An anchoring system is not a list of equipment. It is a route, and every item on it sits at one point of that route. The anchor holds at the seabed end. The cable carries the load inboard. At the deck edge, machinery controls the cable where it passes through the deck. Two separate passages carry it through the ship's structure. A compartment receives it, and the inboard end is made fast inside that compartment.
Read an equipment list in that order and each line acquires a job. Read it as a list and two things go wrong immediately: the two deck-end devices that look most alike — the windlass brake and the chain stopper — appear to do the same work, and the two passages through the hull collapse into one pipe. Neither reading survives contact with the rule text or the drawing.
This article is a map of the route, not a study of any one item. Each component gets enough space to place it and to say what it connects to; where a subject belongs to another article — anchor types, chain construction, connecting parts — the sentence stops and points instead of expanding.
The route, and the two kinds of item on it
Anchoring equipment is intended for temporary mooring of a ship in a harbour or sheltered area, and the normal assumption is one bow anchor and its chain cable at a time [2]. That is a different operation from mooring, which secures the ship with several lines or cables to a pier or other fixed points [2]. The two use different hardware at different points on the ship, and the term "mooring" in a specification should not be read as covering the anchor cable.
Along the anchoring route there are two kinds of item, and keeping them apart is the most useful thing a buyer can do with a general arrangement drawing:
- Items on the load path. These take chain force and pass it into the ship's structure: the anchor at one end, the chain stopper with the hull structure that supports it, the windlass brake and cable lifter at the deck edge, and the fastening of the inboard end inside the locker.
- Items on the passage. These guide the chain and keep water out, and they are not designed to carry the anchoring load: the hawse pipe, the spurling pipe, and the chain locker that receives the cable.
A component can be both prominent on the drawing and purely a passage. That is exactly the case with the hawse pipe, which is a large visible feature at the bow and is not designed to take the anchoring load.
One warning about the map itself. The sequence below is the conventional arrangement described in the sources read for this article, not a standard system drawing, and it is not a configuration to copy. Whether a particular ship has a chain stopper at all depends on the rule set it is built to and on the project's arrangement [1][5].
The anchor and the cable: where the route starts, and where this article stops
At the outboard end, the anchor takes hold of the seabed, and when housed it sits in the hawse pipe [1]. Inboard of it, the chain cable carries the load along the route; the connections at either end of the cable are positions on that route rather than subjects of this article, and the terminology and construction behind them are covered in our anchor chain pages [2].
Two sentences are enough here because the rest of this article is about what happens once the cable reaches the ship. The anchor's own design and type are a separate question, and so is the cable's grade and construction.
The deck edge: a windlass and a chain stopper are two different devices
This is the first place where a parts list misleads. "Windlass" and "chain stopper" appear next to each other in the deck machinery section, both are steel, both sit near the bow, and both are described in the same paragraph of many specifications. They are not the same kind of item, and the rule text keeps them apart.
The windlass is a machine for lowering and raising the anchor. It carries one or more cable lifters on a horizontal shaft, each fitted with its own brake, and the cable lifters can be declutched from the drive [1]. Three parts of it matter for this map:
- The cable lifter — a deeply grooved drum shaped to engage the links of the chain cable, and named gypsy in some documents. The name varies between makers, so the drawing call-out is what identifies it, not the word [1].
- The brake, whose function is to control and stop the run-out of the cable, including during a free drop, and which is designed to absorb the energy released in that drop without overheating or fading [1].
- The stripper bar, which breaks the chain out if it clings or sticks to the cable lifter above the spurling pipe while the cable is being recovered [1].
The engagement between chain and lifter is a functional requirement rather than a detail. One classification guideline defines chain jumping — links jumping while the anchor is weighed or cast — as the consequence of the chain not being properly engaged with the cable lifter [7]. A cable lifter that is the right shape for a different chain is therefore not a fit, whatever the drum diameter on the drawing says.
The chain stopper is a separate fitting, not a function of the windlass. Where installed, it is located in front of the windlass and acts both as a guide for the chain into the hawse pipe and, when closed, as the part that transfers the chain forces into the ship's structure [1]. Its defined jobs are to hold the chain when the ship is riding at anchor, relieving the strain on the windlass, and to secure the anchor in the housed position; a hinged bar dropped between two links keeps the chain from running out when the windlass brake is released [2].
Read those two descriptions side by side and the division of work is visible. The brake acts on a chain in motion and brings it to rest. The stopper, closed, holds the chain as the ship rides to her anchor and puts its force into the hull [2]. That division is written into the rules in three places:
- The windlass rule treats them as separate design items. In the anchor windlass requirement read for this article, brakes are listed among the windlass components while the chain stopper is given a design clause of its own, and the holding condition is defined with the brake fully applied and the cable lifter declutched. The capacity required of the brake is stated differently depending on whether a stopper is fitted [5]. That last point is the clearest evidence that the two are not interchangeable: the presence of a stopper changes the basis on which the brake is assessed.
