au0340 pump troubleshooting pocket assistant_replacement front cover_lores.pdf

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Pump Troubleshooting Pocket Assistant

™



Table of Contents Table of Contents

Pump Troubleshooting Symptoms

Hopper Overflows 1

Overheating or seizure of pump 2

Short bearing life 3

Vibration & noise from pump 4Packing has short life 5

Leakage from stuffing box 6

Excessive motor power required 7

Pump loses prime 8

Insufficient pressure 9

Reduced discharge delivery 10

Failure to discharge 12

Pump Troubleshooting for Glands

Problem | Cause | Solution 13

Basic Pumping Formulae

Calculating quantity to be pumped from weight of solids 16

Calculating slurry sg (sm) 17

Calculating slurry Cv (solids concentration by volume) 17

Durand’s settling velocity chart 18

Calculating average velocity through a circular pipe 19

Calculating limited settling velocity 19

Calculating static head 20

Copyright © 2011, Weir Minerals Australia Ltd. All rights reserved.

CAVEX, WARMAN, HAZLETON and MULTIFLO are registered trademarks of Weir Minerals Australia Ltd; LEWIS PUMPS is a registered trademark of Envirotech PumpsystemsInc; GEHO is a registered trademarks of Weir Minerals Netherlands bv; FLOWAY is a registered trademark of Weir Floway Inc.; VULCO is a registered trademark of Vulco S.A.;

ISOGATE is a registered trademark of Weir do Brasil Ltda; LINATEX is a registered trademark of Linatex Limited (UK).”



1

Pump Troubleshooting

2


SYMPTOMS - Hopper Overows

Pump not primed

Excessive amount of air or gas in liquid

Inlet of suction pipe insufficiently submerged

Blocked suction line

Suction valve closed

Inlet pipe diameter too small or length of inlet pipe

too long

Speed too slow or wrong direction of rotation

Coupling or drive belts not transmitting power

Total head of system higher than design

Specific gravity of liquid different from design

Entrained air in pump, pump hopper requires baffles

Badly installed pipe line or gaskets partly blocking pipe

Foreign matter in impeller

SYMPTOMS - Overheating or seizure o pump

Pump not primed

Insufficient margin between suction pressure and

vapour pressure

Operation at very low capacity

Drive misalignment

Lack of lubrication

Improper installation of bearings

Rotating part rubbing on stationary part

Impeller out of balance, resulting in vibration

Excessive thrust caused by a mechanical failure inside the

pump

Excessive amount of lubricant in bearing housing causing

high bearing temp



3


4


SYMPTOMS - Short bearing lie

Drive misalignment

Shaft bent


Bearings worn

Impeller out of balance, resulting in vibration

Shaft running off-centre because of worn bearings or misalignment

Lack of lubrication

Excessive amount of lubricant in bearing housing causing high bearing temp

Improper installation of bearings

Dirt getting into bearings

Rusting of bearings due to water getting into housing

SYMPTOMS - Vibration & Noise from Pump

Pump or suction pipe not completely filled with liquid

Suction lift too high

Insufficient margin between suction pressure and vapour pressure

Foot valve too small

Foot valve partially clogged


Operation at very low capacity


Drive misalignment






5


6


SYMPTOMS - Packing has short life

Misalignment

Shaft bent

Shaft or shaft sleeves worn or scored at the packing

Packing improperly installed


Gland sealing water flow inadequate due to worn shaft seal components

Gland sealing water pressure inadequate

Dirt or grit in sealing liquid, leading to scoring shaft sleeve

Expeller worn or blocked

Excessive clearance at bottom of stuffing box, forcing packing into pump

SYMPTOMS - Leakage from stuffing box

Misalignment

Shaft bent

Shaft or shaft sleeves worn or scored at the packing

Packing wrong size


Incorrect type of packing for operating conditions


Gland sealing water pressure too high causing packing extrusion

Dirt or grit in sealing liquid, leading to scoring shaft sleeve

Expeller worn or blocked

Excessive clearance at bottom of stuffing box, forcing packing into pump



7


8


SYMPTOMS - Excessive motor power required

Speed too high

Wrong direction of rotation


Total head of system lower than design

Specific gravity of liquid different from design

Viscosity of liquid differs from that for which designed

Misalignment

Shaft bent



Gland too tight, resulting in no flow of liquid to lubri cate packing

SYMPTOMS - Pump loses prime




Air pocket in suction line

Air leaks into suction line

Air leaks into pump through stuffing box




Inlet pipe diameter too small or length of inlet pipe too long

Entrained air in pump. Pump hopper requires baffles




9


10


SYMPTOMS - Insufficient pressure


Speed too slow





Impeller damaged or worn

Casing gasket defective, permitting internal l eakage


SYMPTOMS - Reduced discharge delivery



Insufficient margin between suction pressure and vapour

pressure



Air leaks into suction line

Air leaks into pump through stuffing box

Foot valve too small

Foot valve partially clogged





11


12


SYMPTOMS - Reduced discharge delivery (cont)


Speed too slow - slippage of vee belts

Speed too slow – incorrect size pulleys

Speed too slow – incorrect “pole” of electric motor

Speed too high

Wrong direction of rotation






SYMPTOMS - Failure to discharge

Pump not primed



Insufficient margin between suction pressure and vapour pressure





Speed too slow


Impeller damaged or worn




13

Pump Troubleshooting - Glands

14

Pump Troubleshooting - Glands

Problem Cause Solution•Short packing lie

•Short sleeve lie

•Slurry exits gland

•Slurry wears packing

•Slurry wears shat sleeve

•Packing over heating and burning

due to low GSW pressure

• Increase gland sealing water (GSW) pressure

• Increase GSW owrate

•Loosen gland to increase ow

•Stop, cool down, repack and then restart with

correct GSW pressure and ow

•Flow rom gland too

low, in worst case

steam exits rom gland

•Pressure too high causing packing

extrusion and ow restriction

•Gland too tight

•Packing too sot or high pressure

•Stop, cool down, repack and then restart with

correct, GSW pressure and ow

•Loosen gland

•Review packing type

•Use packing retainer ring

•Reduce GSW pressure

•GSW ows around

outside o packing rings

•Packing rings wrong size or ft-up

wrong

•Repack gland with correct packing

•Review order o assembly

•Too much ow rom

gland

•Shat sleeve worn

• Wrong size o packing

• Worn packing

•Disassemble and reurbish gland with new parts

Caution1. On no account should the gland be loosened to such an extent that it disengages from the stuffing box.

