Tag Archives: wear rings

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

 

Catacarb® Pump Case Study

A single installation of Vespel® CR-6100 saved a lot of money and troubles.

Several years ago, a refinery upgraded a Catacarb® pump with Vespel® CR-6100 case rings. The pump was a single-stage, between bearings, double suction pump. Catacarb® is a mixture of potassium carbonate and other chemicals which is used to strip gases such as CO2 and H2S from hydrocarbon streams.

For two years after the installation, the pump ran perfectly, and no one thought about the Vespel® CR-6100 wear rings in the pump.

 

Then, one day…

One day, the Operators heard one of the Catacarb® pumps making a loud pounding sound. They shut it down and switched to the spare. The noisy pump stopped without issue. The pump did not seize, the seals did not leak, and there was no release of the process to the atmosphere.

When the pump arrived in the shop, the Maintenance crew found the problem. A piece of metal had broken from an upstream valve, lodged itself in the impeller and proceeded to pound against the pump volute. The impeller suffered substantial damage shown in Figure 1:

Damaged Impeller

Figure 1: Impeller damaged by a piece of metal lodged in the pump

Disassembly revealed that the pump had been fitted with Vespel® CR-6100 case rings. The rings showed signs of contact and perhaps a negligible amount of wear, but remained in working condition as shown in Figure 2:

Vespel CR-6100 Case wear ring

Figure 2: Vespel® CR-6100 case wear ring after the incident

 

Conclusion

According to the refinery Maintenance team, without the Vespel® CR-6100, the pump would have likely seized, causing severe damage to the pump, along with the potential for seal failure and leakage of the process to the atmosphere. Instead, the plant continued to run. How much money did they save? How much trouble did they avoid? Fortunately, no one will ever know. Because the pump did not seize, the only cost was a standard repair plus a new impeller.

If you want to help your pumps avoid seizure, 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, Merry Christmas, enjoy the holidays and 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

Marché de Noël, Strasbourg, France

Marché de Noël, Strasbourg, France

 

 

 

 

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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

 

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! 

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

Prepping Your Metal Parts

Prepare your pump parts for an upgrade to DuPont™ Vespel CR-6100

Review on Pump Parts and upgrading to Vespel CR-6100

The National Geographic Channel used to run a show called Doomsday Preppers where survivalist families would prepare for apocalyptic disasters and societal collapse. Although that sounds like a lot of fun, at Boulden, we are more concerned with helping your pumps survive adverse process conditions with an upgrade to DuPont™ Vespel® CR-6100.

 

Last month, we outlined the measurements required for a Vespel® CR-6100 installation. When you have decided to go forward with the upgrade, the first step will be to prepare the metal parts to facilitate the installation.

 

Start with a Little Chamfer

Vespel® CR-6100 is used for stationary wear components–throttle bushings, case wear rings, center-stage bushings, inter-stage case rings, vertical pump shaft bearings, throat bushings, agitator bearings, API separator bearings-basically any product lubricated wear part.

 

The material is installed with a significant press fit. To facilitate the press fit operation, the metal bore into which you will be pressing the Vespel® CR-6100 requires a small chamfer or radius (Figure 1). It is very important that any corners or sharp edges are fully broken and smoothed with a stone so that the metal edge does not remove material from the outside surface of the Vespel® CR-6100 during the press operation.

Figure 1: Chamfer or Radius Leading Edge to facilitate press fit. (Note shoulder on low-pressure side.)

 

 

 

 

 

 

 

 

 

Make Sure There is a “Shoulder” or “Step”

For any part exposed to differential pressure, it is important that the design features a shoulder or step at the low-pressure end (shown on the right side of Figure 1) to ensure the differential pressure does not dislodge the Vespel® CR-6100 during operation.

 

Some radially split multi-stage pumps (BB4 and BB5) pumps feature metal wear rings welded into the pump diffusers with no step or shoulder incorporated in the design. In this case, you can consider modifying the diffusers so that the case wear rings have an “L” shaped profile like the rings below which were used in a hydrocracker charge pump.

Figure 2: “L” Shaped wear ring profile for BB4 or BB5 pump type.

 

Conclusions

Vespel® CR-6100 can help you avoid pump seizure during extreme events like running dry. The temperature limit is 500 F (260 C), allowing it to survive infernal heat waves. The material is not affected by electromagnetic pulses. polar shifts, or solar flares. As an added bonus, Vespel® CR-6100 has an indefinite shelf life, making it an ideal material to stockpile in your underground bunker, and the material is likely to hold its value in the case of hyperinflation.

 

In reality, you don’t have to stockpile the material. Boulden carries a huge inventory of stock sizes in the USA, Europe, and Singapore. You can generally receive whatever material you need in a matter of days.

 

To prepare your pump for whatever the future holds, please contact Boulden with your application details and dimensions. We’ll be happy to walk you through the installation details–assuming we have not been wiped out by an asteroid strike.

Todays Photo

All this talk of disaster is making me hungry. This is some excellent Bun Cha in Vietnam.

 

 

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!

 

 

The Effect of Wear Ring Clearance on NPSHR

Recommended reading from the 32nd Pump Users Symposium, 2016

A Short Break

In recent weeks, we have discussed how an upgrade to composite wear rings allows you to avoid pump seizure, and therefore reduce the wear ring clearance in your pump. This reduction in clearance increases the Lomakin Effect in the pump and improves pump efficiency.

