Today we take a final look at the above graph. We have already looked at Energy and Maintenance costs. Today we look at Operating, Environmental, and Downtime Costs.
When you upgrade pumps with composite materials like Vespel® CR-6100, Boulden B-Series, or Metcar® composites, you eliminate the metal-to-metal contact points in the pump, which essentially eliminates the risk of pump seizure. The pump is far more likely to survive running dry at start-up or during off-design events.
Benefits of Upgrading Pumps With Composite Materials
These are hidden bonuses to upgrading your pumps with composite materials. High quality composite materials act like a safety net in your pump, and sometimes, the savings from this benefit pay for all of the composite upgrades your company will ever do. Consider the following case studies:
Case Study: Condensate Return Pumps
Many years ago, a refinery upgraded the vertical pump shaft bearings in one of their 3 condensate return pumps to Vespel® CR-6100. The other two pumps had their original bronze bearings. The pumps were located in the hot well of a condensing steam turbine. The turbine was driving a critical compressor in one of the refinery process units.
Something happened which changed the pressure in the hot well and the pumps started operating in a vacuum intermittently for 9 hours. The two pumps with bronze bushings seized and had to be removed from service. The pump with Vespel® CR-6100 survived and allowed the process unit to continue operating. An upgrade which cost about $2000 likely saved the refinery millions.
Case Study: Potassium Carbonate Pumps
Plant operators heard a loud noise coming from a hot potassium carbonate pump. They were concerned because if potassium carbonate is released into the atmosphere, it creates a respiratory hazard. They shut down the pump and switched to the spare.
When the pump arrived in the shop, they found a piece of metal had broken from a valve and lodged in the pump impeller. Fortunately, during the previous repair, the maintenance shop had upgraded the pump to Vespel® CR-6100 case rings. During the incident, the pump did not seize, the seals didn’t leak, and a potentially major incident was likely avoided. A $3000 upgrade to the wear rings likely saved hundreds of thousands of dollars.
Case Study: Hydrocracker Charge Pump
Improved efficiency can also translate into increased production. A refinery upgraded their 9-stage hydrocracker charge pump, operating at 6400 rpm to Vespel® CR-6100 wear rings with reduced clearance. This $25,000 upgrade increased unit throughput by 4% creating millions of additional revenue for the refinery over the life of the installation.
Upgrading your pumps to composite materials reduces pump life cycle costs by making your pumps safer, easier to operate, more reliable and more efficient. When unexpected events occur or where you can increase throughput, a single installation can save you millions of dollars.
Take a look at the pumps coming into your workshop. Use the repair as an opportunity to make the pump better by upgrading to composite wear parts. Boulden has the material you need in stock and can deliver raw material or machined parts with very short lead times. Get in touch with us today!
Part 1: Minimize the Risk of Pump Seizure
Welcome to our series on upgrading pumps with composite materials. Over the next few months, we’ll cover the basics of why and how to use composite materials, specifically DuPont™ Vespel® CR-6100, to make your pumps more reliable, efficient, and safe.
Metal Parts Seize
Centrifugal pumps contain contact points between rotating and stationary parts. Most designs use replaceable wear components at these contact points: wear rings, inter-stage rings, throttle bushings, center-stage bushings, vertical pump shaft bearings, throat bushings. In the past, both the rotating and stationary parts would typically be metal.
With metal rotating and stationary components, there is a risk of galling or pump seizure. Galling can cause your pump to stick during assembly in the workshop, during alignment, or when the pump is slow-rolling in the field. This is a nuisance which can cause costly delays, returning the pump to the shop for disassembly, clean-up, re-assembly, and a return to the field. If a pump seizes during full-speed operation due to running dry, low flow, valve failure, bearing failure, shaft breakage, or another off-design scenario, the welding of metal parts together will generally cause the pump to stop abruptly, causing severe pump damage along with the potential for safety and environmental impacts.
Eliminate the Metal-to-Metal Contact Points in Your Pump
At a very basic level, the reason to upgrade the wear components in your pumps to composite materials is because composite materials are completely dissimilar to metal. Due to the totally different material compositions, metal-to-composite contact does not result in seizure like metal-to-metal contact.
So, our first objective when we are upgrading our pump with composite materials is to eliminate the metal-to-metal contact points within the pump. When using Vespel® CR-6100, the rotating parts will typically remain metal and the stationary parts will become Vespel® CR-6100. With this simple change, we now have metal-to-composite contact points in the pump and the risk of seizure is minimized.
Eliminate the metal-to-metal contact points in your pumps by upgrading the stationary components to Vespel® CR-6100. This simple upgrade will minimize your risk of pump seizure, eliminate nuisance repairs from pumps galling during alignment or slow-roll, and will help mitigate the risks and damage due to off-design operational events including dry-running operation.
Because the risk of pump seizure is minimized, you can now safely reduce the clearance at the wear components, setting up several additional benefits. We’ll talk about reducing the clearance in Part 2.
