Tag Archives: PERF-seal

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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Measuring Your Pump

Upgrading pumps with composite wear components

Which information is needed in order to upgrade your pump to DuPont™ Vespel® CR-6100?

Review

Using Vespel® CR-6100 wear parts with reduced clearance can help your pumps be more reliable, efficient, and easier to operate. Which measurements and which process data do we need to assemble for the upgrade?

Dimensions Needed for a Quote

Let’s start with the 3 dimensions we need to determine material sizes and availability shown in Figure 1:

  • “R” Outside diameter of the rotor running against the Vespel® CR-6100
  • “B” Inside diameter of the bore the Vespel® CR-6100 will press into
  • “L” Length of the bore
  • Alternative: the O.D., I.D., and Length of the existing parts

If we have those 3 dimensions for each part plus the quantity of each part required, we can provide a quote

Dimensions of Design

Figure 1: Dimensions for designing a Vespel® CR-6100 part

To design parts for fabrication, we will need the dimensions of the mating hardware. While many wear parts have a simple O.D., I.D., and Length profile, some parts have additional features for which we will want the dimensions:

  • Some pump wear rings have profiles like an “L”, “T”, or “Z”. In those situations, we need to know each of the diameters and widths of any of the “shoulders” or “ribs” of the parts
  • Is the pump axially or radially split?
  • Are any of the parts are axially split?
  • For vertical pump shaft bearings, it will be helpful to know if there is any groove profile required-spiral grooves, axial grooves, how many, what diameter, how deep…
  • What is the existing material and clearance of the vertical pump shaft bearings?

Process Conditions

Vespel® CR-6100 works in most process services. It is manufactured from Teflon™ PFA and carbon fibers, so it is chemically resistant to nearly all process chemicals and it has a broad temperature range. There are only two general limitations:

  • Temperature range is cryogenic -300 F (-200 C) to 500 F (260 C)
  • Avoid abrasive slurries, slops, and bottoms services

To design the parts, the pump operating temperature is required in order to determine the correct press fit for the Vespel® CR-6100 parts.

 

Differential Pressure

If the components are going into a high-energy pump, such as a multi-stage horizontal charge pump or boiler feed water pump, we recommend that the patent-pending Boulden PERF-Seal™ design be used on all horizontal multi-stage pumps. The PERF-Seal™ design is fabricated from Vespel® CR-6100 and increases the efficiency gain and rotor damping associated with the upgrade. If the PERF-Seal™ is not used, we will need to know the differential pressure across the components in order to verify that they are designed correctly.

 

Figure 2: PERF-Seal center bushing from a boiler feed water pump

Conclusions

In the ideal situation, you can supply the dimensions of the parts required, the pump cross-sectional drawing, and the API data sheet for the pump. From this information, we can confirm that the service is a good fit for Vespel® CR-6100, quote the material or machined parts required, and make a recommendation on how to install Vespel® CR-6100 into the pump.

Please feel free to contact Boulden with your application details and dimensions. We’ll be happy to provide a budget estimate or a fixed quote depending on the information available. Once you decide to go forward with the upgrade, we have whatever material you need in stock in the USA, Europe, and Singapore.

Todays Photo

Petronas Towers, Kuala Lumpur, Malaysia

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!

 

 

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

 

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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.

Today’s Photo

Skull Island, Trang An, Vietnam

Skull Island, Trang An, Vietnam

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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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.

Todays Photo

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: 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!