Category Archives: Boulden News

Over the past decade, Boulden Company has grown into a global distributor of DuPont™ Vespel® CR-6100, supplying to North America, EMA (Europe, Middle East, Africa), Australia, New Zealand, and Singapore. We have a huge inventory of material to supply end users, OEMs, and repair shops with raw material or machined parts. In recent years. Contact Boulden to learn more!

Useful Links for using DuPont™ Vespel® CR-6100

Upgrading pumps with composite wear componentsTools to help you improve your pump operability, reliability, and efficiency

20 Years of  Vespel® CR-6100

Our favorite material recently passed a milestone. The first pump ever fitted with Vespel® CR-6100 was upgraded 20 years ago in November 1997.

 

The first pump was a vertically suspended condensate pump at a refinery in California. The pump was notorious for running dry, and it had failed once or twice per year for as long as the maintenance records went back. An engineer at the refinery “found” Vespel® CR-6100 and decided to put it to the test on the condensate pump. The pump survived repeated episodes of running dry and subsequently ran for many years without failure.

 

Since then, over 10,000 pumps across the globe have been upgraded with Vespel® CR-6100.

 

Useful Links For DuPont™ Vespel® CR-6100

When you are using Vespel® CR-6100 in your shop, or if you are recommending your favorite repair shop to perform the upgrade for you, the following links should prove helpful:

Standard Stock Sizes of Vespel® CR-6100

Boulden Installation Guide for Vespel® CR-6100

Vespel® CR-6100 Product Data Sheet

Vespel® CR-6100 Machining Guide

3MW Boiler Feed Pump Case Study

If you need any material or have any questions. Please contact us today. Until next time, be safe, and enjoy the holidays with your friends and family

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Proboscis Monkeys, Borneo

Proboscis Monkeys, Borneo

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Case Study: DuPont™ Vespel® CR-6100 in 3MW Boiler Feed Water Pump with PERF-Seal™ design.

Better operability, reliability, and efficiency

The PERF-Seal™

A while back, we introduced the PERF-Seal™ design for center bushings, throttle bushings, and pump wear rings.

 

Below you can see the center bushing and case wear rings of a 2-stage pump which was upgraded to Vespel® CR-6100 with the PERF-Seal™ design

Center Bushing of a 2-stage pump.

Center Bushing of a 2-stage pump.

2-stage pump upgraded to Vespel® CR-6100 with the PERF-Seal™ design.

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.

 

Boiler Feed Pump Case Study

 

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.

 

We applied the PERF-Seal™ design to all of the stationary wear components–case rings, throttle bushing, and center bushing. The pump had demonstrated the following

  • No issues stopping and starting the pump during plant cycles
  • 10% lower power consumption during full load operation
  • Motors no longer run in the safety factor during full load operation

The pumps have now been running for 2 years. A full case study was recently published in POWER Magazine and is available here.

 

Until Next Time

 

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.

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Skull Island, Trang An, Vietnam

Skull Island, Trang An, Vietnam

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Contact Us Today To Learn More About Vespel and Boulden Company!

 

 

 

 

 

 

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The Effect of Wear Ring Clearance on NPSHR

Recommended reading from the 32nd Pump Users Symposium, 2016

A Short Break

In recent weeks, we have discussed how an upgrade to composite wear rings allows you to avoid pump seizure, and therefore reduce the wear ring clearance in your pump. This reduction in clearance increases the Lomakin Effect in the pump and improves pump efficiency.

One thing we did not discuss is that reducing the wear ring clearance also reduces the pump NPSHR.

In the past, discussion of the relationship between pump NPSHR, wear ring clearance, and cavitation has led to many questions. Unfortunately, the answers to these questions are somewhat restricted due to limited testing on this topic.

Last year, there was a paper which provided some clear data on this subject. The authors used a pump test stand, two different impeller configurations, and wear rings at various clearances. We recommend taking a look at the following paper for greater technical insight into the relationship between wear ring clearance and pump NPSHR.

