pressure safety devices
Post on 02-Aug-2015
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Pressure Safety Devices
“Grace Under Pressure”
-Earnest Hemingway
Faizan Ahmad
ICET, Punjab University
Lahore, Pakistan
Pressure Terminologies
Accumulation Design Pressure Set Pressure Operating Pressure Overpressure Underpressure Popping Pressure
Causes of Over Pressure Causes of Under Pressure
Operating Problem Operating Problem
Equipment Failure Equipment Failure
Process Upset
Utility Failures
Safeguards
Safety InterlocksSafeguard Maintenance SystemsShort Stopping
Safety Interlocks
Agitator not workingAbnormal TemperatureAbnormal PressureAbnormal Heat Balance
For all these Abnormalities: Stop Feed and Add full Cooling
Safeguard Maintenance System
Routine Maintenance Mechanical Integrity Checks Records
Short Stopping Add Reaction Stopper Add Agitation with no Electrical Power
ReliefsPressure Relief Devices
1. Spring-Loaded Pressure Relief Valves
2. Rupture Disc
3. Buckling Pin
4. Miscellaneous Mechanical Means
Spring Loaded Pressure Relief Valve
Rupture Disc
Buckling Pin Relief Valve
Closed Pressure below Set Pressure
Full Open Pressure at or above Set Pressure
(Buckles in precise milliseconds at a precise set Pressure)
Simple Mechanical Pressure Relief
Other Types of Safety Valves
Balanced Bellows Pilot Operated
Balanced Bellows Safety Valve
Pilot-Operated Safety Valve
When to Use Spring-Operated Safety Valve
Spring-Operated Valve is used in following cases
Fluids above normal boiling point
Used where toxic fluids are handled
Return to normal conditions quickly
Withstand process pressure changes, including vacuum
When fluid is of the Prime Importance
When to Use Rupture Disc/Safety pin Valve
Capital and maintenance savings When fluid is not so expensive For Benign Service (Non-toxic, Non-Hazardous) Need for fast acting device Potential for Relief valve plugging Used for High Viscosity Liquids
When to Use Both Types
Need a positive Seal (Toxic Material, Material Balance Requirements)
Protect Safety Valve for Corrosion
System Contain Solids
Anything wronghere?
Bellows pluggedin spite of sign
FailedInspectionProgram
Signs ofMaintenance
Issues
Anything wronghere?
Anything wronghere?
DischargesPointing Down
Mexico City DisasterMajor Contributing Cause: Missing Safety Valve
References:
Mohammad A. Malek --- Pressure Relief Devices Chapters # 1, 3, 21
Crowl, Louver --- Chemical Process Safety Chapter # 8
End of Presentation
Thank-you
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