Tag Archives: throttle bushing

Diesel Charge Pump Case Study

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.

Figure 1: Process flow data for the diesel charge pumps during the process upset

 

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.

 

Conclusion

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.

 

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

October in the forest, Mullerthal, Luxembourg

 

Prepping Your Metal Parts

Prepare your pump parts for an upgrade to DuPont™ Vespel CR-6100

Review on Pump Parts and upgrading to Vespel CR-6100

The National Geographic Channel used to run a show called Doomsday Preppers where survivalist families would prepare for apocalyptic disasters and societal collapse. Although that sounds like a lot of fun, at Boulden, we are more concerned with helping your pumps survive adverse process conditions with an upgrade to DuPont™ Vespel® CR-6100.

 

Last month, we outlined the measurements required for a Vespel® CR-6100 installation. When you have decided to go forward with the upgrade, the first step will be to prepare the metal parts to facilitate the installation.

 

Start with a Little Chamfer

Vespel® CR-6100 is used for stationary wear components–throttle bushings, case wear rings, center-stage bushings, inter-stage case rings, vertical pump shaft bearings, throat bushings, agitator bearings, API separator bearings-basically any product lubricated wear part.

 

The material is installed with a significant press fit. To facilitate the press fit operation, the metal bore into which you will be pressing the Vespel® CR-6100 requires a small chamfer or radius (Figure 1). It is very important that any corners or sharp edges are fully broken and smoothed with a stone so that the metal edge does not remove material from the outside surface of the Vespel® CR-6100 during the press operation.

Figure 1: Chamfer or Radius Leading Edge to facilitate press fit. (Note shoulder on low-pressure side.)

 

 

 

 

 

 

 

 

 

Make Sure There is a “Shoulder” or “Step”

For any part exposed to differential pressure, it is important that the design features a shoulder or step at the low-pressure end (shown on the right side of Figure 1) to ensure the differential pressure does not dislodge the Vespel® CR-6100 during operation.

 

Some radially split multi-stage pumps (BB4 and BB5) pumps feature metal wear rings welded into the pump diffusers with no step or shoulder incorporated in the design. In this case, you can consider modifying the diffusers so that the case wear rings have an “L” shaped profile like the rings below which were used in a hydrocracker charge pump.

Figure 2: “L” Shaped wear ring profile for BB4 or BB5 pump type.

 

Conclusions

Vespel® CR-6100 can help you avoid pump seizure during extreme events like running dry. The temperature limit is 500 F (260 C), allowing it to survive infernal heat waves. The material is not affected by electromagnetic pulses. polar shifts, or solar flares. As an added bonus, Vespel® CR-6100 has an indefinite shelf life, making it an ideal material to stockpile in your underground bunker, and the material is likely to hold its value in the case of hyperinflation.

 

In reality, you don’t have to stockpile the material. Boulden carries a huge inventory of stock sizes in the USA, Europe, and Singapore. You can generally receive whatever material you need in a matter of days.

 

To prepare your pump for whatever the future holds, please contact Boulden with your application details and dimensions. We’ll be happy to walk you through the installation details–assuming we have not been wiped out by an asteroid strike.

Todays Photo

All this talk of disaster is making me hungry. This is some excellent Bun Cha in Vietnam.

 

 

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

If you need any material or have any questions. Please contact us today. Until next time.

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

 

 

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.

 

new boulden

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.