The Influence of Impeller Wear Ring Geometry on Suction Performance

by Thomas Leibner, David Cowan, and Simon Bradshaw

Published at the 32nd Pump Users Symposium

Houston, TX, September 2016

Until Next Time

In the near future, we will return to our series on upgrading pumps with Vespel® CR-6100, addressing how to upgrade specific pump configurations.

Contact Boulden For More Information

Until then, if you have a pump operating at less than 500 F (260 C) where you want to reduce the NPSHR, contact Boulden today. We have a huge inventory of Vespel® CR-6100 standard sizes in stock ready for immediate shipment almost anywhere in the world.

For application and installation details, download the Boulden Installation Guide for Vespel® CR-6100

7 Rules for Using Vespel® CR-6100

Upgrading pumps with composite wear componentsWe just completed our series on upgrading pumps with DuPont™ Vespel® CR-6100, getting into details on how to upgrade various horizontal and vertical pump types. We discussed reducing the clearance of the wear rings, upgrading throttle bushings with the PERF-Seal design, and upgrading vertically suspended pump shaft bearings.

Today, let’s try to condense it all down into a short list of guidelines which we can apply to just about any pump. Follow these rules and we can ensure we are using Vespel® CR-6100 properly and improving our pump reliability.

7 Rules for Using DuPont™ Vespel® CR-6100 

  • Stay under the temperature limit of 500 F (260 C)
  • Only stationary parts, mounted in compression
  • Shoulder on the low pressure side to retain the part against differential pressure
  • Avoid extremely abrasive services such as slurries, bottoms, or slops
  • Press fit, clearance, and axial length of part from the Boulden Installation Guide
  • Pump rotor must turn freely when the pump is assembled and ready for commissioning
  • Use PERF-Seal™ design for throttle and center bushings of multi-stage pumps

What do you think?

Did we miss anything? Contact us to let us know your ideas.

Until next time, if you have an application you would like to discuss, contact Boulden.

Need Vespel CR-6100 or other materials?

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.

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Borobodur, Indonesia

The Borobudur temple. The largest buddhist temple, and most visited site in Indonesia

 

Contact Us Today To Learn More About Vespel and Boulden Company!

Contact Us Today To Learn More About Vespel and Boulden Company!

 

 

 

 

 

 

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Upgrading Pumps With Composite Wear Components Part: 10

Upgrading pumps with composite wear componentsPart 10: Vertically Suspended Pump Installation Tips

Review

We have discussed how upgrading your pumps with Vespel® CR-6100 helps to eliminate pump seizures, allowing you to reduce wear ring clearance, which improves pump efficiency and improves pump reliability by increasing the Lomakin Effect in the pump.

Quality repair and installation practices are an essential counterpart to the success of upgrading pumps with Vespel® CR-6100. This is true of all pump types–horizontal and vertical. When you are finished with the overhaul, the rotor should turn freely.

Vertically suspended pumps with their multiple fits and pilots require some additional consideration. To ensure the best possible results in these pumps, below are some tips which have been passed on to us from our customers.

Vespel CR-6100 for LPG Pumps

Vertically suspended LPG pumps fitted with Vespel® CR-6100.

 

Mechanical Alignment of Pump Components

Multi-stage vertical pumps pose a challenge for the shop performing the overhaul because there are multiple fits and pilots. Keeping the whole pump assembly concentric and square will give you the best results with your upgrade.

Good practices should be followed from the machine shop through the final alignment in the field.

