Download PDF - Calgary Pump Symposium

Weir Minerals North America 

Presentation to: 

Calgary Pump Symposium 

November 2009 

Prepared by: 

Michael Bootle 

Senior Design Engineer 

Excellent 

Minerals 

Solutions 

Wear in Rotodynamic 

(Centrifugal) 

Slurry Pumps


Excellent 

Minerals 

Solutions 

Modes of Wear in Slurry Pumps 

•Abrasion 

•Corrosion 

•Erosion 

2


Excellent 

Minerals 

Solutions 

Wear Locations 

• Fully Lined Pump 

3


Excellent 

Minerals 

Solutions 

Wear Locations 

• Unlined Pump 

4


Excellent 

Minerals 

Solutions 

Abrasion


Excellent 

Minerals 

Solutions 

Abrasion 

• Forcing of hard particles against a wear surface 

6


Excellent 

Minerals 

Solutions 

Abrasion 

• Locations within a 

slurry pump: 

• between shaft 

sleeve and packing 

• between impeller 

and suction side 

liner at tight 

clearance area 

adjacent to impeller 

wear ring/dam near 

impeller eye 

7


Excellent 

Minerals 

Solutions 

Abrasion 

• Worn Sleeve: Hourglass wear within 12 hours of seal water failure 

8


Excellent 

Minerals 

Solutions 

Corrosion


Excellent 

Minerals 

Solutions 

Corrosion 

• Abrasion resistant white irons used in slurry 

pumps consist of hard carbides in a ferrous 

matrix. 

• The M 7 C 3 carbides are electrochemically 

passive and essentially protected from 

corrosion. 

• The corrosion resistance of the material is 

therefore a function of the corrosion resistance 

of matrix, which in turn is a function of the 

chromium content with in the matrix. 

• Corrosion of the supporting ferrous matrix can 

lead to premature fracture and spalling of the 

carbides. 

Chromium carbides in 

supporting ferrous matrix 

10


Excellent 

Minerals 

Solutions 

Corrosion 

• Inter-phase corrosion can occur at the interface between the M 7 C 3 

carbides and the ferrous matrix resulting in intergranular corrosion: 

11


Excellent 

Minerals 

Solutions 

Corrosion 

• Corrosion pitting from 

low pH flue gas 

entering a scrubber 

pump during shut-down 

12


Excellent 

Minerals 

Solutions 

Corrosion 

• Above water line 

corrosion on 27% 

high chrome iron 

material 

13


Excellent 

Minerals 

Solutions 

Corrosion 

• Depth of Corrosion 

Pitting can be substantial 

14


Excellent 

Minerals 

Solutions 

Corrosion 

• 30% Potash Tailings in 

brine solution 

• Corrosion on 

unsubmerged portion 

of high chrome impeller 

• Severe imbalance due 

to uneven weight loss 

15


Excellent 

Minerals 

Solutions 

Corrosion/Erosion 

• 8 inch Froth Pump: 

Cyclone Feed Service 

in concentrate flotation 

regrind circuit at a 

Nickel Mine 

• Large inlet 

• Progressive reduction in 

corrosion from aerated 

inlet to pump discharge 

16


Excellent 

Minerals 

Solutions 


• 8 inch Froth Pump on Cyclone 

Feed service in concentrate 

flotation regrind circuit at a Nickel 

Mine 

• Severe corrosion to throatbush 

on aerated inlet side of the pump 

17


Excellent 

Minerals 

Solutions 


• 8 inch Froth Pump at Nickel Mine: 

• Less corrosion on impeller 

18


Excellent 

Minerals 

Solutions 


• 8 inch Froth Pump at Nickel Mine: 

• Slightly less corrosion on volute and frameplate liner insert 

19


Excellent 

Minerals 

Solutions 


• 10/8 AH on Heavy Media 

circuit in Potash Mine: 

• Magnetite, potash, 

brine solution 

• “Dry running” centrifugal 

shaft seal 

• Progressive reduction in 

corrosion from aerated 

seal area to pump 

discharge 

20


Excellent 

Minerals 

Solutions 


• 10/8 AH on Heavy Media 

circuit in Potash Mine: 

• Magnetite, potash, brine 

solution 

• Expeller ring/stuffing box 

• Note slurry/air interface 

21


Excellent 

Minerals 

Solutions 


• 10/8 AH Expeller on Heavy Media circuit in Potash Mine: 

• Magnetite, potash, brine solution 

22


Excellent 

Minerals 

Solutions 


• 10/8 AH Back Liner on Heavy Media circuit in Potash Mine: 


• Note demarcation line of level of wear just outboard of Back Liner ID. 

