Page 1
Instruction Manual
D104263X012
March 2018
Model DFA 7236
Detonation Flame Arrestor
Table of Contents
Introduction ............................................................................1
Principle of Operation ............................................................2
Specifications ........................................................................2
Factors Affecting Flame Arrestor Performance ......................2
Installation .............................................................................4
Piping Expansions and Reductions Adjacent to
Detonation Flame Arrestor.....................................................4
Maintenance ..........................................................................6
Element Assembly, Disassembly and
Reassembly Instructions .......................................................6
WARNING
!
Model DFA 7236
Failure to follow these instructions or to
properly install and maintain this equipment
could result in an explosion, fire and/or
chemical contamination causing property
damage and personal injury or death.
Enardo detonation flame arrestor
must be installed, operated and
maintained in accordance with federal,
state and local codes, rules and
regulations and Emerson Process
Management Regulator Technologies Tulsa,
LLC (Emerson) instructions.
Failure to correct trouble could result in a
hazardous condition. Call a qualified service
person to service the unit. Installation,
operation and maintenance procedures
performed by unqualified person may
result in improper adjustment and unsafe
operation. Either condition may result in
equipment damage or personal injury. Only
a qualified person shall install or service the
detonation flame arrestor.
Introduction
Scope of the Manual
This Instruction Manual provides instructions for
installation, startup and maintenance information for the
Model DFA-7236 detonation flame arrestor.
Figure 1. Typical Model DFA-7236
Detonation Flame Arrestor
Product Description
The DFA Series detonation flame arrestor represents the
best value in flame arrestor protection. The detonation flame
arrestor provides protection against flame propagation in piping
systems that are manifolded or have long run-up distances.
These are typically used for extended pipe length or multiple
pipe bend configurations to stop high pressures and flame
velocities with detonations and overdriven detonations. It
also stops confined and unconfined, low and high-pressure
deflagration. The design is unique in the ability to provide large
flame channels which requires less frequent maintenance and
greater ease in cleaning when service is required, translating
to less down time. DFA Series detonation flame arrestors are
bi-directional and proven to stop an ignited flammable vapor
mixture approaching from either direction that can be travelling
at subsonic or supersonic velocities. The element assembly
offers maximum flow to pressure drop characteristics enhancing
the value of the flame arrestor in any system.
The DFA Series is designed with flanged connections. The
arrestor provides the option of the removal of the flame cell
element assembly for cleaning and replacement with the
arrestor removed from the ping.
North America Only
Page 2
Model DFA 7236
Specifications
The Specifications table lists the specifications for the detonation flame arrestor. The following information is stamped on the
nameplate attached to the arrestor: model number, flange size and rating, maximum initial operating pressure, gas group, date
of manufacture and serial number; other identification and customer tag number are optional.
Construction
Model DFA-7236
Gas Group
D (IIA)
Flange Sizes and Rating
36 in. CL150
Housing Size
72 in.
Maximum Experimental Safe Group (MESG)
0.035 in. / 0.90 mm for Group D Vapors
Maximum Initial Operating Pressure
17.7 psia / 1.22 bar a
1. The pressure/temperature limits in this Instruction Manual and any applicable standard or code limitation should not be exceeded.
(1)
Principle of Operation
Detonation flame arrestors prevent 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.
A detonation flame arrestor has the heat capacity and
structural design to withstand all dynamic conditions of
flame propagation and still stop the flame. A detonation
flame arrestor is used when the flame can be in any of the
deflagration or detonation states of flame propagation.
Factors Affecting Flame
Temperature Rating of Fiber Gasket
450°F / 232°C
Maximum Operating Temperature
140°F / 60°C
Burning Rating
5 minutes
Housing Material
Carbon steel
Element Material
304 Stainless steel, 316 Stainless steel
Certification
None
the flame cell to absorb the heat more quickly and efficiently.