- The stopper has its own hull support. The supporting hull structures of the anchor windlass and of the chain stopper are required to be sufficient for the design and sea loads, and the two are listed as two structures [6]. A stopper is therefore not a bracket hung off the windlass foundation; it has a load path into the hull of its own.
- Whether a stopper is required depends on the rule set. The common structural rules for bulk carriers and oil tankers require chain stoppers to secure each chain cable once it is paid out, and require the securing arrangement to take the chain load without permanent deformation [3]. Those rules apply to bulk carriers and oil tankers. Elsewhere the stopper is treated as fitted where provided — the industry guidance quoted above says "if chain stoppers are installed", and the windlass requirement carries the phrase "if fitted" [1][5]. Neither wording supports a statement that every merchant ship has one, and neither supports a statement that most ships do not.
A source note belongs here, because it affects how the next paragraph should be read. The windlass requirement used for the points above was read in a reproduction that is not an official IACS publication, and its wording is to be confirmed against the IACS original — an internal check before this article is published, not a qualification the reader needs to carry. What is used from it is structural only: that brakes belong to the windlass, that the stopper has a separate design clause, that the holding condition is defined with the brake applied and the lifter declutched, and that the brake requirement differs with and without a stopper. No figure from that document appears in this article.
The two passages: hawse pipe and spurling pipe are not one pipe
The second place where a list misleads is the pipe. A single phrase — "chain pipe from deck to shell" — describes a route, not a component, and it hides the fact that the chain passes through the ship's structure twice, in two different items with two different jobs.
The hawse pipe is the outboard passage. Its main function is to guide the chain from deck level through the ship's side, and it is built large enough to let the chain run and to stow the anchor so that the anchor drops freely when released [1]. In the common structural rules it is defined by the lead of the chain from the chain stopper through the ship's side, it must be of a suitable size and configuration to give adequate clearance and an easy lead, and it must be of sufficient strength [3]. Note what that definition does: it fixes the hawse pipe's inboard end at the stopper, not at the windlass.
The spurling pipe, called the chain pipe in some documents and listed as "chain pipe" in trial items, is the inboard passage: a heavy pipe fitted directly under the windlass to lead the chain down into the chain locker [2]. The rules require it to be closable — the windlass is to be arranged so that access to the chain pipe permits fitting a cover or seal of adequate strength over the spurling pipe [3].
That the two are separate items is not an editorial preference. They appear as separate rule items [3], and they appear as separate checks in the windlass sea trial: proper riding of the chain over the cable lifter, proper transit of the chain through the hawse pipe and the chain pipe, and proper stowage of the chain and the anchor [3]. A trial list that names both passages is treating them as two things to be verified, which is what they are.
The closure and watertightness requirements then fall where the water would come from. For ships built under the load line conventions, above the length threshold those conventions set, spurling pipes and cable lockers are to be watertight up to the weather deck; where access is provided it is to be closed by a substantial cover secured by closely spaced bolts, with hinged bolts and wing nuts not accepted as the securing mechanism, and spurling pipes through which anchor cables are led are to have permanently attached closing appliances to limit water ingress [4]. None of that applies to the hawse pipe, because the hawse pipe is the opening that faces the sea and stows the anchor.
So the sentence to delete from a specification is the one that runs a single pipe from the deck to the shell. It cannot say where the stopper leads, it cannot carry the closure requirement, and it gives the yard nothing to build or the buyer nothing to check.
The route as a table
| Position on the route | What it does | What to check, or what governs it |
|---|---|---|
| Anchor | Takes hold at the seabed end of the route and is stowed in the hawse pipe when housed [1] | That the hawse pipe opening is sized and shaped for that anchor's stowage, with adequate clearance and an easy lead for the chain [1][3] |
| Chain cable and connections | Carries the load from the anchor inboard to the deck machinery [1] | Grade, size and certificate scope for the cable and its end fittings; the construction and the connecting parts are covered in the chain articles, not here |
| Chain stopper | Guides the chain into the hawse pipe and, when closed, takes the chain forces into the ship's structure [1] | Whether the applicable rule requires one or treats it as fitted where provided, and that its own hull support is designed for the load [3][5][6] |
| Windlass — cable lifter, brake, stripper bar | Engages the chain on the lifter, controls and stops run-out with the brake, and breaks a clinging chain out with the stripper bar [1] | The holding condition the rule defines, and whether the brake requirement is stated for a ship with a stopper or without one [5] |
| Hawse pipe | Guides the chain from deck level through the ship's side and houses the stowed anchor [1][3] | Lead and clearance measured from the stopper through the ship's side, and strength as a rule item of its own [3] |
| Spurling pipe (chain pipe) | Leads the chain from the windlass down into the chain locker [2] | That the windlass arrangement allows a cover or seal over the pipe, and the closure requirements for the pipe and the locker [3][4] |
| Chain locker | Receives and stows the cable in the compartment below the windlass [2] | Watertight boundaries and access openings, drainage, and separate spaces for the port and starboard cables [3] |
| Bitter end | Fastens the inboard end of the cable to structure inside the locker [2] | That the fastening can be released from an accessible position outside the locker in an emergency [3] |
Every cell is a check rather than a specification, and the middle column is short on purpose: what each item does fits in a clause, while what governs it does not.