Until then, if you have had troubles with a pump which galls or seizes, contact Boulden to discuss upgrading the wear parts to Vespel® CR-6100. 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.
A long-term success story
Almost 10 years ago, a refinery in Europe upgraded their Reformer Feed pumps to DuPont™ Vespel® CR-6100. Last month, we checked in to see how the pumps are running.
The Reformer Feed pumps are 10-stage, axially-split, between-bearings pumps (API Type BB3), running at 2950 RPM. The product is naphtha at 185 C (365 F). There is one pump in the service, plus a spare rotor in the warehouse.
Problems in the Past
Marginal suction conditions make this a very tough service. The pumps take suction from a stabilizer tower bottom with NPSHA of only about 3 meters (10 feet). Due to the low NPSHA, it is very easy for the fluid to vaporize in the pump during start-up, causing the pump to run dry. This was formerly the normal reason for repairs due to the metal wear parts galling and seizing. If the metal parts did not seize, the throttle bushing would wear out, causing seal failures at the non-drive end.
Vespel® CR-6100 Survives
In 2009, the first pump in the service was upgraded with Vespel® CR-6100 case wear rings, center bushing, and throttle bushing. By eliminating the metal-to-metal contact points in the pump, the risk of pump seizure was essentially eliminated. Once the original pump upgrade proved successful, the spare rotor was also upgraded, but it has never been installed. The original pump upgraded is still running today. The refinery engineer commented:
We know for sure the product has vaporized in the pump at least 3 times since the upgrade, with seal failures as the only damages. We haven’t exchanged the rotor yet, although we have the spare rotor upgraded in 2010 in the warehouse. So far, no one expects the rotor to be exchanged.
As an added bonus, the site notes that they achieved a significant efficiency increase with the upgrade, which allowed an increase in unit throughput of 10%.
Vespel CR-6100 Conclusion
Where the refinery suffered with multiple failures of metal parts in the past, the Reformer Feed pump has now been running nearly 10 years with Vespel® CR-6100. The upgrade has paid for itself many times over with better reliability, efficiency, and ease of operation.
If you have a service causing you headaches, or if you are looking to increase throughput on one of your feed pumps, 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.
Moselle river between Luxembourg and Germany
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.
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.
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.
3MW Boiler Feed Pump Case Study
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?
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 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.
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.
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.
If you increase the clearance, the long-term reliability and efficiency of the pump will suffer.
We hope you have had a chance to enjoy your summer holidays. From New Orleans to Narvik, it’s hot out there, so be safe, and wear sunscreen.
In our messages, we frequently highlight how Vespel® CR-6100 does not seize and therefore allows you to reduce the clearance at the wear parts in your pumps: wear rings, inter-stage rings, throttle bushings, and center bushings.
Today we want to look at things from another perspective–negative effects which can happen to your pump when you increase the clearance at the wear parts.
What can happen when you increase clearance?
If a process plant has a problem with a pump seizing during operation or galling during commissioning, the traditional response has been to increase the clearance at the wear parts.
Although increasing the clearance might make the pump operable in the short term, there are several negative consequences from increased clearance.
|Hydraulic Effects||Mechanical Effects|
|Lower head||Reduced rotor stability|
|Lower flow||Potentially higher vibration|
|Lower efficiency–increased power consumption||Potentially higher shaft deflection|
|Higher NPSHR–greater risk of cavitation||Increased risk of shaft breakage|
|Higher motor load||Potentially shorter seal life|
|Need to run steam turbines at higher speed||Potentially shorter bearing life|
|Higher likelihood of needing to run pumps in parallel||Higher risk of motor over-heating or tripping from excessive load|
So, while you don’t want your pumps to seize, increasing the clearance can create some major issues. At a minimum increased clearance drives up the operating cost of the pump and likely compromises the long term reliability of the machine.
The Poster Pump
A while back, one of our clients had an 11-stage horizontal pump which was originally supplied with metal wear components. The pump seized soon after start-up, and the recommendation from the OEM was to increase the clearance. The pump seized again. The second recommendation was to use a “non-galling” metal alloy to address the problem. The pump seized again. The clearance was increased one more time. When the pump was started again, the overall pump vibration levels were beyond alarm limits. The multiple increases in clearance had resulted in a loss of rotor stability to the point that the pump was no longer operable.
The end of the story will be in our next email…
Until next time, if you have a pump in your shop which has galled or seized, contact Boulden to discuss an upgrade to Vespel® CR-6100. We will be happy to work through the details of the upgrade with you and we have material in stock and available for immediate shipment.
Helpful Links for Vespel and Pump Case Studies:
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.
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
|5 Years After
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:
Setting the final dimensions of your DuPont™ Vespel CR-6100 component
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.
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 3a and 3b show the clearance recommendations for vertical pump components like vertical pump shaft bearings, wear rings, and throat bushings.
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.
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.
The interference fit value for DuPont™ Vespel CR-6100
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.
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.
If you need any material or have any questions. Please contact us today. Until next time.
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