TL;DR — The SWL must be marked on the heel of every cargo boom, crane, or derrick in contrasting colors at least one inch high, and all associated loose gear must be commensurable with that SWL; a biennial proof load test at minimum SWL is required, and records must be available to Coast Guard representatives on request. 46 CFR §28.885
What the Rule Says
SWL Marking and What It Means
The safe working load for the assembled gear must be marked on the heel of each cargo boom, crane, or derrick. The marking must be in contrasting colors to the background and at least one inch in height. The SWL is defined as the load the gear is approved to lift, excluding the weight of the gear itself. 46 CFR §28.885
Every piece of lifting and rigging gear also carries a breaking strength (BS) — the load at which it fails — and the SWL is derived from the BS by applying a safety factor (the ratio of BS to SWL). For general rigging the safety factor is commonly about five to one; for gear that lifts personnel or is subject to severe dynamic loading the factor rises to six, eight, or ten to one. NAVEDTRA 14343 §8-4
The SWL of an assembled rig is set by its weakest component. A strong runner on a weak shackle is only as safe as the shackle.
Loose Gear Requirements
All wire rope, chains, rings, hooks, links, shackles, swivels, blocks, and any other loose gear used in cargo loading or unloading must be commensurable with the SWL of the boom, crane, or derrick it serves. This gear must be visually inspected by the vessel's captain or a designee at frequent intervals, and in no case less than once in each operating month.
Any loose gear without a legible SWL mark or current certificate is taken out of service immediately. NAVEDTRA 14343 §9-5
Biennial Proof Load Test
In addition to the monthly visual inspection, a biennial (every second year) thorough examination and proof load test at a minimum of the SWL rating must be performed and witnessed by competent personnel. The proof load is applied with the ship's normal tackle, with the boom or derrick at the lowest practicable angle. Once the load is lifted, it must be swung as far as possible in both directions. All results, dates, and locations must be maintained and made available to Coast Guard representatives upon request.
Blocks and Tackle
A block is a pulley in a frame. Its parts are the shell (frame), the sheave (grooved wheel), the pin (axle), and the strap or hook/shackle by which it is secured. The swallow admits the rope; the becket is a fixed eye for making the standing part fast. A tackle is an assembly of blocks and rope (the fall) used to gain mechanical advantage or change the direction of pull. NAVEDTRA 14343 §8-2
The theoretical mechanical advantage equals the number of parts of the fall supporting the moving (load) block:
- A single whip (one fixed block) gives no mechanical advantage — direction change only.
- A gun tackle (two single blocks) gives an advantage of two or three depending on which block moves.
- A luff tackle (a double and a single block) gives three or four.
In practice, friction reduces the ideal advantage — allow roughly ten percent loss per sheave. Blocks must be sized to the rope: the sheave groove must fit the rope and the sheave diameter must be large enough to avoid overbending wire rope. Hooks must be moused (the hook opening seized) so they cannot jump off. Snatch blocks have a hinged shell that lets a rope be laid in on the bight without reeving from the end.
Cargo Boom Components
A cargo boom is a spar stepped at its heel to a mast or kingpost. Key components:
- Gooseneck fitting — secures the heel and allows the boom to swing and top. NAVEDTRA 14343 §9-1
- Topping lift — wire and tackle (often led to a topping-lift winch) that raises and lowers the boom head to set its angle.
- Cargo runner (whip) — reeves over a head block at the boom head and a heel block, then leads to the cargo winch to hoist the load.
- Guys (preventer and working/slewing guys) — control the boom's swing athwartships and hold it against the load's side pull.
- Kingpost (samson post) and mast — take the compression from the boom and the pull of the standing rigging.
The SWL marked on a boom applies to that boom's rigged configuration.
Single Swinging Boom Rig
In the single swinging rig, one boom lifts the load, is slewed over the side or the hatch by its guys, and lowers the load to or from the pier or hold. The rig is flexible — the boom can spot a load anywhere within its swing — but it is slow because the boom must be slewed for every lift. A load hanging off the boom head puts a heavy side load into the guys, so careful guy tending is essential. Greater lifting power can be obtained by reeving the runner as a purchase (multiple parts) at the cost of speed; heavy lifts use a specially rigged heavy-lift (jumbo) boom with doubled topping lifts and guys. NAVEDTRA 14343 §9-2
Yard-and-Stay (Burton) Rig
The yard-and-stay rig uses two fixed booms — one (the hatch or "yard" boom) topped to plumb the hatch, the other (the stay or "burton" boom) topped to plumb over the ship's side and pier. The two cargo runners are shackled together at a single cargo hook (the falls are "married"). The hatch winch heaves the load up; when high enough, the ship-side winch heaves while the hatch winch slacks, transferring the load across and out over the pier. NAVEDTRA 14343 §9-3
The rig is fast because the booms are fixed and cargo cycles continuously, but the combined pull on the married falls when the load is midway between the booms can be very high. Critically, the SWL of the yard-and-stay rig is lower than the SWL of a single boom used alone. Jerky or out-of-step heaving by the two winch operators overloads the guys and the union purchase.
