Author Archives: Patrice Isdahl

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

Amine Stripping Pump Case Study

Vespel® CR-6100 with the PERF-Seal® design survived where metal parts failed

In case you missed it…

The October 2018 issue of Hydrocarbon Processing featured a case study of Vespel® CR-6100 with the PERF-Seal®  design installed in a 2.7 MW amine stripping pump.

Amine Stripping Pump
2-Stage, 2.7MW, 4500 RPM Amine Stripping Pump

Amine pumps upgraded for improved operations and reliability

An excerpt…
The amine circulation pumps are controlled to gradually ramp up to operating speed. During this ramp-up period, the pumps produce insufficient head to generate any flow into the gas absorber. Therefore, the pumps must run on a minimum flow bypass back to the suction header. This flow is controlled by a minimum flow line valve (MFLV), which should be opened before startup and then closed once full-speed operation of the pumps is established.
With a steam turbine driver, ramping up to 4,500 rpm requires approximately 15 min, which is far too long to run the pump at zero flow.
Periodically over the past 10 yr, the MFLV has been opened too late during the startup procedure, which has led to the pump seizing at the center bushing and non-drive-end (NDE) and drive-end (DE) throat bushings (FIG. 1). These components have the tightest clearance and are, therefore, the first metal-to-metal contact points inside the pump.

To read the full case study, visit the Boulden website:
https://www.bouldencompany.com/dupont-vespel/case-studies/amine-pumps
If you have a pump running at low flow, or suffering from operational issues, running dry, or seizing contact Boulden today. We can provide all of the information you need to upgrade your pump and reduce your operational headaches. We have the material you need in stock and ready for immediate shipment almost anywhere in the world.

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
3MW Boiler Feed Pump Case Study

 

Today’s Photo

The Acropolis in Athens Greece
The Acropolis in Athens Greece