Testing of Safety Valves
-
Upload
carl-stevens -
Category
Business
-
view
8.535 -
download
9
description
Transcript of Testing of Safety Valves
Workshop Delta Process AcademyTesting of Safety Valves
Pressure Relief Devices
Protect Personnel and Property.
Last Line of Defence.
*
Usages
*
Pulp & PaperPetrochemicalPetrochemical
NuclearNuclear
RefiningRefining
Oil & Gas ProductionFossil PowerPower ChemicalChemical
AerospaceAerospace
Food & BeverageBeverageTankTank CarsSubmarine ServiceService PharmaceuticalPharmaceutical
What Is A Pressure Relief Device ?A device that opens in a state of
emergency or when in abnormal conditions.
Prevents a rise in pressure in excess of a specified value:
Blocked DischargeBlocked Discharge Thermal ExpansionThermal Expansion Exposure to External FireExposure to External Fire Failure of other Equipment such as a Failure of other Equipment such as a
Control ValveControl Valve
Can be eitherCan be either a safety valve.a safety valve. a non reclosing pressure relief device.a non reclosing pressure relief device. or a vacuum relief valve. or a vacuum relief valve.
*
Must open at a predetermined pressure.(Set Pressure)
Achieve a rated relieving capacity at a specified pressure above the opening point. (Overpressure)
After a given drop in inlet pressure below the opening point, it should close and reseat tightly.
(Blow down)
*
Pressure Relief Valves
DEAD-WEIGHT SAFETY VALVE
Open Discharge Pattern
Jean Disaquliers 1718
*
Weight
FORCE
Balance Beam Style
7
Pressure / Vacuum Vent
(Breather Valve)
*
Inlet AirInlet Air
OutletOutlet
Change Over Valve, Rupture Disc and
Purge
Pilot Operated Safety
?? ??
Pilot Op. Vs Spring Loaded ?
150# Inlet150# Inlet
116 cm116 cmw/out Leverw/out Lever
227 kg227 kg
Direct SpringDirect SpringSet 5 barg Set 5 barg
6R8 Valve6R8 Valve
64 cm64 cm111 kg111 kg
Pilot OperatedPilot OperatedSet 20 bargSet 20 barg
Control (Blowdown) RingControl (Blowdown) Ring
The Control Ring: Huddling chamber Blowdown Ring up :
Small chamber Sharp opening Long blowdown
Blowdown Ring down : Large Huddling Chamber Sluggish Opening (Simmer) Short Blowdown
Can be DANGEROUS The valve may never reach its
full flow before 10% over-pressure
F d
P
A
A’
*
HuddlingHuddlingChamberChamber
Different Different disk designsdisk designs
NozzleNozzle
A = OrificeA = Orifice
Spring BonnetSpring Bonnet
BodyBody P1P1
P2P2Back
PressureBack
Pressure
A New Factor: Back Pressure
*
Protected Protected SystemSystem
Superimposed Back Pressure
PRV (Closed)PRV (Closed)
DischargeDischarge Header SystemHeader System
To Flare, Recovery To Flare, Recovery System, or AtmosphereSystem, or Atmosphere
Possible Pressure SourcePossible Pressure Source
Possible Pressure SourcePossible Pressure Source
Possible Pressure SourcePossible Pressure Source
Constant Purge?Constant Purge?
BPBPSS
*
Most Important Characteristics Needed for Overhaul and Testing:
Inlet Size Outlet Size MSDS + cleaning declaration Bellow Present (vent always open) Back Pressure On Site Required Back Test Pressure Max. Set Pressure (Cold Set) NB Witness / Lloyds O2 – FDA Service Type of Soft Good Materials
Test pressures in writing
Transport
Overhaul & testing
*
Valve testing Procedures Conventional Spring Valve:Conventional Spring Valve:
Adjusted & Verify Set Pressure Repeatability Test Seat Tightness Test According API
527 Shell Test / Body Test Bellow Integrity
Pressure %Pressure %110110
100100
9595
9090
Where PRDs Normally Sized (Except Fire Case)
Where PRDs Normally Sized (Except Fire Case)
MAWPMAWPMAWPMAWP
AllowableAllowableOverpressureOverpressure
Typical Set PressureTypical Set Pressure
Typical OperatingPressure
(“the money maker”)
Typical OperatingPressure
(“the money maker”)
Reseat Pressure of PRV
Reseat Pressure of PRV
Blowdown % of SetBlowdown % of Set
Set Pressure Tolerance
Set Pressure Tolerance
*
*
•SHELL TEST
External pressure source 100 PSIG
(7 BAR/G )
Valve testing Procedures
External pressure source 14.5 PSIG
(1 BAR/G )
•BELLOWS INTEGRITY
*
Valve testing Procedures
Vent has to be always open!
