Page 1
The Blue Flame Series
Make-Up Air Engineering Manual
Midco International Inc.
4140 West Victoria Street Chicago, Illinois 60646
tel 773.604.8700 fax 773.604.4070
web www.midco-intl.com e-mail sales@midco-intl.com
HMA-2
Quality Designed for Proven Performance
703
8471 34
Printed in USA
Reduced NO2and CO Emissions: Lower emissions
levels that easily pass the new ANSI Z83.4 and Z83.18
standards.
Higher Temperature Rise: The two stage combustion
process lowers NO
2
emissions which is the limiting
factor in temperature rise. (See page 3)
Increased Capacity: Up to 750,000 BTU'S per foot.
(Higher BTU levels can be achieved if ANSI Z83
Standards for CO and NO
2
emissions are not of a
concern. Process heaters can fire up to 1,000,000
BTU'S a foot or more.)
Increased Differential Pressure Drop and Higher
Velocities: HMA-2 burners can operate between 0.05"
to 1.4" W.C. differential pressure range or in air
velocity between 800 fpm to 4000 fpm.
Flame Stability: Two st age combustion provides better
flame stability and emission control, allowing for a
shorter flame and easier profile configuration.
Reduced Inventory Costs: Single burner casting can
be fired with natural, propane or butane gas
1
, reducing
burner inventory.
Reduced Shipping Costs: A smaller, lighter casting
than the competition’s, can cut your freight costs up to
50%.
Turndown: 30-1 turndown can easily be achieved with
proper modulating controls and valves. (Higher
turndown possible depending on equipment design.)
1
Consult Midco for applications using butane fuels.
DIRECT FIRED MAKE-UPAIR BURNERS are used in
industrial and commercial applications to maintain the
desired environmental temperatures required by critical
processes i.e. health purposes, production systems,
quality control, comfort and loss prevention where it is
necessary or required to exhaust large amounts of
conditioned air.
Make-up Air Systems used as stand alone heating
systems or operating in combination with central
heating plants systems can be cost effective in three
ways: 1) reducing the initial expenditures, 2) tempering
incoming air which may extend the life of expensive
central heating plants and 3) reducing excessive
equipment cycling or premature component failures
due to increased heating demands.
Our innovative two stage combustion burner is not
just a modification or improvement of the old, but a
completely new approach to direct-fired combustion.
The two-stage combustion improves control of the
flame process, meets or exceeds the new ANSI
Standards while outperforming the competition. By
incorporating two separate flames within the burner
combustion zone, the flame is more stable, shorter
and cleaner, permitting the reduction of emissions
levels and allowing for higher temperature rise and
higher tolerance to varying conditions when placed in
the profile opening.
Features and Benefits
New Technology in
Direct-Fired Gas Burners
Patent Pending
#10/306,199
Page 2
Specifications
2
*Firing Rate .............................................................. Up to 750,000 Btu/hr/ft
750,000 + Contact Midco
Burner Manifold Pressure
Natural Gas ................................................. 4.2 to 8 inch W.C.
Propane Gas .............................................. 1.6 to 3 inch W.C.
Pilot Capacity ............................................................ 12,000 Btu/hr
Pilot Manifold Gas Pressure
Natural Gas ................................................. 3.5 inch W.C.
Propane Gas .............................................. 2.0 inch W.C. **
Pressure Drop Across the Burner ............................ 0.05 to 1.4 inch W.C.
Air Velocity Across the Burner ................................... 800 to 4,000 FPM
Burner Turn-down Ratio ........................................... 30 to 1
Flame Length ............................................................. 10 inches at a full firing rate
* Firing rate is dependent on the pressure across the burner. Please see the included
charts for recommended burner sizing.
** Using a natural gas pilot on propane.
*Burner Configurations *Pilot Configurations
Part # Part #
6 inch Straight Section (15.24cm) 1050700 Spark rod and flame rod 1190800
6 inch Straight Section with Back Inlet (15.24cm) 1230700 Spark rod and UV 1200300
12 inch Straight Section (30.48cm) 1010700 Remote flame rod 1220800
12 inch Straight Section with Back Inlet(30.48cm) 1060700 Remote UV 1240800
Elbow Section 1070700 Pilot with spark rod only 1210800
Tee Section 1080700 Flame rod 1360-03
Spark rod 1342-00
Table 1 - Burner and Pilot Configurations
Midco International Inc. reserves the right to change the construction or configuration of its products at
any time.
