Safety on Deck — Stored Energy, Isolation and Hazardous Areas

1. What makes deck work dangerous

Deck machinery is different from engine room machinery in three ways that shape every precaution that follows:

• It is worked in the open, on a moving, wet, cold and often dark platform, by people who are also standing on that platform.
• It handles loads, not fluids. The energy is stored in a wire, a cable or a suspended mass, and it is released suddenly when something lets go.
• It is controlled from a distance, or by one man at the machine. Remote control and duplicated controls (Chapter 1) mean that a machine can be started by somebody the man at the winch cannot see.

2. Ropes, wires and cables under load

Never stand in the bight of a rope or wire. This applies at every machine in this volume — the mooring winch, the warping capstan, the cargo winch and the crane. A wire that parts under load whips back along its own length, and the bight is where it will be.

The specific handling points from the machine chapters:

• Wire rope is difficult to handle and does not float (Chapter 5), so a parted mooring wire is also a wire in the water.
• Synthetic ropes of polypropylene, nylon or terylene have a tendency to fuse if scrubbed against themselves or the barrel (Chapter 5). A fused rope loses strength where it has been rubbing, and the failure happens later and somewhere else.
• Multi-layer spooling damages the wire beneath (Chapter 5), which is why a divided barrel is used. A wire whose lower layers are crushed has lost strength that cannot be seen.

3. Anchoring

The anchor is let go at cable speeds of 5 to 7 m/s (Chapter 4), which is fast, and it is controlled by a brake that the operator applies by hand.

The safety points that follow:

• The operator must be able to see the cable and the anchor. That is why the windlass is normally controlled locally, and why the operator stands at the windlass or at the shipside when heaving anchor for housing (Chapter 4).
• Nobody stands over the cable or in the cable's path during letting go or heaving.
• The cable lifter brake is the only thing controlling the run (Chapter 4), and on a remotely controlled windlass it is spring applied and hydraulically released — so a loss of hydraulic pressure applies the brake rather than releasing it. That fail-safe direction is what makes remote letting go acceptable.
• The slipping clutch exists to protect the gear train from shock loading when the anchor is housed (Chapter 4). It protects the machinery, not the people, and it is not a reason to stand close.

4. Mooring

Mooring is where most deck injuries happen, because it is done often, in a hurry, and with a great deal of stored energy in the lines.

• The purpose of the automatic mooring winch is to limit the render value and avoid broken wires (Chapter 5). A broken wire is a safety failure as much as a maintenance one.
• The tension band at each step of automatic control is deliberate (Chapter 5). A winch that hunts is a winch that is paying out and recovering continuously, and nobody should be working near a wire while it does.
• Where the control is, matters. Remote and shipside controllers exist so that the operator can see the wire and the ship's position (Chapter 5), and the control is placed to suit the mooring technique — not for convenience.
• The greatest asset to the operator is knowledge of the wire tensions and the amount of wire paid off (Chapter 5). An operator who does not know the tension is working blind.

5. Cargo gear

The cargo winch and crane requirements in Chapter 6 and Chapter 7 are, read closely, safety requirements:

• The winch must hold the load from running back, lower it under control, and stop it running back if the power supply fails (Chapter 6).
• It must not restart when power is restored until the controller is in the correct position (Chapter 6). A winch that starts by itself with a load on the hook is the classic cargo-handling accident.
• Cargo handling machinery is designed to fail safe, with the automatic application of the disc brake on the motor if the supply fails or the controller returns to OFF (Chapter 6).
• The crane brakes are spring-loaded and fail safe, and operate with motor cut-outs at the hoisting and luffing limits, or if slack turns occur on the hoist barrel (Chapter 7).
• The luffing limit must not be overridden except to stow the jib (Chapter 7). The level luffing geometry can make the jib luff up on its own when the ship is inclined inwards and the jib is near minimum radius (Chapter 7), and the limit is what prevents it.
• The hook can swing, which produces the same effects as inclination (Chapter 7). Nobody works under a swinging load.

6. Hatch covers

The hatch cover is a heavy structure moved by hydraulic power, and it is the place where the most easily avoidable injuries happen.

