For gas appliances, a flame supervision device (FSD) – alternative name: flame failure device (FFD) – is a general term for any device designed to stop flammable

gas Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...

going to the burner of a gas appliance if the

flame A flame (from Latin '' flamma'') is the visible, gaseous part of a fire. It is caused by a highly exothermic chemical reaction taking place in a thin zone. When flames are hot enough to have ionized gaseous components of sufficient density they ...

is extinguished. This is to prevent a dangerous buildup of gas within the appliance, its chimney or the room. Causes of flame failure include chimney downdraught, temporary interruption of the gas supply, gas under-pressure, liquid overspill on cooker hotplates or the draught from an oven door being opened and closed. FSDs may utilize one of several technologies: thermoelectric valves, flame conductance, flame rectification,

ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation ...

sensing devices and liquid expansion valves. FSD usage in consumer products differs among political units – in the U.S., FSDs are not required by law or regulation for gas range (or gas stove) top burners and consequently are not present on ranges in the U.S. Cooker hotplates may not have a FSD on each burner. If a hotplate is to be used in a multi-occupancy building every burner must have its own FSD. When the FSD activates it should stop (or reduce to safe levels) gas flow to the burner until it is reset manually. Older devices, such as bimetallic strips, were used in conjunction with

pilot light Merker Tankless water heating, tankless gas-fired water heater from the 1930s, with pilot light clearly visible through the aperture in the front cover. The large opening allowed for the manual lighting of the pilot light by a lit match or taper ...

s. The pilot light is no longer used in new devices, but may still be encountered on old appliances still in service. Pilot lights were withdrawn because their continual small flame represented a waste of fuel. Pilot lights required their own FSD, typically a thermocouple which held the valve open. Regular testing of FSD is a part of routine maintenance for gas appliances. Other safety devices may be fitted in addition to an FSD. One type of these are the Vitiation Sensing Devices, that detect an adequate supply of

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...

for efficient combustion, thus avoiding the production of poisonous

carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...

. As well as detecting a blocked supply of oxygen, these must also detect a blocked exhaust or reversed flow in the exhaust flue owing to wind conditions. Two methods are used to provide these, an Oxygen Depletion System (ODS) that measures the availability of oxygen for combustion or an Atmospheric Sensing Device (ASD) measures excess heat rise in the exhaust.

References

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External links

Gas Flame Supervision Devices: Information at Falkirk Council, UK (Archived 14 December 2013; Accessed 2 January 2017)
Gas technologies Heating, ventilation, and air conditioning Natural gas safety

See also

References

External links