The industry "rule of thumb" says to reduce the wear ring clearance by 50%, but this isn't always true.
What Problem am I Trying to Solve with Vespel® CR-6100?
Vespel® CR-6100 can be used to improve pump reliability and performance in many ways. Some benefits require reduced clearance, some do not. The following table gives some examples of where reducing clearance is needed vs. where it is not needed.
Is There Differential Pressure Across the Part?
Efficiency Improves: The leakage across the part will be reduced, improving pump efficiency and reducing the operating cost of the pump.
Improved Rotor Stability: The Lomakin Effect in the pump will be increased, increasing the hydraulic forces produce by the wear rings.
Both of these factors are driven by differential pressure across the part.
If the specific component you are upgrading to Vespel® CR-6100 is not exposed to differential pressure (i.e. vertical pump shaft bearing) there is no need to reduce the clearance.
Wear rings, throttle bushings, center bushings, balance bushings are all exposed to differential pressure. These are the parts where you want to reduce the clearance to obtain performance and rotor stability improvements. The rule of thumb is to reduce the clearance to 50% of the API minimum for metal parts. For most pumps in the hydrocarbon processing industry, this works.
These benefits are augmented using the patented PERF-Seal™ design from Boulden, which further reduces leakage across the part and dramatically increases the hydraulic damping from these components.
Because pumps come in all shapes and sizes, there are some places where we need to make exceptions and reduce the clearance by less than 50%.
Throat bushings-the throat bushing clearance often helps to control the mechanical seal flush rate. We recommend using the clearance recommended by your mechanical seal OEM to set the clearance of this part.
Wear rings in vertically suspended pumps-You don't want to have the wear ring clearance tighter than the shaft bearing clearance. Therefore, our recommended minimum clearance for wear rings in vertically suspended pumps is the shaft bearing clearance + 0.002″ (0,05 mm).
Over the years, we have seen pump repair shops use a range of clearance values when applying Vespel® CR-6100 with great results. There is no single "best" way. That said, if you want to increase efficiency, you need to reduce the clearance of the parts exposed to differential pressure. If you are only trying to solve a run-dry or seizing problem, reducing the clearance is optional. For vertical pump shaft bearings, staying with the original design clearance is usually the best answer.
Until next time, please feel free to contact Boulden if you would like to discuss the appropriate clearance for your pump upgrade. We'll be happy to help and we have whatever material you need in stock in the USA, Europe, and Singapore.
This entry was posted in Boulden News, DuPont™ Vespel® CR-6100 Solutions and tagged boiler feed water pumps, boulden, case wear rings, composite wear rings, CR-6100, Lomakin Effect, Pumps With Composite Wear Components, throat bushing, throttle bushings, Vespel CR-6100, wear ring clearance on February 21, 2018 by admin.
Case Study: DuPont™ Vespel® CR-6100 in 3MW Boiler Feed Water Pump with PERF-Seal™ design.
A while back, we introduced the PERF-Seal™ design for center bushings, throttle bushings, and pump wear rings.
2-stage pump upgraded to Vespel® CR-6100 with the PERF-Seal™ design.
The holes drilled in the PERF-Seal™ create a turbulence field, thereby reducing leakage across the component–acting in a way similar to a labyrinth. However, unlike a labyrinth design, the PERF-Seal™maintains the same hydraulic stiffness as a plain wear ring and discourages tangential whirl of the process fluid.
Boulden worked with Mechanical Solutions to create an FEA model of the design and to create a custom test rig to validate the performance of the design. If you are interested in the results of this testing, Contact Boulden and we will be happy to share with you.
We were approached by a power plant looking to upgrade their 3MW boiler feed pumps. Their process had changed over the years to require frequent cycling and they wanted to use Vespel® CR-6100 to avoid pump seizure. Due to the size of the pumps, increased efficiency was an added bonus.
The pumps have now been running for 2 years. A full case study was recently published in POWER Magazine and is available here.
Contact us if you have a boiler feed water pump you would like to upgrade.
If you need material, we have a huge inventory of standard stock sizes available for immediate shipment.
For details on how to install Vespel® CR-6100 into nearly any pump type, download the Boulden Installation Guide.
This entry was posted in Boulden News, DuPont™ Vespel® CR-6100 Solutions and tagged boulden, case wear rings, CR-6100, dupont vespel cr-6100, Lomakin Effect, PERF-seal, throttle bushings, Vespel CR-6100, vespel stock sizes on December 13, 2017 by admin.
Last week, we looked at vertically suspended pumps with the discharge through the column. This week, we take a look at vertically suspended pumps with a separate discharge (API Type VS4).
Vertically suspended pumps with separate discharge are generally used for sump pumps or wastewater pumps. It seems that these pumps cause headaches at most plants. The shaft bushings wear out leading to chronic repairs. Over the years, Vespel® CR-6100 has been used in a lot of these pumps, sometimes the pump life has been extended from a few months to several years; sometimes the pump life has not improved. Therefore, it is important to identify the failure mode before making the upgrade. We have used our experience to create the roadmap below.
