Testing Safety valves

1. Workshop Delta Process
Academy
Testing of Safety Valves

2. Pressure Relief
Devices
Protect Personnel and
Property.
Last Line of Defence.
*

3. Usages
Petrochemical
Nuclear Pulp & Paper
Aerospace
Refining
Fossil Power Oil & Gas Production Chemical
Submarine Service Pharmaceutical Tank Cars Food & Beverage
*

4. 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 Discharge
 Thermal Expansion
 Exposure to External Fire
 Failure of other Equipment such as a Control
Valve
Can be either
a safety valve.
a non reclosing pressure relief device.
or a vacuum relief valve.
*

5. Pressure Relief
Valves
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)
*

6. Balance Beam
Style
Jean Disaquliers 1718
DEAD-WEIGHT SAFETY
VALVE
Open Discharge Pattern
FORCE
Weight
*

7. Pressure / Vacuum
Vent
(Breather Valve)
Inlet Air
Outlet
Change Over Valve,
Rupture Disc and
Purge
7 *

8. Pilot Operated
Safety
? ??
?

9. Pilot Op. Vs Spring Loaded ?
6R8 Valve
Direct Spring 150# Inlet
Set 5 barg
Pilot Operated
116 cm Set 20 barg
w/out Lever
227 kg
64 cm
111 kg

10. The Control Ring: Huddling
chamber up :
 Blowdown Ring
 Small chamber
 Sharp opening
 Long blowdown Fd Different
disk designs
 Blowdown Ring down :
 Large Huddling Chamber A’
 Sluggish Opening (Simmer)
 Short Blowdown
Huddling
A Chamber
 Can be DANGEROUS
 The valve may never reach its full A = Orifice
flow before 10% over-pressure
P
Control (Blowdown) Ring Nozzle
*

11. A New Factor: Back Pressure
Spring
Bonnet
P2 Back
Pressure
Body P1
*

12. Superimposed Back Pressure
To Flare, Recovery
System, or Atmosphere
Possible Pressure Source
Discharge
Header System
Possible Pressure Source
BPS
PRV (Closed)
Possible Pressure Source
Protected
System
Constant Purge?
*

13. 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

14. Transport

15. Overhaul & testing

16. Valve testing Procedures
 Conventional Spring Valve:
 Adjusted & Verify Set Pressure
 Repeatability Test
 Seat Tightness Test According API 527
 Shell Test / Body Test
 Bellow Integrity
*

17. Pressure %
Where PRDs Normally Sized
(Except Fire Case) 110
Set Pressure
Tolerance Allowable
Overpressure
100 MAWP
Blowdown % of Set Typical Set Pressure
95
Reseat Pressure of
PRV Typical Operating
Pressure
90 (“the money maker”)
*

18. Valve testing Procedures
•SHELL TEST
External pressure
source 100 PSIG
(7 BAR/G )
*

19. Valve testing Procedures
•BELLOWS INTEGRITY
Vent has to be
always open!
External pressure
source 14.5 PSIG
(1 BAR/G )
*

20. Testing Specs
Tolerance On Set Pressure
CDTP(PSIG) TOLERANCE
5 TO 70 +/- 2 PSIG
+70 TO 300 +/- 3%
+300 TO 500 +/- 2%
+500 TO 6000 +/- 1%
Temperature adjustment
%TEMPERATURE
OPERATING 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%

21. 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
*

22. In line testing
 Requires accurate knowledge of
 system pressure
 nozzle area
 Valve always opens
 Time consuming
Hydraulic
Unit
Recorder
Force / Lift
*

23. Safety Valve Nomenclature
MAWP
Maximum 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 Pressure
The normal working pressure in a pipe or vessel.
Set Pressure
The pre determined pressure at which a safety valve
starts to open and relieve.

24. Safety Valve Nomenclature
Overpressure
The pressure over and above the set pressure
required for the safety valve to fully open – expressed
as a percentage.
Accumulation
The pressure rise above the MAWP (term often
confused with overpressure which can be different).
Blowdown
Difference between set and reseating pressure of a
safety valve expressed as a percentage.

25. 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 Pressure
A pressure opposing the set pressure that is present in the
outlet side of the safety valve. Influences valve size, style
and selection.
Inlet Temperature
The fluid temperature at the moment of relief.

26. Other Important Safety Valve Terms
Orifice Area
The minimum cross sectional area of the inlet flow path
(nozzle) of a safety valve. This is what is “sized”.
Lift
Actual travel of the disc away from the closed position
when a safety valve is relieving.
Seat
The area formed between the contact of non moveable
and moveable components that maintain safety valve
tightness.

27. Guided Tour or
Documentation
Questions
?
 Carl.stevens@cofelyfabricom-gdfsuez.com
 Wim.morel@cofelyfabricom-gdfsuez.com

28. 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
Belangrijkste normeringen
USA ASME I Boiler applications
ASME III Nuclear applications
ASME VIII Unfired Pressure Vessel Applications
ANSI/ASME PTC 25.3 Safety and Relief Valves - performance test codes
API RP 520 Sizing selection and installation of pressure relieving devices in refineries, Part 1 Design, Part 2 Installation
API RP 521 Guide for pressure relieving and depressurizing systems
API STD 526 Flanged steel pressure relief valves
API STD 527 Seat tightness of pressure relief valves
Europe EN ISO 4126 Safety devices for protection against excessive pressure
International ISO 4126 Safety valves - general requirements