The International Electrotechnical Commission (IEC) groups
gases and vapors into Groups IIA through IIC categories
depending on a number of factors including the Maximum
Experimental Safe Gap (MESG) of the gas. The National
Electrical Code (NEC) groups gases into A, B, C, D and
G.M. categories.
Maximum Experimental Safe Gap (MESG)
Verify that the detonation flame arrestor being
installed has the appropriate gas group rating
for your process. This information is included
in the nameplate attached to the element
housing. Do not remove or alter this nameplate.
Arrestor Performance
The Maximum Experimental Safe Gap (MESG) is the
Gas Group
WARNING
!
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.
The type of gas in the system determines its gas grouping
and therefore predetermines the type of arrestor element
required. The element must be designed to accommodate
the specific gas group that could possibly ignite and
propagate in the system. The more explosive gases require
measurement of the maximum gap between two equatorial
flanges on a metal sphere that prevents a flame from being
transmitted from the sphere to the surrounding flammable
mixture. MESG is dependent on gas composition. The
stoichiometric mixture (the ideal air/fuel ratio for the most
efficient combustion) is used to determine the minimum
MESG for a given gas.
Maximum Initial Operating Pressure,
Detonation Rating and Burn Rating
Unlimited burning should not be allowed in
any flame arrestor, regardless of its rating.
If burning can occur for a period exceeding
5 minutes starting at ambient temperature,
WARNING
!
CAUTION
(1)
North America Only
2
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Detonation
Flame
Arrestor
DFA =
Concentric
Figure 2. Cut-away view of DFA Series Detonation Flame Arrestor
/ - -
Housing
Size
72 = 72 in. 36 = 36 in. IIA (D) C = Carbon steel
Connection
Size
IEC
Gas
Group
Housing
Material
4 = 304 SST
6 = 316 SST
Element
Material
4 = 304 SST
6 = 316 SST
Model DFA 7236
Connection
Type
F = Flat face
flange
R = Raised face
flange
Options
1 = Drain Plug
2 = Pressure Tap
3 = Temperature Probe Tap
4 = Miscellaneous
5 = Protective coating
6 = Special feature
Figure 3. DFA Series Detonation Flame Arrestor Available Constructions and Model Numbering System
it is required that a temperature alarm and
shutdown system must be installed.
If the temperature sensor(s) indicate a
temperature excursion beyond anticipated
normal operating temperature, shutdown
should be initiated and review of the process
should be commenced, as necessary.
Maximum initial operating pressure is the pressure of the
system at or near static flow conditions. High pressure
deflagration and detonations can occur more easily at
higher system operating pressures than at pressures near
atmospheric. Elevated pressures condense the ignitable gas
giving the flame more matter and energy to release thereby
boosting the flame heat intensity.
Unstable (over driven) detonations exist during a deflagration
to detonation transition (DDT) before a stable detonation is
reached. This is the most severe condition where pressures
and velocities are at maximum values. Detonation arrestors
rated for unstable detonations may be placed at any location
in a piping system, provided that installation is in accordance
with all sections of this manual.
Pipe Length
Extended lengths of pipe allow the flame to advance into more
severe states of flame propagation such as high-pressure
deflagration and detonations. Although the Enardo detonation
flame arrestor is not limited by pipe length, using a minimum
length is a preferred design and installation practice.
Bends and/or Flow Obstructions
CAUTION
For maximum safety, avoid bends and flow
obstructions within 10 pipe diameters on the
protected side of the detonation flame arrestor.
Valves or other equipment that can obstruct
the flow due to restricting the piping flow area
(e.g. partially closed valves) shall be reviewed
to ensure that they cannot be in a partially
closed position during normal operation. Flame
transmission can occur due to restrictions on
the downstream side of the flame arrestor.
North America Only
3
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Model DFA 7236
Bends in piping, pipe expansions and/or contractions,
valves orifice plates or flow obstructing devices of any kind
cause turbulent flow. Turbulent flow enhances mixing of the
combustible gases, greatly increasing the combustion intensity.
