCD) has found wide use as an abrasive and as a cutting element, with an annual market of $4 billion (3 billion carats in 2005).
What is the secret to continuously baking or processing cakes, pizza, chicken, beer and thousands of other foods and beverages? Mechanical carbon materials used in the food processing equipment produce these foods safely and cost effectively.
Lubricants for rotating machinery primarily serve to separate rolling and sliding contact surfaces, protect highly finished bearing surfaces from corrosion, protect against contaminants (in the case of grease) and serve as a heat-transfer medium (in the case of oil). An effective lubricant management program-grounded in proper lubricant monitoring and analysis practices-can help reinforce these functions and, in the process, deliver vital information about the machinery's condition and health.
Q. Our pumps take their suction from an open tank. When the liquid level drops, surface vortices are formed that allow air to be drawn into the pumps. What changes can be made to the tank to correct this problem?
Bearings perform vital roles in enabling optimized operation and service life of pumps used throughout industry. In centrifugal pump applications, for example, crucial functions abound.
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For more than 100 years, machine parts composed of mechanical carbon have provided an alternative solution in applications where temperature and atmosphere prevent the use of oil-grease lubricants. Mechanical carbon materials contain graphite, which is relied on for its self-lubricating characteristics.
In December 2008, we discussed some reasons ball bearings run hot. In December 2006 (ref. [1]), we described the common pitfalls of incorrectly dimensioning shafts during repairs. This time, we will examine the cousin of a ball bearing-a roller bearing-and some of the pitfalls that occasionally cause hot operation.
Frequently, guide bearings are incorrectly blamed for a problem that has nothing to do with the bearings. Unless the bearings have a material defect (which would be unusual), guide bearings do not cause pump problems. Rather, guide bearing failures are the result of other problems that the pump is experiencing.
Magnetic bearing systems represent a different approach from rolling bearings to support rotating machinery, and in recent years, their benefits have attracted attention for more applications.
Rolling bearings play vital roles as the hearts of rotating machinery (pumps included) by supporting shafts, locating loads, enabling rotation and reducing friction. When bearings need to be replaced, improper dismounting and mounting techniques can shorten their life expectancy.
Babbitt bearings, frequently found in large steam turbines and generators in major power plants, can provide years of service if properly maintained. By using state-of-the-art technology and repair practices, aftermarket suppliers who specialize in Babbitt bearings can repair equipment and increase the life of Babbitt bearings.
The initial cost of a pump is a small component of the pump's total life cycle cost. Progressive, proactive maintenance practices are vital to maximize pump life, minimize downtime and avoid costly repairs and lost production.
Given time, every component of the rotating machinery will eventually fail, even when operating in a perfect environment. For instance, rotation of the shaft subjects it to alternating load, changing from tension to compression with each shaft revolution.
Pump manufacturers in a variety of industries are increasingly asked to deliver more with less; they need to handle increased loads with improved system efficiency but reduce envelope, environmental impact and total system cost.
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In this multi-part series, we will investigate several aspects of centrifugal pump efficiency.
First of Five Parts
Since the original publication of this draft standard in the January 2008 issue of Pumps & Systems, I have received feedback, encouragement, numerous questions and criticism. The draft listed three basic levels of repair.
The McGraw-Hill scientific dictionary [5] states that a volute is "a spiral casing for a centrifugal pump... designed so that speed will be converted to pressure."
