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Dupont Vespel CR-6100 pump wear rings

Vespel® CR-6100 wear rings installed in a multi-stage LPG pump

Vespel wear rings

Vespel® CR-6100 wear rings installed in a boiler feed water pump.

Centrifugal Pump Wear Rings

Vespel® CR-6100 Application and Improving Pump Performance:

Upgrading your pump wear rings to Vespel® CR-6100 is one of the simplest, fastest ways for you to improve your pump reliability and efficiency. The basic idea is to eliminate the metal-to-metal interface within the pump and replace it with a metal-to-Vespel® CR-6100 interface. By eliminating the metal-to-metal contact points within the pump, the risk of seizure is nearly eliminated, the clearance at the wear rings can be reduced, and several potential reliability and performance benefits become possible.

What to do When Replacing Wear Ring with Vespel CR-6100:

  • Replace the stationary wear rings with Vespel® CR-6100 and continue using the current metallic components on the rotating rings. (There are no special requirements for the surface finish or hardness of the metal components running against the Vespel® CR-6100. Standard wear ring materials and finishes work fine.)
  • Depending on the part geometry and operating temperature, the Vespel® CR-6100 can be installed as either an insert or a solid ring (see photos above).
  • Reduce the wear ring clearance to a minimum of 50% of the API recommended wear ring clearance (depending on pump geometry)
  • Make sure the pump overhaul results in good rotor concentricity. (The rotor should turn freely after assembly. Slight rubbing at the wear rings from shaft sag is normal, but any hard rubs should be corrected before putting the pump into service.)

Benefits of Vespel® CR-6100 with Pump Wear Rings:

  • Eliminating the metal-to-metal contact points nearly eliminates the risk of pump seizure
  • The wear rings will not seize or gall during slow roll or alignment
  • The pump will have a better tolerance of run-dry events and other process upsets, with a chance of surviving extended off-design conditions
  • Lower vibration due to improved damping at the wear rings
  • Fewer seal leaks due to reduced vibration and reduced shaft deflection due to tighter wear ring clearance
  • Higher efficiency due to lower leakage losses across the wear rings
  • Reduced risk of cavitation because tighter wear ring clearances improve NPSHR

Long-term, large scale field studies have shown that Vespel® CR-6100 can improve pump life by up to 100%, reduce vibrations, and reduce seal leaks. Field tests and pump test stands have shown that reduce clearance can improve pump efficiency anywhere from 2-5% for typical process pumps.

3 Things to Know About Pump Wear Rings

Pump wear rings are simple components, but they have a profound impact on pump reliability, efficiency, and safety.

Most centrifugal pump designs include replaceable rotating wear rings on the impeller (impeller wear rings) and stationary wear rings inside the casing (case wear rings). The wear rings serve 3 purposes:

  • Create the contact area between rotating and stationary parts inside the pump
  • Reduce internal recirculation from pump discharge to pump suction or between stages
  • Create hydraulic forces which stabilize the pump rotor

The wear ring running clearance impacts pump discharge pressure, flow, efficiency, power consumption, vibration, and cavitation. Using composite wear rings with reduced clearance has a positive impact on all of these factors.

Pump Wear Rings Experience Wear

Pump wear rings are the contact zone between rotating and stationary parts. During start-up, shut down, and off-design operation, the rotating and stationary rings come into contact. This contact creates friction and wear. Under adverse conditions, the wear rings can seize causing severe damage. To avoid seizure, the pump industry has adopted two main approaches.

One approach uses metal wear rings, with which there is an inherent risk of seizure. Per API610, to minimize the risk of seizure using metal rings, the impeller and case rings should have a Brinnell hardness number difference of at least 50, unless both rings have a Brinnell hardness number greater than 400. Furthermore, the rings should use a generous clearance as spelled out in the API610 11th Edition Standard for Centrifugal Pumps. For hot pumps or pumps which still seize, clearance is further increased.

A more modern approach is for the impeller wear rings to remain metal and the case ring to be manufactured from a composite material like DuPont™ Vespel® CR-6100. This upgrade eliminates the metal-to-metal contact points within the pump, essentially eliminating the risk of pump seizure. This allows for easier assembly, alignment, and operation of the pump and allows the pump to reliably run with clearances significantly less than API610 recommended clearances for metal parts (Table 1).

 

Table 1: API610 Wear Ring Clearance vs. Vespel® CR-6100 Clearance

Inches

mm

Diameter

Clearance Metal

Clearance Vespel® CR-6100

Diameter

Clearance Metal

Clearance Vespel® CR-6100

3.000—3.499

0.013”

0.007”

80—89.99

0.33

0.17

3.500—3.999

0.014”

0.007”

90—99.99

0.35

0.18

4.000—4.499

0.015”

0.008”

100—114.99

0.38

0.19

4.500—4.999

0.016”

0.008”

115—124.99

0.40

0.20

5.000—5.999

0.017”

0.009”

125—149.99

0.43

0.22

6.000—6.999

0.018”

0.009”

150—174.99

0.45

0.23

7.000—7.999

0.019”

0.010”

175—199.99

0.48

0.24

8.000—8.999

0.020”

0.010”

200—224.99

0.50

0.25

9.000—9.999

0.021”

0.011”

225—249.99

0.53

0.27

10.000—10.999

0.022”

0.011”

250—274.99

0.55

0.28

11.000—11.999

0.023”

0.012”

275—299.99

0.58

0.29

12.000—12.999

0.024”

0.012”

300—324.99

0.60

0.30

13.000—13.999

0.025”

0.013”

325—349.99

0.63

0.32

14.000—14.999

0.026”

0.013”

350—374.99

0.65

0.33

15.000—16.000

0.027”

0.014”

375—399.99

0.68

0.34

 

Additional DuPont™ Vespel® CR-6100

Dupont™ Vespel® CR-6100 Stock Sizes
Dupont™ Vespel® Machined Parts
Vespel® CR-6100 Applications
Problems Vespel® CR-6100 Solves /Case Studies
Industries Vespel® CR-6100 Serves
Vespel® CR-6100 Resources

Looking to Replace Your Wear Rings? Contact Boulden today to learn more about the Vespel® CR-6100.

Contact Boulden today with your application details to upgrade your pumps to Vespel® CR-6100. We have the material you need in stock and can ship immediately. Or if you want to know more about Vespel CR-6100, sign up for our newsletter!