Weird and Wonderful Pump Failures - Calgary Pump Symposium

Weird and Wonderful Pump
Failures
Or:
It was not so wonderful at the time but I did
learn something.

Topics
1. Reactor Feed Pumps
2. Wash Water Pumps
3. Amine Pumps
4. Fertilizer Plant pump
5. Sulphur Transfer Pump
6. Stripper Sour Water Pump
7. Low Flow Recirculation
8. Foreign Objects

1: Reactor Feed Pumps
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Three 100% pumps, two are steam drive, one is electric drive.
Typically the steam drives are running (1 per train) with
electric drive on stand-by.
Pumps are 8 stage 3” IJ’s, BB5 design
Single bellows style seal with SC rotating face, TC stationary
face,
Plan 32 seal flush (66 °C gas oil) and Plan 62 steam quench
Tilt pad axial and radial bearings, full vibration probe suite

14.6 ft

Reactor Feed Pumps
o 1304 KW at 5600 rpm
o Rated Flow: 140 m3/hr (616 gpm)
o Rated Head: 2201 m (7221 ft)
o Discharge Pressure: 20,021 kPag (2903 psig)
o Normal temperature: 232 C (450 F)
o Max. Temperature: 288 C (550 F)
o NPSHa: 13 m (42 ft)
o NPSHr: 11 m (36 ft)
o Material class is API A-8 (316 AUS) but case is carbon steel
with 316L cladding

Reactor Feed Pumps
3000
NOTE FLAT SLOPE
HEAD and PWR
2500
2000
1500
1000
Min. Flow
Rated Point
500
0
0 20 40 60 80 100 120 140 160 180 200
FLow (m3/hr)
HEAD (m)
PWR (kW)

Start-up and Operation issues:
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When units are started for the first time (at minimum flow)
the vibration levels and performance are acceptable.
But after being in service for a couple of weeks one of the
units goes down on high vibration.
Teardown shows rubbing damage to wear-rings and balance
bushing, some loose case wear rings, and
movement of the 7’th stage impeller away from suction then
back towards suction into the diffuser ring.

Back of 7’th stage impeller and 7’th stage
diffuser

Start-up and Operation issues:
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Initial failure is thought to be due to breakdown of the wearring
material and internal rubs caused by poor warm-up
procedures, hot misalignment, and cavitation.
This leads to a great deal of work doing hot alignment and
base deflection measurements with lasers, baseplate grouting
repairs, warm-up piping and procedures mod’s etc.
The initial failed unit is re-built with the wear ring coatings
applied using a different process and the Operations staff are
told to monitor/control the warm-up process better.

Start-up and Operation issues:
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There are more failures of a similar nature…..even on the first
unit with the repaired base-pad, the tighter warm-up controls
and more accurate hot alignment.
Other issues with the units are discovered
• Seal failures due to poor balancing of seal flush rates to
each end of the machine…the piping gets changed.
• More insulation is added to the casing, balance line loop
and warm-up piping to prevent blockage.
• Modifications to warm-up piping are proposed to improve
flow control when units are cold but never implemented.

Start-up and Operation issues:
o
• Seal face damage due to wet quench steam flashing inside
the seal. Additional steam traps are added.
• The anti-rotation keys at each case ring are increased in
length to positively clamp the rings in place axially.
• Lube oil water contamination caused by steam leaking
from the turbine glands (2-3 gallons/day) fixed by
installing In-Pro seals on the bearing housings.
After a few more failures, sometimes 7’th stage, sometimes
8’th stage we finally started to zero-in on the main failure
cause…..

Start-up and Operation issues:
o
The minimum flow control system
• During normal operation the closed minimum flow valve
would cool off and not open properly when forward flow
to the process was cut back at the fired heater.
• The small filters in the pump discharge flow meter purge
oil system would continually plug up taking the flow
meter off-line or make the measurement in-accurate. The
operators had to manually control the min-flow valve with
absolutely no information as to the actual pump flow rate.
• The pump discharge pressure at less than min-flow was
enough to force the min-flow valve closed. The actuator
was not sized big enough to keep the valve open!

Summary
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We got caught up believing the drop in flow was caused by
damage in the pump when it was actually the other way
round….the drop in flow (dead-heading) was causing the
pump damage.
When the min-flow control system was fixed the pump
reliability went way up.
Keep going back to the physical evidence….the backward
moving impellers should have focused us to a hydraulic
cause.

2: Wash Water Pumps
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Three 100% pumps, One for each train, one spare.
Electric drive with gearbox reduction to 203 rpm
Pumps are 3 3/8 X 6 VTEM vertical triplex recips
Class S-1 design, sour specification for fluid end
Sleeve bearings, forged crank, aux lube oil system
Two amine pumps are similar design but different operating
speed.

Wash Water Pumps
o 300 hp at 203 rpm
o Rated Flow: 30.5 m3/hr (616 gpm)
o Suction Pressure: 340 kPag (49 psi)
o Discharge Pressure: 18,453 kPag (2676 psig)
o Normal temperature: 95 C (203 F)
o Max. Temperature: 98 C (208 F)
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NPSHa: 27 m (88 ft)
NPSHr: 15 m (49 ft)

Wash Water Pumps
o Numerous issues from day 1
• Packing leaks due to poor
plunger and push rod
alignment
• Poor valve life
• Broken crankshafts due to
fatigue initiating at hotshort
tears in forging
• Cracked fluid head
allowing water into
crankcase

Wash Water Pumps
o
Failure of forged pressure head

Wash Water Pumps
o Failure of forged pressure head

Wash Water Pumps
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Major review conducted of operating history and
head design including FEA by OEM
Fortunately we had lots of pressure data due to valve
performance and cavitation studies.

