The document compares changes made between editions of API 560 standards regarding specifications for fired heaters and burners. Some key changes include: the 4th and 5th editions specify that burner design ensure complete combustion and limit flame length; minimum burner clearances have been updated and specifications added for ultra low NOx burners; and material requirements have been specified for components operating in high H2S environments. Furnace Improvements Services is an engineering company that provides design and consulting services for fired heaters and boilers, including CFD modeling, revamps, and new installations.

1. API 560 Standards Comparison
Furnace Improvement Services, Texas
Furnace Improvements
www.heatflux.com
Uniform Heat Transfer for Fired Heaters 1
Inclined Firing System Split Flow Technology Flue Gas Injection Draft Control System
API 560
Changes in Burner Specifications
1
1st
, 2nd
, and 3rd
Edition- 10.1.1
Burner design and installation shall ensure against flame impingement on
tubes and tube supports when burners are operating at maximum heat
release.
4th
and 5th
Edition- 14.1.1
Burner design, selection, spacing, location, installation and operation shall ensure against flame impingement on tubes, tube
supports and flame exiting the radiant section of the heater throughout the entire operating range of the burners. The location and
operation of burners shall ensure complete combustion within the radiant section of the heater.
2
Added in 2nd
Edition 2nd
& 3rd
(10.1.2), 4th
and 5th
Edition- 14.1.2
Burners shall be designed in accordance with all local and national statutes and regulations.
3
1st
Edition- Table 11
Minimum Clearance for Burners in Natural Draft Operation
-Burner clearances specified for conventional burners only
2nd
and 3rd
Edition- Table 12
Minimum clearances for Natural Draft Operation-
a. The values of longitudinal clearances A and D for conventional burners mentioned in 2nd
edition table should be multiplied a
factor of 1.3 and 1.5 respectively to get clearances for Low NOx burners.
b. In 3rd
Edition clearances are specified directly for Low NOx burners. For conventional burners, the longitudinal clearances are to
be reduced by a factor of 0.77 and 0.67 respectively.
4th
(Table 13) and 5th
(Table 15) Edition
Minimum clearances for Natural Draft Operation-
-In addition to changes in 2nd
and 3rd
editions, the minimum natural draft clearances are also specified for Ultra Low NOx burners.
The values of longitudinal clearances (A & D) mentioned for Low NOx burners should be increased by 20%.
Inclined Firing System
Most tube failures in fired heaters occur due to high tube metal temperatures (TMTs). Flame impingement due to long burner flames results in higher TMTs and
coking that affect the performance of the heater. Furnace Improvements developed the patented Inclined Firing System (IFS) to reduce flame impingement on
heater tubes.
With this burner arrangement, a heater will have the following advantages:
• Elimination of hot spots
• Longer tube life
• Increased heater run lengths
• More uniform heat transfer along the tubes’ lengths
Lower coking rates of internal tube surfaces

2. API 560 Standards Comparison
Furnace Improvement Services, Texas
Furnace Improvements
www.heatflux.com
Uniform Heat Transfer for Fired Heaters 2
Inclined Firing System Split Flow Technology Flue Gas Injection Draft Control System
4
Added in 4th
and 5th
Edition 4th
and 5th
Edition- 14.1.4
In addition to 14.1.3 (Minimum burner clearance for natural draft operation), the following shall apply-
a) The number and size of burners shall ensure that the visible flame length is a maximum of two-thirds of the radiant section
height. For floor-fired heaters the CO content at the bridge wall shall be a maximum of 40 ppm by volume for gas-fired heaters
or 80 ppm by volume for oil-fired heaters, at maximum design firing conditions.
b) For horizontal opposed firing, the minimum visible clearance between directly opposed firing flame tips shall be 4 ft.
5
Added in 4th
and 5th
Edition 4th
(Table 14) and 5th
(Table 16) Edition-
Minimum Clearances for Forced Draft Operation-
Horizontal distance to centerline of wall tubes from burner centerline is included.
6
1st
(10.1.3), 2nd
and 3rd
Edition (10.1.4)
Burners shall be sized for a maximum heat release at the design excess
air based on the following:
Burner Sizing 1st
– 3rd
Edition
Number of burners % of Normal Heat Release
Less than 5 125
6- 7 burners 120
Greater than 8 115
4th
and 5th
Edition (14.1.7)
All burners shall be sized for a maximum heat release at the design excess air based on the following:
Burner Sizing 4th
– 5th
Edition
Number of burners % of Normal Heat Release
Less than 5 120
6- 7 burners 115
Greater than 8 110
7
1st
Edition- 10.1.5
Gas pilots shall be provided for all burners firing liquid fuels
2nd
& 3rd
(10.1.6); 4th
& 5th
(14.1.9) Edition
Gas pilots shall be provided for each burner, unless otherwise specified
N 744 Boiler NOx Reduction Project
Furnace Improvements (FIS) was approached to convert a CO boiler in Unit 40 to be a standalone refinery fuel gas fired boiler, and reduce NOx emissions. The
existing boiler was revamped into a fuel gas fired boiler with a maximum capacity of 400,000 lb/hr of steam @ 625 psig, 750 °F and reduced the NOx emissions down
to 0.02 lb/MMBTU.
FIS developed a heat transfer model of the boiler. Analyzed the performance of the boiler with NOx reduction and provided the client with various options for NOx
reduction. They selected the option of ultra low NOx burners with external flue gas recirculation and steam injection into the burners.
FIS scope of services included the following:
1. Replace existing burners with new Ultra-Low NOx Burners and FGR Fan
2. Provide new Economizer: FIS installed a new economizer which increased the efficiency of the boiler
3. Steam Super Heater Modifications: The existing heat transfer surface was inadequate and steam temperature was to drop to about 680°F after the revamp.
4. Firebox Modifications: FIS maximized the heat transfer surface in the firebox by sealing the CO ports with water wall panels, and removing the refractory from
the floor and the roof.
5. New Attemperator: FIS installed a new attemperator to maintain a constant super heat temperature at all boiler loads.

