The technology stipulates conditions, operational process, security measures and requirements for ship launching works.
Quoted standard: CB/T3837-1998《Ship launching and pulling airbags technology》;《Qingdao LuHang Marine Airbag and Fender Co., Ltd. Ship Launching Standard》
1.Prepare work before ship launching
1.1 All external works of the vessel under the water line are done, especially the sea chest, axle steering system, propeller, zinc spelter, drain plug and depth meter etc. should be set up and pass the inspection.
1.2 Burrs and weld beadings on vessel bottom plate and other accessories should be rubbing down.
1.3 The welding line on outside plate of vessel body should pass the inspection and tightness test.
1.4 The measurement of vessel`s main dimension is done, water gauge of load waterline and vessel body mark should pass the inspection.
1.5 The last painting of shell plating is finished.
2. Requirements on slipway before ship launching
2.1 No iron nail and sharp and rigid objects on the path where air bags will roll during ship launching.
2.2 Ramp way should be smooth and flat. Levelness should not over 80mm, all low-lying places should be filled and level up by sand pocket.
2.3 Ramp way should have a certain length inside of water, the ship bottom should not contact with the ground when the air bag is on the lowest working height.
3. Selection principle of air bags
3.1 Air bags should pass the inspection according to CB/T 3795 standard. Every time before ship launching the air bag should do air inflating test without load, the inflating pressure is 1.25 times more than it`s working pressure.
3.2 Air bags numbers calculation
Air bag number =1.3*(DWT*9.8)/(coefficient *25*average length)+3
3.3 The distance between each rolling air bag should assure to load the ship and do not overlay on each other. Generally, the distance is bigger than the diameter of air bag.
4. Winch and handcart
4.1 Low speed winch is better, its cable laying speed is around 9~13 m/min.
4.2 Tractive force of winch cable should be no less than glide force of the vessel.
4.3 Under the control of tractive force of winch cable, the movement speed of the vessel should not bigger than 6 m/min.
4.4 The handcart should be set on the top middle of slipway and its force should be no less than the glide force of the vessel.
5. Operational process of shipping launching
5.1 Clear all sundries and other objects that could interfere air bags` rolling under the vessel and on the way to pass.
5.2 Use mooring rope to tie up pulley blocks on winch, the tractive force of mooring rope should be meet requirements. The pulley block should hook on the handcart.
5.3 Dismantle blocks under the vessel one by one, take a 50t jack instead and fill air bags in according to calculated distance. Inflate airbags and remove the jack until airbags can bear the vessel.
5.4 All personnel on board, remove ladder and approach bridge.
5.5 Start winch by order, let out steel ropes, make the vessel move to water in virtue of rolling airbags.
5.6 Then based on the condition of water area and ramp way to launching whether in a fast speed or under the control of winch.
5.7 Let the vessel berth at dock
5.8 Take back all airbags.
5.9 Measure keel draft of the vessel, check out if there is any water leakage.
6. Matters need attention on dismantling block and moving vessel
6.1 During dismantling blocks, under the same cross section, blocks in the middle should be removed firstly, then in turn in both sides. When remove the last block, make sure no one is under the vessel. Along the broadside, there could put some blocks or jacks and remove them before launching work.
6.2 All workers should know well about airbags. Operating personnel should stand on the side of airbag mouth.
6.3 During the launching work, airbags should be filled in constantly. Stop the vessel when necessary. Attention that the vessel should be stopped slowly to prevent the big impact force of sudden stop.
6.3 It`s better to put all rolling airbags in single row under the vessel. The longitudinal centre line of airbags should perpendicular to the moving direction. It`s recommended for the airbag head not stretch out too long from boardside. For some tug boats and fishing boats which have small block coefficient, airbag head should be stretch out from boardside longer than diameter of airbag to insure the stability during launching work.
6.4 For some very wide ships, airbags can be put in double row. Be sure that the distance between two rows should no less than 0.5m.
6.5 When launching the vessel, the working height of airbags should be as much as low. Generally the height should no bigger than 0.3m under condition that rudder, sternpost and propeller do not touch the ground.
7. Entry water
7.1 The buoyancy increase of vessel stern is slow, so the two airbags under stern will take much pressure. High pressure airbags is an option when necessary.
7.2 From the stern entry water to the vessel is float on water entirely, the
buoyancy of the vessel is still smaller than its gravity, it may occurs that the fore body drop suddenly. So it is recommended to increase the airbag numbers under fore body, shorten the distance between two airbags.
Remark:The above ship launching operation process and matters need attention are provided by LuHang technical department. For reference only! Please contact us for more consultation if you have vessels need to be launched. Airbag is pressure container, operating personnel should be very carefully during operational process.
We are top runner on Ship Launching Airbags. Airbags are developed independently by our company. Luhang is the biggest pioneer manufacturer of ship launching airbags in China. Many other irregular small workshops copy our design and make counterfeits. However, only the appearance that those small workshops can copy, the real technology which is projected by 3D simulation is mastered by us, Luhang! There has no ship launching accident occurred since Luhang was built on 1988. Vessels launched by us is countless, the biggest one has 12000T DWT! Choose Luhang, Worry-free!
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