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1 st PUMP HANDS-ON MAINTENANCE AND RELIABILITY CONFERENCE Session 1: CENTRIFUGAL PUMPS ATLANTA, GA SEPTEMBER 22-23, 20 PowerPoint Presentation
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1 st PUMP HANDS-ON MAINTENANCE AND RELIABILITY CONFERENCE Session 1: CENTRIFUGAL PUMPS ATLANTA, GA SEPTEMBER 22-23, 20 - PowerPoint PPT Presentation


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1 st PUMP HANDS-ON MAINTENANCE AND RELIABILITY CONFERENCE Session 1: CENTRIFUGAL PUMPS ATLANTA, GA SEPTEMBER 22-23, 2005. Centrifugal pumps – Head generators Positive Displacement pumps – Flow generators. CENTRIFUGAL. Let’s Get to the Hardware!. PERFORMANCE CURVE - COMBINED. Max OD.

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slide1

1st PUMP HANDS-ON MAINTENANCE AND RELIABILITY CONFERENCE

Session 1: CENTRIFUGAL PUMPS

ATLANTA, GA

SEPTEMBER 22-23, 2005

Pumping Machinery, Pump School

slide2

Centrifugal pumps – Headgenerators

Positive Displacement pumps – Flow generators

Pumping Machinery, Pump School

centrifugal
CENTRIFUGAL

Pumping Machinery, Pump School

let s get to the hardware
Let’s Get to the Hardware!

Pumping Machinery, Pump School

performance curve combined
PERFORMANCE CURVE - COMBINED

Max OD

NPSHR lines

Efficiency lines

BestEfficiencyPoint line

MCSF line

BHP lines

Rated point

Min. OD

Pumping Machinery, Pump School

affinity laws what happens to flow head and power with speed
AFFINITY LAWSWhat happens to Flow, Head and Power with Speed?

Flow changes DIRECTLY (linear) with RPM…

Head changes as a SQUARE of RPM…

Power is proportional to Flow times Head – it changes as CUBE of RPM…

Q ~ RPM

H ~ RPM2

BHP ~ RPM3

Pumping Machinery, Pump School

more affinity laws
More Affinity Laws…

When impeller OD is trimmed – Flow, Head and Power follow the Affinity Laws very similar to the case of speed change:

ODold

Q ~ x

H ~ x2

BHP ~ x3

ODnew

where x is a cut ratio: x = ODnew/ODold

(Note: additional correction applies for cuts over 10%)

Pumping Machinery, Pump School

let s test some pumps
Let’s test some pumps!

Pumping Machinery, Pump School

slide10

a SYSTEM CURVE

System Hydraulic Losses

Friction (hf)

hf ~ V2/2g

Static (h0)

Flow

Pumping Machinery, Pump School

parallel operation
Parallel Operation

Head

Flow

500

500x2 = 1000

Pumping Machinery, Pump School

it depends on a system
It depends on a System!

1000 ft (static head)

… long pipe, elbows, valves – a lot of friction…

Case B

Case A

Pumping Machinery, Pump School

case a mostly static head
Case A – mostly static head

Head, ft

h0 = 1000 ft

Flow, gpm

500

500x2 = 1000

Pumping Machinery, Pump School

case b mostly friction
Case B – mostly friction

If the system can not handle it – more pumps will not add any more flow!

Head, ft

Flow, gpm

1000

500

550 !?

Pumping Machinery, Pump School

suction characteristics cavitation npsh
SUCTION CHARACTERISTICSCAVITATION, NPSH

Basically, if there is not enough pressure – liquid boils!

Pumping Machinery, Pump School

slide17

In your kitchen, the water boils at 100 oC (212 o F)

– and that is at atmospheric pressure

If pressure drops, the water will boil at lower pressure

On top of high mountain water boils at perhaps 95 oC ?

Pumping Machinery, Pump School

npsh definition
NPSH DEFINITION

NPSHA = available

NPSHR = required

NPSHA is a total available suction pressure - over the vapor pressure - (expressed in feet of head). In other words, it is Net Suction Head minus vapor pressure (expressed as head)

NPSHA is NOT simply the level of liquid in the suction tank…

Pumping Machinery, Pump School

slide19

A lot of bubbles…

More bubbles…

Incipient

Head, ft

3%

NPSHR3%

NPSHA, ft

Pumping Machinery, Pump School

npshr
NPSHR

With suction pressure dropping, a point may be reached that liquid starts to transform into vapor somewhere inside the pump.

This is not good.

But how bad is bad?