23


Excellent 

Minerals 

Solutions 


• 10/8 AH Impeller and Volute on Heavy Media circuit in Potash Mine: 


• Note further reductions in level of corrosion on Impeller and Volute. 

24


Excellent 

Minerals 

Solutions 


• Corrosion/Erosion with Erosion being a large contributing factor: 

25


Excellent 

Minerals 

Solutions 

Erosion


Excellent 

Minerals 

Solutions 

Erosion 

• Three primary modes of erosion: 

• Deformation wear: Direct impact to the leading edge of the impeller vanes, 

the back shroud of the impeller and the “protruding” cutwater of the volute. 

• Random impingement: Random impacts to the impeller shroud and trailing 

edge of the main pumping vanes 

• Low angle impact: Wear from the tangential or near tangential movement of 

particles against the volute casing or vane surface 

27


Excellent 

Minerals 

Solutions 

Erosion 

• Factors affecting erosion: 

• Contact conditions 

• Kinetic energy of particle: 

Particle mass (specific gravity) and 

velocity 

• Particle size 

• Particle shape: 

Sharp particles have small contact 

area and high local stress 

• Particle hardness 

• Slurry concentration: 

A higher percentage of solids 

results in more impacts for a given 

flow 

• Material properties 

28


Excellent 

Minerals 

Solutions 

Erosion 

• Fine particle slurries eat away at the softer matrix leaving the hard 

carbides vulnerable to spalling and flaking off. 

29


Excellent 

Minerals 

Solutions 

Erosion 

• Fine particles tend to follow fluid flow streamlines 

• Large particles tend to travel straight 

30


Excellent 

Minerals 

Solutions 

Erosion 

• Effect of Particle Size on Wear: 

D85 = 650 micron particle 

D85 = 6000 micron particle 

31


Excellent 

Minerals 

Solutions 

Erosion 

• Large particle wear to back 

side of impeller 

• Copper mine ball mill 

discharge 

• 400+ micron d50 particle 

size 

• Operation near best 

efficiency flow 

• 1848 hours 

32


Excellent 

Minerals 

Solutions 

Erosion 

• Large particle wear to back side of impeller: copper ball mill discharge 

33


Excellent 

Minerals 

Solutions 

Erosion 

• Zinc Tailings application: 

• 55 to 65% C w 

• 3.79 sg of dry solids 

• 25 micron d50 

• 11 to 12 pH 

• 3/2 DHH High Head Pump: 

• 70 m3/hr @ 44.8 to 75.6 m 

• 1052 to 1350 rpm 

• 54 to 69% of BEP 

• Fine particle “eddy current” 

wear 

• Minimal wear to leading 

edge of main pumping vanes 

34


Excellent 

Minerals 

Solutions 

Erosion 

• Fine Particle Zinc 

Tailings Application 

• 54 to 69% of best 

efficiency flow 

• Low flow suction liner 

wear 

• Fine particles follow 

eddy currents 

• Vortex/Rat Holing type 

wear 

35


Excellent 

Minerals 

Solutions 

Erosion 

• Fine Particle Zinc Tailings 

Application 

• 54 to 69% of best efficiency 

flow 

• Low flow volute liner wear 

• Eddy current wear beyond 

“cutwater” 

• Leading edge of cutwater in 

reasonably good shape 

36


Excellent 

Minerals 

Solutions 

Erosion 

• Effect of Operation Below BEP: 

(throatbush) 

37


Excellent 

Minerals 

Solutions 

Erosion 

• Wear on Casing Liner and Throatbush as a Result of Low Flow: 

