Tag Archives: Vespel CR-6100 Data Sheets

Diesel Charge Pump Case Study

DuPont™ Vespel® CR-6100 helps the pump survive and keep pumping.

The Diesel Charge Pump

A refinery in North America experienced recurring issues with their diesel charge pumps. The pumps provide feed into the refinery HDS unit. Loss of feed to the unit can result in reduced refinery production and significant losses.

The refinery has 3 total pumps in this service–two pumps running in parallel with an installed spare. The pumps are 1200 HP (900 kW), 13-stage, axially-split, between-bearings pumps (API Type BB3), running at 3550 RPM. The product is diesel fuel at approximately 250 F (120 C).

The original design of these pumps included metal wear rings, throttle, and center bushings. During the previous process upsets, these metal wear parts had seized, requiring expensive pump overhauls. The overhauls required the services of an outside shop, exposing the refinery to production risk due to operating without a spare pump for several weeks.

 

Vespel® CR-6100 is Put to the Test

Earlier this year, the refinery upgraded the first of the three pumps to Vespel® CR-6100, using Boulden’s patented PERF-Seal design for all of the stationary wear parts. The rotating wear parts remained metal, using the original metallurgy and surface finish.

Soon after the upgrade, a process upset caused a temporary loss of flow to the pumps. Figure 1 shows the process flow data during the upset condition. Each box along the x-axis represents one hour and the y-axis represents flow rate. Without sufficient flow to the pumps (blue and cyan lines), minimum flow (yellow line) could not be immediately established, causing the pumps to run at extremely low flow rates for nearly an hour. Partial flow was re-established, but the pumps continued to operate far below the design flow rate for nearly 4 more hours.

Figure 1: Process flow data for the diesel charge pumps during the process upset

 

normal process conditions were finally restored, the pumps were individually shut down for inspection. The pump with metal wear components seized upon shut down had damage to both bearings and required significant repair work.

The pump with Vespel® CR-6100 rotated freely, with the inspection revealing some damage to the thrust bearing. The thrust bearing was replaced in the field and the pump returned to service where it ran at full rate with no evidence of reduced performance or vibration issues.

 

Conclusion

In an ideal world, plant processes always operate per design. Unfortunately, there are times when things do not go as planned. When that happened to this refinery, the pump with Vespel® CR-6100 survived where the pumps with metal components could not.

Beyond surviving this incident, the refinery also reports that the pump is running with lower vibration than the pumps with metal components. With reduced clearance at the wear parts, the pump is almost certainly consuming less power, further reducing the life cycle cost of the pump.

If you have a service causing any issues at your plant, contact Boulden today. We have Vespel® CR-6100 in stock in a wide range of sizes in the USA, Europe, and Singapore and we can assist with any application or design questions you have. If you know what you need, just request a quote. Until next time, be safe.

 

Helpful Links:

Standard Stock Sizes of Vespel® CR-6100

Vespel® CR-6100 Product Data Sheet

Vespel® CR-6100 Machining Guide

3MW Boiler Feed Pump Case Study
Today’s Photo

October in the forest, Mullerthal, Luxembourg

 

14 Reasons to Avoid Increased Wear Ring Clearance

If you increase the clearance, the long-term reliability and efficiency of the pump will suffer.

Happy Summer!

We hope you have had a chance to enjoy your summer holidays. From New Orleans to Narvik, it’s hot out there, so be safe, and wear sunscreen.

In our messages, we frequently highlight how Vespel® CR-6100 does not seize and therefore allows you to reduce the clearance at the wear parts in your pumps: wear rings, inter-stage rings, throttle bushings, and center bushings.

Today we want to look at things from another perspective–negative effects which can happen to your pump when you increase the clearance at the wear parts.

 

What can happen when you increase clearance?

If a process plant has a problem with a pump seizing during operation or galling during commissioning, the traditional response has been to increase the clearance at the wear parts.

