Tag Archives: PERF-seal

Case Study: Repeat Failures of Boiler Feed Water Pumps

Vespel®CR-6100 centrifugal pump components

Boiler Feed Pump Seizing Problems

The low lubricity of boiler feed water along with operational challenges can lead to pump seizures. How do you avoid the problem? Or, if it happens, what is the best way to solve the problem? This case study is about repeat seizures of two, new, 1.2 MW boiler feed water pumps operating in a refinery. The pumps were fitted with metal wear parts, ran at 2980 rpm, and experienced failures immediately after commissioning.

The Tale of the Terrible Boiler Feed Pumps

Here is a brief summary of the problems this site faced with their boiler feed pumps:
  1. The first failure was due to pump seizure, the original failure analysis suggested the pumps failed due to sand or debris lodging into the close clearance between rotating and stationary wear parts. The filters on the suction strainer were changed to a finer mesh to limit particle size which could enter the pump.
  2. Soon after, one of the pumps seized again–this time, the metal parts had galled before start up and the pump could not be rotated by hand. The clearances at the wear rings, center bushing, and throttle bushing were increased.
  3. The pumps seized again.
  4. Repeated start-up attempts against seized pumps had also damaged the pump motors.

The failure analysis led the engineers to re-check the entire design and installation of thepumps:

  • Re-checking the design basis of the pumps
  • Re-checking the materials of construction
  • Re-checking assembly and rotor run-out
  • Re-balancing the rotor
  • Performing a new pump rotordynamic analysis
  • Verifying soundness of foundation and that pipe strain within limits
  • Evaluation of operational practices and function of the minimum control valve

Minimum Flow Valve Problem

Ultimately, the site realized the minimum flow valve was not functioning properly, leading to low flow rates at start up. The low flow rates caused localized flashing inside the pump and the metal parts would seize.

Their corrective action was to change the minimum flow valve, increase the clearance at the center bushing, throttle bushing, and wear rings, and “upgrade” to a “non-seizing” metal alloy. Because they increased the clearance at all of the internal parts, they ran a new rotor dynamic analysis to verify that the rotor would remain stable.

How Much Did It Cost?

Between repeated pump repairs, motor overhauls, engineering resources to troubleshoot and re-verify the design, the problem undoubtedly cost hundreds of thousands of dollars. If start up was delayed or the site lost production, the losses were probably in the millions.
The solution was also extremely expensive. The clearance at the pump wear parts was permanently increased. We’ll generously assume the increased clearance resulted in a 2% efficiency loss. Assuming a power price of $0.12/kw-hr, this loss of efficiency will cost about $50,000/year. Over the life of the pumps, the site will lose another million dollars or more!

Avoid Pump Seizure By Using Vespel® CR-6100

If the site had specified Vespel® CR-6100 wear parts when the pump was ordered, the pump would not have seized. Most likely, the pumps would have made it through the low flow transients without issue and all of the efforts above could have been avoided. The motors would not have been damaged, and they would not have had to increase the internal clearances. Even after the first seizure occurred, they could have easily converted to Vespel® CR-6100 and saved time, effort, and cost. The small adder to specify Vespel® CR-6100 would have saved several hundred thousand dollars at a minimum.

Furthermore, because Vespel® CR-6100 does not seize, clearance at the wear rings, center bushing, and throttle bushing could have been reduced, resulting in an efficiency gain instead of an efficiency loss. So, instead of losing $50,000 per year in operating costs, the site could have saved at least $50,000 per year–a net $100,000 annual savings from using Vespel® CR-6100. Combined with the Boulden PERF-Seal® design, the pump would be more reliable, easier to operate, and more efficient than a pump with metal parts and increased clearance.

Conclusion

If you are buying or overhauling a boiler feed water pump, specify Vespel®CR-6100 for all of the stationary wear parts (the rotating parts will remain metal). You’ll have a better pump that is easier to operate with a lower life cycle cost due to higher efficiency. If you have an existing pump that seizes, contact Boulden today. We can help you solve this problem in just about any pump service.