38


Excellent 

Minerals 

Solutions 

Erosion 

• Copper Mine Ball Mill Discharge Cyclone 

Feed Pump 

• High Efficiency Volute Design: 

• True volute 

• Tight impeller to cutwater clearance 

• Severe low flow large particle wear 

beyond cutwater 

• d50 = 250 microns 

39


Excellent 

Minerals 

Solutions 

Erosion 

• Copper Mine Ball Mill 

Discharge Cyclone Feed 

Pump 

• Severe erosion at wear 

dam area adjacent to 

impeller eye 

• d50 = 250 microns 

40


Excellent 

Minerals 

Solutions 

Solutions


Excellent 

Minerals 

Solutions 

Solutions 

•Materials 

•Geometry 

•Application/Process 

42


Excellent 

Minerals 

Solutions 

Materials: Duplex Stainless Steels 

• Duplex stainless steels: 

• CD4MCu 

• Ferrallium 255 

• Two phase structure of ferritic and austenitic stainless steel 

• Good resistance to stress corrosion cracking 

• Nominal hardness of 250 HBN better than austenitic stainless steels 

but far poorer than high chrome irons (400 - 800 BHN) 

• Therefore, relatively poor erosion resistance for slurry service 

43


Excellent 

Minerals 

Solutions 

Materials: White Cast Irons 

• Consist of hard carbides within a supporting ferrous matrix 

• Carbide types: 

• Iron Carbide: 

• Chromium Carbide (M 7 

C 3 

): 

• Matrix types: 

• Ferrite: 

• Austenite: 

• Martensite: 

850 to 1000 HV 

1200 to 1500 HV 

150 to 250 HV 

300 to 500 HV 

500 to 1000 HV 

• Bulk hardness dependent upon carbide and matrix type and the 

volume of carbides in the matrix 

• Typical hardness of silica sand: 

1200 HV 

44


Excellent 

Minerals 

Solutions 

Materials: White Cast Irons 

• Medium to large particle applications: 

• Bulk hardness important 

• Small particle applications: 

• Fine carbide microstructure with smaller inter-carbide spacing important 

to minimize erosion of the softer matrix 

• Very large particle applications: 

• Fracture toughness of the matrix most important 

• Corrosive applications: 

• Corrosion resistance of the matrix most important 

45


Excellent 

Minerals 

Solutions 

Materials: White Cast Irons (Conventional) 

40 

Chemistry of White Cast Irons 

Chromium 

30 

20 

10 

ISO 21988 AS 2027 

HBW555XCr26 

HBW555XCr21 

HBW555XCr16 

HBW555 

27Cr 

20Cr-2Mo 

15Cr-3Mo 

Ni-hard 4 

ASTM A532 

Class IIIA 

Class II D 

Class II B 

Class I D 

HBW510 

Ni-Hard 1 

Class I A 

2 3 4 5 

Carbon 

46


Excellent 

Minerals 

Solutions 


• Approximately the same carbon content: 

• 3% carbon 

• Therefore, similar microstructure for Class II & III : 

• 20 to 25 volume % of hard chromium carbides in a 

ferrous matrix. 

• 27% Cr developed and patented in 1917. Cr-Mo 

& Ni-Hard quickly followed. 

