Wednesday, January 18, 2012

Specifying Common Igniters

Specifying Common Igniters

Igniters are devices or assemblies that produce a specific level of heat in order to initiate a larger combustion reaction. Within industrial applications, igniters are manufactured for various engine and burner systems and applications including process heaters and high pressure washers. They are produced in simple and complex designs according to application use. This guide distinguishes the characteristics, functions and common issues associated with several of the most common industrial igniters, including pyrotechnic, hot surface and spark (or electrode) devices. Pyrotechnic Igniters

Pyrotechnic igniters are frequently controlled electrically. They are initiated to ignite materials that generally have complex ignition requirements. Thermites are apyrotechnic mixture of metal powder and oxide, which generates a reaction called a thermite response. While this reaction is not typically explosive, it can produce rapid bursts of high temperatures under the right conditions. This reaction’s higher temperatures are generally concentrated on a very small area for a short period of time.

Additional Considerations

These devices may require maintenance to adhere to safety standards, which should be verified through the manufacturer. In some applications, they may be demanding devices to operate as they require installation for individual engine tests. Hot Surface Igniters

Invented in 1969, these igniters are composed of advanced ceramic materials. These devices are also the most commonly used electronic ignition systems today. They are generally employed for applications such as space furnaces and heaters. Hot surface igniters are commonly used for their reliability and durability potential. Hot Surface Igniter Configuration

The two composition materials generally associated with hot surface igniters are silicon carbide and silicon nitride.

Silicon carbide is a compound of carbon and silicon and is characterized by a low density and oxidation resistance. This compound, seen in igniters, has good high temperature strength.

Silicon nitride is a chemical compound of silicon and nitrogen. It is a hard ceramic with a high strength and is durable over a broad temperature range. Its notable characteristics include durability over a high temperature range.

Additional Considerations

Because these igniters are made of ceramics, they are considered durable and thermally robust and may last from 3-5 years. However, they may gradually weaken over time and use and will eventually generate less heat than their full potential; they should be replaced when this occurs. Hot surface igniters may also experience premature burnout.

Spark Igniters

Spark igniters are also known as flame igniters, according to their application. Generally, they are considered efficient devices because they are easy and safe to handle. They are electric and no gas leaks are involved. Spark igniters function as a device that ignites compressed fuels, such as aerosol gas, petroleum gas that is generally liquefied, and ethanol. Some manufacturers produce spark igniters (also called spark plugs) that produce an ultra thrust ignition, which provides reduced emissions and a faster start.

A spark plug may be considered either hot or cold. The difference is hot spark plugs generally hold more heat in the physical tip of the spark plug, while cold spark plugs generate more heat out of the tip and lower its temperature. Spark igniters include a subcategory called chatterboxes. Spark Igniter Configuration Chatterboxes are considered the least sophisticated of the spark-igniter systems. Various manufactured chatterbox devices are self-cleaning. Spark igniters of this type are capable of igniting more than one burner at a time, and they can be controlled by an on and off switch. The spark is produced at a set of make and break contacts. These are made of tungsten for extended durability.

Tungsten is a steel gray metal that is distinguished by its robust physical properties. It has the highest melting point of all metals it its pure form, and is often utilized in rocket engine and vehicle applications. Additional Considerations

Sometimes a spark igniter will fail to ignite. A certain energy level must be maintained or the spark will dissipate. Manufacturers of these igniters suggest inspecting coloring of the tip (which should appear light brown) of the igniter block to ensure proper function. Changes in color and deformations may signal contamination or chipping, which can lead to misfire. To prevent a malfunction, tools like spark plug reading viewers are available.

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