In the machine shop:

  • Ensure all pilot fits within the pump are 0.002″ (0.05 mm) or better.
  • Ensure all mating faces of assembly elements are square.
  • If possible, assemble the pump in a vertical position.
  • Install Vespel® CR-6100 shaft bearings, bowl bearings, and wear rings, then final machine with the lathe indexed to the pilot fit of the part-this will ensure all bores at wear interfaces are concentric within the assembly. (Alternatively, all wear part fits can be machined concentric to the pilot fits prior to the installation of the Vespel® CR-6100 components.)
  • Install the Vespel® CR-6100 shaft bearings with the same clearance as the original design for the pump. If the original clearance is not available, See Table 3a (imperial) or 3b (metric) in the Boulden Installation Guide for recommended minimum clearances for vertically suspended pump shaft bearings.
  • When the assembly is complete, make sure the rotor turns freely within the pump with no hard rubs. If there are hard rubs, disassemble, try to find the source of the rub and correct the concentricity of the misaligned component. If clearances are very tight, consider a slight increase of the bushing clearance and re-check to make sure there is no hard rub.
  • Our recommended clearance for Vespel® CR-6100 wear rings in vertically suspended pumps is the shaft bushing clearance plus 0.002″ (0.05 mm) or 50% of the API minimum clearance for metal parts-whichever is larger.
  • If the pump is operating in very cold liquid (temperature below 0 C), increase the clearance at the shaft bearings by 0.002″ (0.05 mm) above the minimum values shown in table 3a or 3b.

In the field:

Generally, vertically suspended pumps incorporate a rigid coupling and the pump does not have its own rolling element bearings. The purpose of the rigid coupling is to make the pump shaft and motor shaft act as one unit with the pump relying upon the rolling element bearings in the motor. When dealing with a rigidly coupled vertical pump, traditional alignment methods can introduce misalignment. You also cannot rely upon the register fits from the motor to motor mount to the pump to be concentric.

Here are some tips for aligning a vertical pump with line shaft bushings and no rolling element bearings. (The motor bearings carry the axial load and coupling is rigid)

  • The pump must hang as close to plumb (vertical) as possible. This requires inspection of the base plate at the sump to ensure it is flat and level, and inspection of the mounting plate on the pump to ensure it is also flat and square to the assembly. If the pump is hanging “at an angle” the shaft will bend as it tries to hang plumb and pump life can be reduced.
  • Install the pump without the seal installed
  • Verify that the pump is level on the base
  • Install the motor on the pump.
  • Mount a dial indicator on the motor shaft, reading the ID and face of the seal chamber
  • Correct any radial misalignment by moving the motor and/or motor mounts in their fits. Squareness should be corrected by machining mounting faces (shims are sometimes used).
  • Lock the motor in position (installing 2 dowel pins is a proven method).
  • At this point, you may want to couple the pump and check for any run-out.
    • Any run-out that shows up after the alignment is likely due to a fault in the coupling
    • If resistance is still encountered after alignment and run-out are corrected, the source of rubbing is likely eccentric pump internals, which will need to be corrected back in the shop.
  • Install the seal (if the motor must be removed to install the seal, care must be taken to ensure motor returns to aligned position)
  • Install the rigid coupling (Coupling should be dimensionally checked and checked for trueness in the lathe before installation)
  • Measure the shaft run out between the coupling and the seal. This should be as close to zero as possible. The purpose of the rigid coupling is to make one shaft out of the driver and driven shafts. The end of the motor shaft is the zero point, so just a small run out at 15 cm below the coupling translates into huge side loads on the shaft bushings 1-2 meters down the assembly.

Side note: if you experience misalignment of the rigid coupling, the evidence will likely be wear of the bushing and/or shaft concentrated at the top bushing in the pump.

If you have anything to add to the above notes, please contact us. We’d love to hear your thoughts.

Conclusion

We hope you have found this series on how to upgrade your pumps with Vespel® CR-6100 helpful. In future weeks, we’ll have a couple of bonus sections on special topics. Until then, if you need any Vespel® CR-6100, contact Boulden. We have whatever size and quantity you need in stock and ready for immediate delivery.

For information on how to install Vespel® CR-6100 into nearly any centrifugal pump type, download the Boulden Installation Guide.

The Sydney Opera House , just out of frame is the Sydney Harbor Bridge

The Sydney Opera House, just out of frame is the Sydney Harbor Bridge

 

Contact Us Today To Learn More About Vespel and Boulden Company!

