Principle Of Operation; Factors Affecting Flame Arrestor Performance - Emerson Enardo DFA Series Instruction Manual

Enardo DFA Series
inTErnATiOnAL
nATiOnAL ELECTriC ELECTrOTECHniCAL
CODE (nEC) COMMiSSiOn (iEC)
Group D Group IIA
Group C Group IIB3
Group B Group IIC
Table 3. Detonation Arrestor Size Ranges and Rating, Maximum Initial Pressure and Burn Rating
DETOnATiOn
DETOnATiOn
FLAME ArrESTOr
FLAME ArrESTOr
SiZE rAnGE
MODEL
in.
Enardo DFA***/D 2 to 12
Enardo DFA***/D 14 to 20
Enardo DFA***/D 24
Enardo DFAE***/D 2 to 20
Enardo DFA***/C 2 to 20
Enardo DFAE***/C 2 to 20
vapor mixture approaching from either direction that can
be travelling at subsonic or supersonic velocities. The
patented element offers maximum flow to pressure drop
characteristics enhancing the value of the flame arrestor
in any system.
The Enardo DFA Series is designed with flanged
connections, the arrestor provides the option of the
removal of the flame cell element for easy cleaning and
replacement without disconnecting the pipe connection.

Principle of Operation

Detonation flame arrestor prevents flame propagation
as it enters the exposed side of the unit to the protected
side by absorbing and dissipating heat using spiral wound
crimped ribbon flame cells. This detonation flame arrestor
utilizes an element assembly that dampens the high
velocities and pressures associated with deflagration and
detonations while quenching the flame front. These cells
allow maximum flow with maximum protection.
Detonation flame arrestor has the heat capacity and
structural design to withstand all dynamic conditions of
flame propagation and still stop the flame. Detonation
flame arrestor is used when the flame can be in any of the
detonation states.
Limits of Use for Detonation/Deflagration
Flame Arrestors:
• The following vapors are not within the scope of the
products covered by this IOM:
4
Table 2. Maximum Experimental Safe Gap (MESG)
in.
GrOUP
0.035
0.026
0.020
MAXiMUM iniTiAL
GAS GrOUP
mm
50 to 300 D (IIA)
350 to 500 D (IIA)
600 D (IIA)
50 to 500 D (IIA)
50 to 500 C (IIB3)
50 to 500 C (IIB3)
MESG
mm
>0.90
≥0.65
<0.50
DETOnATiOn
PrESSUrE
rATinG
psia bar a
22.7 1.56 Unstable
20.7 1.43 Unstable
16.0 1.1 Unstable
20.7 1.43 Unstable
20.7 1.43 Unstable
20.7 1.43 Unstable
- Explosive mixtures of vapors and gases, which tend
to self-decompose (e.g. Acetylene) or which are
chemically unstable
- Carbon Disulphide, due to its special properties;
- Mixtures other than gas-air or vapor-air mixtures
(e.g. higher oxygen-nitrogen ratio, chlorine as
oxidant, etc.)
• Minimum distance between flame arrestor connection
and a restriction on the protected side is 10 L/D, but
not less than 3 m.
• Arrestors shall only be installed into piping with a
nominal size that is smaller than or equal to the
nominal size of the flame arrestor connection.
Factors Affecting Flame
Arrestor Performance
Gas Group
Methanol is classified as a Group-D (IIA)
vapor. However, our lab tests indicate
that methanol exhibits characteristics
unlike other Group-D (iiA) vapors
under certain conditions. We therefore
recommend that an arrestor rated for
Group-C (IIB3) vapors be specified for
methanol service.
TEST GAS LiST
Propane
Ethylene
Hydrogen
BUrn rATinG
ATEX (En 12874) USCG
Stabilized Type 1 (2 hours)
Stabilized Type 1 (2 hours)
N/A Type 2 (15 minutes)
1 minute Type 2 (15 minutes)
Stabilized Type 1 (2 hours)
1 minute Type 2 (15 minutes)
WArninG
!