All information is based on laboratory testing. Different unit size and/or configurations may affect data.
* See Page 15, Figure 1b for configuration reference.
Page 3
Burner Performance
3
______________________________________________
Chart 1 - CO and NO2Emissions Data
*For temperature rise up to 160°F that meets the ANSI Z83 standards contact Midco.
Page 4
4
Installation
Chart 3 - BTU's verses Gas Pressure ( " W.C.)
Chart 4 - Pressure Across the Burner verses Profile Velocity
Chart 2 - BTU's verses Pressure Drop
Page 5
1. Required BTU:
BTU/hr = Blower SCFM x Desired Temp. Rise x 1.08
2. Required Burner Length:
Feet of burner = [Required BTU/hr]÷[Burner Firing Rate (BTU/hr/ft)]
The Burner Firing Rate should correspond to the pressure drop across the burner
shown in Chart 2.
3. Required Profile Area:
Total Burner Area = Number of burner sections x burner area
Net Profile Area = Rated Fan (SCFM) ÷ Profile Velocity (SFPM)
The Profile Velocity can be determined from the following:
∆ P is the pressure drop across the burner
Profile Area = Net Profile Area + Total Burner Area
______________________________________________
Sizing the burner and the corresponding profile for a 5,000 SCFM and a 115 degrees
temperature rise.
1. Required BTU:
BTU/hr = Blower SCFM x Desired Temp. Rise x 1.08
BTU/hr =5,000 (SCFM) x 115 (∆T) x1.08 = 621,000 BTU/hr
2. Required Burner Length:
Feet of burner = [Required BTU/hr]÷[Burner Firing Rate (BTU/hr/ft)]
To determine the optimum burner length we can choose from a combination of 12
inch or 6 inch burner sections referring to Table 1. We can either fire the burner
at a rate of 621,000 BTU/hr per ft, or we can fire the burner at 414,000 BTU/hr per ft
(1.5 feet of burner). Refer to Chart 3 for the fuel pressures requirements at different
firing rates.
3. Required Profile Area:
Total Burner Area = Number of burner sections x burner area
Total Burner Area = 1.0 (ft) x 0.65 = 0.650 ft
2
Or
Total Burner Area = 1.5 (ft) x 0.65 = 0.975 ft
2
5
Profile Setup Example
Profile Setup
Installation
(Burner Section) Burner Area
6 inch 0.32 sq. ft.
12 inch 0.65 sq. ft.
T Section 0.77 sq. ft.
Ell Section) 0.65 sq. ft.
(Burner Section) Burner Area
6 inch 0.32 sq. ft.
12 inch 0.65 sq. ft.
T Section 0.77 sq. ft.
Ell Section 0.65 sq. ft.
Page 6
6
Installation
Net Profile Area = Rated Fan (SCFM) ÷ Profile Velocity (SFPM)
The Profile Velocity should be determined based on the burner firing rates. If
we choose to fire the burner at 621,000 BTU/hr/ft then the profile opening
should be sized for a pressure drop of 0.8 inch W.C. across the burner. If the
firing rate is 414,000 BTU/hr/ft then the profile opening should be sized for a
pressure drop of 0.4 inch W.C. across the burner. The corresponding profile
velocity across the burner should be determined from Chart 4 or use the
following equation.
For the 621,000 BTU/hr/ft
Net Profile Area = 5000 (SCFM) ÷ 3086 (SFPM)=1.62ft
2
For the 414,000 BTU/hr/ft
Net Profile Area = 5000 (SCFM) ÷ 2182 (SFPM)=2.29ft
2
To calculate the profile area needed for both cases:
Profile Area = Net Profile Area + Total Burner Area
For the 621,000 BTU/hr/ft
Profile Area = 1.62 + 0.650 = 2.27 ft
2
For the 414,000 BTU/hr/ft
Profile Area = 2.29 + 0.975 = 3.265 ft
2
To calculate the length of the profile opening add burner length to the desired clearance:
For the 621,000 BTU/hr/ft case
12 inch + 4 inch (2 inch on each side) = 16 inch (1.3ft)
For the 414,000 BTU/hr/ft case
18 inch + 4 inch (2 inch on each side) = 22 inch (1.83ft)
To calculate the height of the profile opening divide the profile area by the profile length:
For the 621,000 BTU/hr/ft case
2.27 ft
2
÷ 1.3 ft = 1.75 ft (21 inch)
For the 414,000 BTU/hr/ft case
3.265 ft
2
÷ 1.83 ft = 1.78ft (21.5 inch)
______________________________________________
IMPORTANT: Furnace cement must be used to join and seal all burner casting sections,
and end flanges only. If this procedure is not performed, gas leakage will
occur. Use
10-24x3/8" stainless steel screws and nuts or stainless steel rivets. UNDER NO
CIRCUMSTANCES SHOULD STANDARD GRADE HARDWARE OR ALUMINUM RIVETS
BE USED.
