Tag Archives: throttle bushings

A Look at Pump Life Cycle Costs – Part 2: Energy Savings

 

Typical Life-Cycle Cost For A Pump System Infographic

Typical Life-Cycle Cost For A Pump System

Today we continue our look at the above graph. Last week we looked at maintenance costs. Today, we look at energy consumption.

When you upgrade pumps with composite materials like Vespel® CR-6100, Boulden B-Series, or Metcar® composites, you can reduce the energy consumption. Reducing the energy consumption of the pump creates continuous and long lasting savings.

Higher Pump Efficiency = Energy Savings

Composite materials reduce the operating cost of a pump through increased efficiency. Because composite materials do not seize, the clearance at the main wear parts – wear rings, throttle bushings, center bushings, balance drums–can be reduced. These parts separate areas of high pressure and low pressure within the pump and reducing the clearance reduces the internal recirculation across these parts.

The target for this upgrade should be the higher power pumps in the plant, as the payout tends to increase with pump power. Multi-stage horizontal pumps tend to offer the best return on investment because they produce high pressure and the recirculation across many internal components has a significant impact on pump efficiency.

Average Energy Savings Of A Pump Running Full Time

Over the years, many boiler feed pumps, charge pumps, and product shipping pumps have been upgraded to Vespel® CR-6100. It is typical for the efficiency gain from reducing clearance in these pumps to fall within the range of 3-5% compared to the “as new” condition of the pump. So, if you have a 1000 HP (750 kW) pump running full time, the energy savings will likely be in the range of $20,000 – $30,000 per year. If we assume an 8 year run at higher efficiency, savings will accumulate to around $200,000.

Conclusion – Using High-Quality Composite Materials Help With Energy Savings 

In short, using quality composite materials like Vespel® CR-6100 with reduced clearance in your high energy pumps will pay for itself quite easily on energy savings alone. Next month, we’ll discuss some special situations where you can save even more money.

Until then, whatever the temperature, chemical, or operating conditions for your pump, it is likely that Boulden has a non-seizing, non-galling composite material to help you improve your pump efficiency and reliability. Boulden has a large inventory of material in stock and we can supply raw material or finished parts with very short lead times. We can provide all of the technical support required for you to make the upgrade a success.

Contact us today and use your next repair as an opportunity to upgrade your pump.

Solving Vertically Suspended Barrel Pump Failures

Between 2011 and early 2012, a refinery suffered repeat failures of a pair of vertical pumps. Looking at the cross section, you can see this is not an ordinary pump. It is essentially a BB5 multi-stage diffuser pump mounted vertically.
The pumping conditions are also uncommon–0.61 specific gravity hydrocarbon running at 300 F (149 C). The vapor pressure is nearly 50 psi (3.3 bar), well into the range of a flashing hydrocarbon.
In short, not an easy application–a vertically mounted, multi-stage, barrel pump in a hot, light, flashing, low viscosity hydrocarbon.
Vertically Suspended Barrel Pump

Vertically Suspended Barrel Pump

 

 

Repeat Pump Failures

The pumps were failing due to seizure of the original metal parts, which were 12% chrome alloy with a hardness difference. At the point where the refinery contacted Boulden, the pumps had failed several times in the previous year.

The Upgrade

The engineers at the plant had heard that Vespel® CR-6100 wear parts would not seize. They discussed with Boulden that the material could handle the service conditions. The temperature limit for Vespel® CR-6100 is 500 F (260 C) and it resists all hydrocarbons without issue, so this application was well within the capabilities of Vespel® CR-6100. After several failures with the metal parts, the refinery decided to go forward with Vespel® CR-6100.
Vespel® CR-6100 wear rings, inter-stage rings, and throttle bushings were installed. Clearance at the wear rings was reduced to approximately 50% API recommended values for metal parts. A year later, the spare pump was also upgraded.

Results of Upgrading to Vespel® CR-6100

The first pump finally came out of service in early 2021 after nearly 9 years. From the look of the components, the Vespel® CR-6100 survived some really tough conditions. There was evidence of running dry, hard contact between rotating and stationary parts, and local temperatures well over 300 F (149 C). Yet, the pump never seized, and the Vespel® CR-6100 parts remained in usable condition all the way to the end of the run.
The MTBR for these pumps went from a few months to 9 years with a simple upgrade to Vespel® CR-6100. The investment in Vespel® CR-6100 has probably paid for itself 100 times over. The pumps clearly last longer, are easier to operate, and arguably much safer because they do not seize in this hot, flashing hydrocarbon service.

Conclusion

Do you have an application more difficult than this? Tell us about it.
Take your next repair as an opportunity to upgrade your pump. Boulden has a large inventory of material in stock and we can supply raw material or finished parts with very short lead times. We can provide all of the technical support required for you or your preferred workshop to make the upgrade a success.
Whatever the temperature, chemical, or operating conditions, it is likely that Boulden has a non-seizing, non-galling composite material to help you improve your pump reliability. Contact us today with the process conditions and we will let you know what we can do.

 

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

 

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

Frequently Asked Question:

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

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

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

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

Put it in the Bid Spec

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

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

Direct Questions to Boulden

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

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

Helpful Links:

Boulden Installation Guide for Vespel® CR-6100

Standard Stock Sizes of Vespel® CR-6100

Vespel® CR-6100 Product Data Sheet

Vespel® CR-6100 Machining Guide

2MW Boiler Feed Pump Case Study

Amine Stripping Pump Case Study

 

Today’s Photo

Lanzarote, Spain

Lanzarote, Spain

Upgrading Pumps With Composite Wear Components: Part 3

Part 3: Reduce Clearance – Improve Pump Efficiency

Welcome to Part 3 in our series on upgrading pumps with composite wear parts.