Metal Case Ring After a Boiler Feed Pump Seizure

 

Although increasing the clearance might make the pump operable in the short term, there are several negative consequences from increased clearance.

Hydraulic Effects Mechanical Effects
Lower head Reduced rotor stability
Lower flow Potentially higher vibration
Lower efficiency–increased power consumption Potentially higher shaft deflection
Higher NPSHR–greater risk of cavitation Increased risk of shaft breakage
Higher motor load Potentially shorter seal life
Need to run steam turbines at higher speed Potentially shorter bearing life
Higher likelihood of needing to run pumps in parallel Higher risk of motor over-heating or tripping from excessive load

So, while you don’t want your pumps to seize, increasing the clearance can create some major issues. At a minimum increased clearance drives up the operating cost of the pump and likely compromises the long term reliability of the machine.

 

The Poster Pump

A while back, one of our clients had an 11-stage horizontal pump which was originally supplied with metal wear components. The pump seized soon after start-up, and the recommendation from the OEM was to increase the clearance. The pump seized again. The second recommendation was to use a “non-galling” metal alloy to address the problem. The pump seized again. The clearance was increased one more time. When the pump was started again, the overall pump vibration levels were beyond alarm limits. The multiple increases in clearance had resulted in a loss of rotor stability to the point that the pump was no longer operable.

The end of the story will be in our next email…

 

Conclusion

Until next time, if you have a pump in your shop which has galled or seized, contact Boulden to discuss an upgrade to Vespel® CR-6100. We will be happy to work through the details of the upgrade with you and we have material in stock and available for immediate shipment.

 

Helpful Links for Vespel and Pump Case Studies:

Standard Stock Sizes of Vespel® CR-6100

Vespel® CR-6100 Product Data Sheet

Vespel® CR-6100 Machining Guide

3MW Boiler Feed Pump Case Study

Today’s Photo’

Rossio Square in Lisbon Portugal with famous wave pattern stone pavement.

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

 

 

 

 

 

Make Your Vertical Pump Shaft Bearings Last Longer

DuPont™ Vespel CR-6100 resists seizing, can run dry, has high impact resistance, and a low wear rate for a long life under a wide range of process conditions.

Vertically Suspended Pumps

Vertically suspended pump types (API types VS1-VS7) use long, flexible shafts which are supported by a series of product-lubricated shaft bearings. Vespel® CR-6100 is a great upgrade for these components.

 

Typical Vespel Services

Vertically suspended pumps can be divided into two general categories: discharge through column (API Types VS1, VS2, VS3, VS6, and VS7) and separate discharge (VS4 and VS5).

 

Discharge through column pumps tend to be used in light, flashing products like butane, LPG, and natural gas liquids, or in water condensate or cooling water intake service. In flashing services, it is not uncommon for these pumps to run dry temporarily at start up, which can be a challenge for the shaft bushings. In many of these pumps the flexible shaft can create very large loads, leading to high wear rates of traditional materials.

 

Separate discharge pumps tend to be used as sump pumps. In API Type VS4 pumps, the shaft 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 bearing grease is insufficient. In a chemical sump, the mix of chemicals can cause corrosion issues.

Vespel® CR-6100 Replaces Traditional Materials

Most vertical pump shaft bearings are made from either bronze/cast iron, carbon/graphite based materials, or stainless steel alloys. Bronze/cast iron bearings can have a high wear rate. Carbon/graphite bearings can break. Stainless steel bearings can seize.

 

Vespel® CR-6100 can replace all of these materials in process conditions from cryogenic to 500 F (260 C). Vespel® CR-6100 is low friction with a low wear rate. It is durable and impact resistant so it resists breakage during installation, transport, and operation. Plus, Vespel® CR-6100 does not seize like metal parts and is capable of surviving the run dry conditions which can occur with the flashing process fluids.