47


Excellent 

Minerals 

Solutions 


Microanalysis of White Cast Irons 

Cr27 

Fe-27Cr-3.0C 

Phase Vol% Cr C 

• Carbide 25 55 8.8 

• Matrix 75 18 1.1 

• Total 100 27 3.0 

(Fe,Cr) 7 C 3 

27%Cr is essentially an 18%Cr - 1.1%C tool steel 

containing 25 volume% chromium carbides 

48


Excellent 

Minerals 

Solutions 


Microanalysis of White Cast Irons 

15Cr-3Mo 

Fe-15Cr-3.0C 


• Carbide 20 47 8.7 

• Matrix 80 7.0 1.6 

• Total 100 15.0 3.0 

(Fe,Cr) 7 C 3 

15Cr-3Mo is essentially a 7%Cr - 1.6%C tool steel 

containing 20 volume% chromium carbides 

49


Excellent 

Minerals 

Solutions 

Materials: 27% Cr versus 15 Cr–3 Mo 

• Comparison of 27% Cr & 15% Cr–3% Mo 

Worn Impellers at Mexican Copper Mine 

50


Excellent 

Minerals 

Solutions 

Materials: Hyperchrome Chemistry 

Chromium 

40 

30 

20 

10 

ISO designation 

HBW600XCr35 

HBW555XCr26 

HBW555XCr21 

HBW555XCr16 

HBW555 

27Cr 

35C 

Hyperchrome 

r 

20Cr-2Mo 

15Cr-3Mo 

Nihard 4 

35Cr 

AS designation 

HBW510 

Nihard 1 

2 3 4 5 

Carbon 

51


Excellent 

Minerals 

Solutions 

Materials: Hyperchrome 

Microanalysis of WCI-4.5%C 

Fe-31Cr-4.5C 


• Carbide 48 52 8.7 

• Matrix 52 12 0.6 

• Total 100 31 4.5 

(Fe,Cr) 7 C 3 

WCI-4.5%C has a Hypereutectic microstructure 

with a high M 7 C 3 carbide content and a ferrous 

matrix containing 12 wt% chromium. 

52


Excellent 

Minerals 

Solutions 

Materials: 27% Cr versus Hyperchrome 

Effect of Carbide Content on Wear Resistance 

60 

55 

27% Cr 

W eight Loss (m illigram s) 

50 

45 

40 

35 

30 

25 

31Cr- 4.5 C 

Hyperchrome 

w/60% carbides 

20 

20 30 40 50 60 70 80 

Total Carbide Content (Volume %) 

53


Excellent 

Minerals 

Solutions 

Materials: 27% Cr versus Hyperchrome 

• Oilsands Tailings Pump Suction Side Liner: 

27% Cr: 1790 hours holed through 

Hyperchrome: 1748 hours 50% worn 

54


Materials: High Cr, Low C White Irons 

Excellent 

Minerals 

Solutions 

40 

Patent Protected 

Chromium 

30 

20 

10 

27 Cr 

Corrosion Resistant White Cast Irons 

2 3 4 5 

Carbon 

55


Excellent 

Minerals 

Solutions 

Materials: High Cr, Low C White Irons 

• 28% Chromium, Low Carbon White Iron: 

• Iron and chromium carbides in austenite matrix 

• 320 BHN minimum 

• Suitable for pH 3 to 14 

• Corrosion resistance similar to 300 series austenitic stainless steel 

• 30+% Chromium, Low Carbon White Iron (Ultrachrome-Patented): 

• Eutectic carbides in a duplex stainless steel matrix 

• 380 BHN minimum 

• Suitable for phosphoric acid duties, high chloride FGD duties, sulphuric 

acid duties and other moderately corrosive applications 

• Corrosion resistance similar to a duplex stainless steel 

56


Excellent 

Minerals 

Solutions 

Materials: 27% Cr versus High Cr-Low C 

27% Cr High Cr-Low C 

57


Excellent 

Minerals 

Solutions 

Materials: Elastomers 

• Natural Rubber versus 27% Cr in Nickel Application 

58


Excellent 

Minerals 

Solutions 


450 

400 

Wear Coefficient (m 3 /J)*10 -17 

350 

300 

250 

200 

150 

100 

50 

0 

0 200 400 600 800 1000 1200 1400 1600 1800 2000 

Particle Diameter (Microns) 

Hi-Cr Hyper-Cr Elastomer Ceramic 

Chart 12.28 from ANSI/HI 12.1-12.6 slurry pump standard 

59


Excellent 

Minerals 

Solutions 


• Utilize resilience and tear strength to combat wear 

• Resilience: 

• A measure of how high a ball of the material will drop as a percentage of 

the original drop height 

• Typically, 65 to 90 percent dependent upon the rubber blend 

• Softer rubber tends to have higher resilience 

• Tear strength (actually tear initiation resistance): 

• 30 to 110 N/mm for natural rubber dependent upon blend 

• Harder rubber tends to have higher tear resistance 

• Resilience important for fine particles ( 300 microns) 

60


Excellent 

Minerals 

Solutions 

Materials: Synthetic Elastomers 

• Used in applications where natural rubber would be subject to 

chemical attack, causing swelling, hardening or reversion 

• Common synthetic elastomers: 

• Nitrile: Fats, oils and waxes. Moderate erosion resistance. 