In the first part of this series, we discussed how upgrading your pumps with composite wear parts can help avoid galling and seizing. Because composite parts do not gall or seize like metal parts, this allows you to reduce the clearance at these components in your pump.

In Part 2, we discussed how reducing the clearance at the wear rings, throttle bushings, and center-stage bushings creates a stabilizing force in your pump called The Lomakin Effect. This force helps to reduce vibration and shaft deflection, leading to longer seal and bearing life in your pumps.

Today, we will discuss how reducing the clearance in your pump also improves pump efficiency.

Centrifugal Pump Background

According to a major centrifugal pump OEM, energy consumption accounts for 44% of the life cycle cost of a centrifugal pump. You can reduce this cost by upgrading the wear components to a composite material like Vespel® CR-6100 and reducing the clearance in your pump.

The specific components where you want to reduce the clearance are the pump wear rings, inter-stage rings, center-stage bushing, and throttle bushing. These components form the barriers between high-pressure and low-pressure areas within the pump. The differential pressure across these components creates internal recirculation within the pump, resulting in a loss of pump efficiency (Figure 1).

Loss of pump efficiency

Leakage past the wear rings (QL) creates efficiency loss

 

 

 

 

 

 

When you upgrade these components to Vespel® CR-6100, you can typically reduce the clearance by 50% compared to the API minimum for metal parts. If you reduce the clearance by 50%, you reduce the internal recirculation by approximately 50%, leading to a significant efficiency gain.

Which Pumps Produce the Biggest Gains?

If we consider only efficiency gains, horizontal multi-stage pumps usually offer the best return on investment from an upgrade to Vespel® CR-6100 with reduced clearance. These pumps have multiple leak paths across wear rings, inter-stage rings, center bushings, and throttle bushings. Because they have many stages, these pumps also tend to consume a lot of power. Consider the following cases where process plants have reduced the operating costs of their multi-stage horizontal pumps:

  • A power station upgraded a 3MW boiler feed water pump with Vespel® CR-6100 along with the Boulden PERF-Seal™ design and reduced clearance and recorded a 7% efficiency gain compared to a newly rebuilt pump with original clearances.
  • A refinery upgraded their hydrocracker charge pumps with Vespel® CR-6100 along with the Boulden PERF-Seal™ design and reduced clearance and recorded 4% more throughput to their hydrocracker-a hugely profitable upgrade.
  • A product pipeline company upgraded their LPG shipping pumps with Vespel® CR-6100 and reduced clearance, resulting in a 4% efficiency gain.

Another area to consider is process pumps which are marginally undersized, requiring parallel pump operation to achieve 100% of the target process rate. Sometimes, a modification as simple as reducing the wear ring clearance can get you back to one-pump operation with a full-capacity spare pump.

The PERF-Seal™

To further increase the efficiency gain associated with reduced clearance, the components can be modified with the Boulden PERF-Seal™ design. Internal testing has shown that the PERF-Seal™ creates an additional reduction in flow across throttle bushings, center-stage bushings, and wear rings beyond what can be achieved with reduced clearance alone.

Conclusion

When you eliminate the metal-to-metal contact surfaces in your pumps and use Vespel® CR-6100 stationary wear components, you can then reduce the clearance. This reduction in clearance improves pump efficiency and lowers the operating cost of the pump. Numerous field examples exist where customers have saved tens of thousands of dollars on their annual pump operating costs with this simple upgrade.

If you have a pump where improved efficiency will save you money, contact Boulden today. We have a huge inventory of Vespel® CR-6100 standard sizes in stock ready for immediate shipment almost anywhere in the world.

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

Today’s Photo

Cape Town, South Africa

Cape Town, South Africa

Upgrading Pumps With Composite Wear Components: Part 2

Part 2: Reduce Clearance – The Lomakin Effect

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

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

Reducing Clearance – The Lomakin Effect

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

Your Wear Rings are Bearings

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

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

The Lokamin Effect

Figure 1: The Lokamin Effect

 

 

 

 

 

 

 

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

Potential benefits for your pumps include:

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

Which Pumps?

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

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

Conclusion

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

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

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

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

Today’s Photo

Le Louvre, Paris, France

Le Louvre, Paris, France

Upgrading Pumps With Composite Wear Components: Part 1

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.

Vertical LPG Pump with metal shaft bearings

Vertical LPG pump with metal shaft bushings seized, shaft broke, impellers and bowl assemblies destroyed.

 

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.

Vespel® CR-6100 wear ring

Horizontal LPG pump ran dry with Vespel® CR-6100 case rings. No damage to impellers, case, shaft, or bearing housings.

 

 

 

 

 

 

 

Conclusion

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.

Today’s Photo

Fresh coconuts

Fresh Coconuts – Terengganu, 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

 

 

 

 

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

 

 

 

 

 

 

 

 

14 Reasons to Avoid Increased Wear Ring Clearance

If you increase the clearance, the long-term reliability and efficiency of the pump will suffer.

Happy Summer!

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.

Metal Case Ring After a Boiler Feed Pump Seizure

 

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…

 

Conclusion

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:

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’

Rossio Square in Lisbon Portugal with famous wave pattern stone pavement.

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