Standardpräsentation Farbe Detusch - Tank Storage International

Tank Storage Istanbul 2011
29-30 November 2011
Grand Cehavir Hotel, Istanbul, Turkey
News regarding venting of atmosheric
and low-pressure storage tanks
News regarding use of flame arresters
(why do p/v-vents not function as flame arrester?)
Dipl.-Ing. Axel Sommer
PROTEGO® – Braunschweiger Flammenfilter GmbH
1

API 2000
5 th edition
API 2000
6 th edition
New International Standard:
Venting of atmospheric and low-pressure
storage tanks ISO 28300
ISO 28300
Petroleum,
petrochemical and
natural gas industries –
Venting of atmospheric
and low-pressure
storage tanks
EN 14015
Annex L
TRbF 20
2

Background and development of ISO 28300 Standard
ISO 28300 was mainly developed based on the API 2000
standard 1998 6 th Edition and the EN 14015 Standard
Annex L and the German TRbF 20
Contradiction towards the venting requirements for
normal venting
Contradiction towards the use of vents as flame
arresters
Committee goal:
This standard shall consider all state of the art
knowledge concerning tank venting and safety and
provide best practice to the user
3

Why new calculation methods for determining normal
venting requirements?
Prof. Salatino from the University of Napoli predicted
that the calculation method of API 2000 may
underpredict thermal breathing
The German TRbF 20 standard developed by Dr. Hans
Foerster from the Federal Institute if Physiks (PTB) also
results in higher values for thermal breathing
The EN 14015 Standard developed by Dr. Wheyl from
BASF also results in higher breathing values
All the above methods depend on a detailed
thermodynamic model and provide higher inbreathing
rates than the API 2000 standard
4

Validation of results for inbreathing
Prof. Salatino Model calculation at University of
Napoli, 1999
• Tank: V = 63000 m 3 ; D = 70 m; H = 15 m
• Δ T = 40 °C
• Water (rain) flow density
• Refined model calculation
- Dynamic simulation (pressure
differential at vent)
- Different start temperatures of roof, shell
and product
5

Validation of results for inbreathing
API 2000
TRbF 20
ISO 28300
Prof. Salatino Model calculation at University of Napoli, 1999
6

Validation of results for inbreathing
Life field tests and model calculation at
Hoechst in 1980 and 1981
• Tank: V = 617 m 3 ; D = 8,5 m; H = 10,6 m
• 17 °C ≤ Δ T ≤ 26 °C
• Water (rain) flow density: about 60 kg/m 2 h
• TRbF-model calculation
7

Validation of results for inbreathing
8

Summary
The new section is based on the European EN 14015 Standard.
The approach used is more general than API (the API approach
is centered around hexane or similar services).
Calculated vent rates with the new approach can be substantially
higher for certain tank sizes than what is shown in API-2000.
A research paper from Prof. Salatino and research results from
Hoechst in Frankfurt, which had been provided by Dr. Hans
Foerster from the PTB justified this change.
An advantage of the new calculation method is that it does allow
to consider full and partial insulation of the tank for normal in- and
out-breathing.
9

ISO 28300 venting requirements
Normal out-breathing and normal inbreathing flows
are defined as the combination of tank vent flows
due to:
Liquid flows into and out of the tank
Ambient weather (thermal) effects
V = V + V
out thermal−
out pump−in
V = V + V
in thermal−
in pump−out
10

Liquid filling capacities - out-breathing
out-breathing rate = filling rate
special calculation have to be done for spike products, and at storage
temperature > 40°C and vapour pressure > 50 mbar:
11

Liquid filling capacities - inbreathing
in-breathing rate = discharging rate
12

Basis: Model calculations for a fixed roof above
ground storage tank of steel
General assumptions and approximations:
Uniform (time dependent) temperatures of wall, tank
atmosphere, ambient air and rainwater-film
Primary result is the temperature of the tank atmosphere in
dependence on time ; volume flow rates are then deduced
by an isobaric approach (constant ratio of volume to
temperature)
Tank atmosphere is air at ambient pressure
Wall thickness is according to common tank standards ( ≥
4 mm)
No heat flux via tank bottom
13