• Butyl: Hydrochloric acid, phosphoric acid, and sodium hydroxide. 

• Hypalon: Acid conditions 

• Neoprene: Moderate resistance to oils, fats, grease, some hydrocarbons 

and moderate oxidizing acids. Highest resilience of the synthetic 

elastomers (58%). Widely used in oilsands. 

• Polyurethane: Used in applications where there is a good chance of 

large particle, “tramp” damage. High tear strength (50 to 100 N/mm). 

May be subject to hydrolysis at elevated temperature. 

61


Excellent 

Minerals 

Solutions 


• Can be used in large particle applications where not subject to direct 

impact: Oilsands Hydrotransport Suction Side Liner 

27% Cr: 2 to 3 month life 

Hyperchrome: 4 month life 

Neoprene: 12 to 18 month life 

62


Excellent 

Minerals 

Solutions 

Materials: Tip Speed Limits 

• Tip Speed and Head Generation 

Head at BEP: 

 

(0.5)( tip speed) 

( g) 

2 

Where: tip speed: 

impeller peripheral speed in m/sec 

g: acceleration due to gravity (9.8 m/sec2) 

63


Excellent 

Minerals 

Solutions 

Materials: Conservative Tip Speed Limits 

• Tip Speed/Head Generation Limits 

Wear resistant soft natural rubber: 25.0 m/sec 32 m head 

Typical natural rubber: 27.5 m/sec 39 m head 

Anti-thermal breakdown rubber 30.0 m/sec 46 m head 

Nitrile 27.0 m/sec 37 m head 

Neoprene 27.5 m/sec 39 m head 

Butyl and Hypalon 30.0 m/sec 46 m head 

Polyurethane 30.0 m/sec 46 m head 

Hard metal (impellers) 38.0 m/sec 74 m head 

64


Excellent 

Minerals 

Solutions 


• Neoprene Suction Liner on Oil Sands Tailings Service 

437 rpm gear box & max speed 

33.1 m/sec adjacent tip speed 

454 rpm gearbox, 480 rpm overspeed 

36.4 m/sec adjacent tip speed 

65


Excellent 

Minerals 

Solutions 


Reversion of Neoprene Suction Liner @ 36 m/sec Peripheral Speed 

Compromised material properties 

Area with softened, 

“gummy” consistency 

Area with hard, 

charcoal like consistency 

66


Excellent 

Minerals 

Solutions 

Materials: Ceramics 

• Ceramic Wear Coatings: 

• Aluminum-titanium dioxide 

• Chrome oxide 

• Tungsten carbide/cobalt 

• Tungsten carbide/chromium/nickel 

• Application: 

• HVOF – bond strength? 

• Plasma - lower bond strength, prone to spalling 

• Laser etched - metallurigical bond, resistant to spalling 

• Brazed – high bond strength, resistant to spalling 

• High bulk hardness: 1400 to 1700 HV 

67


Excellent 

Minerals 

Solutions 

Geometry: Casing Types 

• Casing Types, Radial Load and Recommended Operating Ranges: 

a) True/near volute 

80 to 120 % of BEP 

b) Semi volute 

60 to 110 % of BEP 

c) Circular/annular volute 

40 to 100 % of BEP 

68


Excellent 

Minerals 

Solutions 

Geometry: Impeller Types 

• Differences between Heavy 

Duty and High Efficiency 

Impeller styles. 