When assembling Make-Up Air Burners, a few simple but important assembly procedures
must be followed to insure Burner Performance. Care should be taken when removing,
assembling and placing the burner into the heater.
1. Examine the baffles for structural integrity; only new undamaged components
should be used.
Profile Setup Example
Continued
Burner Assembly
Page 7
2. Assemble individual burner cast iron sections first.
3. When joining the baffle sections to the burner casting, place a gasket between the
casting and the baffles, do not tighten the cast iron sections until the entire unit is
assembled. Baffles can be riveted together with stainless steel rivets or joined with
stainless steel screws.
4. Prepare a mixture of furnace cement thinned to the consistency of a heavy cream.
5. Apply furnace cement to both mating surfaces of the burner castings and
end flanges only.
6. After sections are joined,wipe off excess furnace cement and make sure you do not clog
any gas or air ports.
7. After all baffle plates are tight, secure all baffle plates to the burner casting. Make
sure all bolts and rivets are tight.
8. After all sections are assembled, check for potential gas or air leaks. If necessary,
close up any remaining gaps with furnace cement.
9. For high fire start systems, the first adjacent gas port hole (next to the pilot) should be
plugged with furnace cement. See Figure 8 - Pilot Configuration.
______________________________________________
The performance of the HMA-2 burner depends on the unit in which the burner is located.
The burner can perform differently in different units and can obtain different end results.
Maintaining a relative laminar flow around the burner and providing a sufficient space
between the burner and the blower is a key factor in obtaining best burner performance.
The unit should be free of any obstructions that can create turbulent effect on the air.
The burner performance is highly dependent on its application and installation in the heater.
Factors such as airflow around the burner, burner positioning in the profile , as well as, the
profile sizing have high influence on the final emissions levels . Midco does not guarantee
combustion results prior to performing actual combustion tests.
The burner should be located in the center of the profile. The profile clearance from ends of
the burner should be kept at approximately 1 to 4-inches. Typically setting the profile 2" from
the end plates is recommended. Any reinforcements used on the edge of the profile opening
should be on the downstream side of the profile. The burner can be mounted either
vertically or horizontally. Since the airflow varies from unit to unit best results should be
determined by actual testing.
7
Installation
Burner Placement
in the Profile
Note: Any reinforcements around the profile plates
should be down stream of the profile plate
Figure 1a - Burner Placement in the Profile
Page 8
______________________________________________
The HMA-2 Burner is designed to operate in a make-up air heater and in an air stream
taken directly from outdoors. To avoid stratification of the heated air, the burners should be
located on the intake side center to the blower. Such positioning will take advantage of the
blower mixing effect and ensure minimum temperature stratification. It will also allow for a
relatively uniform airflow across the burner resulting in a clean combustion.
The total pressure of the blower must include allowance for the resistance of the heater and
pressure drop across the burner, together with pressure losses at the inlet screen, inlet
louvers, filters, plus the external pressure rating of the heater, if any. Contact equipment
manufacturer for proper information.
______________________________________________
8
Installation
Pull-Thru System
Figure 2a - Pull-Thru System
Figure 1b - Burner Placement in the Profile
Figure 2b - Pull-Thru System
Page 9
The HMA-2 Burner will operate satisfactorily when located downstream of the blower. A
mixing plenum may be required at the heater discharge opening to insure minimum temperature stratification. Blower and motor selection must be made on the basis of corrections for
the coldest anticipated inlet temperature. In the push-thru system the heater outlet CFM will
vary due to the expansion of air.
Push-Thru System
Installation
9
Figure 4 - Installation in a Duct
Figure 5a - Gas Train Assemblies
Figure 3 - Push-Thru System
Page 10
______________________________________________
10
Installation
Figure 5b - Direct Spark Gas Train Assemblies
Gas Inlet Capacities
Maximum Feet of Burner
Inlet Size Natural Propane Mfd.