Determining of normal & emergency venting requirements
General Basic Equation for ISO 28300 Model:
V
Q
=
V
T
g
⋅
dT
dt
Energy balance to describe temperature
distribution with respect to time
g
( T −T
)
= k ⋅ A ⋅ = V ⋅ ρ
g
s
g
⋅ c
g
⋅
dT
dt
g
14

Heat flows during heating by solar radiation
(outbreathing)
convection
solar irradiation
convection
far IR radiation loss
15

Volume Flow V in m 3 /h
Solution if solving differential equation:
80
60
40
20
Maximum volume flow
0
15
0 900 1800 2700 3600 4500 5400 6300 7200
Time t in s
ϑ W
ϑG ϑG
V VG,B G,B
Maximum volume flow occurs
at maximum delta T
30
25
20
16
Temperature ϑ in o C

Thermal out-breathing simplified as in ISO 28300
=
0,9
Vthermal−out Cout
VT
R
C out = 0,2 latitude : > 58°
C out = 0,25 latitude : 58°-42°
C out = 0,32 latitude : < 42°
R in = reduction factor insulation
V t = tank volume
in
17

convection
and
evaporation
Heat flows during cooling by rain
(inbreathing)
conduction
convection
Rain water flow to wall
Rain water drain from wall
18

Volume Flow V in m 3 /h
Solution if solving differential equation:
300
240
180
120
60
Maximum volume flow
Maximum volume flow occurs
at maximum delta T
0
15
0 180 360 540 720 900
Time t in s
V G,B
ϑG ϑG
ϑ W
55
45
Temperature ϑ in o C
35
25
19

Thermal - inbreathing
0,7
Vthermal−in = Cin
VT
Cin
R
R in = reduction factor insulation
V t = tank volume
vapour pressure
latitude < 25 °C ≥ 25°C < 25 °C ≥ 25°C
> 58° 2,5 4 4 4
42° - 58° 3 5 5 5
< 42° 4 6,5 6,5 6,5
in
haxane or similar higher than hexane,
or unkown
storage temperature
20

Calculation – Examples
Tank 1
Tank:
Height: 5m
Diameter: 7m
Tank volume: 192.4 m3
Pump in rate: 96 m3/h
Pump out rate: 96 m3/h
Vertical tank
No insulation
MAWP: + 7.5 mbar
MAWV: - 2.5 mbar
21

Venting requirements [m3/h]
400
350
300
250
200
150
100
50
0
Inbreathing Requirements (Total) for Tank 1
API 2000 EN 14015,
North, VP
Hexane
EN 14015,
North, VP>
Hexane
Inbreathing requirements Tank 1
EN 14015, 42-
58, VP Hexane
EN 14015, 42-
58, VP>
Hexane
Pump out Thermal
EN 14015,
South, VP
Hexane
EN 14015,
South, VP>
Hexane
TRbF 20
22

Venting requirements [m3/h]
250
200
150
100
50
0
226
API 2000, FP
=37.8C
EN 14015,
North
EN 14015, 42-
58
EN 14015,
South
Pump in Thermal
H/D = 0.71
H/D = 0.5
118 122
H/D = 2
109
TRbF 20 TRbF 20-2 TRbF 20-3
23

Calculation – Examples
Tank 2
Very Large Size Tank (outside of scope of API 2000):
Height: 15 m
Diameter: 75 m
Tank volume: 66,268 m3
Pump in rate: 1,400 m3/h
Pump out rate: 1,400 m3/h
Vertical tank
No insulation
MAWP: + 7.5 mbar
MAWV: - 2.5 mbar
24

Venting requirements [m3/h]
18000
16000
14000
12000
10000
8000
6000
4000
2000
0
Inbreathing Requirements (Total) for Tank 2
API 2000 EN 14015,
North, VP
Hexane
Inbreathing requirements Tank 5
EN 14015,
North, VP>
Hexane
EN 14015, 42-
58, VP
Hexane
EN 14015, 42-
58, VP>
Hexane
Pump out Thermal
EN 14015,
South, VP
Hexane
EN 14015,
South, VP>
Hexane
TRbF 20
25