• Heavy duty impellers are 

preferred for large particle 

slurries (d50 > 150 microns) 

• High efficiency impellers are 

preferred for fine particle 

slurries (d50 < 150 microns) 

69


Excellent 

Minerals 

Solutions 

Geometry: Impeller Type 

• Effect of Particle Size on Impeller Wear 

Reference: Warman Technical Bulletin 24, Figure 6 

70


Excellent 

Minerals 

Solutions 

Geometry: Impeller Type 

• Effect of Particle Size & Impeller Type on Suction Liner Wear 

Reference: Warman Technical Bulletin 24, Figure 7 

71


Geometry: Liner Wear vs. Impeller Type 

Excellent 

Minerals 

Solutions 

• Suction Side Liner Wear vs. Impeller Type and Particle Size 

HE 

Style 

Impeller 

650 μ d 85 

270 μ d 85 

150 μ d 85 

_____________________________________________________ 

Heavy 

Duty 

Impeller 

1200 μ d 85 

355 μ d85 

50 μ d 85 

72


Excellent 

Minerals 

Solutions 

Application: Slurry Factors 

• The kinetic energy of the particle: 

• Particle mass (specific gravity and size) and velocity 

• The particle shape: 

• Sharp particles have small contact area and high local stress, so wear is 

more severe than with rounded particles 

• The slurry concentration: 

• Higher percentages of solids result in more impacts for a given flow 

73


Excellent 

Minerals 

Solutions 

Application: Weir Slurry Classification 

• Heavy Duty 

• Medium Duty 

• Light Duty 

C w > 35% 

D85 > 400 μ m 

SG s > 2.0 

Sharp Particles 

20% < C w < 50% 

150 μm < D85 < 400 μm 

SG s > 1.4 

Angular Particles 

C w < 20% 

D85 1.4 

Rounded Particles 

74


Excellent 

Minerals 

Solutions 

Application: Weir Head Recommendations 

Recommended Tip Speed & Head Limits 

for Slurry Type 

• Heavy Duty: 

25 m/sec max. 32 m head @ BEP 

• Medium Duty: 


• Light Duty: 


75


Excellent 

Minerals 

Solutions 

Application: Impeller Type & Flow Range 

Recommended Impeller & Flow Range 

for Slurry Type 

• Heavy Duty: 

Heavy Duty Impeller @ 0.60 to 0.80 BEP 

• Medium Duty: 

Heavy Duty Impeller @ 0.70 to 0.90 BEP 

• Light Duty: 

High Efficiency Impeller @ 0.80 to 1.1 BEP 

76


Excellent 

Minerals 

Solutions 

Application: Proper Pump Selection 

• Copper Mine Ball Mill Discharge: 

• 400+ micron d50 particle size 

• Larger replacement pump: 

• Operation at 74% of BEP, 

instead of 95% of BEP 

• Severe, but even impeller wear 

• Longer life: 

• 2436 hours versus 1848 hours 

• > 30% improvement in life 

77


Excellent 

Minerals 

Solutions 

Application: Proper Pump Selection 

• Computer Generated Composite view of New and Worn Impeller: 

• Copper Mine Ball Mill Discharge Application 

78


Excellent 

Minerals 

Solutions 

Application: Specific Speed 

Impeller Geometry and Its Effect on Specific Speed 

• Values of Specific Speed, Ns, using m 3 /sec and meters 

Courtesy of Hydraulic Institute 

79


Excellent 

Minerals 

Solutions 


Calculation of Specific Speed: 

N Q 

N s 3/ 4 

H 

Where: 

N = pump speed in rpm 

Q = capacity in m3/sec at BEP 

H = total head per stage in meters at BEP 

80


Excellent 

Minerals 

Solutions 


Specific Speed Recommendations 

Severe duty applications: Ns of 20 to 25 

Medium to heavy duty applications: Ns of 25 to 33 

Medium duty, less than 30 meters head: Ns of 42, OK 

*Maximum efficiency occurs at Ns = 42 

81


Excellent 

Minerals 

Solutions 

Application: General Rules 

Slurry type: Heavy Duty Light Duty 

Particle size: large particle fine particle 

Head: minimize higher allowed 

Impeller type: heavy duty high efficiency 

Flow rate: below BEP (≈ 75%) near BEP 

Volute type: semi-volute true volute (if near BEP) 

Expelling vanes: aggressive smooth shrouds 

Specific speed: lower higher 

Impeller diameter: larger smaller 

Pump speed: low higher 

• Refer to presentation for more specific recommendations 

82

Download PDF - Calgary Pump Symposium

Create successful ePaper yourself

Delete template?

Save as template?