Marine Engineering

The test is carried out to prove the performance of the windlass.  Preparation: It is performed when the vessel is out in sea trials. This test is conducted at a minimum sea depth of 82.5 m (three shackles or shots of 27.5 m each) and the ship is at standstill and headed into the wind.  It is conducted under calm conditions of the sea. Ensure that all moving parts of the windlass and chain compressor have been lubricated. Make sure that the motive power (electric/engine) to the windlass is available. Procedure: Lower the port side anchor to water level by controlling the windlass drive. Let go by free-fall three (3) shots of port anchor chain to water. During this operation, test the windlass brake by holding it every half (1/2) shot. Check whether there is three (3) shots anchor chain between chain compressor and anchor. Hoist the port side anchor until the anchor is stowed at its home position. During this process measure the time and calculate the...

Types of Anchors Ordinary anchors High holding power (HHP) anchors Super high holding power (SHHP) anchors Ordinary anchors Ordinary anchors of “stockless” type are to be generally adopted and they are to be of the appropriate design in compliance with the rules or practice of each individual Society. The mass of the heads of stockless anchors including pins and fittings are not to be less than 60% of the total mass of the anchor. The mass, per anchor, of bower anchor, is required for anchors of equal mass. The mass of individual anchor may vary to 7% of the Table mass provided that the total mass of anchors is not less than that required for anchors of equal mass. High holding power (HHP) anchors A “high holding power” anchor is to be suitable for ship’s use and is not to require prior adjustment or special placement on the sea bottom. When special type of anchors designated “high holding power anchor” of proven superior holding abi...

Anchor weight is determined by a Classification Society formula that throws up a number which we call as Equipment number. The Equipment number is the trigger to decide the anchor weight the chain size and the length of cable to be used. The equipment number, EN, on which the requirements of equipment are based is to be calculated as follows:- EN = K * ENc where, ENc = Δ^2/3 + 2BH + 0.1*A ENc is the function of the ship displacement, Deck height, Area of the superstructure. Δ = moulded displacement, [t], to the summer load water line H = effective height, [m], from the summer load waterline to the top of the uppermost deckhouse, to be measured as follows: H = a + Σhi a = distance [m] from summer load waterline amidships to the upper deck at side hi = height [m] on the centreline of each tier of houses having a breadth greater than B/4. For lowest tier, hi is to be measured at centre line from upper deck, or from a notional deck line where there is a local discontinu...

Most of the modern anchors for large ships are now made of cast steel so that they are tough and can resist shock loading and breakage especially if the anchor strikes a rock or rocky surface whilst anchoring. About 80 years back all anchors were made of cast iron and the method of testing them were by dropping them on hard prepared ground from a height of 75 feet. If it survived this test without breaking or cracking, it was sent to the ship and if it cracked or broke it went back to the foundry for recasting. This is destructive testing and not used now. Modern anchors are subjected to non-destructive testing and the procedure is as follows. The anchor is placed on the test bed of a chain testing machine. The shank end is connected to either the fixed end of the machine and the head is connected to the ram end of the machine which moves inwards by hydraulic pressure. The pressure is monitored on the pressure gauge fitted to the hydraulic cylinder. The required proof load i...

Most of us know what is an anchor but do you really understand how does a ship anchor work? Anchoring a ship is a very important function that a boat or a ship has to do in order to stay stable in water. Whenever a vessel has to stay afloat in a stationary position on water when the engines are turned off, the anchor is cast into the sea so that the vessel does not drift unnecessarily from its position due to wind or water currents. We will now discuss how a ship can be anchored. This process can be followed for both small boats and ships though with a slight variation. The first step that a boat must follow is to find a location to anchor the ship. The location is selected by the pilot or captain of the ship. When he informs the crew about where exactly the ship must be anchored then accordingly the ship is anchored as per the directions given. The ship must slow down and then move into position. The ship or boat can be slowed down by reversing the thrust. This will slow down ...

An anchor is used by a ship to make itself fast to the sea-bed so that it will stay in one place and will not drift due to wind and current. A shop normally carries three anchors, two working anchors, one on each bow, attached to cables and stowed up the hawse pipes. These are called Bower Anchors. One Spare Bower anchor lashed and well secured in the vicinity of the forecastle deck. If one of the working bower anchors is lost, this spare anchor is shackled on to the anchor cable and used. A fourth anchor may also be carried on small vessels known as Stream anchor, lashed and secured at or near the stern of the vessel. It is meant to be used in narrow channels for preventing the stern of the vessel from swinging. But these days it is hardly ever used for this purpose. Earlier all anchors had a stock, which was just before anchoring, fixed in position at right angles to the arms. The stock helped the anchors to turn itself so that the arms became vertical and one of the flukes...