Contact Us Today To Learn More About Vespel and Boulden Company!

 

 

 

 

 

 

 

 

 

 

 

 

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Upgrading Pumps With Composite Wear Components Part: 9

Upgrading pumps with composite wear componentsPart 9: Vertically Suspended Pumps with Separate Discharge (API Type VS4)

Review

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.

Define the Service

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.

The Road Map

Considering the above, we have created the following table to guide your selection of where to use Vespel® CR-6100 in sump pump services:

Vespel CR-6100 sump pump services.

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.

Vertical Pump Conclusion

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.

For information on how to install Vespel® CR-6100 into nearly any centrifugal pump type, download the Boulden Installation Guide.

Contact Us Today To Learn More About Vespel and Boulden Company!

Contact Us Today To Learn More About Vespel and Boulden Company!

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Late Night Snack, Thailand

Late Night Snack, Thailand

 

 

 

 

 

 

 

Boulden Company

Conshohocken, PA, USA

1-610-825-1515

 

Boulden International, S.ar.L

Ellange, Luxembourg

+352 26 39 33 99

Upgrading Pumps With Composite Wear Components Part: 8

Upgrading pumps with composite wear components

Part 8: Vertically Suspended Pumps (API Types VS1–3, VS6, VS7)

Review

To date, we have addressed how to install DuPont™ Vespel® CR-6100 into the various horizontal pump types to eliminate metal-to-metal contact points in the pump and minimize the risk of pump seizure. This allows a reduction of clearance which improves efficiency and rotor stability.

This segment will discuss how to use Vespel® CR-6100 in vertically suspended pump types (API types VS1-VS7). These types can be further broken down as “discharge through column” (VS1, VS2, VS3, VS6, VS7) and “separate discharge” (VS4 and VS5).

Which Parts?

In vertically suspended pumps, we can upgrade the same components as horizontal pumps (wear ringsthrottle bushingsthroat bushings) for the same reasons-to eliminate the metal-to-metal contact areas in the pump and reduce the clearance resulting in improved reliability and efficiency.

Today we will focus on the components which are unique to vertically suspended pumps-the vertical pump shaft bearings: line shaft bearings, bowl bearings, and bottom bearings. Vespel® CR-6100 is ideally suited to this application, particularly in services which suffer from a lack of lubricity or may run dry at startup. Vespel® CR-6100 does not seize like metal alloys, it can survive running dry, and it can withstand mechanical impacts and thermal shocks so it doesn’t break like carbon or graphite.

Multi-stage LPG pump bowl assemblies being upgraded to Vespel® CR-6100.

Multi-stage LPG pump bowl assemblies being upgraded to Vespel® CR-6100.

One thing of note is that vertical pump shaft bearings do not have differential pressure across the parts, therefore, they do not impact pump efficiency. Because the clearance of these components tends to be rather tight, to begin with, a further reduction in clearance can easily lead to assembly issues with a limited upside associated with the tighter clearance. Therefore, our recommendation for these parts is to install the Vespel® CR-6100 into the spiders or bowl assemblies with the press fit shown in our installation guide, then final machine to the original design clearance.

In our installation guide, you will find two clearance charts–one for horizontal pump types, one for vertical pump types. Because we don’t want the wear ring clearance tighter than the shaft bushing clearance, we simply recommend making the wear ring clearance 0.002″ (0.05 mm) larger than the shaft bushing clearance in these pumps. In short, we highly recommend that you download the Boulden Installation Guide for Vespel® CR-6100.

Discharge Through Column

Vertically suspended pumps are often selected because the service offers poor suction conditions such as light hydrocarbon service or condensate. In a long-term study, a refinery upgraded 22 vertical pumps to Vespel® CR-6100 wear parts. The pumps were operating in light hydrocarbons, flare knockout drum, and several stop/start services like product transfer. In the 5 years prior to upgrading the pumps, this population of pumps comprised many “bad actors” with poor reliability. In the 5 years after upgrading the pumps to Vespel® CR-6100, there were only 8 repairs on the entire population of pumps and the MTBR of this group of pumps increased to more than 10 years!

