Tag Archives: CR-6100

Measuring Your Pump

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

Pump Measurement 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. Contact us if you have any questions.

Dimensions for designing a Vespel CR-6100 part

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

 

Dimensions to Design

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.

PERF-Seal™ center bushing from a boiler feed pump

PERF-Seal™ center bushing from a boiler feed pump

 

Conclusion

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.

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:

Petronas Towers, Kuala Lumpur, Malaysia

Petronas Towers, Kuala Lumpur, Malaysia

 

How to get Vespel® CR-6100 in a new pump?

Frequently Asked Question:

“Are the OEMs using Vespel® CR-6100?” is a question we hear every month. The answer is definitely, “yes.” All of the major API pump manufacturers use Vespel® CR-6100 for both new pumps and aftermarket upgrades.

A related question: “If Vespel® CR-6100 is so great, why don’t the OEMs include it as a standard material?”

To answer that, we need to look at how pumps are usually purchased…

Most pumps are sold into projects. The EPC contractor generally selects the pump with the lowest price which meets the bid specification. Therefore, if the bid spec allows bronze or cast iron wear rings, the OEM will probably quote bronze or cast iron because they are the cheapest materials. These materials might result in a higher life-cycle cost, but procurement personnel will not care if their decision is driven by the initial price.

Put it in the Bid Spec

If you want to maximize your pump reliability and efficiency, specify Vespel® CR-6100 for the stationary wear components in your next project. When it is part of the specification, the OEMs are happy to quote and supply Vespel® CR-6100.

If your company does not allow using brand names in the project specification, you can use the generic description for Vespel® CR-6100 from API610, Table H.3: PFA/CF reinforced composite, 20% mass fraction random X-Y oriented carbon fiber. For clarity, you can add the note “one example of which is DuPont™ Vespel® CR-6100.”

Direct Questions to Boulden

If there are any questions from the Project Engineer, EPC contractor, or OEM, please ask them to contact Boulden. We will be happy to answer any questions they have and make sure that the Vespel® CR-6100 is used correctly throughout the project.

In short, if you want Vespel® CR-6100 wear rings, vertical pump shaft bearings, or throttle bushings in your new pumps, all you have to do is ask–i.e. spell it out in the bid spec. Until next time, if you need any material for your pumps, we have a wide range of sizes in stock and ready for immediate shipment.

Helpful Links:

Boulden Installation Guide for Vespel® CR-6100

Standard Stock Sizes of Vespel® CR-6100

Vespel® CR-6100 Product Data Sheet

Vespel® CR-6100 Machining Guide

2MW Boiler Feed Pump Case Study

Amine Stripping Pump Case Study

 

Today’s Photo

Lanzarote, Spain

Lanzarote, Spain

Upgrading Pumps With Composite Wear Components: Part 3

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.

Centrifugal Pump 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).

Loss of pump efficiency

Leakage past the wear rings (QL) creates efficiency loss

 

 

 

 

 

 

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.

Which Pumps Produce the Biggest Gains?

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 throughput 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.

Today’s Photo

Cape Town, South Africa

Cape Town, South Africa

Upgrading Pumps With Composite Wear Components: Part 2

Part 2: Reduce Clearance – The Lomakin Effect

Welcome back to our series on upgrading pumps with composite materials. In part 1, we discussed how using composite materials like Vespel® CR-6100 in your pumps allows you to eliminate the metal-to-metal contact points in the pump and minimize the risk of pump seizure:

  • In the shop during assembly
  • In the field during alignment
  • During slow-roll, start-up, and shut down
  • During off-design events like dry-running or low flow

Reducing Clearance – The Lomakin Effect

Minimizing the risk of seizure in your pump sets the stage for reducing the clearance at the wear parts in your pump. Reducing clearance can be a significant pump reliability upgrade due to a phenomenon known as the “Lomakin Effect“.

Your Wear Rings are Bearings

During pump operation, the flow created by differential pressure across the wear parts in the pump (wear rings, throttle bushings) creates a force called The Lomakin Effect. The force arises from an unequal pressure distribution around the circumference of the component during periods of rotor eccentricity. This force counteracts shaft deflection in the pump.

