4.3 Chain Sling Marking, Certification & Safe Use
Key Takeaways
- Every chain sling must be fitted with a durable, metallic identification tag detailing WLL, nominal chain size, number of legs, manufacturer mark, serial number, and compliance symbols (CE/UKCA).
- Mode factors derate chain sling capacity based on leg angle: for 2-leg slings, the mode factor is 1.4 for 0°--45° to vertical (0°--90° included angle) and 1.0 for 45°--60° to vertical (90°--120° included angle); angles above 60° to vertical (120° included angle) are strictly prohibited.
- Choke hitch applications derate a chain sling's WLL by a factor of 0.8 (20% reduction) due to local link bending and friction around the load.
- Statutory regulations (LOLER 1998 in the UK) require an EC Declaration of Conformity / Initial Test Certificate upon commissioning and mandatory Thorough Examinations by a Competent Person at least every 6 months.
4.3 Chain Sling Marking, Certification & Safe Use
The safe operation of chain slings in industrial lifting depends on strict compliance with statutory marking requirements, precise load rating calculations, and sound rigging practices. Riggers and lifting inspectors must accurately determine the Working Load Limit (WLL) of multi-leg slings across varying leg angles and reeving modes. Operating a chain sling beyond its rated capacity or outside permitted angular boundaries risks sudden structural failure.
1. Statutory Identification & Tagging (BS EN 818-4 / LEEA)
In accordance with BS EN 818-4 and LEEA codes of practice, every chain sling assembly must be permanently fitted with a heavy-duty, metallic identification tag (typically stainless steel or brass) attached to the master link.
+-------------------------------------------------------------+
| ACME LIFTING SERVICES |
| Serial No: CS-884920 Grade: 8 (T) |
| Chain Size: 10 mm Legs: 2 |
| --------------------------------------------------------- |
| WLL 0°-45° (to vert) / 0°-90° (inc): 4.25 t |
| WLL 45°-60° (to vert) / 90°-120° (inc): 3.00 t |
| --------------------------------------------------------- |
| CE UKCA Year: 2026 |
+-------------------------------------------------------------+
Mandatory Tag Information
- Working Load Limit (WLL): Stated clearly in tonnes ($t$) or kilograms ($kg$). For multi-leg slings, the tag MUST show the WLL for both standard angular ranges ($0^\circ\text{--}45^\circ$ and $45^\circ\text{--}60^\circ$ to the vertical).
- Nominal Chain Size ($d$): Nominal wire diameter in millimeters (e.g., $10\text{ mm}$).
- Number of Legs: Total count of active lifting legs ($1$, $2$, $3$, or $4$).
- Grade Identification: Metal grade number or letter (e.g.,
8/Tfor Grade 80;10/Vfor Grade 100). - Manufacturer Identification: Mark, symbol, or full name of the certified sling assembler.
- Unique Serial / Identification Number: Traceable link to the manufacturer's test certificate and inspection register.
- Regulatory Compliance Marks: CE and/or UKCA marking.
Tag Shape Conventions
- Grade 8 Slings: Industry standard convention utilizes an octagonal (8-sided) metal tag.
- Grade 10 Slings: Industry standard convention utilizes a 10-sided metal tag, providing immediate visual differentiation for riggers on site.
2. Load Rating Calculations & Mode Factors
When a multi-leg sling lifts a load, the tension in each sling leg increases as the angle between the leg and the vertical increases. The European standard BS EN 818-4 enforces the Uniform Load Method for rating multi-leg slings.