 

Documented Results

Consider the results from a long term study at an oil refinery. The plant upgraded 22 vertical pumps to Vespel® CR-6100 wear parts. The pumps were operating in light hydrocarbons, flare knock out drum, and several stop/start services like product transfer, comprising many “bad actors” in the plant. Looking at the number of repairs within this population for 5 years before Vespel® CR-6100 and 5 years after, the plant found the following.

 22 Vertical Pumps Number of Pump Repairs MTBR for the Population
5 Years Before

Vespel® CR-6100

40 2.75 years
5 Years After 

Vespel® CR-6100

8 13.75 years

Final Notes

Next time you are rebuilding a vertically suspended pump, consider upgrading the shaft bearings to Vespel® CR-6100. Contact Boulden with your process conditions and we will be happy to let you know if Vespel® CR-6100 is a good fit for your pump.

 

The Vespel® CR-6100 installation guide will walk you through the installation process. Vespel® CR-6100 is easy to machine and install, and Boulden is always happy to help if you have any questions. Finally, we have large quantities of Vespel® CR-6100 in stock and ready for immediate delivery in North America, Europe, and Southeast Asia.

 

Helpful Vespel Links:

Standard Stock Sizes of Vespel® CR-6100

Vespel® CR-6100 Product Data Sheet

Vespel® CR-6100 Machining Guide

3MW Boiler Feed Pump Case Study

 

Todays Photo

Bernkastel-Kues, Germany

 

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

The Final Installation Steps: Length and Clearance

Upgrading pumps with composite wear componentsSetting the final dimensions of your DuPont™ Vespel CR-6100 component

Review

We have discussed how to measure your pump, prepare the metal parts, and establish the press fit for your Vespel® CR-6100 installation. The final two dimensions you need to establish are the part length and the clearance.

The Part Length

Vespel® CR-6100 has an extremely low coefficient of thermal expansion in the radial plane (perpendicular to rotation). This is one of the principal reasons it performs so well in centrifugal pump components. The low coefficient of thermal expansion is achieved through the use of radially-oriented, long carbon fibers.

Conversely, the coefficient of thermal expansion along the axis is relatively high. Therefore, the part length for a Vespel® CR-6100 component should account for the axial thermal expansion at operating temperature. Table 4 of our installation guide provides the details on how to make this adjustment.

Table 4 of our installation guide provides the details on how to make this adjustment.

The Clearance

The clearance for the part is set depending on the diameter and component type. Tables 2a and 2b in the installation guide show the clearance recommendations for horizontal pump components such as pump wear rings, throttle bushings, center bushings, inter-stage rings, balance bushings, and throat bushings.

Tables 2a and 2b provide recommended minimum clearance for horizontal pump components.

Tables 3a and 3b show the clearance recommendations for vertical pump components like vertical pump shaft bearings, wear rings, and throat bushings.

Tables 3a and 3b provide recommended minimum clearances for vertically suspended pump parts.

The best way to set the clearance is to press the component into place, and then final machine the bore to the desired clearance. This is shown in steps 5a-7a in our installation guide, pages 8-9.

Where final machining after the press fit is not practical, you can design the component to have the correct clearance after the press fit. For most component geometries, you can assume the Vespel® CR-6100 will reduce at a 1:1 ratio with the press fit. This method is shown in steps 5b-7b in our installation guide, page 9.

Some sites have implemented a hybrid method. They measure the inside diameter of the Vespel® CR-6100 case wear ring after installation, and then machine the metal impeller wear ring to set the desired clearance.

Conclusions

Installing Vespel® CR-6100 is an easy upgrade to make your pumps more reliable, safe, and efficient. Follow the steps in our  installation guide and you can make your pump even better than the day it was new. If you need material, Boulden carries inventory of stock sizes in the USA, Europe, and Singapore.

Until next time, please feel free to contact Boulden with your application details or to request a quote. We’ll be happy to answer any questions you might have.