Testing SpecsCDTP(PSIG) TOLERANCE
5 TO 70 +/- 2 PSIG
+70 TO 300 +/- 3%
+300 TO 500 +/- 2%
+500 TO 6000 +/- 1%
Tolerance On Set Pressure
OPERATING TEMPERATURE%TEMPERATURE COMPENSATION
0 TO 150ºF
-18 TO 65ºC NONE
151 TO 600ºF
66 TO 315ºC
1%
601 TO 800ºF
316 TO 426ºC
2%
801 TO 1000ºF
427 TO 537ºC
3%
Temperature adjustment
Causes of Seat Leakage
Damaged valve seating surfaces. Operating pressure to close to set pressure. Pipe strains Incorrect installation Incorrect maintenance Incorrect calibration Misapplication of materials Vibration Damaged springs Rough handling / transport / montage Manipulation of lift handle Yousing lift handle as means of transportation
*
In line testing Requires accurate Requires accurate
knowledge ofknowledge of system pressuresystem pressure nozzle areanozzle area
Valve always opensValve always opens Time consumingTime consuming
HydraulicHydraulicUnitUnit
RecorderRecorderForce / LiftForce / Lift
*
Safety Valve Nomenclature
MAWPMaximum Allowable Working Pressure.
The specified maximum safe “design pressure” of a vessel or system. It is often the “Set Pressure” of the safety valve.
Operating PressureThe normal working pressure in a pipe or vessel.
Set PressureThe pre determined pressure at which a safety valve starts to open and relieve.
OverpressureThe pressure over and above the set pressure required for the safety valve to fully open – expressed as a percentage.
AccumulationThe pressure rise above the MAWP (term often confused with overpressure which can be different).
BlowdownDifference between set and reseating pressure of a safety valve expressed as a percentage.
Safety Valve Nomenclature
Operating Gap (or difference)Difference between the working (normal operating) pressure of the vessel or system and the set pressure of the safety valve.
Back PressureA pressure opposing the set pressure that is present in the outlet side of the safety valve. Influences valve size, style and selection.
Inlet TemperatureThe fluid temperature at the moment of relief.
Safety Valve Nomenclature
Other Important Safety Valve Terms
Orifice AreaThe minimum cross sectional area of the inlet flow path (nozzle) of a safety valve. This is what is “sized”.
LiftActual travel of the disc away from the closed position when a safety valve is relieving.
SeatThe area formed between the contact of non moveable and moveable components that maintain safety valve tightness.
Questions?
Guided Tour or Documentation
Sources Tyco Formation
Main Valve Maintenance
Model Numbering
Pilot Valves
Spring Valves Operations
Poor Performance
Safety Valve Terminologie
Test Procedures
Valve Types
Sarasin Manuel
Sapag Manuel
Crosby Manual
USA ASME I Boiler applicationsASME III Nuclear applicationsASME VIII Unfired Pressure Vessel ApplicationsANSI/ASME PTC 25.3 Safety and Relief Valves - performance test codesAPI RP 520 Sizing selection and installation of pressure relieving devices in refineries, Part 1 Design, Part 2 InstallationAPI RP 521 Guide for pressure relieving and depressurizing systemsAPI STD 526 Flanged steel pressure relief valvesAPI STD 527 Seat tightness of pressure relief valves
Europe EN ISO 4126 Safety devices for protection against excessive pressureInternational ISO 4126 Safety valves - general requirements
Belangrijkste normeringen