1.5 " NPT End Inlet 4' 5' 3'
2" NPT Back Inlet 6.5' 8' 4.5'
Centrally Located
Table 2 - Gas Inlet Capacities
Page 11
Burner operation depends on the unit control setup in which the HMA-2 burner is used. A
typical setup should consist of a Flame Safety Control with appropriate air flow proving system and a Modulating Gas Control System.
1. Verify the pressure across the burner. The pressure across the burner can be
measured by placing two static pressure probes, one downstream and one
upstream of the profile opening and measure the differential pressure. The
pressure should be within burner operating specifications and within the expected
calculated pressure.
2. With the burner off check the Flame Safety Air Proving System
a. Check the operation of the air proving system for low and high airflow setting.
Refer to the Specifications of the Flame Safety Control for setup
instructions and air switch operational characteristics.
3. Adjust the main gas pressure regulator to the pressure needed for the high fire
according to Chart 3. Take into account pressure drops thru the gas valves and other
components in the valve train.
4. For continuous, intermittent, or interrupted ignition systems
a. Pipe the pilot gas supply line up stream of the main gas valve.
b. Adjust the pilot pressure regulator to 3.5 inch W.C. for Natural Gas or 2.0 inch
W.C. for propane gas.
5. For direct spark ignition system
a. Pipe the pilot gas supplied line to the main gas line downstream of the main
gas valve.
b. Adjust the pilot pressure regulator to 3.5 inch W.C. for Natural Gas or 2.0 inch
W.C. for propane gas.
6. Depending on the pilot configuration make following adjustments.
a. For Spark rod and flame rod configurations
Make sure the flame rod is pointing towards burner manifold.
Make sure the flame rod is not touching baffles or burner manifold.
Make sure the spark rod is positioned above the pilot gas tube and that it will
spark to the end of the gas tube. See Pilot Detail Drawings for this setting on
page 16.
b. Spark rod and UV
Make sure the spark rod is positioned above the pilot gas tube and that it will
spark to the end of the gas tube.
7. Pilot ignition
a. Make sure the main gas valve to the burner is closed for intermittent or
interrupted ignition.
b. Observe the pilot flame, the flame should be blue and should extend
approximately to the half of the burner end plate.
c. Check the flame signal.
8. Main burner ignition
Close the manual gas valve.
a. Set the Modulating Gas Control System to high fire position.
· Slowly open the manual gas valve.
· Observe the flame at high fire; the flame should be blue approximately 10
to 12 inches long. If the flame is long, lazy and orange the air to fuel ratio
is not correctly adjusted . The pressure across the burner should be
increased, refer to Chart 2.
· Check the flame signal.
· Check the manifold pressure to the corresponding firing rate. If the manifold
pressure does not correspond to the pressures shown in Chart 3. Check
for gas leaks.
Close the manual gas valve.
b. Set the Modulating Gas Control System to low fire position.
Slowly open the manual gas valve.
· The flame should be evenly extending in the burner.
· The flame should be located in the casting of the burner.
· Check the flame signal.
11
Burner Installation
Installation
Page 12
Installation & Trouble Shooting
For a high fire start system the first gas port next to the pilot might require to be blocked
using furnace cement to prevent potential pilot blow outs and flame failures. See page 7
(Burner Assembly) and see Figure 8 - Pilot Configuration.
Slight redness and warpage of the baffle plates may occur at the high and intermediate fire
inputs. This will not harm the burner. Once an initial discoloration and warp has taken ("set")
no further permanent change will take place.
If the end plates redness occurs during high and intermediate fire inputs, the distance
between the end plates and the profile opening might not be sufficient for the air to cool the
end plates. Profile readjustments might be necessary.
______________________________________________
Annual maintenance of HMA-2 burner is recommended to ensure trouble free operation.
1.Make sure the system is off
2.Inspect the burner baffles for plugged openings
a.Clean baffles with wire brush
b.Make sure the baffles are tightly attached to each other and to the burner casting.
3.Inspect the burner casting for plugged openings
a.Clean casting with wire brush
b.If necessary re-drill gas ports with a number 31 drill size and air ports with a number
43 drill size.
4.Turn the system on and visually inspect the flame.
5.For Service Bulletins on the cleaning and maintenance of burners contact Midco.