The combination of excellent reliability with ease of machining and installation along with immediate stock availability has made Vespel® CR-6100 the material of choice in these applications.

Vertically suspended pumps assembled with Vespel®CR-6100 shaft bearings, wear rings, bowl bushings and bottom bearings

Vertically suspended pumps assembled with Vespel®CR-6100 shaft bearings, wear rings, bowl bushings, and bottom bearings

Vespel® CR-6100 can handle significant periods of dry running with minimal wear, making it easier to bring the pump online. When you upgrade your wear rings to Vespel® CR-6100 and reduce the clearance, you might also find the pump easier to start due to a reduction in the NPSHR (Net Positive Suction Head Required).

To be continued…

In the next two issues, we will address vertically suspended pumps with a separate discharge (API Type VS4) and then we will discuss installation and assembly issues unique to vertically suspended pumps.

Until then, if you have a vertical pump which is giving you headaches, consider upgrading the wear parts to Vespel® CR-6100. Contact us today. We have the Vespel® CR-6100 in stock in a wide range of sizes available for immediate delivery to nearly anywhere in the world.
For details on installing Vespel® CR-6100 into nearly any centrifugal pump type, download the Boulden Installation Guide.

Contact Us Today To Learn More About Vespel and Boulden Company!

Contact Us Today To Learn More About Vespel and Boulden Company!

 

 

 

 

 

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Gardens by the Bay, Singapore

Gardens by the Bay, Singapore

Upgrading Pumps With Composite Wear Components Part: 7

Upgrading pumps with composite wear componentsPart 7: Between Bearings, Radially Split Pumps (API Types BB2, BB4, and BB5)

Review

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.

Radially Split Pumps

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.

Multi-stage BB4 and BB5 designs are used in several ideal applications for Vespel® CR-6100: unit charge pumps in refinery, petrochemical, and gas processing along with boiler feed water in many different industries. Upgrading the wear rings and throttle bushings of these pumps with Vespel® CR-6100 and reducing the clearance can produce significant efficiency gains of 4-6%. Higher efficiency translates to either lower operating cost as your pump uses less energy to produce the same flow, or increased throughput which can pay for the upgrade in a matter of days

Wear Rings

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.

Vespel® CR-6100 case rings for a hydrocracker charge pump

Vespel® CR-6100 case rings for a hydrocracker charge pump

 

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.

Throttle Bushings (aka Balance Drums)

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.

To be continued…

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.
For details on installing Vespel® CR-6100 into nearly any centrifugal pump type, download the Boulden Installation Guide.

Contact Us Today To Learn More About Vespel and Boulden Company!

Contact Us Today To Learn More About Vespel and Boulden Company!

Upgrading Pumps With Composite Wear Components Part: 6

Upgrading pumps with composite wear componentsPart 6: Between Bearings, Axially Split Pumps

Review

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).

Upgrading your pumps with Vespel® CR-6100 wear parts allows you to eliminate the metal-to-metal contact points in the pump and reduce the clearance at the wear parts. This simple change allows you to minimize the risk of pump seizure and helps to improve pump reliability and efficiency.

Axially Split Pumps

Today, we cover the details on using Vespel® CR-6100 to upgrade your between-bearings, axially-split pumps. The components we want to upgrade in these pumps are the case rings, center bushing, throttle bushing, and throat bushings.

Single and two-stage BB1 style pumps are often used in product transfer, water, or low NPSH applications. Upgrading the wear rings (and inter-stage bushing in two-stage designs) with Vespel® CR-6100 will help maintain rotor stability and improve efficiency. Reducing wear ring clearance can also help reduce the pump NPSHR

Multi-stage BB3 designs are used in several ideal applications for Vespel® CR-6100: boiler feed water, naphtha charge, amine stripping, and product pipeline and shipping applications. These pumps are designed with inherently flexible rotors which rely upon the Lomakin Effect for rotor stability. Upgrading these pumps with Vespel® CR-6100 and reducing the clearance can reduce vibration levels and make your pump more reliable.

