Centrifugal Pump Isolation Hazards:

Case Histories and Prevention Methodologies

Peter N. LodalEastman Chemical Company

What is a B.L.E.V.E.?

Boiling

Liquid

Expanding

Vapor

Explosion

Boiling liquid expanding vapor explosion, often referred to by the acronym BLEVE, is a phenomenon which occurs when a vessel containing a pressurized liquid substantially above its boiling point is ruptured, releasing the contents explosively.

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Heat

P

Liquid

Vapor

PressureIncreases

TemperatureIncreases

T

What Causes a BLEVE?

ClosedSystem

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Heat

P

Liquid

Vapor

PressureRapidlyDecreases

LiquidFlashVaporizes

VesselRuptures

1600xVapor

Volumetric

Expansion

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

Case 1

Sludge Pump

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Case 1:Description of Incident

A loud sound was heard and a 20 foot long white to whitish-gray cloud was seen in the area of Sludge Pump. Inspection showed Pump was fractured and small pieces were 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

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)

Pump fracture analysis suggests approximately 200-210 psig pressure was generated.

Pegged pressure gauge on pump discharge suggests 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)

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

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 up enough temperature to raise the vapor pressure to 200-210 psig which caused the pump to fail.

Case 2

Caustic Pump

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Case 2: Data

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

Material was non-flammable, so deflagration was ruled out.

Root Cause = Pump was inadvertently started and 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.

Case 3

Condensate Pump

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Case 3: Data

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

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

1. Complete Isolation (Suction and Discharge Blocked), not deadheaded (discharge only blocked).

2. Fluid Filled

3. Remote Start Capability

4. 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 solids

Case 2 1750 RPM, 10 HP,55 psig

50% SodiumHydroxide solution

Case 3 2600 GPM, 75 HP,110 psig

Steam condensate

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Conclusions

Pump Explosions can occur with completely isolated fluids, 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 safe assumption

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Recommendations

So, what are the best ways of preventing pump explosions?

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

Centrifugal Pump with Remote Stop

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Recommendations

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 application—reliability issues)

Next

Centrifugal Pump with Relief

Back

Centrifugal Pump with SIF

Back

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Pump Protection Selection MatrixPump Protection Selection Guidance

Type of Pump Hazard Pump Service TypesVersion: B 3/2/2011By KBYount (HPCC)

PRELIMINARY DRAFT

<- Protec

tion Metho

d

Centrifical

Pumps

Variable Speed Drive

Centrifical

Pump

Positive Displacement Pump

Reactive

Chemical

Exotherm

Liquid Vapor

Pressure

Expansion

Hazard (Bleve)

Thermal

Expansion

Hazard (Casing

Bust Open)

Pump Seal/Be

aring Failure

Safety Rated

Protection

Required (SIL 1-

3)

Batch (ON/OF

F) Pumpin

g Service

Analog Control Valve/L

oop Involve

d

Auto Pump

Throwover

Service

Variable Process Composition

Variable Process Temp

Slurry Service

Interlock On-line

Testing Require

dPump Type, Process Service/Conditions -> 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

YBlock Valve Position Indication Interlock 9 Y Y Y

Y Y Y C Y C C Y Y

Operational Locks on Manual Isolation Valves 10 Y Y Y

Y Y Y Y N N N N Y Y Y na

Local Only 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 explosion

hazards in our areas• Remote start capability

Evaluate each potential pump explosion hazard

Make recommendations to mitigate risk

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Questions?