______________________________________________
The Midco HMA-2 Burner is only a component of the complete system. For trouble shooting
of the equipment contact the OEM (Original Equipment Manufacturer) or the component
manufacturer.
If the pilot fails to light, install a manometer on the pilot pressure tap. Check for 3.5" W.C.
for natural gas or 2" W.C. for propane. If no gas check for voltage to pilot solenoid valve. If
no voltage check operating controls or primary flame safeguard. If voltage to pilot solenoid
valve is present and if there is 3.5" W.C. gas pressure at pilot pressure tap then check for
spark or flame rod settings. If there is no voltage to pilot solenoid valve, refer to Flame
Safety control specifications or contact the original equipment manufacturer.
If Main Burner fails: If no main flame check manifold pressure. If no manifold pressure
check for voltage to the gas solenoid valve and check if main manual valve is open. If no
voltage to gas valve refer to Flame Safety control specifications or contact the original
equipment manufacturer.
If the pilot fails as main gas valves open, the first adjacent gas port hole (next to the pilot)
should be plugged with furnace cement. See Figure 8 - Pilot Configuration.
______________________________________________
12
Burner Installation
Continued
Burner Maintenance
Trouble Shooting
I.
II.
III.
IV.
Page 13
13
Burner Configuration
Figure 6 - Burner Sections - Assembly
Page 14
14
Parts - Isometric View
Figure 7 - Burner Assembly Parts - Isometric View
Page 15
Parts List for Isometric View
Burner Configuration 6" Straight 6" Back Inlet 12" Straight 12" Back Inlet Ell Section Tee Section
Part Number 1359-09 1398-05 1364-05 1361-07 1362-07 1365-06
Item
No. Part Description Part No Quantity Quantity Quantity Quantity Quantity Quantity
1 Burner Casting 1 1 1 1 1 1
2 HMA-2 6" Baffle 1395-23 2 2 4 4 2 2
HMA-2 Tee Baffle 1395-11 12
HMA-2 Outside Corner Baffle 1395-35 1
3 HMA Blank End Plate 1354-50 1 1 1 1 1 2
4 HMA Pilot End Plate 1354-60 1 1 1 1 1 1
5 Pilot See pilot listing on Page 16 - Pilot Configuration (For selection)
6 Baffle Clamp 1356-00 2 2 4 4 2 2
Inside Baffle Clamp 1356-10 24
7 6" Baffle Gasket 1373-02 2 2
12" Baffle Gasket 1373-03 2 2 1
Outside Baffle Gasket 1373-04 2
Inside Baffle Gasket 1373-05 24
8 Blank Flange 1372-02 1 1 1 1 1 2
9 Inlet Flange (Tapered) 1352-02 1 1 1 1 1 1
10 Support Bracket 1374-00 2 2 2 2 2 3
11 5/16-18x1-1/2 Hex
Head Cap Screw 6 6 6 6 6 9
12 5/16 Lock Washer 6 6 6 6 6 9
13 5/16-18 Brass Hex Nut 6 6 6 6 6 9
14 10-24x9/16 Phillips Rd
Hd S.S. Mach Screw 4 4 8 8 8 12
15 S62 Steel Rivet Body 12 12 22 22 22 25
Table 3 - Burner Assembly Parts List
15
Page 16
______________________________________________
1. Conversion of SCFM to Actual CFM of air
SCFM = CFM x
ρ
_____
0.075
2. Air density as a function of Temperature --
ρ
= 1.35 x
Barometric Pressure (in Hg)
____________________
T
(out)
+ 460
3. Change in Standard Barometric Pressure as a function of Altitude
Barometric Pressure (in.Hg) = 29.921x (1_6.8753 x 0.000001x altitude (ft))
∧
5.2559
4. Temperature difference -- Temperature Rise = T
(out)
- T
(in)
5. Energy equation - - BTU/hr = SCFM x Temperature Rise x 1.08
Where: 1.08 is a sensible heat equation constant
1.08 = 0.2397
(
BTU
)
x 60
(
min
)
x 0.075
(
lb
)
_____ ___ ___
lb H ft
3
16
703
8471 34
Printed in USA
Midco International Inc. 4140 West Victoria Street * Chicago, Illinois 60646
tel 773.604.8700 fax 773.604.4070 web www.midco-intl.com email sales@midco-intl.com
Figure 8 - Pilot Configuration
Parts - Pilot Configuration & Mounting / Equation Reference
Equation Reference
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