ArDee
Legendary Member
- Location
- North of Buntingford, Hetfordshire
Sorry about the length of this post
Halogen lamps work by recycling the tungsten in a halogen cycle. Tungsten that evaporates off the filament due to its high temperature would be deposited on the inside of the quartz which would cause it to go black. However as the quartz is relatively cold (in comparison to the filament) at this lower temperature the tungsten combines with the halogen and is carried back to the filament by the thermal currents in the gas inside the lamp. When the Tungsten/Halogen combination gets back to the filament the high temperature causes the Tungsten/Halogen to break down redepositing the Tungsten on the filament
Hence there are a number of things that can make Halogen lamps blow;
As has been said if you touch the quartz it creates a spot on the quartz, that when it get hot, becomes porous and allows oxygen into the lamp causing premature failure of the filament through oxidation.
The lamp is designed to operate on one plane for optimum temperature control and thermal gas current movement in the lamp, installed upside down or on its side will reduce lamp life and long thin lamps, normally found in security lights, need to be install with the lamp level so that the thermal gas currents in the lamp do not preferentially deposit tungsten back at one end of the lamp starving the other end and leading to premature failure by thinning.
The lamps are susceptible to voltage variation and unlike incandescent lamps are normally more susceptible to lower voltages than burning out due to higher voltages; low voltage lamps have a maximum length of cable from the transformer to the fitting to minimise volt drop and low voltage at the lamp. If the voltage drops the temperature of the quartz drops faster than the temperature of the filament and the halogen cycle stops as the Tungsten/Halogen combination does not form at the quartz sleeve; hence, allowing the filament to evaporate tungsten without it being redeposited and the thinning of the filament.
Dimmers have the same effect and should be run at full power or at less than around 80% to reduce the filament temperature below the point at which the tungsten evaporation comes down to about the level to that of a normal incandescent lamp
Vibration has been mentioned and this does affect the filament; car halogen lamps are robustised by design to allow vibration without affecting operation while house lamps aren’t as robust. If anybody ever had an incandescent hand held lamp for when working on the car and the lamp went, you needed to buy a “Rough Handling” replacement or if you used a normal lamp, the first time you knocked the lamp against the car the bulb would fail. The principle is the same.
Halogen lamps work by recycling the tungsten in a halogen cycle. Tungsten that evaporates off the filament due to its high temperature would be deposited on the inside of the quartz which would cause it to go black. However as the quartz is relatively cold (in comparison to the filament) at this lower temperature the tungsten combines with the halogen and is carried back to the filament by the thermal currents in the gas inside the lamp. When the Tungsten/Halogen combination gets back to the filament the high temperature causes the Tungsten/Halogen to break down redepositing the Tungsten on the filament
Hence there are a number of things that can make Halogen lamps blow;
As has been said if you touch the quartz it creates a spot on the quartz, that when it get hot, becomes porous and allows oxygen into the lamp causing premature failure of the filament through oxidation.
The lamp is designed to operate on one plane for optimum temperature control and thermal gas current movement in the lamp, installed upside down or on its side will reduce lamp life and long thin lamps, normally found in security lights, need to be install with the lamp level so that the thermal gas currents in the lamp do not preferentially deposit tungsten back at one end of the lamp starving the other end and leading to premature failure by thinning.
The lamps are susceptible to voltage variation and unlike incandescent lamps are normally more susceptible to lower voltages than burning out due to higher voltages; low voltage lamps have a maximum length of cable from the transformer to the fitting to minimise volt drop and low voltage at the lamp. If the voltage drops the temperature of the quartz drops faster than the temperature of the filament and the halogen cycle stops as the Tungsten/Halogen combination does not form at the quartz sleeve; hence, allowing the filament to evaporate tungsten without it being redeposited and the thinning of the filament.
Dimmers have the same effect and should be run at full power or at less than around 80% to reduce the filament temperature below the point at which the tungsten evaporation comes down to about the level to that of a normal incandescent lamp
Vibration has been mentioned and this does affect the filament; car halogen lamps are robustised by design to allow vibration without affecting operation while house lamps aren’t as robust. If anybody ever had an incandescent hand held lamp for when working on the car and the lamp went, you needed to buy a “Rough Handling” replacement or if you used a normal lamp, the first time you knocked the lamp against the car the bulb would fail. The principle is the same.
