what went wrong lol . At 1:00 , the crap hits the fan . I donít understand how these huge anchors work ,and was wondering what the guy did wrong ,or could it have been avoided ?
I could hardly imagine how noisy this job must be . Ear plugs and safety head phones on a hard hat imo https://youtu.be/25Us_VcMb8g
My first job out at sea was on deck, and I was the guy who operated the windlasses. It was a great mixture of excitement and terror when lowering the anchor, especially putting out 10+ shots of chain. Definitely needed hearing protection, goggles, and a dust mask, because whatever was in the chain locker (rust, mud, etc) was coming your way when the chain payed out. Fun times.
Some of those video clips are pretty old, I don't know why they are tagged as 2018.... The one at the 4 minute mark is the one that scares me. That was a failure caused by the seas working on the vessel, and shows the stored energy in the chain.
The most of the other ones were caused by either improperly adjusted brakes, or by the operators. Almost all of these brakes are simply a band of brake lining on a steel shell that is tightened by either a screw thread or the return spring in a hydraulic cylinder (so the brake fails ON if hydraulics are lost). The band in the picture below does not have the lining on it, but that's the only picture I have at home.
When the cause is human error, it is usually because people don't take the brake off far enough. This causes the lining to drag on the drum when the anchor chain is paying out, and it causes the surface of the brake lining to glaze over and not be effective. Then the operator tries to stop the chain by tightening down all he can, and it's not effective at anything but generating more heat and causing a fire. In my 28+ years I can thankfully say I have only seen one lost, and this was the reason. The drum was glowing dull red according to the guy on the bow that morning.
The brake linings are usually 5/8" or more thick when new, and they do wear. You have to make adjustments to the brake assembly so that it renders at the correct load (you want it to slip before it does damage to the systems), but if it's too loose or tight it can cause a failure. Some of the hydraulic systems have a simple 'go-no go' gage that you check the distance between the brake band and the cylinder when the brake is on for a check, but most of them require us to use a very large hydraulic jack and actually apply force to slip the brake to make sure it's set right. We do this every few months.
Improper procedures in anchoring can be to blame as well. We do not 'drop' the anchors from the hawsepipe, we lower the anchor to the water's edge or just below by using the anchor windlass to feed it out slowly under control. We do this for two reasons; the first is sometimes the anchor won't drop on its own from the hawse, the second is that we don't want to risk damaging the bulbous bow with the anchor. Lowering it down this way also adds an additional safety factor, being the windlass has it's own brake, so you can make sure the main brake is function properly with a backup.
Once the anchor is down out of the hawse there is enough chain weight to make sure it will drop normally. I would bet most of the anchoring operations in the video were dropping from the hawse, as the anchor didn't go right away... you could see the operator slowly opening up more and more on the brake. Then when it did go, he couldn't check it's speed before it built up too much momentum.
The bridge team is sometimes to blame, putting too much dynamic load on the chain. If they have the vessel moving too quickly when anchoring it can pull chain out of the pipe overwhelming the brake.
When we are anchored, it's not the weight of the anchor that holds the ship, it's the weight of the chain. We usually use a scope of 5 or 7 (5x or 7x the depth of the water) of chain to hold the vessel, depending on the type of bottom, the weather, and expected currents. Sometimes this isn't enough, and we will actually have to use the engine to take some load off of the anchor. Every 30 minutes an anchor check is done by the deck sailor to verify the weight on the chain (is it hanging up and down, or stretched out like a piano wire) and the direction of it's lead. This lets the guys on the bridge know if we need more chain or the engines. We also put an electronic mark on the navigation system to make sure we are staying in the expected swing circle, and not dragging anchor.
Hopefully I haven't bored you to death by now!