Venting requirements [m3/h]
10000
9000
8000
7000
6000
5000
4000
3000
2000
1000
0
Outbreathing Requirements (Total) for Tank 2
API 2000, FP
=37.8C
Outbreathing requirements Tank 5
EN 14015, North EN 14015, 42-58 EN 14015, South TRbF 20
Pump in Thermal
26

Calculation example considering insulation:
• Tank volume 592,000 barrel (94.120 m³)
• Stored liquid Bitume
• Pump in 4542 barrel/h (722 m³/h)
• Pump out 5458 barrel/h (867 m³/h)
• Insulation Calciumsilicate
• Insulation thickness 2”
27

Overview Venting Requirements
(API 2000, ISO 28300)
API 2000 (without consideration of insulation):
• Inbreathing: 6.600 Nm 3 /h
• Outbreathing: 4.200 Nm 3 /h
ISO 28300 (without consideration of insulation):
• Inbreathing: 16.020 Nm 3 /h
• Outbreathing: 7.920 Nm 3 /h
28

How to consider insulation during thermal in-
and out-breathing
Reduction factor for insulation according to ISO 28300
h
LIN
R
IN
=
1+
1
h ⋅
λ
L
IN
IN
λ = heat conduction coefficient
= heat transfer coefficient
= thickness of insulation
Here: RIN
= 0.2145
29

Overview Venting Requirements
(API 2000, ISO 28300)
API 2000 (without consideration of insulation):
• Inbreathing: 6.600 Nm 3 /h
• Outbreathing: 4.200 Nm 3 /h
ISO 28300 (with insulation):
• Inbreathing: 4.140 Nm 3 /h (vs. 16.020 Nm³/h)
• Outbreathing: 2.280 Nm³/h (vs. 7.920 Nm³/h)
30

How to determine inert gas blanketing rates
ISO 28300 Annex F provides guidance for inert
gas blanketing of tanks for flashback protection
This guidance is based on the German TRbF 20
standard
The concept has provided proven safety to the
industry for decades
It is simple way to assure sufficient inert gas
blanketing levels
The amounts result from the inbreathing rates of
the ISO 28300 equations
31

3 different levels of inert gas blanketing
Level 1
minimum inert gas blanketing requirements in
combination with a specific flame arrester classification
Level 2
more stringent inert gas blanketing requirements with
different flame arrester classification
Level 3
the highest inert gas blanketing requirements with no
flame arrester
32

Tank inbreathing needs to be considered
inbreathing due to changes in weather
inbreathing due to emptying of tank
Inert gas supply needs to be determined
minimum amount of inert gas volume flow
amount of reserve inert gas
VI
VI
33

Inert gas level 1:
V C V V
expressed in m3 /h
= 0,1×
×
0,7
+
I T pe
V = 0,04 × V
expressed in m3 I T
Additional conditions:
monitor inert gas supply
alarm shall be triggered when set pressure of the vacuum vent is
reached.
inside of the tank can be classified as Zone 1 (according to the
IEC)
An end-of-line flame arrester shall be installed which has been
tested for atmospheric deflagration and endurance burning for IEC
explosion group IIA (NEC Group D) vapours.
34

Inert gas level 2:
V C V V
= 0, 2×
×
0,7
+
I T pe
V = 0,08 ×
V
I T
Additional conditions:
expressed in m 3 /h
expressed in m 3
The alarm specified under inert gas stage 1 shall activate the
shutdown of the liquid outflow.
At this level of inert gas blanketing the inside of the tank can be
classified as Zone 2 in accordance with IEC 60079-10.
An end-of-line flame arrester shall be installed which has been
tested for atmospheric deflagration for IEC explosion group IIA
(NEC Group D) vapours.
35

Inert gas level 3:
V C V V
V = 0,12 ×
V
= 0,5 × ×
0,7
+
I T pe
expressed in m 3 /h
expressed in m 3
I T
Additional conditions:
The tank pressure shall be kept above atmospheric pressure and the monitoring
system shall have redundancy in the design.
The inert gas supply shall be kept above the tank pressure and in particular the
required flow rate of shall be achieved with a tank pressure at least equal to the
atmospheric pressure.
The trip pressure at which the liquid outflow will be shut down shall be set above
atmospheric pressure. (Pump Shut Off)
Alarms shall be triggered at the trip pressure.
At this level of nitrogen blanketing the inside of the tank can be classified as
Zone 2 in accordance with IEC 60079-10. At this level of inert gas blanketing no
additional protection against flame propagation from the outside to the inside of
the tank is required.
36