2. Putting more things into a stuffi ng box when problems occur will only be a short-term fix. Extra packing will exacerbate any general wear and

eventually lead to excessive leakage.

3. Corrosion by saline GSW may be minimised by the use of appropriate alloys. The leakage of saline GSW from the gland must be trapped and

conveyed to waste to avoid corrosion of the pump base and other components.

Steps for the correct fitting of packings into the stuffing box.

1. Packing is normally available in pre-cut and formed rings, or alternatively the user can cut rings from a roll.

2. It is critical that each packing ring is cut to the correct length.

3. The packing cut should be at an angle of 450, ie, a scarf joint.

4. The packing should fill the annulus. A length of key steel or similar should be used to push the packing into

the stuffing box. Care should be taken to start fitting the packing on the joint side and then work around the

ring to the opposite side. This should prevent stretching the ring, which could lead to overlap at the cut.

5. The packing should push in easily. If not, check the section dimensions. If incorrect the packing should be

replaced. Do not roll formed rings.

6. Each packing should be tamped into position before fitting the next packing. Optimum arrangements for multiple rings of packing are shown below.

7. When all packing rings have now been fitted, assemble the gland and nip the bolts to flatten packing rings

evenly. Do not tighten fully.

8. Run the pump. If excessive leakage occurs, tighten the bolts slightly and leave for at least an hour. Repeat

if excessive leakage continues. Note that a good steady even drip or constant stream is desirable to cool and

lubricate the gland.

PACKING CUT

DETAIL

450

GLAND

PACKING

4 RING ARRANGEMENT 3 RING ARRANGEMENT



15


16


Calculating quantity to be pumped from weight of solids

Weight o solids in slurry = 65 tonnes (at SG = 2.65/hr)

Weight o volume o water = 65 = 24.5tequal to solids volume 2.65

Weight o water in slurry = 70% x 65t = 151.7t

o 30% Cw 30%

Total weight o equal volume = 24.5 + 151.7 = 176.2t/hr o water to slurry

Given 1 tonne o water = 1m3

then slurry ow = 176.2m3/hr = 49 litres/second

Example: Sand slurry

65 tonnes per hour of sand

Solids SG = 2.65

Particle d50 = 211mm

Cw of solids = 30%

Zd static discharge head = 20m

zS

Dz



17


18


Calculating slurry sg (sm)

Total weight o slurry = 65t solids + 151.7t water = 216.7t/hr (from previous calculation)

Total weight o equal volume = 24.5 + 151.7 = 176.2 t/hr o water to slurry

Sm = actual weight of slurry

weight o equal volume o water = 216.7tph176.2tph

= 1.23

Calculating slurry Cv (solids concentration by volume)

For Cv apply a simple ormula:Cv = [(Sm - Sl) / (S-Sl)] x 100

= [(1.23 - 1) / (2.65 - 1)] x 100= [0.23 / 1.65] x 100

Cv = 13.9% (solids concentration by volume)

Durand’s SettlingVelocity Chart

Where:

Sm = SG mixture

SI = SG liquid

S = SG solidsd

50= AVERAGE PARTICLE SIZE μm

EXAMPLE:

VALUES OF FL

FOR

D50

= 0.6mm

Cv

= 5% TO 40%



19


20


Calculating static head

Static head is the dierence in vertical heighto the inlet liquid level and the dischargeliquid level at the air interace.

It is given by the formula:Z = Zd - Zs

Where: Zd and Zs are the static discharge head from pump centreline to discharge liquid level and static inlet (suction) head from pumpcentreline to inlet liquid level respectively. Suction Lift applications have negative valuesfor Zs.

In this instance, by substitution:Z = 20 - 1

= 19 m

Calculating average velocity through a circular pipe

V = (Q X 1273) / d2

= (49 x 1273) / 1502

V = 2.8 m/s

Calculating limiting settling velocity

VL = FL 2gD (S -Sl)Sl

= 1.04 x [2 x 9.81 x 0.15 ((2.65-1)/1]

VL = 2.3 m/s

Therefore, the 150mm pipe is suitable as:

V > VL (ie 2.8 m/s actual velocity > 2.3 m/s settling)

Where:

V = flow velocity m/s

Q = flow rate in l/s

d = pipe diameter in millimetres

Durand’s Formula:

VL = FL 2gD (S -Sl)Sl

Where:

VL = critical velocity m/s

FL = Durand’s Settling Factor (from chart)

g = gravitational constant

D = pipe inside diameter m

S = SG solids

Sl = SG liquid

zS

Dz



Weir Minerals Australia Ltd

Tel: +61 2 9934 5100

Fax: +61 2 9934 5201

www.weirminerals.com

1 Marden Street

Artarmon NSW 2064

Australia

ExcellentMineralsSolutions

AU0340 01.03.11

au0340 pump troubleshooting pocket assistant_replacement front cover_lores.pdf

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