Preventers and stoppers requirements

Under 1918.52(a)(1) preventers must be strong enough for the job and secured independently of working guys unless the cast fitting is stronger than all lines combined. Employers must make sure preventers are "of sufficient strength for the intended purpose" and that they are "secured to the head of the boom independent of working guys" except when a cast fitting’s strength exceeds the total strength of all lines secured to it (Requirement in 1918.52(a)(1).

• Any tails, fittings, or deck attachments used to make the preventers fast must have strength equal to the preventer itself.
• Inspect preventers and attachments for wear or damage and replace parts that reduce strength.

Cite: 1918.52(a)(1).

Under 1918.52(a)(1) preventers must be secured to the head of the boom independent of the working guys unless a cast fitting’s strength exceeds the total strength of all lines secured to it. This means you generally must rig an independent preventer line rather than relying on the same guys used for normal boom control, except where the fitting itself is demonstrably stronger than the combined lines (Requirement in 1918.52(a)(1).

• If you rely on a cast fitting as the single attachment, keep documentation or inspection evidence showing the fitting’s strength exceeds the sum of the lines attached.

Cite: 1918.52(a)(1).

Under 1918.52(a)(1) tails, fittings, or other means of making preventers fast on deck must provide strength equal to the preventer itself. In practice that means any hardware or line used to secure the preventer must be rated to at least the same strength as the preventer line being used (Requirement in 1918.52(a)(1).

• Verify rated capacities of shackles, thimbles, chain, and other fittings to ensure they are not the weak link.

Cite: 1918.52(a)(1).

Under 1918.52(a)(2) you must not use wire rope clips or knots to form eyes or join sections of preventer guys. The standard explicitly prohibits using wire rope clips or knots for eyes or splices in preventer guys (Requirement in 1918.52(a)(2).

• OSHA’s long-standing interpretation on wire rope knot prohibition explains that knots in wire rope are a recognized hazard and are not acceptable to secure or splice wire rope; see the Letter of Interpretation "Wire rope knot prohibition" (Wire rope knot prohibition, 12/14/1977).

Cite: 1918.52(a)(2) and Wire rope knot prohibition (1977).

Under 1918.52(b)(1) chain topping lift stoppers must be in good condition, have fiber tails, and be long enough to allow at least three half-hitches in the chain. In short: keep them serviceable, fitted with fiber tails, and long enough for three half-hitches to secure the chain (Requirement in 1918.52(b)(1).

• Inspect for corrosion, stretched links, or damaged tails before use.

Cite: 1918.52(b)(1).

Under 1918.52(b)(2) chain stoppers must be shackled or otherwise secured so that their links are not bent by being passed around fittings. That means you should use proper shackles or equivalent hardware rather than forcing chain links around fittings, which could bend and weaken the chain (Requirement in 1918.52(b)(2).

• Use shackles or properly sized fittings and inspect for bent or distorted links.

Cite: 1918.52(b)(2).

Under 1918.52(b) the point of attachment must be strong enough and placed so the stoppers are in line with the normal topping lift lead when the stopper is applied. In other words, attach stoppers where they will take load in the same direction as the topping lift so they don't introduce side loads or unexpected stresses (Requirement in 1918.52(b).

• Proper alignment reduces shock loads and wear on fittings and lines.

Cite: 1918.52(b).

Under 1918.52(b)(3) patent (clamp) style stoppers must be appropriate for the rope size, in good condition, and free of anything that would prevent them from being drawn tight. Select clamps sized for the rope and keep them clean and serviceable so they can grip properly (Requirement in 1918.52(b)(3).

• Follow manufacturer guidance for proper placement and number of clamps where applicable.

Cite: 1918.52(b)(3).

Under 1918.52(c)(1) the end of the winch fall must be secured to the drum by clamps, U-bolts, shackles, or other methods at least as strong — and you must not use fiber rope fastenings. Use mechanical metal fastenings that match the required strength (Requirement in 1918.52(c)(1).

• Do not use fiber rope to fasten the fall to the drum; inspect securing hardware for tightness and corrosion.

Cite: 1918.52(c)(1).

Under 1918.52(c)(2) winch falls must have at least three turns on the winch drum. Do not operate a winch fall with fewer than three wraps of rope around the drum to ensure adequate friction and holding capacity (Requirement in 1918.52(c)(2).

• Maintain proper drum loading and avoid loose or crossed wraps during operation.

Cite: 1918.52(c)(2).

Under 1918.52(c)(3) you must not form eyes in wire rope cargo falls by knots, and in single-part falls you must not form eyes using wire rope clips. The standard prohibits knots for eyes and disallows clips for single-part falls to maintain proper strength and reliability (Requirement in 1918.52(c)(3).