These designs also experience significant efficiency gains when you reduce the clearance at the wear rings, center bushing, and throttle bushing. Most of the multi-stage designs will show at least 3-4% efficiency gain and several customers have reported efficiency gains in excess of 5%.

Solid or Insert?

The first question to address with an axially split assembly is whether or not to make the components out of solid Vespel® CR-6100 or to use Vespel® CR-6100 as an insert into a metal holder (figure 1).

Figure 1: Operating temperature determines whether or not you need to install Vespel® CR-6100 as an insert in these pumps.

Figure 1: Operating temperature determines whether or not you need to install Vespel® CR-6100 as an insert in these pumps.

Consider that Vespel® CR-6100 has a coefficient of thermal expansion which is about 60% less than carbon steel in the radial plane. In a hot pump, the metal parts are going to thermally expand more than the Vespel® CR-6100 parts. We compensate for the thermal expansion difference by installing the Vespel® CR-6100 with a press fit into a metal holder. As the metal holder expands, part of the press fit is relieved, and the Vespel® CR-6100 “follows” the growth of the metal parts.

Therefore, if your pump operating temperature is > 140 F (60 C), the Vespel® CR-6100 needs to be installed as an insert into a metal holder to maintain the clearance up to pump operating temperature. If it is an ambient temperature application, you can install Vespel® CR-6100 as a solid component or as an insert, whichever is easier for you.

One advantage of using inserts in these pumps is that during a repair, you can often salvage the used metal parts, machine the bores and reuse the old parts as holders for the Vespel® CR-6100 inserts. This can save time and reduce the cost of upgrading the pump with Vespel® CR-6100.

Split Parts

Another feature unique to axially split pumps is that the center bushings and inter-stage rings might also be axially split (Figure 2).

Figure 2: Split center bushing with PERF-Seal™ design insert.

Figure 2: Split center bushing with PERF-Seal™ design insert.

When the parts are split, we apply the same rule concerning solid or insert parts based on operating temperature. If the pump is operating at ambient temperature, the parts can be manufactured from solid Vespel® CR-6100; if the pump is operating at elevated temperature, we need to install the Vespel® CR-6100 as an insert with a press fit.

The press fit for split parts is achieved by modifying the metal components such that they bolt together. The bolting force is sufficient to create the press fit of the Vespel® CR-6100 component.

If you need to fabricate split parts, please contact Boulden and we will send you specific instructions based on your application details.

Center and Throttle Bushings

Another unique characteristic of multi-stage axially split pumps is that the center and throttle bushings can be exposed to high differential pressures. For these components, Boulden has developed a patent-pending design called the PERF-Seal™ (also shown in Figure 2) which improves the performance and dramatically increases the differential pressure capability of composite materials used in these positions.

Boulden recommends the PERF-Seal™ design for all center and throttle bushings in multi-stage 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.

Until next time…

In the next months, we will discuss radially-split between bearings pumps and vertically suspended pumps.

Until then, if you have an axially 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.
For details on installing Vespel® CR-6100 into nearly any centrifugal pump type, download the Boulden Installation Guide.

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Todays Photo

Chris Froome in Mondorf Les Bains, Luxembourg, ville-départ, Tour de France, Stage 4 on July 4th, 2017. Walking distance from Boulden’s European Office

Chris Froome in Mondorf Les Bains, Luxembourg, ville-départ, Tour de France, Stage 4 on July 4th, 2017. Walking distance from Boulden's European Office

Chris Froome in Mondorf Les Bains, Luxembourg, ville-départ, Tour de France, Stage 4

Contact Us Today To Learn More About Vespel and Boulden Company!

Contact Us Today To Learn More About Vespel and Boulden Company!