The inboard end: locker and bitter end
The chain locker is the compartment below the windlass where the cable is stowed, and it is normally divided inside [2]. The rule requirements read for this article treat it as an enclosure with three jobs: its boundaries and access openings are to be watertight, drainage is to be provided, and the port and starboard cables are to have separate spaces [3]. The same rule requires the locker to have adequate capacity and a form that lets the cable lead directly into the chain pipes when fully stowed [3].
The reason the locker belongs on the load path discussion at all is the bitter end — the inboard end of the cable, secured inside the locker [2]. The rule requires the inboard ends of the chain cables to be secured to structure, and requires the fastening to be arranged so that, if the anchor and cable have to be sacrificed, the chain can be readily released from an accessible position outside the chain locker [3]. That is a design requirement on the arrangement, not an instruction to be followed at sea, and it is why the fastening is drawn and approved rather than left to the yard.
Two consequences for a buyer. The locker and its closing arrangements are a structural and watertightness scope, which usually sits with the hull rather than with the deck machinery package. And the bitter end fastening is part of that same scope, even though the cable it holds comes from a different supplier.
Four ways the same list gets misread
These are the errors that survive a careful reading of the parts list because they are errors of grouping, not of detail.
The brake read as a stopper. The brake is a windlass component; the stopper is a separate fitting with its own design clause and its own hull support [5][6]. The brake controls and stops a running chain and absorbs the energy of a drop [1]; the stopper, closed, is the fitting that puts the chain's force into the ship's structure [1]. A specification that lists "brake/holding device" as one line has merged two items with two approval paths.
Two passages read as one pipe. The hawse pipe is defined from the stopper through the ship's side; the spurling pipe runs from the windlass to the locker [3]. They are separate rule items and separate trial checks [3]. Merging them loses the stopper end of the hawse pipe and the closure requirement of the spurling pipe in one sentence.
"On the list" read as "applies to this ship". A component appearing in a rule text, a guide or a previous vessel's specification is not a statement that this vessel has it. The stopper requirement quoted above is scoped to bulk carriers and oil tankers, and the windlass text says "if fitted" [3][5]. The closure requirements are scoped to ships under the load line conventions above their length threshold [4]. Ask which instrument governs the hull, then read the list against it.
A passage item read as a load-bearing one. The hawse pipe, the spurling pipe and the locker guide and enclose. They are required to be strong, closable and watertight, and the hawse pipe has a strength requirement of its own [3], but the anchoring load is taken by the stopper and its hull support, by the brake and lifter at the deck edge, and by the bitter end fastening. Treating a passage item as part of the holding arrangement is how a hawse pipe ends up dimensioned for a load it was never meant to carry.
Next step
To place the items on your own drawing rather than on a generic one, four documents do most of the work: the bow arrangement drawing showing the chain route from the locker to the hawse pipe opening, the deck machinery specification as issued, the rule set the vessel is built to with its date and revision, and the equipment list with each line's item number and maker.
With those, each item can be placed on the route and assigned to the scope that owns it — structure, deck machinery, or cable and fittings. Our marine windlass and chain stopper pages show the categories of those two items; the anchor chain itself is covered on the anchor chain pages. Category pages describe what a product is, not what a given vessel is approved with.
If the route on your drawing is incomplete or the items are grouped in a way that does not match the rule text, contact us with the arrangement drawing and the governing rule set, and the items can be read against positions on the route rather than against a list.
