离岸直升机起落甲板设计指南 OFFSHORE HELIDECK DESIGN GUIDELINES 2(12)

曝光台 注意防骗 网曝天猫店富美金盛家居专营店坑蒙拐骗欺诈消费者

The blowdown system should have venting points that are as remote as possible from the helideck and, in prevailing winds, downwind of the helideck.  It is common to have this vent on the flare boom, and this will normally be a good location. However, it should be noted that dilution of the gas to 10% LFL may not occur until the plume is a considerable distance from the venting point.  This distance could be anywhere between 200m – 500m depending on vent size, venting rate and wind speed.
Drilling rigs often have ‘poor-boy degassers’ which are used to release gas whilst circulating a well, but a drilling rig is unlikely to release any significant quantities of gas without warning, unless there is a sudden major crisis such as a blow-out.  As with production platforms it is unlikely to be possible to locate the helideck sufficiently distant from the potential gas sources to guarantee 10% LFL or less, and so the rig should not accept helicopter flights when well circulation activity is going on, or when there are problems down the well.  Helideck status lights should be connected to the appropriate gas detection systems and automatically initiated.
10.5  SPECIAL CONSIDERATIONS FOR FLOATING SYSTEMS AND VESSELS
10.5.1 General
As well as experiencing the aerodynamic effects and potential hazards outlined above, floating installations and vessels experience dynamic motions due to the ocean waves.
These motions (see Figure 10.6) are a potential hazard to the helicopter, and operational motion limits are set in order to avoid unsafe conditions.

The setting of these operating limits should involve consideration of two aspects:
.  
motion limits for executing a safe landing, and 

.  
limits for safely remaining on the deck for the period necessary to effect passenger and cargo transfer (usually not more than 10 minutes).

The former is mainly affected by the rate of the heave (vertical) motion, but also by the roll and pitch motions, and is relatively easy for the pilot to judge visually.  The pilot can see the movements of the vessel, and can judge whether it is safe to make the landing, and can choose the appropriate moment to set the helicopter down.
The latter is mainly affected by helideck accelerations, which can be generated directly by the motion of the vessel (heave, surge and sway), and indirectly due to the inclination of the helideck (component of gravity due to pitch or roll angle). Limits for remaining safely on the deck are also much more difficult to judge because they should involve a prediction of the helideck motions over the next 10 minutes, and an assessment of the statistical risk of unsafe motions.  Furthermore, the options available to the pilot in the event of excessive motions building up whilst the aircraft is on the helideck are limited.
10.5.2  Wave Motion Characteristics and Criteria
The setting of helideck performance limitations due to vessel motion is the responsibility of the helicopter operator as AOC holder. Currently in the UK offshore helicopter-operating environment the motions limitations for a variety of vessels have been agreed and set jointly by the helicopter operators, and these are published by BHAB Helidecks in the Helideck Limitations List. It is recommended that vessel owners and designers consult with BHAB Helidecks during conceptional design of new vessels or refits to determine the limitations that are likely to be applied to the class of vessel for given helicopter types.
　
中国航空网 www.aero.cn
航空翻译 www.aviation.cn
本文链接地址：离岸直升机起落甲板设计指南 OFFSHORE HELIDECK DESIGN GUIDELINES 2(12)