• OSHA’s "Wire rope knot prohibition" Letter of Interpretation reinforces that knots in wire rope are a recognized hazard and are unacceptable for securing wire rope eyes (Wire rope knot prohibition, 12/14/1977).

Cite: 1918.52(c)(3) and Wire rope knot prohibition (1977).

Under 1918.52(c)(4) when the winch design permits, wind the fall so pulling the control lever back raises the cargo hook and pushing it forward lowers the hook. This standard sets a preferred control-to-motion relationship to avoid operator confusion and improve safety (Requirement in 1918.52(c)(4).

• If the winch design prevents this orientation, ensure operators are trained and controls are clearly marked.

Cite: 1918.52(c)(4).

Under 1918.52(d)(1) you must rig a preventer of at least 3/4 inch (1.91 cm) diameter wire rope or use an equally effective means to hold the heel block and fall if the heel block attachments fail. That preventer must be securely rigged to protect an employee working in the bight (Requirement in 1918.52(d)(1).

• Ensure preventer attachment points and hardware are inspected and rated for the load.

Cite: 1918.52(d)(1).

Under 1918.52(d) when physical limitations prohibit fitting the required 3/4-inch preventer, two turns of 1/2 inch (1.27 cm) wire rope are sufficient. The standard provides this specific, acceptable alternative when space or design prevents installing the larger preventer (Requirement in 1918.52(d).

• Mark and inspect the substitute rigging to ensure it remains serviceable.

Cite: 1918.52(d).

Under 1918.52(d)(2) a heel block that isn’t rigged to prevent falling when not under strain must be secured to stop alternate raising and dropping, unless the heel block’s lowest position is at least 10 feet (3.05 m) above the deck. So secure loose heel blocks unless they cannot reach less than 10 feet above deck (Requirement in 1918.52(d)(2).

• If the heel block is 10 feet or more above the deck at its lowest point, this particular securing requirement does not apply.

Cite: 1918.52(d)(2).

Under 1918.52(e) portable coaming rollers must be secured by wire preventers in addition to their regular coaming clamps. In other words, use a wire preventer as a backup to the clamp to keep the roller from falling or shifting (Requirement in 1918.52(e).

• Inspect the preventer and clamps before use to ensure both are in good condition.

Cite: 1918.52(e).

Under 1918.52(f) cargo hooks must be as close as the assembly allows to the junction of the falls and never farther than two feet (0.61 m) from it, unless the vessel construction and operation produce fall angles less than 120 degrees—in which case the two-foot limit does not apply. Keep hooks close to the junction to reduce slippage and uneven loading (Requirement in 1918.52(f).

• Check fall geometry during operations; if fall angles are under 120 degrees, the two-foot restriction is excepted.

Cite: 1918.52(f).

Under 1918.52(f) overhaul chains must not be shortened by bolting or knotting. The standard forbids shortening overhaul chains using bolts or knots because those methods weaken the chain or create unsafe connections (Requirement in 1918.52(f).

• Use manufacturer-recommended shortening fittings or properly rated components if adjustments are required.

Cite: 1918.52(f).

Under 1918.52(c)(1) and 1918.52(c)(2) you may not use fiber rope fastenings to secure the end of the winch fall to the drum, and winch falls must have at least three turns on the drum. Fiber rope fastenings are explicitly prohibited for securing the fall end, and three or more wraps are required for safe operation (Requirement in 1918.52(c)(1) and 1918.52(c)(2).

• Use metal clamps, U-bolts, or shackles sized for the rope and ensure adequate drum wraps to prevent slippage.

Cite: 1918.52(c)(1) and 1918.52(c)(2).

Under 1918.52(d) employers may use two turns of 1/2-inch wire rope when space prevents fitting a 3/4-inch preventer, but they must ensure the substitute is properly rigged and maintained. Use the allowed alternative only when the larger preventer truly cannot be installed, and inspect the smaller rope turns, terminations, and attachment points regularly for wear or damage (Requirement in 1918.52(d).

• Document the physical limitation, train workers on the substitute rigging, and inspect before each use.

Cite: 1918.52(d).

Yes. The 1977 "Wire rope knot prohibition" Letter of Interpretation confirms that knots in wire rope are a recognized hazard and reinforce the prohibitions in the maritime standards such as 1918.52 that forbid forming eyes by knots. OSHA’s long-standing interpretation supports the standard language that forbids knots and improper splicing or fastening of wire rope used for preventers, falls, and similar rigging (Requirement in 1918.52(a)(2) and 1918.52(c)(3) and Wire rope knot prohibition (1977)).

• Do not rely on knots; use approved splices, fittings, or terminations rated for the rope.

Cite: 1918.52(a)(2), 1918.52(c)(3), and Wire rope knot prohibition (1977).