Upgrading Pumps With Composite Wear Components Part: 5

Upgrading pumps with composite wear componentsPart 5: Upgrading overhung pump types with DuPont™ Vespel® CR-6100.

Review

So far, we have discussed how upgrading your pumps with composite wear parts can help avoid galling and seizing, which allows you to reduce the clearance in your pump. This small change increases the Lomakin Effect and makes your pump more reliable. Reduced clearance also improves pump efficiency, leading to a lower pump life cycle cost.

Last month, we highlighted that Vespel® CR-6100 is installed in compression in the stationary parts of your pump–wear rings, throttle bushings, throat bushings, and vertical pump shaft bearings–and can be used in nearly all process chemicals from cryogenic temperatures to 500 F (260 C).

Today, we start discussing how to install Vespel® CR-6100 to upgrade your overhung pumps, which typically make up the majority of the centrifugal pump population in a process plant. For most designs, there are only three parts to upgrade to Vespel® CR-6100: two case wear rings and the throat bushing.

Manufacturer Case Wear Rings from Vespel® CR-6100

You can usually manufacture the case rings from solid Vespel® CR-6100 and press them directly into the case and head of the pump. Because the pump casing can often be quite large and difficult to handle, it is generally easiest to design the case rings such that they do not require final machining. The way to do this is to assume there is a 1:1 ratio between the press fit and the closure of the inside diameter during the press fit.

For example, if your case rings require 0.020″ (0.50 mm) press fit, machine the inside diameter 0.020″ larger than the final target dimension before the press fit. After the ring is pressed into place, the inside diameter will decrease by 0.020″ and will match the target dimension (give or take a small tolerance).

Alternatively, you can use a metal ring as a “holder”. First, press the Vespel® CR-6100 into the metal ring and then final machine the Vespel® CR-6100 to the desired clearance. This is sometimes a better choice for case rings with very large radial walls or rings with “L” shaped profiles (See Photo 1). By using an insert you can use standard stock sizes of Vespel® CR-6100.

case rings with Vespel CR-6100

Photo 1: Insert into “L” profile case ring

Vespel® CR-6100 can be used for the Throat Bushings

Several mechanical seal flush plans require a close clearance throat bushing to increase the seal chamber pressure, to isolate cooled seal flush fluid from hot process fluid, or to isolate clean seal flush fluid from dirty or corrosive process fluid. Vespel® CR-6100 can be used for the throat bushing.

To set the clearance of the throat bushing, consult your mechanical seal supplier. They should recommend a clearance based on your seal flush plan such that your seal operates with the correct pressure and flow rate of seal flush.

Which Pumps

Reducing the clearance at the wear rings will improve the efficiency of all of your overhung pumps. That said, some pumps can be considered with higher priority than others.

The first place to look is older pumps with long slender shafts with high L/D ratios (see Photo 2), especially two-stage overhung pumps. These pumps were typically built for packing and have been converted to mechanical seals. These designs often excessive shaft deflection, making it difficult for seals to meet current reliability and emissions standards. Closing the wear ring clearance will add stability to the rotor and provide the seals a better operating environment. On the two-stage overhung pumps, you can also upgrade the bushing between the stages for additional support.

Overhung pump

Photo 2: Overhung pump with high L/D ratio

Next, look at your largest overhung pumps. These pumps will typically have higher radial loads when running away from their design point and potentially experience more shaft deflection. Plus, they will consume the most power, generally offering the best payout for efficiency gains.

Finally, consider upgrading your OH4-vertical inline, rigidly coupled pumps. Because these pumps have no bearing housing, they rely upon the motor bearing and the wear rings for radial stability. Reducing the wear ring clearance can often improve the reliability of these pumps.

Upgrading Pumps to be continued…

In the next months, we will discuss upgrading horizontal between bearings pumps and vertically suspended pumps.

Until then, if you have an overhung 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 material required for the upgrade in stock is a wide range of sizes available for immediate delivery.

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