 

Helpful Links:

Standard Stock Sizes of Vespel® CR-6100

Vespel® CR-6100 Product Data Sheet

Vespel® CR-6100 Machining Guide

3MW Boiler Feed Pump Case Study

Today’s Photo

Rock of Gibraltar – was one of the Pillars of Hercules and was known to the Romans as Mons Calpe.

 

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The Interference Fit – Setting the interference fit value for DuPont™ Vespel CR-6100

The interference fit value for DuPont™ Vespel CR-6100

Review

We have discussed how to measure your pumps and prepare the metal parts. The next step is to machine the DuPont™ Vespel® CR-6100 part to have the correct dimensions.

Remember, Vespel® CR-6100 is used for stationary wear parts like wear rings, throttle bushings, and vertical pump shaft bearings. The rotating components running against the Vespel® CR-6100 remain metal. The Vespel® CR-6100 components are installed with an interference fit (aka “press fit”).

 

Installation Guide for Vespel CR-6100

The Boulden Installation Guide for Vespel® CR-6100 Tables 1a (Imperial) and 1b (Metric) outline the interference fit values for a Vespel® CR-6100 component based on diameter and the pump operating temperature.

If you only want the right value, follow the guide. You can stop reading and contact Boulden whenever you need material or if you would like to request a quote. If you want to know how we arrived at the values, continue reading.

 

Low Coefficient of Thermal Expansion

Vespel® CR-6100 has an extremely low coefficient of thermal expansion–about 60% lower than carbon steel in the radial plane. This property is one of the reasons Vespel® CR-6100 can survive pumps running dry and avoiding seizure.

The low coefficient of thermal expansion is a main factor in the interference fit value. At elevated temperatures, the metal parts will thermally expand more than the Vespel® CR-6100 parts. Therefore, as pump operating temperature increases, the interference fit increases.

 

Vespel CR-6100 Low Modulus of Elasticity

Vespel® CR-6100 parts press in relatively easily due to a very low modulus of elasticity. Vespel® CR-6100 can be used in temperatures up to 500 F (260 C). At maximum operating temperature, the recommended interference fit can be quite high. Due to the low modulus, the material generally presses in without issue.

 

Small Pilot Fit

To facilitate the large interference fit, machine a small pilot or “step” on the leading edge (Figure 1) of the Vespel® CR-6100 component. This will help the part sit squarely in the bore as it is being pressed in (Figure 2).

Figure 1: Pilot Fit on leading edge to facilitate press fit

Figure 2: Press fit operation

No Pins or Screws Required

Once Vespel® CR-6100 is installed with a press fit and a shoulder to retain the part against differential pressure, no further retention of the components is required. There are thousands of pumps running for many years with Vespel® CR-6100 components without retaining pins or screws.

If you insist on using retaining pins with Vespel® CR-6100, contact Boulden and we will discuss the possible designs given your part geometry.

 

Conclusions

When installing Vespel® CR-6100, make sure you are using the correct interference fit. Download our installation guide for the full installation procedure. If you need material, Boulden carries inventory of stock sizes in the USA, Europe, and Singapore.

Until next time, please feel free to contact Boulden with your application details or to request a quote. We’ll be happy to answer any questions you might have.

 

Helpful Links:

Standard Stock Sizes of 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.

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

 

 

 

 

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Grand Canyon, Arizona USA

 

Boulden Company – Conshohocken, PA, USA | 1-610-825-1515

Boulden International, S.ar.L – Ellange, Luxembourg | +352 26 39 33 99

Upgrade to DuPont™ Vespel® CR-6100: 100%

Upgrading pumps with composite wear componentsThere is great satisfaction in doing a job all the way.

100%

In South Africa, when you make a statement that someone agrees with, they say “100 %”–similar to how other English speakers say “absolutely.” With that in mind, we want the pumps upgraded to Vespel® CR-6100 to be upgraded 100% whenever possible.

