lodal pump bleve mar2011

8/3/2019 Lodal Pump BLEVE Mar2011

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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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3

Heat

P

Liquid

Vapor

PressureIncreases

Temperature

Increases

T

What Causes a BLEVE?

ClosedSystem


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4

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?

lodal pump bleve mar2011

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