This can result in increased flame speeds, higher flame
temperatures and higher flame front pressures than would
occur in normal flow conditions. Obstructions in protected side
piping can cause pressure buildup that might inhibit the effective
performance of the DFA Series under certain conditions.
Installation
WARNING
!
Always make sure that the system is at
atmospheric pressure and that there is no
ignitable gas that could flash when either
installing or maintaining the unit.
Lifting
DFA Series arrestors are not designed for single point lifting. An
appropriately designed spreader bar must be used when lifting
or moving the unit. The angle of the lift lines should be no more
than 5° from the vertical (refer to Figure 4). Recommended
shackles are Crosby 1-3/4" 25t-G-2130 (Stock No. 1019659)
or equivalent.
Connection
The arrestor should be positioned such that the entire
arrestor is accessible for removal. Install the unit such that
the flow arrow located on the unit points in the direction
travelling with the vapor flow. Models that have drain
plugs are designed for horizontal installation and should
be installed with the drain ports aligned at the bottom of
the unit. Models that have pressure taps are designed to
allow pressure gauges to be installed on both sides of the
flame cell assembly to determine blockage. The pressure
taps should be aligned at the top to allow easy viewing of
the gauges. Units that are equipped with optional internal
cleaning systems should be connected to a source of
cleaning media such as water, steam or other suitable
solvent. Observe recommended installation practice as
detailed bends and/or flow obstruction section.
Flow Direction
The DFA Series is not bi-directional when temperature
sensors are installed unless a sensor is installed on both
sides of the arrestor element assembly. All arrestors covered
in this manual can be installed either vertically or horizontally.
Consideration should be given to non-symmetrical assemblies
that include features such as clean-out ports, temperature
monitoring device or other options that might have a preferred
installation direction to suit the needs of the customer.
Piping Expansions and Reductions
Adjacent to Detonation Flame Arrestor
DFA Series arrestors are normally provided with CL150
raised or flat faced flanges. Other flanges such as CL300
are sometimes provided on special request. Make sure the
companion flanges installed in adjacent piping match the
flanges on the detonation flame arrestor.
Standard compressed fiber gaskets that withstands
temperatures of 450°F / 232°C or higher are normally used,
but other materials of equal or higher temperature capability
may be used at the customer’s discretion.
Positioning
CAUTION
The detonation flame arrestor element
is fitted with lugs for lifting the element
assembly during servicing operations. These
lugs are not intended for lifting the entire
unit. Damage to the detonation flame arrestor
may result from improper lifting. The unit
should be lifted using the lugs located on
each end-section or with appropriately rated
Nylon (PA) straps rigged on the outside
of the tension studs. Detonation flame
arrestors fitted with temperature sensors
are directional dependent if the temperature
sensor is only installed on one side of the
arrestor. The sensor must be located on the
unprotected side of the arrestor in that case.
WARNING
!
No instrument, tubing or other device
whatsoever shall circumvent the detonation
flame arrestor in such a manner to allow a
flame path to exist around the flame element
of the arrestor. When instrumentation is
installed in such a manner that it creates
a path circumventing the flame element
of an arrestor, measures must be taken
to prevent passage of flame through the
instrumentation device and/or system.
Instrumentation must be capable of
withstanding the maximum and minimum
pressures and temperatures to which the
device may be exposed and at a minimum
be capable of withstanding a hydrostatic
pressure test of 350 psig / 24 bar.
DFA Series detonation flame arrestors may be installed in
any vapor control line that is smaller than or equal to the
nominal pipe diameter of the arrestor’s connection flanges.
When it is necessary to increase the diameter of the piping
on the downstream side (unprotected) of the detonation
flame arrestor, a length of pipe at least 120 pipe diameters
must be installed between the detonation flame arrestor
and the expansion. A pipe diameter is considered as the
inside diameter of pipe having a nominal size equal to the
detonation flame arrestor’s connecting flanges.