Wash Water Pumps
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Results of studies show that pump should be
safe from fatigue failures even at off-spec
operating conditions.
So why did the block fail?
HINT---The FEA analysis was based on the
OEM’s drawings for the head.

Wash Water Pumps
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Dimensional checks of the failed head showed that the radius
at the bottom of the suction valve pocket was smaller than
design by 1/8 inch!

Wash Water Pumps
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Using the actual radius in the FEA model indicated
that fatigue was possible.
Suspect that the machinist used the wrong size tool
when the suction valve pockets were being machined
All similar heads on site checked… one other head
had to be replaced.
Considered shot-peening the radius area to improve
fatigue resistance but no further failures occurred.

3: Amine Pumps

Amine Pumps
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Lean Amine API Type BB3 pumps protected by three
shutdown systems:
• Low feed drum level
• Low discharge pressure
• High vibration
Nuisance trips cause changes to controls:
• The low discharge pressure SD is removed for start-up but
not reinstated after start-up
• The low level trip on the feed drum is tied to the pump
shutdown.
• High vibration SD’s changed to 2 out of 2 voting
• Vibration SD set points raised
No one caught that the vibration levels were set too high.

Amine Pumps
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Residence time in the feed drum is very short
Low level trip was lowered to 2% from 15% to prevent
nuisance pump shutdowns
Level transmitter sensing legs were equalized with glycol
The glycol in the sensing legs became unbalanced, and
indicated a higher feed drum level than what there actually
was and the pump ran dry
Another incident elsewhere in the plant took the operators
attention away from operating the plant to shutting the plant
down

Amine Pumps
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Outside operator attempted to shut down the operating pump
because it was “making noise”
The control system auto-starts the second pump and shortly
thereafter it starts making a loud noise too.
Vibration instruments did not shut the pumps down.
“Pinning out” the local start button successfully stopped these
pumps.
Remarkably, both pumps were still capable of moving liquid
when drum level was restored.

First rotor, 1’st stage impeller warped and
cracked

First rotor, 2’nd stage impeller thrust
damage

First rotor, general condition of the
case

Second rotor, 2’nd stage impeller thrust
damage, broken wear rings

Second case, bottom half wear ring land
damage

Second rotor, impeller keyway damage

Amine Pumps
Removal and repairs began within 2 days.
Pumps were repaired in tandem utilizing two repair shops,
both shops working 24 hours per day.
Extensive weld repairs needed for cases and impellers
New shafts, wear rings, and bearings installed
A temporary 14 stage rental pump was installed in case there
was an issue with any of the repaired pumps. Skid pump was
never operated.
Pump repair was 16 days stream to stream
Rental pump installation was completed in 14 days.
AN AMAZING AMOUNT OF WORK IN A SHORT TIME
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Rental pump installation

Rental pump installation is ready for
service

4: Fertilizer Plant
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1,500 hp double suction pump running at
3,600 rpm. Double volute
Pump design used extensively in Europe with
very good reliability in similar service
Original impeller is 6 vane design
o Impeller and/or shaft failure approx every 6
months

Impeller Damage

Fertilizer Plant
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Change to 6 staggered vanes and very large radius on keyway
under impeller ….increased life to approx 4 years
Further change to 7 vane staggered and profiled case
cutwaters …. problem has basically gone away.
Thoughts on the service/pump:
• very high energy pump
• 6 vanes and double cutwater, a common European design,
often leads to very large pressure pulsations
• pump initially designed and checked for 50 Hz power
(3000 rpm) but not for 60 Hz (3600 rpm)

5: Sulphur Transfer Pump
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Two vertical centrifugal VS4 style pumps installed in vessel.
“A” pump top bearing deterioration detected by periodic
vibration monitoring
Switched to stand-by “B” pump but very little flow
developed. “B” unit had not been operated for 12 months

Sulphur Transfer Pump
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Pulled “B” pump and found extensive blockage due to chunks
of 3/8 to 3/4 inch sulphurcrete in the impeller and suction.
The original strainer was designed with maximum perforation
of 1”.

Sulphur Transfer Pump
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Raise the pump suction 3 feet by
shortening the column
increase the normal liquid level in
vessel to 20% to maintain NPSHa
at required value.
pump strainer re-designed to block
particles larger than 3/8”
Operating procedure put in place to
switch pumps on a fixed schedule

6: Stripper Sour Water Pump
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Corrosion found on 4140 shaft near stuffing box and
on case wear ring seats of the A216 casing halves

Stripper Sour Water Pump
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Corrosion mechanism is probably related to
selenium concentration…not normally expected in
this process.
Suspect that upstream oil sand feed is responsible
Upgraded the shaft components as follows:
• – Base material to 12Cr.
• – HVOF coated

7: Low Flow Re-circulation
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Ansi 1 X 2 -10 condensate pump
2 years of operation at high head – low flow
2 thrust bearing failures in 2 years
Pulled impeller and found ¼ inch metal loss
due to improper adjustment
Strong evidence of discharge recirculation

Low Flow Recirculation

Low Flow Recirculation

8: Foreign objects

Foreign objects

Comment
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Some say failure analysis is easier now because of the sophisticated data
collection and trending tools we have.
To this I say ……

Comment
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Some say it is failure analysis is easier now because of the sophisticated data
collection and trending tools we have.
To this I say ……

My thanks to:
o
Chris Gilmour
o
Jim Dziadyk
o
C. Dale Alleyne
o
Frank DiRocco
o
Brad Hatton
o
John Hogan
o
Scott Masterson
o
Gordon Lawrence
o
Matt Pickard
o
David Goddard
o
Hector J. Amaya
for providing pictures
and information for
this presentation!