Hydraulic Institute define the NPSHrequired as such value of NPSHR when a pump losses 3% of its developed head. They call this NPSHR3%

For simplicity, they just write it as NPSHR, implying 3%

Pumping Machinery, Pump School

cavitation damage
CAVITATION DAMAGE

Too many candies makes kids hyper.

But it also ruins their teeth.

Pumping Machinery, Pump School

impeller inlet blades cavitation on a suction side
Impeller inlet – blades cavitation on a suction side

As bubbles flow from low pressure to higher, they implode against metal surfaces. These micro-hammer-like impacts erode the material, creating cavities – thus “cavitation”

Pumping Machinery, Pump School

slide23

Good ways to fight suction problems:

  • Make sure a pump is as close to suction source as possible
  • For double-suction pumps, suction valve stem should be oriented for symmetrical feed flow
  • Smaller eye impeller (lower suction specific speed) can help
  • Inlet sump design – critical: vortexing and air entrapment could be a nightmare
  • Metallurgy – 316ss stainless work-hardens, while iron does not very long

Pumping Machinery, Pump School

sealing methods
SEALING METHODS
  • PACKINGS: inexpensive, but - 10 drops per minute
  • MECHANICAL SEALS: most popular, 10 “drops” per day
  • SEAL-LESS: more expensive, but - zero leak
    • CANNED MOTORS
    • MAG-DRIVES

Pumping Machinery, Pump School

packings courtesy durametallic seal manual
PACKINGS(courtesy Durametallic Seal Manual)

Packed Box

Pumping Machinery, Pump School

mechanical seals
MECHANICAL SEALS
  • SINGLE
    • INSIDE
    • OUTSIDE
  • MULTIPLE
  • Unbalanced, balanced, single-spring, multiple-spring, pusher, non-pusher, variety of elastomers, face materials, and hardware materials.
  • Variety of flush plans.

Pumping Machinery, Pump School

slide27

Single Mechanical Seal, multiple springs, unbalanced

(Courtesy Durametallic)

Pumping Machinery, Pump School

slide28

Double Mechanical Seal, multiple springs, unbalanced

(Courtesy Durametallic)

Pumping Machinery, Pump School

slide29

(Courtesy Durametallic)

Pumping Machinery, Pump School

slide30

(Courtesy Durametallic)

Pumping Machinery, Pump School

mag drive pumps courtesy of goulds pumps
MAG-DRIVE PUMPS(Courtesy of Goulds Pumps)

Pumping Machinery, Pump School

pumps and systems reliability
Pumps and Systems Reliability

Pumping Machinery, Pump School

types of misalignment

Horizontal Offset

Horizontal Angularity (Yaw)

Motor

Motor

Pump/Fan/Gearbox/Etc.

Pump/Fan/Gearbox/Etc.

Vertical Angularity (Pitch)

Vertical Offset

Motor

Motor

Pump/Fan/Gearbox/Etc.

Pump/Fan/Gearbox/Etc.

Types of Misalignment

Pumping Machinery, Pump School

effect of water on bearing life

250%

200%

Water in Oil (ppm)

150%

100%

50%

0%

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

Rated Bearing Life

Based on 100% life at 100 ppm water

Effect of Water on Bearing Life

One PPM is one milligram per kilogram.

Pumping Machinery, Pump School

pump to piping alignment
Pump-to-Piping Alignment

Step 1: Pre-installation stage (pump may not have even arrived to site yet) – anchor the main piping properly. Leave room for the final spool pieces (to be made later) by the pump.

Pumping Machinery, Pump School

slide36

Step 2: Rough alignment phase. Pump has arrived. Position it and make spool pieces.

Pumping Machinery, Pump School

slide37

Step 3: Remove all equipment. Level the baseplate to 0.025” from end to end. Clean up and get ready for the grouting.

Pumping Machinery, Pump School

slide38

Step 4: Grouting phase.

Pumping Machinery, Pump School

slide39

Step 5: Reinstall the pump and a motor on a baseplate. Inspect and make sure nothing is binding up.

Pumping Machinery, Pump School

slide40

Step 6: Rough align pump to a motor.

Pumping Machinery, Pump School

slide41

Step 7: Make up final spool pieces.

Pumping Machinery, Pump School

slide42

Step 8: Install the spool pieces between piping and a pump. Leave gaps (1/16” – 1/8”) for the gaskets. This gap is the only distance the piping will be pulled during final bolting, and stresses will be minimal. (The pump will thank you for that).

Pumping Machinery, Pump School

slide43

Step 9: Final alignment of a motor to pump.

Pumping Machinery, Pump School

slide44

Step 10: Final piping verification. Unbolt the pump from the driver. Loosen up piping bolts and retighten. Indicator should not move more then 0.002”. Otherwise modify, adjust or remake spool pieces.

