Introduction to overpressure protection презентация

Why Needed

BLOCKED DISCHARGE
EXPOSURE TO EXTERNAL FLAMES
THERMAL EXPANSION
Most Common Causes
Of Overpressure

Blocked Discharge
FULL INPUT FLOW
OUTLET BLOCK
VALVE CLOSED
(FROM COMPRESSOR
OR PUMP)
PRD
Pressure
Vessel

PRD
External Fire
STORAGE OR
PROCESS VESSEL

PRD
Thermal Expansion
LIQUID FULL PIPE OR PRESSURE VESSEL

Overpressure Relief Devices
PRESSURE RELIEF VALVE
RUPTURE DISC
RUPTURE DISC UNDER PRV

OPENS AT SET PRESSURE
CLOSES AT RESEAT PRESSURE
Pressure Relief Valve
(PRV)

A PREDETERMINED WEAK POINT
IN A PRESSURIZED SYSTEM
OPENS AT BURST PRESSURE
DOES NOT RE-CLOSE
Rupture Disc
(RD)

RD BURSTS OPEN
PRV OPENS IMMEDIATELY
PRV RE-CLOSES AT A PRESSURE BELOW RD BURST PRESSURE
Pressure Relief Valve &
Rupture Disc

Maximum Allowable
Working Pressure (MAWP)

Maximum Operating
Working Pressure (MOWP)

PRESSURE %
110
100
95
90
WHERE PRDS NORMALLY SIZED (EXCEPT FIRE CASE)
MAWP
ALLOWABLE
OVERPRESSURE
TYPICAL SET
PRESSURE
TYPICAL OPERATING
PRESSURE
(“THE MONEY MAKER”)
SET PRESSURE
TOLERANCE
TYPICAL RESEAT
PRESSURE
BLOWDOWN,
% OF SET

% MAWP
100
MAWP
ALLOWABLE
ACCUMULATION
(SYSTEM)
USUALLY 110% MAWP
ALLOWABLE
OVERPRESSURE
(PRD)
SET PRESSURE

100
MAWP
ALLOWABLE
ACCUMULATION
(SYSTEM)
USUALLY 110% MAWP
ALLOWABLE
OVERPRESSURE
(PRD)
(ALMOST NEVER SHOULD IT BE < MAWP )
% MAWP
SET PRESSURE

Back Pressure
Inlet
THE PRESSURE AT THE OUTLET
OF A PRESSURE RELIEF DEVICE.

Built-up Back Pressure
DISCHARGE
PRV IS OPEN
AND IS FLOWING
In

Protected System
SUPERIMPOSED BACK PRESSURE
PRV (Closed)
CLOSED
DISCHARGE
HEADER SYSTEM
TO FLARE
AND/OR
BURNER STACK
TO ATMOS.
Possible Pressure Source
Possible Pressure Source
Possible Pressure Source
Purge?

LIFT
Lift

Orifice Area
AN = AREA OF DN
(NOZZLE DIAMETER),
OR
AC = CIRCUM. OF DN X LIFT, [“CURTAIN AREA”]
WHICHEVER IS LARGER
LIFT
DN

A PRV ACTUATED BY STATIC PRESSURE
RAPID OPENING (POP ACTION)
USED ON COMPRESSIBLE MEDIA (GAS, VAPOR, STEAM)
Safety Valve

A PRV ACTUATED BY STATIC PRESSURE
OPENS GENERALLY IN PROPORTION TO OVERPRESSURE
NORMALLY USED ON NON-COMPRESSIBLE MEDIA (LIQUIDS)
Relief Valve

Safety Relief Valve
(SRV)
A PRV THAT MAY FUNCTION AS
EITHER A SAFETY OR RELIEF VALVE
WITH SATISFACTORY PERFORMANCE

Pressure Relief Valve
(PRV)
A GENERIC TERM WHICH INCLUDES
SAFETY VALVES, RELIEF VALVES, AND
SAFETY RELIEF VALVES (A “SAFE & ALL-ENCOMPASSING TERM”)