One thing we did not discuss is that reducing the wear ring clearance also reduces the pump NPSHR.

In the past, discussion of the relationship between pump NPSHR, wear ring clearance, and cavitation has led to many questions. Unfortunately, the answers to these questions are somewhat restricted due to limited testing on this topic.

Last year, there was a paper which provided some clear data on this subject. The authors used a pump test stand, two different impeller configurations, and wear rings at various clearances. We recommend taking a look at the following paper for greater technical insight into the relationship between wear ring clearance and pump NPSHR.

The Influence of Impeller Wear Ring Geometry on Suction Performance

by Thomas Leibner, David Cowan, and Simon Bradshaw

Published at the 32nd Pump Users Symposium

Houston, TX, September 2016

Until Next Time

In the near future, we will return to our series on upgrading pumps with Vespel® CR-6100, addressing how to upgrade specific pump configurations.

Contact Boulden For More Information

Until then, if you have a pump operating at less than 500 F (260 C) where you want to reduce the NPSHR, contact Boulden today. We have a huge inventory of Vespel® CR-6100 standard sizes in stock ready for immediate shipment almost anywhere in the world.

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

Upgrading Pumps With Composite Wear Components Part: 8

Upgrading pumps with composite wear components

Part 8: Vertically Suspended Pumps (API Types VS1–3, VS6, VS7)

Review

To date, we have addressed how to install DuPont™ Vespel® CR-6100 into the various horizontal pump types to eliminate metal-to-metal contact points in the pump and minimize the risk of pump seizure. This allows a reduction of clearance which improves efficiency and rotor stability.

This segment will discuss how to use Vespel® CR-6100 in vertically suspended pump types (API types VS1-VS7). These types can be further broken down as “discharge through column” (VS1, VS2, VS3, VS6, VS7) and “separate discharge” (VS4 and VS5).

Which Parts?

In vertically suspended pumps, we can upgrade the same components as horizontal pumps (wear ringsthrottle bushingsthroat bushings) for the same reasons-to eliminate the metal-to-metal contact areas in the pump and reduce the clearance resulting in improved reliability and efficiency.

Today we will focus on the components which are unique to vertically suspended pumps-the vertical pump shaft bearings: line shaft bearings, bowl bearings, and bottom bearings. Vespel® CR-6100 is ideally suited to this application, particularly in services which suffer from a lack of lubricity or may run dry at startup. Vespel® CR-6100 does not seize like metal alloys, it can survive running dry, and it can withstand mechanical impacts and thermal shocks so it doesn’t break like carbon or graphite.

Multi-stage LPG pump bowl assemblies being upgraded to Vespel® CR-6100.

Multi-stage LPG pump bowl assemblies being upgraded to Vespel® CR-6100.

One thing of note is that vertical pump shaft bearings do not have differential pressure across the parts, therefore, they do not impact pump efficiency. Because the clearance of these components tends to be rather tight, to begin with, a further reduction in clearance can easily lead to assembly issues with a limited upside associated with the tighter clearance. Therefore, our recommendation for these parts is to install the Vespel® CR-6100 into the spiders or bowl assemblies with the press fit shown in our installation guide, then final machine to the original design clearance.

In our installation guide, you will find two clearance charts–one for horizontal pump types, one for vertical pump types. Because we don’t want the wear ring clearance tighter than the shaft bushing clearance, we simply recommend making the wear ring clearance 0.002″ (0.05 mm) larger than the shaft bushing clearance in these pumps. In short, we highly recommend that you download the Boulden Installation Guide for Vespel® CR-6100.

Discharge Through Column

Vertically suspended pumps are often selected because the service offers poor suction conditions such as light hydrocarbon service or condensate. In a long-term study, a refinery upgraded 22 vertical pumps to Vespel® CR-6100 wear parts. The pumps were operating in light hydrocarbons, flare knockout drum, and several stop/start services like product transfer. In the 5 years prior to upgrading the pumps, this population of pumps comprised many “bad actors” with poor reliability. In the 5 years after upgrading the pumps to Vespel® CR-6100, there were only 8 repairs on the entire population of pumps and the MTBR of this group of pumps increased to more than 10 years!

The combination of excellent reliability with ease of machining and installation along with immediate stock availability has made Vespel® CR-6100 the material of choice in these applications.

Vertically suspended pumps assembled with Vespel®CR-6100 shaft bearings, wear rings, bowl bushings and bottom bearings

Vertically suspended pumps assembled with Vespel®CR-6100 shaft bearings, wear rings, bowl bushings, and bottom bearings

Vespel® CR-6100 can handle significant periods of dry running with minimal wear, making it easier to bring the pump online. When you upgrade your wear rings to Vespel® CR-6100 and reduce the clearance, you might also find the pump easier to start due to a reduction in the NPSHR (Net Positive Suction Head Required).

To be continued…

In the next two issues, we will address vertically suspended pumps with a separate discharge (API Type VS4) and then we will discuss installation and assembly issues unique to vertically suspended pumps.

Until then, if you have a vertical pump which is giving you headaches, consider upgrading the wear parts to Vespel® CR-6100. Contact us today. We have the Vespel® CR-6100 in stock in a wide range of sizes available for immediate delivery to nearly anywhere in the world.
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!

 

 

 

 

 

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Today’s Photo

Gardens by the Bay, Singapore

Gardens by the Bay, Singapore