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Forney Horn Igniters: Reliable and Consistent Burner Ignition

A reliable igniter is critical to the efficient and safe operation of a burner; a poor light off can result in significant financial losses. Top-quality horn igniters are designed with reliability in mind. They provide a dependable ignition source that can be configured to use two fuel sources to further increase the flexibility of the unit. A horn igniter has a high-energy spark igniter (HESI) that can provide sufficient ignition energies in the most adverse conditions and also incorporates a self-cleaning function to further improve reliability. A typical horn igniter is shown in Figure 1 below:

Figure 1: Horn Igniter

What Are Horn Igniters?

A horn igniter is a permanently installed ignition device designed to provide a reliable source of ignition energy to light off a burner. There are three igniter classes that are differentiated by their ignition capacities in relation to full burner load. The Forney horn igniter, in particular, is primarily used as a Class 2 igniter in tangentially fired burners. 

What Are The Parts of a Horn Igniter?

Horn igniters typically consist of seven components as listed below and indicated in Figure 2.

Figure 2: Horn Igniter Parts
  1. Spark Ignition: Igniters like the high-energy spark igniter (HESI) for example can generate a spark ignition energy of up to 12 J (joules). This is much higher ignition energy when compared to older high-tension spark designs. The higher energies also provide a self-cleaning function that removes any buildup of coke on the igniter parts.
  2. Igniter Front Plate: The igniter front plate bolts onto the shell of the boiler and keeps the nozzle and diffuser (horn) secure inside the boiler. The front plate allows for easy removal and maintenance of the igniter assembly. An observation port allows for visual confirmation of ignition if required. 
  3. Atomizing Air inlet: Air supply is required to blow the fuel out of the nozzle, thereby atomizing it to create optimal ignition conditions. A quick coupler port is provided.
  4. Fuel Inlet: The fuel inlet is where either the gas or oil fuel is piped into the igniter via stainless steel braided hoses into quick coupler ports. In the case of a dual-fuel igniter, there would be two ports, one for oil and one for gas. 
  5. Fuel Nozzle: The fuel nozzle disperses the fuel using pressurized air to create an optimal air-fuel ratio for ignition. 
  6. Flame Detector: As an optional extra, the flame detector provides an added layer of safety. It supplies feedback to the control room operators on the status of the ignition flame.
  7. Wind Box: The wind box provides air for both ignition and cooling purposes. A wind box typically supplies air to multiple igniters.

Forney horn igniters do not have an eddy plate – thus reducing the buildup of coke near the nozzle and igniter assembly, which improves overall igniter reliability. Table 1 below lists the Forney horn igniter specifications:

Horn Igniter Specifications
Fuel: No. 2 Oil, Propane, or Natural Gas
Capacity Rating: 2 to 4 MBtu (0.59 to 1.17 MW) Consult factory for higher output, available up to 15 MBtu (4.4 MW)
Fuel Pressure: 60 – 125 psig (4.22 to 8.88 kg/cm2 )
Atomization Media Pressure: 25 psig (1.76 kg/cm2 ) differential over oil pressure
Capacity Rating: 2 – 4 MBtu (0.59 to 1.17 MW) Consult factory for higher output, available up to 15 MBtu (4.4 MW)
Fuel Pressure: 12 – 25 psig (0.84 to 1.76 kg/cm2 )
Cooling / Combustion Air
Flow: 120 SCFM (3.4 Nm3/min) at igniter
Pressure: 4 – 6 inches (102 to 153 mm) w.c. above furnace pressure
HESI Specifications:
Input Voltage: 120 to 240 VAC, 50/60 Hz
Input Power: 120 VAC @ 1.5 A (2-A fuse); 240 VAC @ 0.75A (1-A fuse)
Output Voltage: 2000 VDC
Output Energy: 12 joules per spark
Spark Rate: 3 per second (approximately)
Duty Cycle: 50% at temp 0°F to 135°F (-18°C to 57°C) Ambient

Table 1: Forney Horn Igniter Specification

How do Horn Igniters Work?

A horn igniter works by pumping an atomized fuel mixture into a diffuser or horn by means of a fuel nozzle. The fuel is atomized with the help of pressurized air. A HESI igniter then generates a high-energy spark of up to 12 joules that ignites the atomized fuel mixture. The combustion air is provided via the wind box. 

When Should You Use a Horn Igniter?

A horn igniter is typically used for igniting tangentially fired burners. Tangentially fired burners are designed to create a turbulent, swirling fuel-air mixture to essentially create a rotational fireball in the boiler. This swirling action also increases the residence time of the fuel, creating optimal combustion. 

Igniters can be categorized by their NFPA 85 (Boiler and Combustion Systems Hazards Code) classification. In general, each of the below-listed igniter classes is defined as being designed to ignite the burner fuel under light-off conditions as well as during low load or other adverse operating conditions. 

  • Class 1 Igniter: Larger than 10 % Heat Capacity.
  • Class 2 Igniter: Between 4 and 10 % Heat Capacity.
  • Class 3 Igniter: Less than 4 % Heat Capacity. 

Each class is differentiated by its capacity ranges in relation to full-load burner input. The horn igniter is typically used on Class 1 and Class 2 igniters with either single or dual-fuel configurations. Forney horn igniters, in particular, can also be designed with higher heat rates, depending on specific customer requirements. 

Choose Forney for a Reliable Burner Solutions Partner 

The Forney horn igniter offers a wide range of benefits as described below:

  1. Stability: Provides a stable flame due to the distribution of air throughout the entire horn. 
  2. Dual Fuel: Can use either oil or gas as fuel without any change in equipment required.
  3. Detection: Can incorporate a Forney non-contact optical flame detector to give plant operators peace of mind that the flame has successfully been ignited.
  4. Reliability: Offers reliable ignition due to the incorporation of a HESI (High-Energy Spark Igniter) that is designed to resist fouling.
  5. Capacity: Can service both Class 1 or Class 2 operations, and an auxiliary gun can be used to further increase capacity. 

Ready to Get Your Forney Horn Igniters?

Your plant can’t afford to risk using unreliable burner ignition equipment that can result in poor light-off or dangerous conditions within your burner. Forney’s horn igniters are specifically designed for reliability and can accept two different fuels for maximum flexibility. Our igniters are uniquely designed with the needs of plant operators and managers in mind. 

To learn more about how our horn igniters can provide reliable and consistent burner ignition for your plant, contact a Forney representative today.

About Forney

Forney Corporation has over 93 years of experience manufacturing the safest and most reliable combustion equipment for more than 1,000 power plants in more than 100 countries. The quality and durability of Forney’s state-of-the-art front-end combustion components have been proven by customers in many industries across the globe. Forney igniters, burners, BMS, flame detectors, dampers, and duct burners have provided efficiencies and cost savings for plant operators in electric utilities, chemical processing, pulp & paper, and cement industries.