North America Only
4
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Model DFA 7236
CENTER OF GRAVITY
CENTER OF GRAVITY
Figure 4. Lifting Diagram
North America Only
5
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Model DFA 7236
Maintenance
Detonation Flame Arrestor Element
Assembly Cleaning
1. Keep the element openings clean to prevent loss of
efficiency in absorbing heat. Remove the entire unit
and clean the elements to prevent the clogging of
particulates and other contaminants on the openings.
Clean the element with a suitable cleaning media
(solvent, soap, water or steam) then blow dry using
compressed air. Be careful not to damage or dent the
cell openings as this would hamper the effectiveness of
the unit. Do not clean the arrestor elements by rodding
with wire or other hard objects to remove blockages.
Cleaning the elements with wire or other hard objects
could damage the elements and seriously impair the
arrestor’s performance. If the arrestor element cannot
be cleaned satisfactorily, replace it.
2. For best cleaning results, use a high-pressure sprayer
with spray wand (1500 psig to 3000 psig / 103 to
207 bar) to clean the entire element surface. Hold the
spray nozzle perpendicular to the surface being cleaned
to maximize spray media penetration into the element.
Alternately spray each side of the element surface
until clean.
3. The cleaning interval should be governed by the
amount and type of particulate in the system to which
it is installed and must be determined by the user. To
determine the maintenance interval, the user should
check the element in the first few months of operation to
find how quickly particulate accumulates in the cells.
4. Thoroughly clean the gasket sealing faces being careful
not to damage the sealing surface. For reassembly, use
new gaskets and place them in the machined recess of
each interior flange on the two conical sections.
5. Replace the flame element assembly with a new
assembly or properly cleaned and inspected
existing unit.
6. Locate the flame cell assembly such that it seats onto
the gaskets.
7. Replace all tensioning studs and tighten the outer nuts
hand tight only.
8. Torque the bolts in sequence as shown in the Torquing
Instruction section.
Inspecting Model DFA Element Assembly
Following Flame Propagation Event
1. Inspect the outboard flame cells for damage
immediately following a deflagration, detonation and/or
stabilized burn.
2. Carefully remove the element assembly from the
arrestor with the entire flame arrestor out of the line.
3. Inspect the flame cells and the screens visually for
any signs of corrosion or other damage and inspect
the flame cells with a calibrated pin gauge to ensure
maximum crimp size openings do not exceed the
following values for their respective gas group. Use the
following pin gauges as no-go gauges:
• Model DFA-7326/D Explosion Group D (IIA) –
0.063 in. / 1.6 mm
4. If any damage is noted or crimp openings exceed
maximum size allowable as indicated by the entry of the
no-go gauge, replace the element assembly.
Note
Under no circumstance shall any element
assembly not provided by Emerson be used
in this assembly. Failure to use the correct
screens (internally between the flame cells)
may lead to arrestor failure.
Element Assembly, Disassembly and
Reassembly Instructions
WARNING
!
Isolate gas supply and bring system
to atmospheric pressure to prevent
ignitable gas from flashing while
performing maintenance.
CAUTION
Removal and installation of the detonation
arrestor and associated piping require the
use of adequate equipment and manpower
to prevent injury. The Model DFA-7236
detonation flame arrestor should be entirely
removed from the system for servicing.
To remove the element assembly:
1. Loosen all outermost nuts on tension studs.
2. Tighten the inside jacking nuts on the tension studs
forcing the two conical sections apart. When the two
flange faces have separated, remove the tension studs
that do not have inside jacking nuts, so that the element
assembly can be removed. The inside jacking nuts are
installed on all tension studs that facilitate jacking the
unit apart. The inside jacking nuts are not installed on
tension studs that are taken out, for ease of removal.
3. Thoroughly clean the gasket sealing faces being careful
not to damage the sealing surface. For reassembly,
lightly grease one side of a new gasket and place it in
the machined recess of each interior flange on the two
conical sections.
North America Only
6
Page 7
Model DFA 7236
Table 1. Tightening Steps and Torque Values
MODEL BOLT SIZE
DFA-7236 1.50 in. Snug 80 / 110 250 / 340 450 / 610 700 / 950 1000 / 1360
1. Using machine oil as lubricant. See Bolt Lubrication section on page 7 and torque correction factors for other lubricants in Table 2.
