Tag Archives: Vespel CR-6100

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!

 

 

 

 

Todays Photo

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

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!

 

 

When to Reduce the Clearance in Your Pump with DuPont™ Vespel® CR-6100

The industry “rule of thumb” says to reduce the wear ring clearance by 50%, but this isn’t always true.

Vespel® CR-6100 Upgrade 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 the wear rings and throttle bushings)

However, you don’t always need to reduce the clearance. It depends on what you are trying to do and which component you are looking at. So, to determine whether or not to reduce the clearance, ask two questions:

 

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.

 

Reduced Clearance Required

Reduced Clearance Not Required

 

 

Is There Differential Pressure Across the Part?

Reducing the clearance can generally produce two beneficial effects in your pump:

  • 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.

 

Exceptions to the 50% Wear Ring Clearance Rule

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).

Conclusions

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.

 

In any case, you can use our recommendations as a starting point. We supply these values in the clearance tables in our installation guide which you can download here:

 

Boulden Installation Guide for Vespel® CR-6100

 

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.

 

Helpful Links on Vespel® CR-6100 and Wear Ring Clearance:

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.

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

 

 

 

 

 

 

infbytg

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!

 

 

 

 

 

 

gytinfb

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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Today’s Photo

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: 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: 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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To Learn More About Vespel CR-6100 Click here!

Upgrading Pumps With Composite Wear Components Part: 3

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Part 3: Reduce Clearance–Improve Pump Efficiency

Welcome to Part 3 in our series on upgrading pumps with composite wear parts.

In the first part of this series, we discussed how upgrading your pumps with composite wear parts can help avoid galling and seizing. Because composite parts do not gall or seize like metal parts, this allows you to reduce the clearance at these components in your pump.

In Part 2, we discussed how reducing the clearance at the wear rings, throttle bushings, and center-stage bushings creates a stabilizing force in your pump called The Lomakin Effect. This force helps to reduce vibration and shaft deflection, leading to longer seal and bearing life in your pumps.

Today, we will discuss how reducing the clearance in your pump also improves pump efficiency.

Background

According to a major centrifugal pump OEM, energy consumption accounts for 44% of the life cycle cost of a centrifugal pump. You can reduce this cost by upgrading the wear components to a composite material like Vespel® CR-6100 and reducing the clearance in your pump.

The specific components where you want to reduce the clearance are the pump wear rings, inter-stage rings, center-stage bushing, and throttle bushing. These components form the barriers between high-pressure and low-pressure areas within the pump. The differential pressure across these components creates internal recirculation within the pump, resulting in a loss of pump efficiency (Figure 1).

 

Leakage wear rings

Leakage past the wear rings (QL) creates efficiency loss

 

 

 

 

 

 

Which Pumps Produce the Biggest Gains?
When you upgrade these components to Vespel® CR-6100, you can typically reduce the clearance by 50% compared to the API minimum for metal parts. If you reduce the clearance by 50%, you reduce the internal recirculation by approximately 50%, leading to a significant efficiency gain.

If we consider only efficiency gains, horizontal multi-stage pumps usually offer the best return on investment from an upgrade to Vespel® CR-6100 with reduced clearance. These pumps have multiple leak paths across wear rings, inter-stage rings, center bushings, and throttle bushings. Because they have many stages, these pumps also tend to consume a lot of power. Consider the following cases where process plants have reduced the operating costs of their multi-stage horizontal pumps:

  • A power station upgraded a 3MW boiler feed water pump with Vespel® CR-6100 along with the Boulden PERF-Seal™ design and reduced clearance and recorded a 7% efficiency gain compared to a newly rebuilt pump with original clearances.
  • A refinery upgraded their hydrocracker charge pumps with Vespel® CR-6100 along with the Boulden PERF-Seal™ design and reduced clearance and recorded 4% more through put to their hydrocracker-a hugely profitable upgrade.
  • A product pipeline company upgraded their LPG shipping pumps with Vespel® CR-6100 and reduced clearance, resulting in a 4% efficiency gain.

Another area to consider is process pumps which are marginally undersized, requiring parallel pump operation to achieve 100% of the target process rate. Sometimes, a modification as simple as reducing the wear ring clearance can get you back to one-pump operation with a full-capacity spare pump.

The PERF-Seal™

To further increase the efficiency gain associated with reduced clearance, the components can be modified with the Boulden PERF-Seal™ design. Internal testing has shown that the PERF-Seal™ creates an additional reduction in flow across throttle bushings, center-stage bushings, and wear rings beyond what can be achieved with reduced clearance alone.

Conclusion

When you eliminate the metal-to-metal contact surfaces in your pumps and use Vespel® CR-6100 stationary wear components, you can then reduce the clearance. This reduction in clearance improves pump efficiency and lowers the operating cost of the pump. Numerous field examples exist where customers have saved tens of thousands of dollars on their annual pump operating costs with this simple upgrade.

If you have a pump where improved efficiency will save you money, 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

Camps Bay Beach in Cape Town, South Africa

Camps Bay Beach in Cape Town, South Africa

 

Boulden Company

Boulden Company

Boulden Company

Conshohocken, PA, USA

1-610-825-1515

Boulden International, S.ar.L

Ellange, Luxembourg

+352 26 39 33 99