Chain Block — Animation
Anatomy of a Chain Block
Upper Hook
Suspension hook — attaches the chain block to a rated anchor point, beam clamp, or rigging point. Must have a working safety latch.
Lower Hook
Load hook — connects to the load via slings or shackles. Must rotate freely and have a safety latch.
Hand Chain
Endless loop chain the operator pulls to raise/lower the load. Pull one side to hoist, the other to lower. Never wrap around hand.
Load Chain
Short-link calibrated chain that supports the load. NOT the same as sling chain. Grade 80 or T (Grade 100) only.
Gear Mechanism
Spur gears multiply the operator’s pulling force. Typical mechanical advantage 20:1 to 80:1 depending on capacity.
Weston Brake
Automatic friction brake that holds the load when you stop pulling. Load cannot run back. Self-locking — no external brake required.
Housing / Body
Pressed steel or cast housing that encloses gears and brake. WLL and manufacturer markings are stamped here.
Chain Guide
Directs the load chain onto the chain wheel correctly. Prevents chain jumping, jamming, or misalignment under load.
Purpose & How It Works
A chain block is a manually operated lifting/pulling device that uses mechanical advantage to lift, lower, or position loads. Used for:
- Positioning loads during rigging and dogging operations
- Tensioning wire ropes, slings, and lashings
- Short-distance vertical lifts where a crane is impractical
- Maintaining load position during assembly or installation
Mechanical Advantage
Pulling the hand chain turns spur gears that multiply force. The Weston brake automatically holds the load in position when you stop pulling — the load cannot run back.
Working Load Limits
WLL is stamped on the housing body. Common sizes:
| WLL | Typical Use | Approx. Weight |
|---|---|---|
| 0.5 t | Light positioning, tensioning | 8–12 kg |
| 1 t | General construction lifting | 14–18 kg |
| 2 t | Steel erection, mechanical | 22–28 kg |
| 3 t | Heavy positioning | 35–45 kg |
| 5 t | Structural steel, plant | 55–70 kg |
| 10 t | Heavy industrial | 95–120 kg |
| 20 t | Specialised heavy lift | 180–250 kg |
Never Exceed WLL
- If you can’t read the WLL stamping — do not use
- No side-loading — load must hang vertically below the chain block
- Never use as a substitute for a rated sling
Critical Operating Rules
- Never exceed WLL — if in doubt, use a larger capacity block
- Must be suspended from a rated anchor point — never from scaffold, temporary structure, or unrated steelwork
- Never wrap hand chain around your hand — if the brake slips, the chain will crush or sever fingers
- Ensure load chain is not twisted before applying load
- Lower hook must rotate freely — a stuck hook means internal damage
- Do not use for horizontal pulling unless specifically rated for it
- Keep hands clear of pinch points between chain and housing
- Never leave a suspended load unattended
Inspection & Rejection Criteria
Inspect before every use. Remove from service immediately if ANY defect is found:
Reject Immediately If
- Chain links worn, stretched, twisted, or corroded
- Hooks deformed, cracked, or safety latches broken/missing
- Gear mechanism grinding, skipping, or making unusual noise
- Brake doesn’t hold load — load drifts down when hand chain released
- Housing cracked, dented, or showing signs of impact damage
- Missing markings — WLL, manufacturer ID, or serial number illegible
- Chain guide damaged or missing — chain may jump off wheel
- Hook throat opening has increased (hook “spreading”)
Good Condition Indicators
- All chain links uniform, no stretch marks or deformation
- Both hooks straight, latches snap shut under spring tension
- Gears engage smoothly, hand chain pulls freely
- Brake holds test load securely — no drift
- Housing intact, all markings legible
- Load chain runs straight through guide without jamming
- Lower hook rotates freely 360°
Chain Type — Critical Distinction
Chain blocks use SHORT-LINK CALIBRATED CHAIN specifically manufactured for the chain wheel inside the mechanism.
Never Substitute Chain
- Chain block chain is NOT the same as sling chain
- Never replace load chain with hardware store chain
- Wrong pitch chain will jam, skip, or fail catastrophically
- Only use manufacturer-supplied replacement chain of the correct grade and pitch
| Chain Type | Used In | Interchangeable? |
|---|---|---|
| Short-link calibrated | Chain block load chain | NO — specific to each block |
| Grade 80 sling chain | Chain slings for lifting | NO — wrong pitch |
| Grade T (100) sling chain | High-strength chain slings | NO — wrong pitch |
Storage & Care
- Store indoors or under cover — away from moisture and chemicals
- Hang from upper hook — never coil load chain on the ground
- Lubricate load chain and hand chain periodically per manufacturer’s instructions
- Do not paint over markings or identification plates
- Tag and quarantine defective chain blocks immediately — mark “OUT OF SERVICE”
- Periodic thorough inspection by competent person as per AS 1418.2
- Keep a register of all chain blocks on site with inspection dates