DESCRIPTION COEFFICIENT OF FRICTION MULTIPLY TORQUE VALUE IN TABLE 1 BY
Machine Oil f = 0.15 1.00
API SA2 Grease f = 0.12 0.80
Nickel-based Lubricant f = 0.11 0.73
Copper-based Lubricant f = 0.10 0.67
Heavy-Duty Lubricating Paste f = 0.06 0.40
1 2 3 4 5 6
Table 2. Torque Correction Factors for Common Lubricant
4. Replace the flame element assembly with a new
assembly or properly cleaned and inspected existing unit.
5. Loosen the jacking nuts on the tension rods until the
TIGHTENING STEPS AND TORQUE (FT-LBS / N•m)
• Brush suitable for applying lubricant to the studs.
• Wiping rags necessary for the clean up of
excessive lubricant.
(1)
flame cell assembly seats onto the gaskets.
6. Replace all tensioning studs and tighten the outer nuts
hand tight only. Check to be sure that all the jacking nuts
are completely loose and not making contact with the
flange face.
7. Torque the bolts in sequence as shown in the Torquing
Instruction section.
Torquing Instructions
Procedure
1. Use studs and nuts that are free of visible contamination
and corrosion.
2. Apply lubricant to the threads of the stud protruding
outboard of the interior flanges and to the face of the hex
nuts which will contact the flange.
3. Assemble the nuts to the studs such that the amount
of thread extending outboard beyond the nut is
approximately equal on both ends.
CAUTION
4. Tighten the nuts to the torque values shown in Table 1
following the designated sequence, repeating the
Excessive or uneven torque can cause
permanent damage to gaskets and housing.
sequence as shown. Flange pattern tightening sequences
are shown in Figure 5.
North America Only
Tools/Supplies Required
• Hand operated conventional torque wrench or
power assisted torque wrench appropriate for the
specified torque.
• Socket wrenches of the proper size to fit the hex nuts
being tightened.
• Molydisulfide based lubricating paste. Heavy-Duty
Lubricating Paste.
Bolt Lubrication
Lubrication affects required torque of clean fasteners in good
condition more than any other factor. In fact, 90% of applied
torque goes to overcome friction while only 10% actually
stretches the bolt. Table 1 assumes that only machine oil is used
as a lubricant. Table 2 shows a list of several common lubricants
and their effect on torque required to stretch bolts to 50% of their
yield strength. Most are available from local bearing distributors.
7
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Model DFA 7236
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16
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8
4
70
66
62
58
54
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2
Webadmin.Regulators@emerson.com
Enardo.com
Emerson Automation Solutions
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McKinney, Texas 75070 USA
T +1 800 558 5853
+1 972 548 3574
Tulsa, OK 74146 USA
T +1 918 662 6161
Europe
Bologna 40013, Italy
T +39 051 419 0611
Figure 5. Flange Pattern Tightening Sequence
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D104263X012 © 2018 Emerson Process Management Regulator
Technologies, Inc. All rights reserved. 03/18.
The Emerson logo is a trademark and service mark of Emerson
Electric Co. All other marks are the property of their prospective owners.
Enardo™ is a mark owned by Regulator Technologies Tulsa, LLC, a
business of Emerson Automation Solutions.
The contents of this publication are presented for informational purposes
only, and while every effort has been made to ensure their accuracy,
they are not to be construed as warranties or guarantees, express or
implied, regarding the products or services described herein or their use
or applicability. We reserve the right to modify or improve the designs or
specications of such products at any time without notice.
Emerson Process Management Regulator Technologies
Tulsa, LLC does not assume responsibility for the selection, use or
maintenance of any product. Responsibility for proper selection, use
and maintenance of any Emerson Process Management Regulator
Technologies Tulsa, LLC product remains solely with the purchaser.
North America Only
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