If you simply have an urgent repair and need a great material fast, we have a large inventory of material in stock and can supply raw material or machined parts with very short lead times. If you have dimensions, quantities, and basic service conditions, simply request a quote. We’re here to help you!

7 Rules for Using Vespel® CR-6100

Follow these rules and you’ll be on the road to better pump reliability

A Fresh Look

We 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. 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

Borobodur, Indonesia

Borobodur, Indonesia

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

 

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

Diesel Charge Pump Case Study

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

The Diesel Charge Pump

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

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

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

 

Vespel® CR-6100 is Put to the Test

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

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

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

 

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

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

 

Conclusion

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

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

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

 

Helpful Links:

Standard Stock Sizes of Vespel® CR-6100

Vespel® CR-6100 Product Data Sheet

Vespel® CR-6100 Machining Guide

3MW Boiler Feed Pump Case Study
Today’s Photo

October in the forest, Mullerthal, Luxembourg

 

14 Reasons to Reduce Wear Ring Clearance

Use DuPont™ Vespel® CR-6100 to reduce the clearance in your pumps and improve pump reliability and efficiency.

Vespel CR-6100 Review

A couple weeks ago, we looked at all of the negative consequences from increasing the wear part clearance in you pumps: wear rings, inter-stage rings, throttle bushings, and center bushings. In the past, increasing the clearance was a typical response to pump seizure.

Now, there is a better way to address the issue and make your pump more reliable and efficient at the same time. Instead of increasing the clearance of the metal parts, replace the stationary wear parts with non-seizing, non-galling Vespel® CR-6100 and reduce the clearance. With this simple change, all the contact points in the pump become metal-to-composite and the risk of seizure is minimized.

What if you reduce the clearance?

Because Vespel® CR-6100 is non-seizing, you can safely reduce the clearance at the wear parts in your pumps. Even if the pump runs dry, Vespel® CR-6100 will not seize like metal components.

 

 

When you reduce the clearance at your wear parts, essentially every aspect of the pump hydraulic performance improves. Reduced clearance also tends to produce lower vibration levels. In short, the pump will likely be easier to operate, more reliable, and consume less power.

 

14 Benefits of Reduced Clearance using Vespel CR-6100 

 

Hydraulic Benefits Mechanical Benefits
Higher head Increased rotor stiffness
Higher flow–higher potential maximum flow rate Potentially lower vibration
Increased efficiency–reduced power consumption Potentially reduced shaft deflection
Lower NPSHR–lower risk of cavitation Reduced risk of shaft breakage
Reduced motor load Potentially longer seal life
Steam turbine drivers can run at lower speeds Potentially longer bearing life
Reduced need to run pumps in parallel Reduced potential for motor tripping or over-heating

 

The PERF-Seal™

The benefits of reducing the clearance can be augmented using the patented Boulden PERF-Seal™ design. The design is simple to implement, increases the potential efficiency gain from the upgrade, adds a significant amount of hydraulic damping, and generally amplifies the benefits of your upgrade to Vespel® CR-6100. Contact Boulden for details.

Two-stage product shipping pump upgraded with the PERF-SEAL deign

The Poster Pump, continued…

Two weeks ago, we wrote about an 11-stage horizontal pump which had seized several times. Each time it seized, the wear part clearance was increased. After the clearance had been increased multiple times, the pump would vibrate beyond alarm limits and the pump was no longer operable.

The plant upgraded the pump with Vespel® CR-6100 case rings, center bushing, and throttle bushing, using the Boulden PERF-Seal™ design. They subsequently reduced the clearance to less than the original design clearance. After the upgrade, the pump ran without seizing, very low vibration, and a significant efficiency gain.

 

Conclusion

What do you think of our list of benefits from reduced clearance? Is there anything we should add? Anything you disagree with? Let us know your ideas. We will be happy to hear from you.

 

Until next time, if you have a pump in your shop which can benefit from an upgrade to Vespel® CR-6100 and reduced clearance, contact Boulden. We can answer your questions and we have material in stock and available for immediate shipment.

 

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

Place Stanislas is considered to be one of, if not the most beautiful royal squares in Europe. It was added to UNESCO’s World Heritage List in 1983.

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!

 

 

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

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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