Pumping Machinery, Pump School

pumps troubleshooting
Pumps Troubleshooting
  • Startups
  • Troubleshooting
  • Repair and Overhaul

Note of acknowledgmentisdueto my friend Mr.. JimBrennanof IMO/Colfax, and his excellent articles on pumps startup, troubleshooting and overhaul, published in Pumps & Systems magazine over the years. Jim has over 30 years experience in the pump industry, and is active in various pump committees and organizations. Much of this information was based on his recommendations, as well as our numerous and continued discussions and friendly debates over the years.

Pumping Machinery, Pump School

startups
Startups
  • Most vulnerable time for pumps
  • Read technical manuals and instructions thoroughly
    • Pump
    • Driver
    • Auxiliaries
  • Review piping and valving first
    • Backwards?
    • Absent?
    • No weld beads, no weld rods, no scale
    • Temporarily strainers
    • Permanent strainers
    • Clean start conditions

Pumping Machinery, Pump School

startups cont
Startups – cont.
    • Was piping pressure tested? Design limits observed?
    • Low pressure air to find gasket leaks
    • Check and tighten flange bolts to correct values
    • Is inlet piping straight for long enough distance?
    • Is piping adequately supported? Is your pump condemned to be an anchor?
  • Pressure relief valves present?
  • Entire system should be flushed – by a temporarily pump
    • At least 24 hours
    • Higher flow rates to dislodge junk
    • Some junk may remain for 30 days or more
    • “Pigs” sometimes use to get pipes clean

Pumping Machinery, Pump School

startups cont48
Startups – cont.
  • Make sure valves that should be open – are open
  • Make sure valves that should be closed – are closed
  • Air bleed installed at high point?
  • Observe, and exercise caution
  • Foundation, Alignment and Rotation
    • Level and clean
    • Hold-down bolts tight
    • Cold or Hot alignment
    • Dowelled in-place?
    • Direction of rotation?

Pumping Machinery, Pump School

startups cont49
Startups – cont.
  • Lubrication – is everything greased or oiled?
  • A person should be able to turn over almost all pumps by hand
  • Startup spares
    • Elastomers and gaskets
    • Bearings
    • Seals
    • Critical parts
  • Pressure gages – without them you are working blind
  • How will you verify flow?
  • Speed tachometer
  • Temperature

Pumping Machinery, Pump School

startups cont50
Startups – cont.
  • Fill the pump and inlet piping as much as possible
  • Do not run dry
  • Have safety phone numbers on hand: key vendors, medical, fire, etc.
  • Err on a safe side

Pumping Machinery, Pump School

troubleshooting
Troubleshooting
  • Skill takes time to develop
  • Pump may be a cause of a symptom
  • Regulations may have additional safety precautions
  • Make sure suction and discharge gages are available
  • Verify pump speed
  • Verify motor amps, voltage and power factor
  • Make sure drivers are locked before doing any inspection
  • Information gathering
    • What is different from when it ran fine?
    • When was the last maintenance work done? What was done?
    • How do things look?
    • Get the basics: inlet and discharge pressure, flow, speed, liquid, temperature, viscosity, duty
  • Noise?

Pumping Machinery, Pump School

troubleshooting52
Troubleshooting
  • Rotation
  • Loss of suction
  • Loss of developed head
  • Wear
  • By-pass
  • Viscosity
  • Pulsations, vibrations, noise
  • Amps and power
  • Trending
  • Hydraulics, mechanics, electrics

Pumping Machinery, Pump School

repair and overhaul
Repair and Overhaul
  • Who does it?
    • In-house
    • Manufacturer
    • Third party
  • Cleary identify the scope
    • Sanitary specifications, MSDS sheets, safety
    • Testing (compatible liquids)
    • Failure analysis
    • Report
      • Words
      • Sketches and drawings
      • Analysis
      • Recommendations
  • Costs

Pumping Machinery, Pump School

document and record an example of data records courtesy julien lebleu p s publication may 2004
Document and Record !an example of data records, courtesy JuLien LeBleu, P&S Publication, May 2004

Pumping Machinery, Pump School

repair and overhaul cont
Repair and Overhaul – cont.
  • Steps:
    • Condition report, as received
    • Review MSDS sheets and be safe
    • Disassembly
    • Thoroughly cleaning
    • Inspection to determine parts condition:
      • Scrap
      • Rework
      • Clean and reuse
    • Written inspection report
    • New unit versus repair
    • Test if required
  • Time factor
  • Preservation for storage

Pumping Machinery, Pump School