References
[1] OCIMF, Anchoring Systems and Procedures (© OCIMF 2010), Section 3 extract — https://cdn11.bigcommerce.com/s-ya3gab2q5e/content/pdf/BP101517.pdf. Used for the hawse pipe function and anchor stowage (3.4), windlass, cable lifter, stripper bar and brake functions (3.1.2, 3.7.1, 3.7.2, 3.7.4, 3.7.5), and chain stopper position and force transfer (3.6). This is industry guidance for tanker and terminal anchoring practice, not a classification rule. The PDF was obtained from a third-party content host rather than from OCIMF, and it is a partial extract that ends inside 3.7.5.2, so its completeness and edition could not be verified; nothing in this article rests on it as the sole basis for a normative statement, and no figure from it is used.
[2] Wärtsilä Encyclopedia of Marine and Energy Technology, terms "Anchor", "Mooring", "Chain pipe", "Chain stopper, cable stopper", "Chain locker" and "Bitter end" — https://www.wartsila.com/encyclopedia/term/anchor, https://www.wartsila.com/encyclopedia/term/mooring, https://www.wartsila.com/encyclopedia/term/chain-pipe, https://www.wartsila.com/encyclopedia/term/chain-stopper-cable-stopper, https://www.wartsila.com/encyclopedia/term/chain-locker, https://www.wartsila.com/encyclopedia/term/bitter-end. Used for terminology and for the functional distinctions between anchoring and mooring, and between stopper and brake. Encyclopedia definitions, not rule text; every requirement statement in this article is taken from [3], [4], [5], [6] or [7] instead. The encyclopedia entry that treats the hawse pipe and the spurling pipe in one sentence was deliberately not used for the two-passage section.
[3] IACS, Common Structural Rules for Bulk Carriers and Oil Tankers, January 2019, Part 1 Chapter 11 Section 3 "Anchoring Equipment", read in the imorules mirror — https://www.imorules.com/GUID-AC6535E2-4B3B-4E12-AB63-C3D0F72E4FCA.html. Used for chain locker capacity, boundaries, drainage and separate cable spaces (3.5.1), securing and emergency release of the inboard ends (3.5.2), chain stoppers (3.6.1–3.6.2), the windlass arrangement permitting a cover or seal over the spurling pipe (3.7.2), the windlass sea trial items naming the hawse pipe and the chain pipe separately (3.7.3), and hawse pipes (3.8.1). Scope: these rules apply to bulk carriers and oil tankers within their application; none of the statements taken from this source is presented as a requirement for merchant ships generally. Loading values, percentages and dimensions in this text are not reproduced in the article.
[4] IACS Unified Requirement L4, Closure of Chain Lockers, Rev.3 Corr.2, February 2022, as republished by ClassNK — https://www.classnk.or.jp/hp/pdf/info_service/iacs_ur_and_ui/ur_l4_rev.3_corr.2_feb_2022ul.pdf. Used for the watertightness of spurling pipes and cable lockers up to the weather deck, the substantial bolted access cover, the prohibition on hinged bolts and wing nuts as the securing mechanism, and the permanently attached closing appliances for spurling pipes (items 1–4). Scope: ships above the length threshold of the 1966 Load Line Convention or its 1988 Protocol, built under those conventions. Not applied here to other ship types, and no closure dimension is used.
[5] IACS Unified Requirement A3, Anchor Windlass Design and Testing, New June 2017, read in a non-official reproduction (a third-party bilingual copy) — http://turkloydu.org/pdf-files/iacs-karar-ve-csr-degisimleri/iacs-es-gereklilikleri/UR_A3_New_TR_EN.pdf. The official IACS copy could not be retrieved in this session; the IACS landing page serves the document through a viewer, and the file is therefore cited as read, not as an official text. Used only for structural statements: brakes listed among the windlass components (1.3), the holding condition defined with the brake fully applied and the cable lifter declutched (3.1.1), the brake capacity requirement (3.1.5), the separate chain stopper design clause (3.1.6), and the "if fitted" treatment of the stopper. No percentage, load or dimension from this document appears in the article, and the wording should be confirmed against the IACS original before publication — an internal editorial check, not a qualification on the content above.
[6] IACS Unified Requirement A1, Anchoring Equipment, clause A1.7 "Supporting hull structures of anchor windlass and chain stopper" — https://ww2.eagle.org/content/dam/eagle/regulatory-news/2022/IACS-UR-A1.pdf. Used for the single point that the supporting hull structures of the anchor windlass and of the chain stopper are required to be sufficient for the design and sea loads, and are listed as two structures. The design load values given in the same clause are not used.
[7] China Classification Society, Product Inspection and Testing Guideline D-02(202402) — Windlasses, clause 3.2(1) — https://www.ccs.org.cn/ccswzen/file/download?fileid=202402040196086584. Used only for the definition of chain jumping as links jumping because the chain is not properly engaged with the cable lifter. A product approval and inspection guideline, not an operating procedure and not a requirement on vessel configuration.
