For applications requiring the pumping of low viscosity liquids, avoiding operational problems due to the poor lubricity of these liquids can be tricky. A change in material will go a long way in solving the traditional “run-dry” problem associated with low viscosity fluid handling. In the worst cases, a pump that runs dry under extreme circumstances may require a complete rebuild or an outright replacement. Graphite Metallizing has worked to eliminate these issues with their line of specialty bearings that can withstand run-dry conditions without causing damage to the pump system. Self-lubricating, non-galling Graphalloy® bearings and wear rings solve pumping problems caused by low lubricity liquids such as natural gas liquids (NGL), LNGs, CO2 and other light hydrocarbons.
ADDRESSING POOR LUBRICITY
Graphalloy bearings are used in horizontal and vertical and pumps for low viscosity service to help eliminate operational problems due to the poor lubricity of these liquids. The non-galling, self-lubricating features of Graphalloy allow pumps to continue working even when experiencing run-dry, flashing, or cavitation.
According to Graphite Metallizing, light hydrocarbons can be especially difficult for metallic bearings because the hydrodynamic film provided by these low lubricity fluids is unable to provide enough lubrication, which can lead to metal-on-metal contact, galling or seizing of the pump.
Using Graphalloy bearings and wear rings allows for tighter clearances, improving reliability, lowering vibration and increasing efficiency in vertical and horizontal pumps.
HORIZONTAL AND VERTICAL PUMP SURVIVAL
Graphalloy solves tough application problems and is used by designers, reliability, and maintenance engineers in many different industries. These rings and bushings allow for closer clearances often gaining efficiency improvements, reducing vibration, and reducing NPSH requirements.
Pumps are able to survive repeated run-dry conditions, slow roll operation, and frequent stop/starts—in other words, the conditions where metal and plastics fail.
Plastics, such as Polyether ether ketone (PEEK), may enable a pump to run dry briefly without a catastrophic crash, but generally a rebuild of the pump will be required, including replacement of the thermoplastic parts.
Bearings and wear rings made of Graphalloy operate effectively in run-dry scenarios without loss of performance or the need to replace parts. Part of this ability stems from the wide temperature range that the wear parts can withstand, from cryogenic to 1000 degrees Fahrenheit (540 degrees Celsius). Graphalloy maintains clearances over the entire operating range.
In horizontal and vertical pumps, these parts prevent metal-on-metal contact, galling or seizing of the pump if run dry or with marginal lubrication. The pump is able to survive upsets, dry running, loss of suction, slow roll on standby, and other transient conditions that would damage a conventionally fitted pump.
GRAPHALLOY CAN BE THE SOLUTION
Used in the manufacture of bushings, bearings, and other components for machinery and process equipment, Graphalloy materials are self-lubricating, impervious to temperature extremes from -400 to 750 degrees Fahrenheit (-240 to 400 degrees Celsius) and thrive in harsh environments where other bearings fail. Special grades provide reliable service up to 1000 degrees Fahrenheit (535 degrees Celsius) and higher in non-oxidizing atmospheres.
Graphalloy can be the solution to the toughest bearing, bushing, thrust washer, cam follower, or pillow block bearing design problem. It is available in over 100 grades with specific properties that meet a wide range of engineering solutions and specifications. FDA accepted grades are available for food contact equipment. NSF® International has certified two grades of material for use in municipal well pumps and water treatment plant applications. In some applications, Graphalloy bearings have operated for up to twenty years without maintenance. Standard designs are available but most products are custom designed to the unique requirements of the specific application.
ABOUT THE AUTHOR
For more information about Graphite Metallizing and its products, visit www.graphalloy.com or call 914.968.8400.
MODERN PUMPING TODAY, December 2013
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