Why conservation vents do not function as flame arresters:
37

Why conservation vents do not function as flame arresters:
API 2000 5 th Edition 1998:
A flame arrester is not considered necessary for use in
conjunction with a pressure vacuum valve venting to
atmosphere because flame speeds are less than vapor
velocities across the seat of the pressure vacuum valve
TRbF 20 (German standard):
clearly calls for flame arresters for tanks that contain liquids
that can create an explosive atmosphere
Factory Mutual (Insurance and approval company)
requires installation of flame arresters on tanks which store
liquids with a flash point at or below 43 ◦C or on tanks which
heat the stored liquid to its flash point
38

Conclusion for ISO 28300 committee regarding
atmospheric explosion protection of storage
tanks:
Research work is needed due to contradicting
standards and opinions on the ISO 28300
committee
ISO 16852 shall apply as test standard
Two types of test are needed:
A) atmospheric deflagration test
B) continuous burn test
39

5 major vent manufacturers where tested
pressure
pallet
vacuum
pallet
40

Typical settings for API 650 tanks
set vacuum: -2 mbar (-0.8 in WC)
set pressure:
10 mbar
( 4.0 in WC)
41

Atmospheric Deflagration - Test set-up
1 ignition source
2 plastic bag Ø 1,2 m, length 2,5m
foil thickness >0,05 mm
3 conservation vent
4 explosion proof container
5 mixture inlet with shut-off valve
6 mixture outlet
7 bursting diaphragm
atmospheric deflagration test of end-ofline
flame arrester as described in ISO
16852 part 7.3.2.1 and EN 12874 part
6.3.2.1
42

3
5
Atmospheric Deflagration - Test set-up
7
6
1
2
4
1 ignition source
2 plastic bag Ø 1,2 m,
length 2,5m foil
thickness >0,05 mm
3 conservation vent
4 explosion proof container
5 mixture inlet with shut-off
valve
6 mixture outlet
7 bursting diaphragm
43

Atmospheric
Deflagration –
Test No 1
P/V VALVE –
4,2 vol% propane in air –
28.03.2007
45

Atmospheric
Deflagration –
Test No 2
P/V VALVE –
5,5 vol% propane in air –
28.03.2007
46

Atmospheric
Deflagration –
Test No 3
P/V VALVE –
6,0 vol% propane in air –
28.03.2007
47

High Velocity Burning - Test set-up
1 continuous flame
2 pressure vacuum valve
3 explosion proof container
4 mixture inlet
5 bursting diaphragm
7 pilot flame
10 shut-off valve
Flame transmission test for high velocity vent valves
as described in ISO 16852 part 9.2. and EN 12874
part 9.2.
48

High Velocity Burning
– Test No 4
P/V VALVE
stoichiometric propane
air mixture
V= 85 m³/h
28.03.2007
49

High Velocity Burning
– Test No 5
P/V VALVE
stoichiometric propane
air mixture
V= 100 m³/h
28.03.2007
50

Recommendation of ISO 28300 regarding
explosion prevention:
Different tank selection
Inert gas blanketing
Flame arresters
Flame propagation through pressure/vacuum valves
(4.5.4)
Testing has demonstrated that a flame can propagate through a pressure
vacuum valve and into the vapour space of the tank. Tests have shown
that ignition of a PV's relief stream (possibly due to a lighting strike) can
result in a flash back to the PV with enough overpressure to lift the
vacuum pallet causing the flame to enter the tank's vapour space. Other
tests have shown that, under low flow conditions, a flame can propagate
though the pressure side of the PV.
51

Summary
- p/v valves cannot stop an atmospheric deflagration
- p/v valves are not able to stop a flame by dynamic
effects
hence:
- p/v valves cannot substitute flame arresters
- p/v valves are not high velocity vent valves
- only devices approved according flame arrester
standards* are flame arresters
* ISO 16852, EN 12874, USCG 33 CFR part 154, CSA Z343-98
52

Thank you very much
for your attention !
Any questions?
53