3. API 560 Standards Comparison
Furnace Improvement Services, Texas
Furnace Improvements
www.heatflux.com
Uniform Heat Transfer for Fired Heaters 3
Inclined Firing System Split Flow Technology Flue Gas Injection Draft Control System
8 Added in 2nd
Edition
2nd
& 3rd
(10.1.7); 4th
& 5th
(14.1.10) Edition
a) The pilot shall have a nominal heat release of 75,000 Btu/hr. The minimum heat release shall be approved by the purchaser if it is
for a high capacity burner whose heat release is 15×106
Btu/hr or greater.
b) The pilot burner shall be provided with a continuous supply of air, under all operating conditions. This includes operation with
the main burner out of service.
c) The pilot burner shall remain stable over the full firing range of the main burner. It shall also remain stable upon loss of main
burner fuel, minimum draught, all combustion air flow rates and for all operating conditions.
4th
& 5th
(14.1.10) Edition
In addition to above points, following two more points were included in 4th
and 5th
edition-
d) The pilot shall be positioned and sized to ensure that it is capable of lighting any of the main burner fuels. The purchaser shall
specify the minimum main fuel flow rate during cold-burner light-off.
e) The pilot shall be capable of relighting an individual main burner over the full range of fuels. The combustion air flow rate might
need to be reduced for satisfactory reignition, particularly for forced-draught and Low-NOx burners.
9 Added in 2nd
Edition
2nd
Edition- 10.1.9
Burner tiles shall be pre-fired to no less than 500°F (260°C)
3rd
(10.1.9), 4th
& 5th
(14.1.12) Edition
Burner tiles shall be supplied, pre-dried as required, so as to allow full firing after installation without further treatment. Burner tiles
fabricated from water-based and hydrous materials shall be pre-dried to no less than 260 °C (500 °F).
Improve the flame profiles in the heater and increase the run length to 5-6 years
The heater had frequent decoking requirement (every 2.5 years) and flames were impinging on the radiant tubes. CFD simulations were carried out for
the following cases to analyse the flue gas circulation pattern, flame characteristics and radiant tube metal temperatures. The existing case heater
section with large heat release per burner. FIS proposed to replace each large burner by 4 smaller burners.
Benefits achieved-
1. Significant reduction in radiant tube metal temperatures
2. Flame height is reduced by more than 50% for the proposed case
3. Average CO levels at each cross-section of the heater reduced considerably, showing a faster combustion and lower flame heights

4. API 560 Standards Comparison
Furnace Improvement Services, Texas
Furnace Improvements
www.heatflux.com
Uniform Heat Transfer for Fired Heaters 4
Inclined Firing System Split Flow Technology Flue Gas Injection Draft Control System
10
1st
Edition (10.1.7), 2nd
Edition (10.1.11),
Burners shall have a turndown capability to at least 40% of the
normal heat release without adjusting the air controls
3rd
Edition
Deleted
4th
and 5th
Edition- 14.1.14
The burner shall maintain flame stability when operating at no less than 33 % of the maximum heat release settings without
adjusting the air controls.
11 Added in 2nd
Edition
2nd
& 3rd
(10.1.10); 4th
and 5th
(14.1.13)
The materials used for construction of a burner shall be chosen for strength, as well as temperature- and corrosion-resistance, for the
anticipated service conditions. Burner components shall be designed in accordance with the minimum requirements shown in Table
13 (2nd
/3rd
Edition) / Table 15 (4th
Edition) and Table 17 (5th
Edition).
Table 13 (2nd
/3rd
Edition) / 15 (4th
/5th
Edition)- Materials of Construction
a. In 3rd
edition the material 321L SS is replaced with 316L wherever it was specified.
b. In 4th edition, for fuel gas tip, where fuel content has >100 parts per million H2S and either >300° fuel or >400°F combustion air,
the construction material must be AISI 310 SS. In 3rd
edition for the same condition 316L SS material was specified.
c. In 4th
and 5th
edition wherever mineral oil is specified to be used, it is specified that Castables shall be used for oil firing were
surfaces can be soaked with fuel oil.
12 Added in 2nd
Edition
2nd
(10.1.12); 3rd
(10.1.11); 4th
& 5th
(14.1.15) Edition
At maximum design, the burner shall be selected to use no less than 90 % of the maximum available draught loss for the maximum
specified heat release.
Combustion Modeling of Heater using CFD
The Existing configuration had issues of flames leaning towards the radiant tubes and impingement of hot flue gases
on radiant tubes.
CFD simulations were carried out for the following cases:
• Existing case:
Quarter heater with three burners
• Proposed case:
Similar configuration; burners with higher air side pressure drop and inclining towards the centre of the heater
Benefits-
• Hot flue gas recirculation near the tubes has reduced in the proposed case
• Significant reduction in maximum tube metal temperature

