Last fall, a power plant needed to replace the vertical pump shaft bearings on their cooling water intake pump. They contacted Boulden to find a solution.
The cooling water intake pumps at the plant pump brackish water from the local harbor. The salty water creates corrosion issues, the silt in the water creates abrasion issues. The line shaft bearings are exposed to potentially high loads from the pump at an operating speed of 1500 rpm.
Boulden selected B-1050 for the application due to its excellent dimensional stability, resistance to abrasive wear in dirty water conditions, and high load carrying capability. Unlike most plastic or composite materials used for this application, B-1050 has a coefficient of thermal expansion less than carbon steel. Boulden has found that a coefficient of thermal expansion less than carbon steel is probably the most important material property for the reliable performance and ease of design of a composite bearing or wear ring. For a complete data sheet, contact Boulden today.
Some key properties of B-1050 are shown in Table 1:
Tough, wear resistant shaft bearings from Boulden
Boulden supplied the B-1050 bearings mounted in Duplex Stainless shells. The old bearing spiders were corroded and needed to be re-machined; therefore, the shells were machined to fit after the modification to the spiders. The bearings ran against a 7″ (180 mm) diameter shaft. One line shaft bearing design was 9″ (225 mm) long; the other was 11″ (270 mm) long. The components were manufactured in a few weeks, delivered and installed without issues.
If you are looking for better materials for your vertical shaft bearings, contact Boulden. Consider B-1050 for your cooling water pumps, waste water pumps or other services where you need the ability for the bearings to run in potentially dirty service plus survive off design conditions such as running dry. We have a portfolio of materials with B-Series and Vespel® CR-6100, so whatever your vertical shaft bearing application, we can help.
For consultation on the best material for your application or design assistance, contact Boulden today. We have the material you need in stock and can supply raw material or machined parts with rapid delivery.
A quick tip for the machine shop
Recently, a pump repair shop bought some 2″ solid rods of Vespel® CR-6100. This was their first purchase of solid rods and they asked for instructions to machine the I.D. to size. Below is the method we use in our shop at Boulden:
Step 1: Drill Pilot Hole 0.375–0.500″ (10-12 mm) through the center of the bar
Step 2: Use a spade blade (or larger drill bit) to enlarge the hole
Step 3: Final machine with boring bar
Until Next Time
If you have a pump in your shop where you would like to improve reliability, efficiency, avoid seizing, or reduce vibration, consider an upgrade to Vespel® CR-6100 wear rings with the Boulden PERF-Seal® design. Whatever the pump geometry, Boulden can help you fit the parts into the pump, make drawings and machined parts for you, or simply help you with tips and tricks to use in your shop. Contact us today.
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.
For details on how to install Vespel® CR-6100 into nearly any pump type, download the Boulden Installation Guide.
Tools to help you improve your pump operability, reliability, and efficiency
Our favorite material recently passed a milestone. The first pump ever fitted with Vespel® CR-6100 was upgraded 20+ years ago in November 1997.
The first pump was a vertically suspended condensate pump at a refinery in California. The pump was notorious for running dry, and it had failed once or twice per year for as long as the maintenance records went back. An engineer at the refinery “found” Vespel® CR-6100 and decided to put it to the test on the condensate pump. The pump survived repeated episodes of running dry and subsequently ran for many years without failure.
Since then, over 10,000 pumps across the globe have been upgraded with Vespel® CR-6100.
When you are using Vespel® CR-6100 in your shop, or if you are recommending your favorite repair shop to perform the upgrade for you, the following links should prove helpful:
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
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?
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.
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.
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.
Frequently Asked Question:
“Are the OEMs using Vespel® CR-6100?” is a question we hear every month. The answer is definitely, “yes.” All of the major API pump manufacturers use Vespel® CR-6100 for both new pumps and aftermarket upgrades.
A related question: “If Vespel® CR-6100 is so great, why don’t the OEMs include it as a standard material?”
To answer that, we need to look at how pumps are usually purchased…
Most pumps are sold into projects. The EPC contractor generally selects the pump with the lowest price which meets the bid specification. Therefore, if the bid spec allows bronze or cast iron wear rings, the OEM will probably quote bronze or cast iron because they are the cheapest materials. These materials might result in a higher life-cycle cost, but procurement personnel will not care if their decision is driven by the initial price.
