Centrifugal Pump Wear Rings

 
Dupont Vespel CR-6100 pump wear rings

Composite wear rings installed in a multi-stage LPG pump

Vespel wear rings

Composite wear rings installed in a boiler feed water pump

Improve pump performance and reliability with composite wear rings

Upgrading your pump wear rings to reinforced composite materials like Vespel® CR-6100 or Boulden B-835 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-composite interface. By eliminating the metal-to-metal contact points within the pump, the risk of galling and seizure is nearly eliminated. This allows the clearance at the wear rings to be reduced, enabling several potential reliability and performance benefits.

What to do when upgrading pump wear rings to composite materials

  • Replace the metal stationary wear rings with an appropriate composite material and continue using the current metallic components on the rotating rings. (Standard wear ring materials and finishes generally work fine but contact Boulden with any questions.)
  • Depending on the part geometry and operating temperature, the composite material 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 composite pump wear rings

  • Eliminating the metal-to-metal contact points essentially eliminates the risk of galling or 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

Contact Boulden for Pump Wear Rings today

To know which material is right for your application, send your pump data sheet and cross section when you, contact Boulden or request a quote. We will help you find the best fit for your pump. 

Long-term, large scale field studies have shown that composite materials 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 composite materials like DuPont™ Vespel® CR-6100 and Boulden B-835. 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

 

Contact Boulden today to upgrade your pump wear rings to composite materials

Contact Boulden today with your application details to upgrade your pumps to Vespel® CR-6100 or Boulden B-835. We have the material you need in stock and can ship immediately. Or if you want to know more about the composite materials we offer and applications, sign up for our newsletter!