• The cleats are freed and the panels are raised by hydraulic jacks before the cover moves (Chapter 8). A panel still held by its cleats is under load.
• The jacks are removed before the cover is pulled, and the cover wheels are locked in position first (Chapter 8). The sequence matters; doing it in a different order puts a jack, or a hand, under a moving panel.
• Panels are stacked upright at the end of the coaming (Chapter 8). A stack of steel panels standing on a moving deck is a fall hazard in its own right.
• Hydraulic pressure is stored energy. The hatch cover hydraulic system is a fixed displacement pump with a bypass (Chapter 8), and pressure rises as soon as the output is channelled to the cylinders.
• Never work on a hatch cover with the hydraulic system live unless the isolation is proved and the pressure is released.
• Do not overtighten the cleats (Chapter 8). This is a maintenance rule, but it is also a safety one — the man who leans on a cleat spanner to make a cover tighter is doing it while the cover is under compression.

7. Lifeboats and davits

The lifeboat is launched in the worst conditions the ship will ever see, and it is the one machine whose operation cannot be deferred to better weather.

• Lowering is by gravity alone, and the brake must be held off throughout the outboard movement (Chapter 9). If the operator loses control, the attached weight applies the brake and the boat is held at any intermediate position (Chapter 9). That is the safety design, and it depends on the brake being correctly adjusted.
• The centrifugal brake limits the rate of descent when the handbrake is not engaged, keeping the boat within the pre-designed limit (Chapter 9).
• The ratchet prevents the drums reversing if power fails while a boat is being hoisted (Chapter 9).
• Brakes require regular inspection for wear and must be properly tested after replacement, including arresting the boat after a limited free run to prove the centrifugal brake (Chapter 9).
• Nobody works under a boat on its falls, and the falls are treated as a live load at all times.
• The lifeboat engine must start without the ship's power, which is why a stored-energy hydraulic cranking system is fitted (Chapter 9).

8. Isolation before work

Every machine in this volume is driven by power that has to be positively removed before anybody puts a hand in it.

• Electrical isolation with a permit, and the machine removed from auto start and from priority, before any work on the motor or its control gear. The drive descriptions in Chapter 2 make the point: an a.c. winch can be restarted remotely, and a Ward-Leonard or thyristor-controlled drive can be put in motion from a control position nowhere near the machine.
• Hydraulic isolation and pressure release, because a system with an accumulator holds pressure after the pump has stopped. The accumulator in the Startorque system is precharged to 83 bar (Chapter 9); a hatch cover circuit or a ring main holds pressure in the same way.
• The relief valves are set between 30 and 50 per cent in excess of rated full load pressures (Chapter 3). That is the protection for the system, and a relief valve that has been wound up or plugged to stop it lifting is a protection converted into a hazard.

9. Hazardous areas

On tankers, gas carriers and chemical carriers the deck machinery sits in an area where a spark is a hazard, and the installation reflects that:

• The drive motor for a deepwell pump may be an induction motor of the increased or enhanced safety type (Ex e) (Chapter 1).
• Hydraulic power is intrinsically safe, which is one of the reasons it is so widely used for deck machinery on hazardous cargoes (Chapter 3).
• Air motors may be used for gangway duties (Chapter 1).
• Intrinsically safe circuits are those in which any spark or thermal effect produced normally or accidentally is incapable of igniting the prescribed gas mixture, and the installation rules that follow from that are the electrical officer's, but the deck engineer works inside them.

10. The rules that exist for safety

The survey requirements in this volume are safety requirements written as inspection items:

• Anchoring and mooring equipment is to be examined as part of the load line survey (Chapter 1). The survey exists because the equipment is what holds the ship off a lee shore.
• Gasketted steel hatch covers are to be tested, or alternatively proven tight (Chapter 8). A cover that leaks is a cargo hazard and, in a hold with certain cargoes, a stability hazard.
• Safe working load and identifying marks must always be visible, and the certificate file must be valid (Chapter 10). An appliance whose certificate has lapsed is not a lifting appliance, whatever its condition.
• Hatch covers are surveyed annually with the hull survey, and specially at a maximum interval of five years, with a hose test (Chapter 8).

The wording of the requirements is in the chapters that own them, and in the root index. What belongs here is why each of them is a safety rule rather than a paperwork rule: in every case it is because the item is what stands between a difficult situation and a disaster.