 

Review

 

When you upgrade your pumps to Vespel® CR-6100, there are two steps:

  • Eliminate the metal-to-metal contact points in the pump
  • Reduce the running clearance (of wear rings, center bushings, and throttle bushings)

Upgrading your pumps to Vespel CR-6100 Step #1

Our recommendation when upgrading to Vespel® CR-6100 is to convert all of the stationary wear parts to Vespel® CR-6100. All of the rotating parts remain metal, thus eliminating all of the metal-to-metal contact points in the pump. This essentially eliminates the risk of pump seizure.

 

Yet, once in a while, customers try to make a small change instead of fully upgrading the pump. The three partial upgrades we run into are:

Overhung Pumps

Older pumps with long slender shafts (high L/D ratios) create problems for mechanical seals due to excessive shaft deflection. If you want to increase the rotor stability of these pumps using the wear parts, you will want to upgrade the wear rings to Vespel® CR-6100 and reduce the clearance.

 

The reason is that the Lomakin Effect-the hydraulic force which stabilizes the rotor-is driven by differential pressure and the surface speed at the differential pressure interface. Wear rings have significant differential pressure and high velocity, creating a lot of stability from the Lomakin Effect. Throat bushings? Not so much.

 

Horizontal Multi-Stage Pumps

If a horizontal multi-stage pump like a boiler feed water pump seizes, it will usually occur at the center bushing or throttle bushing, depending on the pump type. These two components generally have the tightest clearance in the pump and will be the first points of contact. In these services, there is a temptation to only upgrade the one or two components which seized.

 

While this approach has been successful in reducing pump seizures, there are some limitations. Metal-to-metal contact points remain and thus there is still a possibility of seizure. If all of the wear parts are upgraded, the risk of seizure is essentially eliminated. Furthermore, the wear rings also add to the rotor stability and efficiency of these pumps. Upgrading the wear rings as well as the center and throttle bushings will make for a much better pump. Especially if you use the Boulden PERF-Seal™ design (patent-pending).

Two-stage kerosene pump with all the components upgrade to Vespel® CR-6100 and the PERF-Seal™ design

 

 

Center Bushing of a 2-stage pump.

 

Vertically Suspended Pumps

Vespel® CR-6100 is a great material for vertically suspended pump shaft bearings in LPG, butane, natural gas liquids (NGL), and other flashing products. It can survive running dry at start up with limited wear. It doesn’t break like a carbon part. This application for Vespel® CR-6100 is so common that Boulden carries a huge inventory of standard stock sizes for the dimensions typically used for shaft bearings.

 

What some users miss is the opportunity to also upgrade the case rings of these pumps and reduce the clearance. This addition to the upgrade eliminates the other potential seizing points in the pump. Furthermore, reducing the clearance increase the pump efficiency and reduces the NPSHR–all of this making the pump easier to operate.

 

In Summary

The only partial upgrade above which we do not recommend is trying to stabilize a rotor with a throat bushing. In our experience, this approach is marginally successful at best. The other partial upgrades have worked and there are situations where they are necessary. But, given the choice, why not do the job 100%?

 

The main point is to recognize that the maximum improvement in reliability, safety, and efficiency will be achieved if you upgrade all of the wear parts (Table 1) in your pump to Vespel® CR-6100.

Table 1: Components to upgrade to Vespel® CR-6100

Overhung Pumps Between Bearings Pumps Vertically Suspended Pumps
Case Wear Rings Case Wear Rings Case Wear Rings
Throat Bushings Throat Bushings Throat Bushings
Inter-Stage Bushings Line-shaft bearings  
Center-Stage Bushings Bowl bearings  
Throttle Bushings Bottom bushings

Contact Boulden Today for your Vespel® CR-6100 Needs!

If you have a pump operating at less than 500 F (260 C) where you want 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 in a wide range of sizes available for immediate delivery.

 

Helpful Links:

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

 

Stay Connected

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

Todays Photo

Proboscis Monkeys, Borneo

Proboscis Monkeys, Borneo

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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