Plant Services - June 2008 - (Page 25)

TECHNOLOGY TOOLBOX Helices and diamonds New features help mechanical seals last longer and handle tougher environments mechanical seals. UNCD has nano-scale roughness, makump seals are vulnerable items. Minimizing wear, ing it smooth enough to avoid degrading a soft counterface. extending equipment service life, and increasing the For hard-on-hard sealing, test results show that a diamondMTBF by using better seals or better seal environments treated seal face is a major improvement. is cheap compared to the cost of an outage. The clean air and UNCD Seals can provide energy savings through rewater acts, and emission suppression goals are further influencduced friction, better tolerance to poor lubrication coning developments in mechanical seal technology. ditions, lower maintenance costs, higher MTBF and Improved seal environments: According to ITT Goulds reduced face temperatures. The price of UNCD seals is Pumps, most seal failures aren’t from bad seal design, but comparable to high-performance, silicon carbide-face a poor sealing environment lacking proper lubrication and seals. A line of component seals is currently cooling, heavy with suspended solids. available, and a line of cartridge seals is exThe ITT Goulds TaperBore Plus seal chamber provides better face lubrication, thus Argonne National pected in late 2008. For high-pressure turbomachinery applipromoting longer life. Heat dissipation is imLaboratory has cations, John Crane developed a variant of proved with an enlarged seal chamber and invented a new its Type 28EXP dry gas compressor seal with greater radial clearances. Liquid continuously form of diamond a new face material. The hard face is silicon flushes the face, while a vane particle ejeccarbide, which provides a high modulus and tor forces solids out. Air and vapor flow away that is being coated with from the seal and exit the seal chamber. commercialized limits pressure deflection, and isto minimize a diamond-like coating (DLC) The company developed a design for subfor mechanical friction and decrease wear. The new face mamersible and end-suction centrifugal pumps. seals. terial operates to 425 bar, which is characThe Cyclone Seal Chamber has a tapered bore teristic of the oil and gas industry. The need and two cast helical grooves in the walls that to exceed traditional limits is being driven modify the flow pattern in the chamber to keep by rising requirements of re-injection compressors that solids away from the seal faces. ITT’s testing revealed that the improve oil extraction yields and the emerging carbon seliquid’s rotational velocity moves solids caught in the grooves questration market. along the helical path until they exit the seal chamber. Another company using diamond-coating technology is Keeping the chamber free of solids prevents erosion, along Burgmann Industries. EagleBurgmann’s DiamondFaces with clogging and wear of the seal hardware. The Cyclone seals have a microcrystalline coating applied using a chemiSeal Chamber’s self-venting design prevents vapor buildup, cal vapor deposition (CVD) process, forming a chemical and its “flushless” operation reduces operating costs, envibond with the silicon carbide facing. The coating is described ronmental liability, product contamination and dilution asas exceptionally hard and long-wearing, with excellent heat sociated with flush water. conductivity, chemical resistance and low friction. Suited for Innovative seal coatings: Argonne National Laboratory the oil and gas, chemical and pharmaceutical industries, it has invented a new form of diamond that is being commercialprotects against wear during dry running, including mixed ized for mechanical seals by Advanced Diamond Technolofriction and abrasive media applications. gies (ADT). The work was supported in part by the National Science Foundation and the U.S. Department of Energy. Diamond adds its low-wear, low-friction attributes to E-mail Contributing Editor Sheila Kennedy, managing director of ADT’s ultrananocrystalline diamond (UNCD) family of Additive Communications, at Sheila@addcomm.com. For more information, see: www.gouldspumps.com www.anl.gov June 2008 P www.thindiamond.com www.diamondseals.com www.PLANTSERVICES.com www.johncrane.com www.burgmann.com 25 http://www.gouldspumps.com http://www.thindiamond.com http://www.johncrane.com http://www.anl.gov http://www.diamondseals.com http://www.burgmann.com http://www.PLANTSERVICES.com

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Plant Services - June 2008

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