The first step is to clarify "sump pump" or "waste water pump", which are generic terms encompassing a wide range of services. Some services are pumping primarily chemicals mixed with water, and some of them are pumping primarily water mixed with dirt. Some of the sumps are so dirty, that the pump suction strainer seems to be immersed in mud. Another variable is that the shaft bearings are flushed with different arrangements. Some of them are flushed with the process fluid, others with clean water, and others are greased.
Given the range of service conditions, there are several different problems which can cause the shaft bearings to fail. However, there are some commonalities. First, by design, the shaft bearings are along the column of the pump with a separate discharge for the process fluid. The bearings can run dry at start-up until the flushing fluid arrives. Sometimes, the external water flush is turned off; sometimes the flush lines from the process fluid are plugged; sometimes the grease supply runs out. In a chemical sump, the mix of chemicals can cause corrosion with metal wear parts. Finally, in very dirty sumps where the bearings are flushed with the process fluid, abrasive wear tends to be the main problem.
Vespel CR-6100 sump pump services.
*Some of the alternatives to consider are switching to a clean water flush or looking at an abrasive resistant, non-seizing combination for the shaft bushings and sleeve. This generally entails a hardened sleeve and an abrasive resistant bushing material. If you have any doubts about whether Vespel® CR-6100 is a good fit for your service, contact Boulden to discuss.
To finish our discussion of vertically suspended pumps, we will talk about assembly and installation issues which impact pump reliability. Until then, use the above information as a guide on how to use Vespel® CR-6100 in your pumps with a separate discharge. If you need any material, contact Boulden. We have whatever size and quantity you need in stock and ready for immediate delivery.
This entry was posted in Boulden News, DuPont™ Vespel® CR-6100 Solutions and tagged boulden, composite wear rings, dupont vespel cr-6100, improve pump efficiency, Lomakin Effect, pump seized, Pumps With Composite Wear Components, reducing pump seizure, Series on upgrading pumps to Vespel, throat bushing, throttle bushings, Vespel, Vespel CR-6100, wear ring clearance on October 12, 2017 by admin.
DuPont™ Vespel® CR-6100 is a composite material which is used for the stationary wear parts of your pump and can be used in nearly all process chemicals from cryogenic temperatures to 500 F (260 C).
The upgrade to Vespel® CR-6100 wear parts involves two steps: eliminate the metal-to-metal contact points in the pump to minimize the risk of pump seizure, then reduce clearance to improve reliability and increase efficiency.
Today, we cover the details on using Vespel® CR-6100 to upgrade your between-bearings, radially-split pumps. The components we want to upgrade in these pumps are the case rings, throttle bushing, and throat bushings.
Single and two-stage BB2 style pumps are widely used in refining and petrochemical applications featuring higher temperatures and low NPSH available. Upgrading the wear rings (and inter-stage bushing in two-stage designs) with Vespel® CR-6100 and reduced clearance will help maintain rotor stability, improve efficiency, and reduce the pump NPSHR.
The key point in upgrading the wear rings in these designs is to ensure the Vespel® CR-6100 is retained against differential pressure. In many designs, the original case wear rings are manufactured with an "L" shaped profile as shown in Figure 1. This shape of this design will, in most cases, retain the rings against differential pressure. You only need to modify the original design to incorporate the press fit required for Vespel® CR-6100 and then final machine the rings after they are pressed into the diffusers.
In some pumps, however, the case rings go straight across the diffusers. When they are metal rings, they are usually welded in place. To replace these designs with Vespel® CR-6100, you may need to modify the diffusers to incorporate an "L" shaped profile, or design another method of retaining the components against differential pressure. If you have any questions, contact Boulden with the pump cross sectional drawing and we can help.
The throttle bushings of BB4 and BB5 pump types can be exposed to high differential pressures. For these components, Boulden has developed a patent-pending design called the PERF-Seal™ which improves the performance and dramatically increases the differential pressure capability of composite materials used in this position.
Boulden recommends the PERF-Seal™ design for all throttle bushings in BB4 and BB5 pumps. Contact us and we can either supply machined parts or provide drawings for you to manufacture the components in your shop for the upgrade.
Our final look at specific pump types will feature vertically suspended pumps. After that, we will cover a few specific topics and wrap up this series.
Until then, if you have a radially split pump where you would like to improve the reliability or efficiency, contact Boulden today. We can provide you all of the details required for your upgrade and have the Vespel® CR-6100 in stock in a wide range of sizes available for immediate delivery.
This entry was posted in Boulden News, DuPont™ Vespel® CR-6100 Solutions and tagged boulden, machined parts, PERF-seal, Series on upgrading pumps to Vespel, throat bushing, throttle bushings, Vespel, Vespel CR-6100, vespel stock sizes on August 22, 2017 by admin.