5. API 560 Standards Comparison
Furnace Improvement Services, Texas
Furnace Improvements
www.heatflux.com
Uniform Heat Transfer for Fired Heaters 5
Inclined Firing System Split Flow Technology Flue Gas Injection Draft Control System
13 Added in 2nd
Edition
2nd
(10.1.14); 3rd
(10.1.13); 4th
& 5th
(14.1.17) Edition
If a natural-draught burner is to be used in forced-draught service, the purchaser shall specify the required heater capacity during
natural-draught operation, if required.
14
1st
Edition- 10.1.9
Burners and gas rings or tips and oil guns shall be removable while
heater is in operation
2nd
(10.1.19) and 3rd
(10.1.18) Edition
Gas manifolds and oil guns shall be removable while the heater is in operation. Purchasers must specify whether they require
removal of the diffuser or the complete burner assembly.
4th
and 5th
Edition 14.1.21
Oil guns shall be removable while the heater is in operation
4th
and 5th
Edition 14.1.22
The purchaser shall specify whether gas guns, diffusers or the complete burner assembly shall be removable.
15
1st
(10.1.10), 2nd
(10.1.15), 3rd
(10.1.14)
Natural draft oil burners shall include double refractory tiles to
maintain flame stability when firing heavy fuels such as vacuum or
atmospheric-reduced crude oils, tars, or other high viscosity fuels
requiring preheat.
4th
and 5th
Edition
Deleted
16 Added in 2nd
Edition
2nd
(10.1.16/17), 3rd
(10.1.15/16), 4th
and 5th
(14.1.18/19)
-Oil burners shall be designed to operate on a maximum oil viscosity of 43 cs (200 SSU).
-Atomizing steam shall be supplied dry at the burner, or with slight superheat.
H-28 Vacuum Heater Performance Improvement Study
A refinery was facing coking problems in their Vacuum Heater. In addition, they also wanted to revamp the heater to handle Canadian Crude and reduce NOx emissions. FIS did the process
study and because of the study, the client decided to build a new Vacuum heater with an existing heater foundation. The new heater is 4 ft wider.
This vacuum heater is a horizontal tube box with a convection section. It is designed for a heat duty of 43MMBtu/hr. FIS’ scope involves design, engineering, structural analysis and supply of
this heater to the site. The heater has an efficiency of 90%.
It was successfully commissioned in March 2009. The heater was delivered within 7 months of starting the job.
We received the following feedback from Client.
“.. we talked about the performance of the VF4 H28 heater since startup. It has been fantastic! The stack temperature is 370-380°F and the fuel gas usage has dropped about
40% from the old heater. This is one of the most efficient heaters in the refinery. The NOx stack testing came back 0.026 lb NOx/MMBtu, which is also outstanding. They are
even trying to reduce the O2 even lower, from 4% to 3%. It's a lot different when you have a tight firebox. Great job!!!”
-Client

6. API 560 Standards Comparison
Furnace Improvement Services, Texas
Furnace Improvements
www.heatflux.com
Uniform Heat Transfer for Fired Heaters 6
Inclined Firing System Split Flow Technology Flue Gas Injection Draft Control System
Furnace Improvement Services
Furnace Improvements Services is a reputed engineering and consulting company which
provides specialized technological services that integrates mechanical and process
engineering with CFD capabilities to design or revamp fired heaters and boilers in Oil &
Gas industry.
Offices
• Headquarters: Sugar Land, Texas, USA
• Process & Mechanical Group: New Delhi, India
• CFD & Process Group: Pune, India
Services
• Turn-key services for design, engineering and supply of new fired heaters
• Revamps of all types of refinery fired heaters
• CFD Modeling
• Troubleshooting