Figure 1 shows how shaft deflection creates this force. As the fluid enters the clearance between the rotor and wear component, it accelerates as it passes from the high pressure end to the low pressure end. Due to the eccentricity of the rotor, there is more clearance on one side of the wear part than the other. There will be more flow and a locally higher velocity on the side of the wear ring with more clearance and lower velocity on the side of the ring with less clearance. Higher velocity results in lower pressure; lower velocity results in higher pressure, creating a net corrective force which acts in the direction opposite of the shaft deflection.
In other words, when your pump experiences shaft deflection, there is a hydraulic “stiffness” (Lomakin Stiffness) which is generated to counteract the shaft deflection.

The Lokamin Effect

Figure 1: The Lokamin Effect

 

 

 

 

 

 

 

Using Vespel® CR-6100 you can typically reduce the clearance at the pump wear rings by 50% compared to the API recommended minimum for metal wear parts. The Lomakin Stiffness is inversely proportional to clearance; therefore, a 50% reduction in clearance doubles this force.

Potential benefits for your pumps include:

  • Less shaft deflection
  • Lower vibration levels
  • Fewer mechanical seal leaks
  • Longer bearing life

Which Pumps?

The Lomakin Effect is generally beneficial to all centrifugal pumps, but some pump types often show significant vibration reductions and reliability improvements with reduced clearance:

  • Multi-stage horizontal pumps
  • Older overhung pumps with long, thin shafts (high L/D ratios)
  • Two-stage overhung pumps

Conclusion

Reducing the clearance at the wear components can be a major reliability upgrade for your pumps. The reduced clearance increases The Lomakin Effect which improves pump rotor stability. The net result is a pump which runs with potentially lower vibration, fewer seal leaks, and longer bearing life.

Reducing the clearance also increases pump efficiency, which we will discuss in Part 3.

Until then, if you are working on a pump with a long, thin, flexible rotor, contact Boulden to discuss upgrading the wear parts to Vespel® CR-6100 and reducing the clearance. We have a huge stock of Vespel® CR-6100 standard sizes in the USA, Europe, and Singapore available for immediate delivery to your workshop.

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

Today’s Photo

Le Louvre, Paris, France

Le Louvre, Paris, France

Amine Stripping Pump Case Study

Vespel® CR-6100 with the PERF-Seal® design survived where metal parts failed

In case you missed it…

The October 2018 issue of Hydrocarbon Processing featured a case study of Vespel® CR-6100 with the PERF-Seal®  design installed in a 2.7 MW amine stripping pump.

Amine Stripping Pump
2-Stage, 2.7MW, 4500 RPM Amine Stripping Pump

Amine pumps upgraded for improved operations and reliability

An excerpt…
The amine circulation pumps are controlled to gradually ramp up to operating speed. During this ramp-up period, the pumps produce insufficient head to generate any flow into the gas absorber. Therefore, the pumps must run on a minimum flow bypass back to the suction header. This flow is controlled by a minimum flow line valve (MFLV), which should be opened before startup and then closed once full-speed operation of the pumps is established.
With a steam turbine driver, ramping up to 4,500 rpm requires approximately 15 min, which is far too long to run the pump at zero flow.
Periodically over the past 10 yr, the MFLV has been opened too late during the startup procedure, which has led to the pump seizing at the center bushing and non-drive-end (NDE) and drive-end (DE) throat bushings (FIG. 1). These components have the tightest clearance and are, therefore, the first metal-to-metal contact points inside the pump.

To read the full case study, visit the Boulden website:
https://www.bouldencompany.com/dupont-vespel/case-studies/amine-pumps
If you have a pump running at low flow, or suffering from operational issues, running dry, or seizing contact Boulden today. We can provide all of the information you need to upgrade your pump and reduce your operational headaches. We have the material you need in stock and ready for immediate shipment almost anywhere in the world.

Helpful Links:
Boulden Installation Guide for Vespel® CR-6100
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

The Acropolis in Athens Greece
The Acropolis in Athens Greece

 

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.

 

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

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.

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

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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