Extractions from the national standard of the People's Repubulic of China GB50051-2002 <design code for chimney text (segment)
13Aviation obstruction light and sign
13.1 general policy conditions
13.1.1
Aviation obstruction light and sign have to be set for the chimneies that may effect the fly of the air craft. 1 chimneies in the protect headroom area of the civil aerodrome ； 2 the chimney higher than 150m built outside of the protect headroom area of the civil aerodrome ， but in the territorial range of control(that is no more than 50Km away from the middle of the racetrack ) 3 chimneies that may effect the fly of the air craft in the cities which have elevated helicopter aerodromes.
13. 2Aviation obstruction light and sign
13.2.1
medium-high light obstruction ： should be red flash operating in the night.The frequency should between 20-60times/min,the efficient strength of the flash should never below 2000cd±25%.
13.2.2
high light obstruction ： should be white flash. The frequency should between 20-60times/min,the efficient strength of the flash should never below 60000cd .
13.2.3
the sign of the chimney has to be orange and white or red and white in bar using paint.,and the bar should be normal to the shaft axis,the width of the bar is min(1/7 of the chimney,30meters),the bar on the top and the bottom of the odd number should be in dark..
13.3distribution of the obstruction
13.3.1
the setting of the obstruction should reveal the top and the upper limb of the chimney(that are the hight and the width of the field of vision )
13.3.2
he chimneies which are not high above 45m,could only set a obstruction on the top.however those higher than 45m,could set obstructions in multilayer but the separation less than 45m and as equal as possible.
13.3.3
the obstruction on the top of the chimney should be set in the range of 1.5~3m from the top,when the heigth above 150m ,the range could be extended to 7.5m .
13.3.4
the number of the obstructions in each layer should be determind by the outside semidiameter of the chimney with sandard heigth:
1 when the outside semidiameter ≤ 6m,set 3 obstructions each layer ；
2 when6m ≤ the outside semidiameter ≤ 3m ,set 4 obstructions each layer ；
3 when the outside semidiameter ≥ 30 m,set 6 obstructions each layer ；
13.3.5
high light flash obstructions should be used in the chimney higher than 150m the separation be control in the range of 75~105m ,and between the high light flashes there should be low and midium high light flashes.
13.3.6
high light white flash obstructions can also be used in the chimney lower than 150m and no coloured bar in paint is needed.
13.3.7
obstructions in each layer may have a maintenance platform
13.4the work request of the obstruction
13.4.1
all the obstructions have to shine,to be open and shut,to be monitored at the same time ,so as to keep them normal.
13.4.2
when construct the obstruction,we should try our best to avoid the discomfort of the resident,and only the scattered light could be seen from the ground.
