Tag Archives: Pumps With Composite Wear Components

Reformer Feed Pump Case Study

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 Application

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 wear parts

Vespel CR-6100 wear parts are installed as “inserts” into the existing metal parts for axial split pumps running at elevated temperatures.

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.

 

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

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Moselle river between Luxembourg and Germany

Moselle River Between Luxembourg and Germany

Moselle River Between Luxembourg and Germany

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When to Reduce the Clearance in Your Pump with DuPont™ Vespel® CR-6100

The industry “rule of thumb” says to reduce the wear ring clearance by 50%, but this isn’t always true.

Vespel® CR-6100 Upgrade Review

When you upgrade your pumps to Vespel® CR-6100, there are two steps:

  • Eliminate the metal-to-metal contact points in the pump
  • Reduce the running clearance (of the wear rings and throttle bushings)

However, you don’t always need to reduce the clearance. It depends on what you are trying to do and which component you are looking at. So, to determine whether or not to reduce the clearance, ask two questions:

 

What Problem am I Trying to Solve with Vespel® CR-6100?

Vespel® CR-6100 can be used to improve pump reliability and performance in many ways. Some benefits require reduced clearance, some do not. The following table gives some examples of where reducing clearance is needed vs. where it is not needed.

 

Reduced Clearance Required

Reduced Clearance Not Required

 

 

Is There Differential Pressure Across the Part?

Reducing the clearance can generally produce two beneficial effects in your pump:

  • Efficiency Improves: The leakage across the part will be reduced, improving pump efficiency and reducing the operating cost of the pump.
  • Improved Rotor Stability: The Lomakin Effect in the pump will be increased, increasing the hydraulic forces produce by the wear rings.

Both of these factors are driven by differential pressure across the part.

 

If the specific component you are upgrading to Vespel® CR-6100 is not exposed to differential pressure (i.e. vertical pump shaft bearing) there is no need to reduce the clearance.

 

Wear rings, throttle bushings, center bushings, balance bushings are all exposed to differential pressure. These are the parts where you want to reduce the clearance to obtain performance and rotor stability improvements. The rule of thumb is to reduce the clearance to 50% of the API minimum for metal parts. For most pumps in the hydrocarbon processing industry, this works.

 

These benefits are augmented using the patented PERF-Seal™ design from Boulden, which further reduces leakage across the part and dramatically increases the hydraulic damping from these components.

 

Exceptions to the 50% Wear Ring Clearance Rule

Because pumps come in all shapes and sizes, there are some places where we need to make exceptions and reduce the clearance by less than 50%.

  • Throat bushings-the throat bushing clearance often helps to control the mechanical seal flush rate. We recommend using the clearance recommended by your mechanical seal OEM to set the clearance of this part.
  • Wear rings in vertically suspended pumps-You don’t want to have the wear ring clearance tighter than the shaft bearing clearance. Therefore, our recommended minimum clearance for wear rings in vertically suspended pumps is the shaft bearing clearance + 0.002″ (0,05 mm).

Conclusions

Over the years, we have seen pump repair shops use a range of clearance values when applying Vespel® CR-6100 with great results. There is no single “best” way. That said, if you want to increase efficiency, you need to reduce the clearance of the parts exposed to differential pressure. If you are only trying to solve a run-dry or seizing problem, reducing the clearance is optional. For vertical pump shaft bearings, staying with the original design clearance is usually the best answer.

 

In any case, you can use our recommendations as a starting point. We supply these values in the clearance tables in our installation guide which you can download here:

 

Boulden Installation Guide for Vespel® CR-6100

 

Until next time, please feel free to contact Boulden if you would like to discuss the appropriate clearance for your pump upgrade. We’ll be happy to help and we have whatever material you need in stock in the USA, Europe, and Singapore.

 

Helpful Links on Vespel® CR-6100 and Wear Ring Clearance:

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.

Upgrading Pumps With Composite Wear Components Part: 9

Upgrading pumps with composite wear componentsPart 9: Vertically Suspended Pumps with Separate Discharge (API Type VS4)

Review

Last week, we looked at vertically suspended pumps with the discharge through the column. This week, we take a look at vertically suspended pumps with a separate discharge (API Type VS4).

Vertically suspended pumps with separate discharge are generally used for sump pumps or wastewater pumps. It seems that these pumps cause headaches at most plants. The shaft bushings wear out leading to chronic repairs. Over the years, Vespel® CR-6100 has been used in a lot of these pumps, sometimes the pump life has been extended from a few months to several years; sometimes the pump life has not improved. Therefore, it is important to identify the failure mode before making the upgrade. We have used our experience to create the roadmap below.

Define the Service

The first step is to clarify “sump pump” or “waste water pump”, which are generic terms encompassing a wide range of services. Some services are pumping primarily chemicals mixed with water, and some of them are pumping primarily water mixed with dirt. Some of the sumps are so dirty, that the pump suction strainer seems to be immersed in mud. Another variable is that the shaft bearings are flushed with different arrangements. Some of them are flushed with the process fluid, others with clean water, and others are greased.

Given the range of service conditions, there are several different problems which can cause the shaft bearings to fail. However, there are some commonalities. First, by design, the shaft bearings are along the column of the pump with a separate discharge for the process fluid. The 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 grease supply runs out. In a chemical sump, the mix of chemicals can cause corrosion with metal wear parts. Finally, in very dirty sumps where the bearings are flushed with the process fluid, abrasive wear tends to be the main problem.

The Road Map

Considering the above, we have created the following table to guide your selection of where to use Vespel® CR-6100 in sump pump services:

Vespel CR-6100 sump pump services.

Vespel CR-6100 sump pump services.

*Some of the alternatives to consider are switching to a clean water flush or looking at an abrasive resistant, non-seizing combination for the shaft bushings and sleeve. This generally entails a hardened sleeve and an abrasive resistant bushing material. If you have any doubts about whether Vespel® CR-6100 is a good fit for your service, contact Boulden to discuss.

Vertical Pump Conclusion

To finish our discussion of vertically suspended pumps, we will talk about assembly and installation issues which impact pump reliability. Until then, use the above information as a guide on how to use Vespel® CR-6100 in your pumps with a separate discharge. If you need any material, contact Boulden. We have whatever size and quantity you need in stock and ready for immediate delivery.

For information on how to install 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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Late Night Snack, Thailand

Late Night Snack, Thailand

 

 

 

 

 

 

 

Boulden Company

Conshohocken, PA, USA

1-610-825-1515

 

Boulden International, S.ar.L

Ellange, Luxembourg

+352 26 39 33 99

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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Gardens by the Bay, Singapore

Gardens by the Bay, Singapore

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.

 

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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.

Horizontal LPG pump ran dry with Vespel® CR-6100 case rings. No damage to impellers, case, shaft, or bearing housings. Photo: Vespel® CR-6100 wear ring as found during disassembly

Horizontal LPG pump ran dry with Vespel® CR-6100 case rings. No damage to impellers, case, shaft, or bearing housings. Photo: Vespel® CR-6100 wear ring as found during disassembly.

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.