Cranes and Winch Safety Devices
A pedestal or slewing crane allows a single operator to hoist, luff (raise/lower the jib), slew (rotate), and spot a load from one cab. Cargo winch brakes must hold the rated load automatically when power or control is lost. Modern cargo machinery includes: a load/overload indicator or cut-out that prevents lifting beyond the SWL; limit switches that stop the hook before two-blocking and stop luffing/slewing at the ends of travel; and a slack-rope/anti-two-block warning. Safety cut-outs must never be overridden to force an overload. Booms must be cradled and cranes secured for sea. NAVEDTRA 14343 §9-4
Sling Angles and Shock Loading
SWL is reduced by the angle of a sling's legs. As the legs spread from the vertical, tension in each leg rises sharply — wide sling angles greatly increase the load on each leg and its fittings. The load is shared safely only at narrow angles.
Shock loading — a sudden jerk from a slack line coming taut — can momentarily multiply the load far beyond the static weight and is a common cause of gear failure. Loads must always be taken up smoothly.
Cargo runners and falls are "running" wire that fatigues quickly and must be inspected far more often than standing rigging; they are renewed on wear criteria, not just on a calendar schedule.
Why It Matters on the Exam
Exam questions on this topic cluster around four areas:
1. Regulatory specifics — Where is the SWL marked? (The heel.) What are the minimum letter/figure height and color requirements? (One inch, contrasting colors.) How often must loose gear be visually inspected? (At least monthly.) How often is the proof load test required? (Biennially.) What is the minimum proof load? (At minimum the SWL.) At what angle is the proof load applied? (Lowest practicable angle.) 46 CFR §28.885
2. Mechanical advantage — Candidates must be able to count parts of fall on the moving block and apply the ten-percent-per-sheave friction deduction. NAVEDTRA 14343 §8-2
3. SWL concepts — The weakest-component rule, the effect of sling angle on leg tension, and the fact that the yard-and-stay rig has a lower SWL than a single boom alone are all frequently tested. NAVEDTRA 14343 §8-4 NAVEDTRA 14343 §9-3
4. Inspection triggers — What removes gear from service (no legible SWL mark or no current certificate), and the distinction between the monthly visual inspection and the biennial proof test. NAVEDTRA 14343 §9-5
Common Pitfalls
Pitfall 1 — Confusing where the SWL is marked. The SWL is marked on the heel of the boom, crane, or derrick — not the head, not a placard in the winch house. 46 CFR §28.885
Pitfall 2 — Misreading the proof test interval. "Biennial" means every second year, not every year and not every five years. The proof load is at a minimum of the SWL — not twice the SWL, not half the SWL.
Pitfall 3 — Forgetting that the SWL excludes gear weight. The SWL is the load the gear is approved to lift, excluding the weight of the gear itself.
Pitfall 4 — Assuming the yard-and-stay rig has the same SWL as a single boom. It does not. The combined pull on the married falls when the load is midway between the booms is very high, so the yard-and-stay SWL is lower than the single-boom SWL. NAVEDTRA 14343 §9-3
Pitfall 5 — Ignoring friction in mechanical advantage problems. Theoretical MA equals parts of fall on the moving block; practical MA is reduced by roughly ten percent per sheave. Failing to apply the friction deduction will produce an answer that is too optimistic. NAVEDTRA 14343 §8-2
Pitfall 6 — Treating shock loading as a minor concern. A slack line coming taut can momentarily multiply the load far beyond the static weight. This is a common cause of gear failure and is a tested safety concept. NAVEDTRA 14343 §8-4
Quick Check
Q1 — Where must the SWL be marked on a cargo boom, and what are the minimum marking requirements?
The SWL must be marked on the heel of the boom, crane, or derrick. The letters and figures must be in contrasting colors to the background and at least one inch in height. 46 CFR §28.885
Q2 — How often must loose cargo gear (shackles, blocks, hooks, wire rope) be visually inspected, and who is responsible?
At frequent intervals, and in no case less than once in each operating month. The inspection must be performed by the vessel's captain or a designee.
Q3 — What is the minimum proof load for the biennial test, at what boom angle is it applied, and what must be done after the load is lifted?
The proof load must be at a minimum of the SWL. It is applied with the boom or derrick at the lowest practicable angle. After the load is lifted, it must be swung as far as possible in both directions.
Q4 — A luff tackle (one double block, one single block) has the hauling part leading from the double block. How many parts of fall support the moving block, and what is the theoretical mechanical advantage?
Count the lines actually pulling on the moving block. With the hauling part leading from the double (moving) block, there are four parts on the moving block, giving a theoretical mechanical advantage of four. In practice, deduct roughly ten percent per sheave for friction. NAVEDTRA 14343 §8-2
Q5 — Why is the SWL of a yard-and-stay rig lower than the SWL of a single boom used alone?
When the load is midway between the two fixed booms, the combined pull on the married falls is very high. The union (schooner) guy and the guys take heavy loads in this configuration, so the rig's rated SWL must be set lower than the single-boom SWL to account for these increased stresses. NAVEDTRA 14343 §9-3
Q6 — What action is required when loose gear is found without a legible SWL mark or a current certificate?
The gear is taken **out