3D Model — Orbit & Inspect
Anatomy of a Safety Hook
Body (Saddle)
The curved main structure of the hook. The bowl/saddle is where the load must always sit — this is the load-bearing area designed to distribute force evenly.
Throat Opening
The gap between the hook tip and the body through which slings are placed. A stretched throat (>5% increase) means the hook must be removed from service.
Safety Latch / Trigger
Spring-loaded gate that closes automatically across the throat. Retains slings in the hook — but the latch itself is NOT load bearing.
Eye / Attachment Point
The top of the hook where it connects to the crane block, chain, or lifting device. May be a fixed eye, clevis pin, or swivel arrangement.
Load Bearing Point
The deepest part of the saddle where the sling naturally rests under load. All force must be directed here — never on the tip of the hook.
Types of Safety Hooks
| Type | Connection | Best For |
|---|---|---|
| Eye Hook | Attached via shackle to sling eye | General sling terminations |
| Clevis Hook | Pin connection (bolt & nut) | Chain slings, permanent fittings |
| Swivel Hook | Rotates freely under load | Preventing sling twist, multi-leg slings |
| Grab Hook | Narrow throat, grips chain link | Chain shortening, adjustment |
All hook types used in dogging operations must be fitted with a self-closing safety latch. Hooks without latches are prohibited on lifting operations.
Safety Latch — How It Works
The safety latch is a spring-loaded gate that automatically closes across the throat of the hook. Its purpose is to retain the sling and prevent it from accidentally coming off the hook during a lift.
Key Principle
The latch is NOT load bearing • It only prevents the sling from escaping the hook
- Spring mechanism ensures the latch closes automatically when released
- Latch must snap shut freely — if it sticks or stays open, the hook is unserviceable
- Never rely on the latch to hold load — the sling must sit in the bowl/saddle
- Latches are designed to be opened by hand to place or remove slings
Critical Loading Rules
Correct loading of a safety hook is essential. Improper loading causes hook failure, dropped loads, and fatalities.
Never Do This
- Tip loading: Never place the load on the point/tip of the hook — this straightens the hook under load
- Back loading: Never load the outside/back of the hook body
- Forcing the latch: Never wedge multiple slings that force the safety latch open
- Disabling the latch: Never wire, tape, or remove the safety latch
- Overloading: Never exceed the WLL stamped on the hook
- Side loading: Never apply load sideways across the hook — hooks are designed for in-plane loading only
Always Do This
- Load must sit in the bowl/saddle of the hook
- Sling eye must move freely in the hook — not jammed or twisted
- Safety latch must close fully after sling placement
- Check WLL marking matches or exceeds the load being lifted
- Use a larger hook or spreader if multiple slings don’t fit
Inspection & Rejection Criteria
Inspect safety hooks before every use. Remove from service if ANY of the following are found:
Reject Immediately If
- Throat opening increased >5%: hook has been stretched/overloaded — permanently deformed
- Latch doesn’t spring closed: broken or weak spring, stuck latch, or missing latch
- Cracks or gouges: any visible cracks, nicks, or gouges on the hook body
- Twist in hook body: the hook has been twisted from side loading or overload
- Worn saddle area: excessive wear in the bowl where slings sit (reduces cross-section)
- No markings: WLL, manufacturer, or identification markings missing or illegible
- Corrosion: significant pitting or rust that reduces material thickness
- Heat damage: discolouration indicating the hook has been exposed to excessive heat
Good Condition Indicators
- Throat opening matches original specification
- Safety latch snaps shut freely and fully under spring tension
- No visible cracks, gouges, or deformation
- Hook body straight — no twist
- Saddle area smooth, no excessive wear grooves
- WLL and identification markings clearly legible
- Swivel (if fitted) rotates freely
Checking Throat Opening
The throat opening measurement is the critical indicator of whether a hook has been overloaded or stretched.
5% Rule (NSW Rigging Guide)
Measure from the tip of the hook to the nearest point on the body
- Use Vernier callipers or a go/no-go gauge to measure throat opening
- Compare against the manufacturer’s original specification
- A stretched hook has been permanently deformed — it cannot be repaired
- Even a small increase indicates the hook has been overloaded at some point
- Record measurements in the equipment inspection register
Storage & Handling
- Store hooks on racks or in purpose-built containers — never on the ground
- Protect the latch mechanism from dirt, paint, and concrete splatter
- Lubricate the latch spring periodically per manufacturer’s instructions
- Do not weld, heat-treat, or modify hooks in any way — this voids the certification
- Do not use hooks as anchor points for tying off
- Tag and quarantine defective hooks immediately — do not return to service
- Re-certify hooks after any suspected overload event, even if no visible damage
- Keep hooks clean and free of grease to allow proper visual inspection