Put it in the Bid Spec
If you want to maximize your pump reliability and efficiency, specify Vespel® CR-6100 for the stationary wear components in your next project. When it is part of the specification, the OEMs are happy to quote and supply Vespel® CR-6100.
If your company does not allow using brand names in the project specification, you can use the generic description for Vespel® CR-6100 from API610, Table H.3: PFA/CF reinforced composite, 20% mass fraction random X-Y oriented carbon fiber. For clarity, you can add the note “one example of which is DuPont™ Vespel® CR-6100.”
Direct Questions to Boulden
If there are any questions from the Project Engineer, EPC contractor, or OEM, please ask them to contact Boulden. We will be happy to answer any questions they have and make sure that the Vespel® CR-6100 is used correctly throughout the project.
In short, if you want Vespel® CR-6100 wear rings, vertical pump shaft bearings, or throttle bushings in your new pumps, all you have to do is ask–i.e. spell it out in the bid spec. Until next time, if you need any material for your pumps, we have a wide range of sizes in stock and ready for immediate shipment.
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).
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.
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.
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.
Part 2: Reduce Clearance – The Lomakin Effect
Welcome back to our series on upgrading pumps with composite materials. In part 1, we discussed how using composite materials like Vespel® CR-6100 in your pumps allows you to eliminate the metal-to-metal contact points in the pump and minimize the risk of pump seizure:
- In the shop during assembly
- In the field during alignment
- During slow-roll, start-up, and shut down
- During off-design events like dry-running or low flow
Reducing Clearance – The Lomakin Effect
Minimizing the risk of seizure in your pump sets the stage for reducing the clearance at the wear parts in your pump. Reducing clearance can be a significant pump reliability upgrade due to a phenomenon known as the “Lomakin Effect“.
Your Wear Rings are Bearings
During pump operation, the flow created by differential pressure across the wear parts in the pump (wear rings, throttle bushings) creates a force called The Lomakin Effect. The force arises from an unequal pressure distribution around the circumference of the component during periods of rotor eccentricity. This force counteracts shaft deflection in the pump.
Figure 1 shows how shaft deflection creates this force. As the fluid enters the clearance between the rotor and wear component, it accelerates as it passes from the high pressure end to the low pressure end. Due to the eccentricity of the rotor, there is more clearance on one side of the wear part than the other. There will be more flow and a locally higher velocity on the side of the wear ring with more clearance and lower velocity on the side of the ring with less clearance. Higher velocity results in lower pressure; lower velocity results in higher pressure, creating a net corrective force which acts in the direction opposite of the shaft deflection.
In other words, when your pump experiences shaft deflection, there is a hydraulic “stiffness” (Lomakin Stiffness) which is generated to counteract the shaft deflection.
Using Vespel® CR-6100 you can typically reduce the clearance at the pump wear rings by 50% compared to the API recommended minimum for metal wear parts. The Lomakin Stiffness is inversely proportional to clearance; therefore, a 50% reduction in clearance doubles this force.
Potential benefits for your pumps include:
- Less shaft deflection
- Lower vibration levels
- Fewer mechanical seal leaks
- Longer bearing life
The Lomakin Effect is generally beneficial to all centrifugal pumps, but some pump types often show significant vibration reductions and reliability improvements with reduced clearance:
- Multi-stage horizontal pumps
- Older overhung pumps with long, thin shafts (high L/D ratios)
- Two-stage overhung pumps
Reducing the clearance at the wear components can be a major reliability upgrade for your pumps. The reduced clearance increases The Lomakin Effect which improves pump rotor stability. The net result is a pump which runs with potentially lower vibration, fewer seal leaks, and longer bearing life.
Reducing the clearance also increases pump efficiency, which we will discuss in Part 3.
Until then, if you are working on a pump with a long, thin, flexible rotor, contact Boulden to discuss upgrading the wear parts to Vespel® CR-6100 and reducing the clearance. We have a huge stock of Vespel® CR-6100 standard sizes in the USA, Europe, and Singapore available for immediate delivery to your workshop.
For application and installation details, download the Boulden Installation Guide for Vespel® CR-6100.
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.