A 2 leg lifting chain sling balances heavy modules, plates, and skids while crews keep angles under control and hardware correctly matched. You protect people and gear when you size each leg from the load path, read the tag math, pair rated fittings, and run short, repeatable inspections. This field guide walks through standards, geometry, sizing steps, installation, and maintenance so you rig quickly and lift cleanly on every shift.

1) Know the Rulebook Before You Rig

You ground your choices in published standards and the manufacturer’s data:

ASME B30.9 (U.S.) and EN 818-4 (EU) define chain-sling construction, marking, proof testing, and use.

Tags record WLL by hitch, leg angle tables, serial numbers, and manufacturer IDs.

You match the sling grade to the job: G80 and G100 support overhead lifting; transport grades (G30/G43/G70) do not.

Read the tag first, then check the data sheet that ships with the sling.

2) Geometry Drives Tension—Use the Math

Two legs share the load, yet angle multiplies tension. You calculate tension per leg as:
T = Load ÷ (2 × sin θ), where θ = angle from vertical of one leg.
Keep legs near 60° included angle (≈30° off vertical) to hold tension close to the tag value.

Angle Factor Table (apply to each leg’s vertical WLL)

You place a spreader or adjust pick points when space tries to close that angle.

3) Size the 2 Leg Lifting Chain Sling—Four Fast Steps

Step 1: Weigh the load. Use a drawing, a load cell, or a supplier weight sheet; do not guess.
Step 2: Choose an angle. Plan for 60° whenever you can; only accept 45° or 30° when geometry forces it.
Step 3: Compute leg tension. Example: a 10-ton load at 60° puts 5 t on each leg (T = 10 ÷ 2). At 45°, tension climbs to 7.1 t per leg (10 ÷ (2×0.707)).
Step 4: Select grade and diameter. Pick G80 or G100 with vertical WLL ≥ computed leg tension, then confirm the tag’s two-leg capacity at your angle. You verify chain diameter, pitch, and grade stamp (“8” or “10”) on the links.

4) Pair Hardware That Matches the Sling

You treat the system as one path, not a pile of parts:

Master link inside width ≥ 5× chain Ø, so the crane hook and latch seat freely.

Hook throat ≥ 4× chain Ø, so links feed without pinch.

Use self-locking hooks when you lift above people or when movement may shake spring latches.

Choose bow shackles on the head when legs may change angle; run the pin through the hardware and the bow toward the legs.

Keep all grade stamps aligned with the sling grade; the lowest grade controls the assembly.

5) Install the Sling—A Short, Repeatable Sequence

Lay out the sling. Roll both legs until stamps face up; remove twists.

Center the master link. Seat it in the crane hook, close the latch, and check free swing.

Attach the hooks. Use rated padeyes or shackles; check that the load points align with the line of pull.

Set the angle. Pull up gently; read legs with an angle card or digital inclinometer; adjust spreader or pick points until you hit plan.

Lift and pause. Raise 150 mm, stop, re-check angle and balance, then continue.

You stop immediately if a hook twists, a leg slackens, or the sling drags across a sharp edge; add protection or re-route.

6) Daily Inspection—Numbers, Not Guesswork

You finish a five-point check before the first pick:

Tag: grade, WLL, angle table, and serial number stay legible.

Pitch: measure five links under light tension; scrap the leg if elongation exceeds the maker’s limit (many programs use >3 %).

Crown wear: gauge the link crown; scrap the leg if wear exceeds the limit (many programs retire at ≈10 % diameter loss).

Hooks: latch snaps shut unaided; throat shows no spread; no cracks at the saddle or neck.

Twist and nicks: legs lie flat; no deep pits, gouges, or peening that catch in a pocket wheel.

You log results in the rigging register with date, inspector, and location.

7) Periodic Actions—Prove It and Record It

Proof test on the schedule your code or company sets (commonly annual, after repair, or after suspected overload). Follow the manufacturer’s procedure and record the load, duration, and serial number.

Component swaps happen as complete legs when you replace chain; you keep traceability and equal length.

Hook kits arrive with springs and latches; you replace worn parts and re-test closure ten times.

You store the certificate set with the sling or in a digital system, tied to the serial.

8) Control Edges, Heat, and Corrosion—Pick the Right Finish

For general shops, G80 alloy with black oxide or phosphate runs clean and simple.

For coastal yards or splash zones, zinc–nickel coated G80 resists red rust and wipes down easily.

For wash-down, food, or chemical plants, stainless G80 (304/316) keeps hygiene and resists pitting.

For hot work, follow the maker’s temperature curve; many alloy slings hold full WLL to a conservative limit, then require derating.

You protect edges with corner guards or wear sleeves and re-inspect those guards after each pick.

9) Common Mistakes and How You Avoid Them

Wrong angle math. Crews eyeball angles and overload legs. You always measure and apply the factor table.
Mixed ratings. A G70 hook sneaks into a G80 sling and drags the assembly down. You read every stamp on link, hook, shackle, and master link.
Short headroom. You cram legs into 30° and double tension. You fit a spreader or extend pick points to reopen angle.
Missing documentation. Audits stall when records vanish. You file certificates and photos of stamps with each job.

10) Quick Field Card—Keep This in the Cab

Weigh the load and plan 60°.

Compute T = Load ÷ (2×sin θ) and size legs by vertical WLL.

Match grades across chain, hooks, and shackles.

Check tag, pitch, crowns, latches, and twists.

Lift 150 mm, pause, re-check, then travel.

Tape this card near the remote or cab window.

Conclusion

Size each leg from the real geometry, pair only rated fittings, verify the tag with numbers, and run short inspections every shift, and a 2 leg lifting chain sling will deliver clean, compliant lifts on demand—contact TOPONE CHAIN today for certified G80/G100 two-leg assemblies with full documentation.