SLING LEG ANGLES TO VERTICAL
[0° - 45° to Vert] [45° - 60° to Vert]
(0°-90° Included) (90°-120° Included)
Mode Factor = 1.4 Mode Factor = 1.0
/ \ / \
/ β1 \ / β2 \
/ \ / \
/ \ / \
[ LOAD ] [ LOAD ]
Multi-Leg Mode Factors (BS EN 818-4 Uniform Load Method)
| Sling Configuration | Angle to Vertical ($\beta$) | Included Angle ($\alpha = 2\beta$) | Mode Factor ($F$) relative to Single Leg WLL |
|---|---|---|---|
| Single Leg (Straight Pull) | $0^\circ$ | $0^\circ$ | $1.0$ |
| 2-Leg Sling | $0^\circ\text{--}45^\circ$ | $0^\circ\text{--}90^\circ$ | $1.4$ ($WLL = 1.4 \times WLL_{\text{single}}$) |
| 2-Leg Sling | $45^\circ\text{--}60^\circ$ | $90^\circ\text{--}120^\circ$ | $1.0$ ($WLL = 1.0 \times WLL_{\text{single}}$) |
| 3 & 4-Leg Sling | $0^\circ\text{--}45^\circ$ | $0^\circ\text{--}90^\circ$ | $2.1$ ($WLL = 2.1 \times WLL_{\text{single}}$) |
| 3 & 4-Leg Sling | $45^\circ\text{--}60^\circ$ | $90^\circ\text{--}120^\circ$ | $1.5$ ($WLL = 1.5 \times WLL_{\text{single}}$) |
| Any Sling Angle | $> 60^\circ$ to Vert | $> 120^\circ$ Included | PROHIBITED (Extreme Overload Hazard) |
Engineering Physics of 3 and 4-Leg Rating ($F = 2.1$)
Why is a 4-leg sling rated at only $2.1 \times \text{Single Leg WLL}$ rather than $4.0 \times \text{Single Leg WLL}$? In practical lifting, unless a load is completely flexible or the sling legs are fitted with automatic load-equalizing sheaves, a rigid load will almost always be supported primarily by only three legs (or even two legs diagonally). The fourth leg merely acts to balance the load. Therefore, international standards restrict 3 & 4-leg mode factors to $2.1$ (for $0^\circ\text{--}45^\circ$), protecting against uneven load distribution.
Sample Calculation
Problem: A Grade 8 single leg chain of $10\text{ mm}$ size has a $WLL_{\text{single}} = 3.15 \text{ tonnes}$. Calculate the maximum safe lifting capacity for a 2-leg sling and a 4-leg sling of this same chain size operating at an angle of $30^\circ$ to the vertical.
- 2-Leg Sling Capacity ($0^\circ\text{--}45^\circ$):
- 4-Leg Sling Capacity ($0^\circ\text{--}45^\circ$):
3. Choke Hitch & Special Rigging Configurations
When a chain sling is wrapped directly around a load and hooked back onto its own standing leg (or passed through a master link eye), it forms a choke hitch.
STRAIGHT LIFT CHOKE HITCH
(Mode Factor 1.0) (Mode Factor 0.8)
| |
| |
| |
( ) ( ) <-- Bending & Friction
| // \ at Choke Point
[LOAD] //===\
[ LOAD ]
Choke Hitch Derating Factor ($F_{\text{choke}} = 0.8$)
Rigging a chain sling in choke hitch subjects the chain link at the choke point to intense localized bending, shear, and interlink friction. To compensate, the rated WLL of the sling must be multiplied by a choke mode factor of 0.8 (a 20% capacity derating):
Edge Protection & Sharp Radii
When chain slings are wrapped around structural steel sections, machinery bases, or sharp concrete edges, the corner radius $r$ of the load must be compared to the nominal chain diameter $d$:
- If $r \ge 2d$: Full WLL applies (no edge derating required).
- If $r < 2d$: Corner protection is mandatory. Approved wooden packing, rubber edge guards, or specialized polyurethane corner protectors must be fitted to prevent sharp metal edges from biting into chain links and causing severe link bending.
Pre-Use Tag-to-Lift Cross-Check
Before connecting a chain sling, compare the tag with the planned configuration in a fixed order: identity and grade; number of legs; single-leg or assembly WLL; angle band; hitch or shortening arrangement; component compatibility; and any temperature or environmental derating. Then inspect the links, master link, connectors, shortening clutch and hooks. A valid tag does not make a damaged sling usable, and an undamaged sling without traceable capacity information is not ready for service. Raise the load only just clear, stop, and confirm balance, seating and load sharing before continuing.
Under BS EN 818-4 (Uniform Load Method), what is the correct mode factor applied to a 2-leg chain sling operating at a leg angle of 30° to the vertical (60° included angle)?
What is the mandatory mode derating factor for a chain sling leg rigged in a standard choke hitch around a load?
In the absence of a competent-person examination scheme specifying another interval, what is LOLER’s default interval for a chain sling used as a lifting accessory?