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Q: Cordova Build fails on iOS with iOS 3.6.3 and cordova 4.0.0 I just upgraded to cordova 4.0.0 and upgraded my iOS platform to version 3.6.3.
Unfortunately all my builds fail right now with the following output on cordova build iOS:
 Ld build/emulator/App.app/App normal i386
     cd /Users/user/<app>/platforms/ios
     export IPHONEOS_DEPLOYMENT_TARGET=7.0
     export PATH="/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin:/Applications/Xcode.app/Contents/Developer/usr/bin:/Users/user/.rvm/gems/ruby-2.0.0-p451/bin:/Users/user/.rvm/gems/ruby-2.0.0-p451@global/bin:/Users/user/.rvm/rubies/ruby-2.0.0-p451/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/opt/X11/bin:/Users/user/.rvm/bin:/Users/user/.adt/tools:/Users/user/.adt/platform-tools"
     /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang -arch i386 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator8.0.sdk -L/Users/user/<app>/platforms/ios/build/emulator -L/Users/user/<app>/platforms/ios/App -L/Users/user/<app>/platforms/ios/App/Plugins/com.liyamahendra.cordova.plugins.flurry -F/Users/user/<app>/platforms/ios/build/emulator -F/Users/user/<app>/platforms/ios/HD -F/Users/user/<app>/platforms/ios/Safe -F/Users/user/<app>/platforms/ios/App/Plugins/com.phonegap.plugins.facebookconnect -filelist /Users/user/<app>/platforms/ios/build/App.build/Debug-iphonesimulator/App.build/Objects-normal/i386/App.LinkFileList -Xlinker -objc_abi_version -Xlinker 2 -weak_framework CoreFoundation -weak_framework UIKit -weak_framework AVFoundation -weak_framework CoreMedia -weak-lSystem -force_load /Users/user/<app>/platforms/ios/build/emulator/libCordova.a -ObjC -framework Lookback -fobjc-arc -fobjc-link-runtime -Xlinker -no_implicit_dylibs -mios-simulator-version-min=7.0 -framework FacebookSDK -framework AdSupport -lFlurryAds_5.3.0 -lz -framework QuartzCore -lFlurry_5.3.0 -framework CoreVideo -framework AudioToolbox -framework AVFoundation -framework CoreGraphics -framework CoreMedia -framework Lookback -framework AssetsLibrary /Users/user/<app>/platforms/ios/build/emulator/libCordova.a -framework Lookback -framework MobileCoreServices -framework CoreLocation -framework StoreKit -weak_framework iAd -Xlinker -dependency_info -Xlinker /Users/user/<app>/platforms/ios/build/App.build/Debug-iphonesimulator/App.build/Objects-normal/i386/App_dependency_info.dat -o /Users/user/<app>/platforms/ios/build/emulator/App.app/App
 duplicate symbol _OBJC_IVAR_$_CDVFilesystemURL._url in:
     /Users/user/<app>/platforms/ios/build/App.build/Debug-iphonesimulator/App.build/Objects-normal/i386/CDVFile-E7AB62C4A5CCC89.o
 duplicate symbol _OBJC_IVAR_$_CDVFilesystemURL._fileSystemName in:
     /Users/user/<app>/platforms/ios/build/App.build/Debug-iphonesimulator/App.build/Objects-normal/i386/CDVFile-E7AB62C4A5CCC89.o
 duplicate symbol _OBJC_IVAR_$_CDVFilesystemURL._fullPath in:
     /Users/user/<app>/platforms/ios/build/App.build/Debug-iphonesimulator/App.build/Objects-normal/i386/CDVFile-E7AB62C4A5CCC89.o
 duplicate symbol _kCDVFilesystemURLPrefix in:
     /Users/user/<app>/platforms/ios/build/App.build/Debug-iphonesimulator/App.build/Objects-normal/i386/CDVFile-E7AB62C4A5CCC89.o
 duplicate symbol _filePlugin in:
     /Users/user/<app>/platforms/ios/build/App.build/Debug-iphonesimulator/App.build/Objects-normal/i386/CDVFile-E7AB62C4A5CCC89.o
 duplicate symbol _OBJC_IVAR_$_CDVFile.fileSystems_ in:
     /Users/user/<app>/platforms/ios/build/App.build/Debug-iphonesimulator/App.build/Objects-normal/i386/CDVFile-E7AB62C4A5CCC89.o
 duplicate symbol _OBJC_IVAR_$_CDVFile.rootDocsPath in:
     /Users/user/<app>/platforms/ios/build/App.build/Debug-iphonesimulator/App.build/Objects-normal/i386/CDVFile-E7AB62C4A5CCC89.o
 duplicate symbol _OBJC_IVAR_$_CDVFile.appDocsPath in:
     /Users/user/<app>/platforms/ios/build/App.build/Debug-iphonesimulator/App.build/Objects-normal/i386/CDVFile-E7AB62C4A5CCC89.o
 duplicate symbol _OBJC_IVAR_$_CDVFile.appLibraryPath in:
     /Users/user/<app>/platforms/ios/build/App.build/Debug-iphonesimulator/App.build/Objects-normal/i386/CDVFile-E7AB62C4A5CCC89.o
 duplicate symbol _OBJC_IVAR_$_CDVFile.appTempPath in:
     /Users/user/<app>/platforms/ios/build/App.build/Debug-iphonesimulator/App.build/Objects-normal/i386/CDVFile-E7AB62C4A5CCC89.o
 duplicate symbol _OBJC_IVAR_$_CDVFile.userHasAllowed in:
     /Users/user/<app>/platforms/ios/build/App.build/Debug-iphonesimulator/App.build/Objects-normal/i386/CDVFile-E7AB62C4A5CCC89.o
 duplicate symbol _OBJC_IVAR_$_CDVFile._persistentPath in:
     /Users/user/<app>/platforms/ios/build/App.build/Debug-iphonesimulator/App.build/Objects-normal/i386/CDVFile-E7AB62C4A5CCC89.o
 duplicate symbol _OBJC_IVAR_$_CDVFile._temporaryPath in:
     /Users/user/<app>/platforms/ios/build/App.build/Debug-iphonesimulator/App.build/Objects-normal/i386/CDVFile-E7AB62C4A5CCC89.o
 duplicate symbol _OBJC_CLASS_$_CDVFilesystemURL in:
     /Users/user/<app>/platforms/ios/build/App.build/Debug-iphonesimulator/App.build/Objects-normal/i386/CDVFile-E7AB62C4A5CCC89.o
 duplicate symbol _OBJC_METACLASS_$_CDVFilesystemURL in:
     /Users/user/<app>/platforms/ios/build/App.build/Debug-iphonesimulator/App.build/Objects-normal/i386/CDVFile-E7AB62C4A5CCC89.o
 duplicate symbol _OBJC_METACLASS_$_CDVFilesystemURLProtocol in:
     /Users/user/<app>/platforms/ios/build/App.build/Debug-iphonesimulator/App.build/Objects-normal/i386/CDVFile-E7AB62C4A5CCC89.o
 duplicate symbol _OBJC_CLASS_$_CDVFilesystemURLProtocol in:
     /Users/user/<app>/platforms/ios/build/App.build/Debug-iphonesimulator/App.build/Objects-normal/i386/CDVFile-E7AB62C4A5CCC89.o
 duplicate symbol _OBJC_CLASS_$_CDVFile in:
     /Users/user/<app>/platforms/ios/build/App.build/Debug-iphonesimulator/App.build/Objects-normal/i386/CDVFile-E7AB62C4A5CCC89.o
 duplicate symbol _OBJC_METACLASS_$_CDVFile in:
     /Users/user/<app>/platforms/ios/build/App.build/Debug-iphonesimulator/App.build/Objects-normal/i386/CDVFile-E7AB62C4A5CCC89.o
 ld: 19 duplicate symbols for architecture i386
 clang: error: linker command failed with exit code 1 (use -v to see invocation)

 ** BUILD FAILED **

 The following build commands failed:
    Ld build/emulator/App.app/App normal i386
 (1 failure)
 Error: /Users/user/<app>/platforms/ios/cordova/build: Command failed with exit code 65
     at ChildProcess.whenDone (/usr/local/lib/node_modules/cordova/node_modules/cordova-lib/src/cordova/superspawn.js:135:23)
     at ChildProcess.EventEmitter.emit (events.js:98:17)
     at maybeClose (child_process.js:743:16)
     at Process.ChildProcess._handle.onexit (child_process.js:810:5)

Any ideas where this could come from?
I'm running Mac OS X 10.10 (Yosemite) and Xcode 6.
Hope you can help :)

A: Ok, I found the problem. Actually I had a source twice in my list of compiled sources in the Build Phase tab. That caused the
ld: 19 duplicate symbols for architecture i386

Error which caused the build to fail.

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