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Centrifugal Pump Isolation
Hazards:
Case Histories and
Prevention MethodologiesPeter N. Lodal
Eastman Chemical Company
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What is a B.L.E.V.E.?
BoilingLiquid
Expanding
VaporExplosion
Boiling liquid expanding vapor explosion, oftenreferred to by the acronym BLEVE, is a phenomenonwhich occurs when a vessel containing a pressurizedliquid substantially above its boiling point is ruptured,releasing the contents explosively.
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Heat
P
Liquid
Vapor
PressureIncreases
Temperature
Increases
T
What Causes a BLEVE?
ClosedSystem
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Heat
P
Liquid
Vapor
PressureRapidlyDecreases
LiquidFlash
Vaporizes
VesselRuptures
1600xVapor
Volumetric
Expansion
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What can BLEVE?
Tanks External pool fire If flammable, fireball is enormous
Hot water heaters BLEVE does not necessarily involve flammables
Drums
External pool fire 15-20 minutes Launch
Cylinders Launch like a missile
Railcars External pool fire
Launch over 1 mile in the air Pumps
Running isolated (suction & discharge closed) As little as 20-30 minutes
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Case 1
Sludge Pump
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Case 1:Description of Incident
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A loud sound was heard and a 20 foot long white to
whitish-gray cloud was seen in the area ofSludge Pump.
Inspection showed Pump was fractured and small pieceswere found as far away as 35 feet. Pump suction and
discharge valves were found closed and the local pump
run switch was found in the auto position.
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Case 1: Data
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Pump suction & discharge valves were closed.
Pump local hand switch was set in Auto.
DCS was set telling the pump to run. Electrical evaluation of the pump power breaker
indicated the pump was running until some incident
tripped the breaker.
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Case 1: Data (continued)
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Pump fracture analysis suggests
approximately 200-210 psig pressure was
generated.
Pegged pressure gauge on pump dischargesuggests pressure reached 200-210 psig.
Vapor pressure data suggests temperature
required to reach 200-210 psig was
approximately 230 C.
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Case 1: Data (continued)
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Differential Scanning Calorimeter (DSC) on actual
pump sample showed no exotherm until 376 C.
Autoignition temperature on actual pump sample was
measured at 485 C.
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Case 1:Conclusions
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No evidence of deflagration.
Material does not appear to be thermally
sensitive at our temperatures.
Autoignition does not appear to be credible.
Root Cause -- Pump was inadvertently started by
DCS and left running with process material
blocked into the pump head which built upenough temperature to raise the vapor pressure
to 200-210 psig which caused the pump to fail.
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Case 2
Caustic Pump
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Case 2: Data
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Pump suction & discharge valves were closed.
Pump was inadvertently started when operator threw
a hand switch thinking it was for a ventilation fan.
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Case 2: Conclusions
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Material was non-flammable, so deflagration
was ruled out.
Root Cause = Pump was inadvertently startedand left running with process material blocked
into the pump head which built up enough
temperature to raise the pressure to a point
which caused the pump to fail.
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Case 3
Condensate Pump
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Case 3: Data
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Pump suction & discharge valves were closed during
a power interruption and system shutdown.
Pump was started remotely 3 days after the
shutdown.
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Case 3: Conclusions
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Material was non-flammable, so deflagration
was ruled out.
One 5-lb piece of the casing was found 400
feet from the pump installation.
Root Cause = Pump was started
automatically and left running with
condensate blocked into the pump head
which built up enough temperature to raise
the pressure to a point which caused the
pump to fail.
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Common Features
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1. Complete Isolation (Suction and Discharge Blocked),not deadheaded (discharge only blocked).
2. Fluid Filled
3. Remote Start Capability4. Seal Failure did not provide adequate pressure relief
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Case Pump Summaries
Case 1 3500 RPM, 15 HP,
140 psig
Organic Acids &decomposition
solidsCase 2 1750 RPM, 10 HP,
55 psig
50% Sodium
Hydroxidesolution
Case 3 2600 GPM, 75 HP,
110 psig
Steamcondensate
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Conclusions
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Pump Explosions can occur with completely isolatedfluids, even when those fluids are non-flammable
Damage potential increases as horsepower increases(increasing inability to dissipate energy)
Seal failure as a relief mechanism is NOT a safeassumption
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Recommendations
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So, what are the best ways of preventing pumpexplosions?
1. Use local start only (remote shutoff is not an issue)
2. Avoid the ability to isolate the pump
Lock open or remove valves on the suction and/or discharge
3. Train operators on the significance of this issue
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Centrifugal Pump with Remote Stop
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Recommendations
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If local start and lock open valving are not options (e.g.,
spared pump installations with auto-throwover), there are
a number of control options that can be evaluated on a
case-by-case basis for adequacy of risk reduction:
Relief device (rupture disc or relief valve) High Temp Shutdown High Pressure Shutdown Limit switches on isolation valves to ensure they are open (or at
least not closed)
Low flow interlock Low power draw interlock (limited applicationreliability issues)
Next
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Centrifugal Pump with Relief
Back
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Centrifugal Pump with SIF
Back
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Pump Protection Selection Matrix
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Pump Protection Selection Guidance
Type of Pump Hazard Pump Service TypesVersion: B 3/2/2011
By KBYount(HPCC)
PRELIMINARY DRAFT
A B C D E F G H I J K L M N O
Low Power Monitor Interlock 1 Y N N N Y C C Y Y N C N N
Low Amps Interlock 2 Y N N N Y C C Y N C N N
Low Flow Interlock (transmitter or switch) 3 Y C N Y Y Y Y Y C Y Y C
High Temperature Interlock (Pump Casing) 4 Y Y N Y Y N Y Y Y Y Y Y Y Y
High Pump Discharge Pressure Interlock 5 Y Y Y N Y Y C Y Y Y Y Y Y YC
Overpressure Relief Valve 6 Y Y Y C N C Y Y Y Y Y CN
Minimum Flow/Recirculation Line 7 Y N na Y N Y Y C Y Y CY
Minimum Flow Control Loop (DCS or Mechanical FC) 8 Y N na Y N Y Y C C
Y
Block Valve Position Indication Interlock 9 Y Y Y Y Y Y C Y C C Y Y
Operational Locks on Manual Isolation Val
ves
10Y Y Y Y Y Y Y N N N N Y Y Y na
LocalOnly Operator Start Switch (New) 11
Y = Yes, Typically good for this service
N = No, Typically not a good fit for this service
C = Conditionally good for the service, additional design details are required, see notes
na = Not Applicable
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Share Learnings
Communicate the hazard
Identify potential pump explosionhazards in our areas
Remote start capability Evaluate each potential pump explosion
hazard
Make recommendations to mitigate risk
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Questions?