Lifting Index on a Fixed-Height Unload Station

Use the NIOSH lifting equation: RWL = LC x HM x VM x DM x AM x FM x CM, with LC = 23 kg.

Factor	Input	Value
HM	H = 50 cm	25/50 = 0.50
VM	V = 80 cm	1 - 0.003 x |80 - 75| = 0.985
DM	D = 40 cm	0.82 + 4.5/40 = 0.9325
AM	no asymmetry	1.00
FM	1 lift/min, <=2 h	~0.95
CM	good coupling	1.00

RWL = 23 x 0.50 x 0.985 x 0.9325 x 1.00 x 0.95 x 1.00

Step by step: 23 x 0.50 = 11.50; x 0.985 = 11.33; x 0.9325 = 10.56; x 0.95 = 10.03 kg

LI = Load / RWL = 15 / 10.03 = 1.50

The task exceeds the plant guideline by 50%. The dominant term is by far the horizontal multiplier at 0.50 - reaching 50 cm out from the ankles halves the permissible load on its own. By comparison, the vertical term costs only 1.5% and the distance term 7%. In other words, the geometry of the reach, not the weight of the tote, is the controlling variable. Note also that the 1.50 is the LI for this task in isolation; if the operator's other rotation tasks also involve lifting, the composite lifting index would be higher still and should be assessed.

The 12 kg proposal would give LI = 12 / 10.03 = 1.20. Still over the 1.0 guideline. It requires re-engineering the tote (which production says is not available at smaller size), it increases the number of lifts per pallet by 25% - which raises cumulative exposure and, at a higher lift frequency, would push FM down and the LI back up - and it does not touch the actual controlling factor. It is the intuitive answer and it does not work.

Better single change: move the pick point closer to the body. Reduce H from 50 cm to 30 cm by relocating the pallet stand or by rotating the pallet so the operator picks from the near corner, or by adding a simple turntable that presents the near face.

• HM = 25/30 = 0.833
• RWL = 23 x 0.833 x 0.985 x 0.9325 x 0.95 = 16.73 kg
• LI = 15 / 16.73 = 0.90

That clears the 1.0 guideline with the totes unchanged and no capital beyond a pallet positioner.

For comparison, the other single changes are weak:

• Raising the pick height from 80 cm to 75 cm: VM goes to 1.00, RWL to 10.18 kg, LI = 1.47. A 2% improvement - the classic 'raise the pallet' answer is nearly useless here because the height is already close to the 75 cm optimum.
• Shortening the carry from 40 cm to 20 cm: DM = 0.82 + 4.5/20 = 1.045, RWL 11.24 kg, LI = 1.33. Helps but does not solve it.
• Reducing frequency: even at 0.2 lifts/min with FM = 1.00, RWL = 10.56 kg and LI = 1.42. Frequency is not the lever.

So the diagnosis is unambiguous: this is a reach problem masquerading as a weight problem. The cheapest effective intervention is horizontal, and it should be trialled and re-measured, because the 30 cm figure must be the actual sustained reach toward the far side of the pallet, not the near side.

If the geometry is truly frozen, the equation says the load must fall. Since H stays at 50 cm, RWL stays at 10.03 kg and the required load for LI <= 1.0 is 10.0 kg - a one-third reduction from 15 kg that the tote cannot deliver. That leaves engineering controls that change the handling, not the box:

1. Vacuum tube lifter or articulated arm over the pallet. This removes the manual component entirely; the LI framework no longer applies to the task. Highest capital, but it is the only option that reliably gets below 1.0 with the geometry locked, and it also removes the 40 cm carry.
2. Pallet positioner / spring pallet lift if the constraint is 'positions fixed' rather than 'floor fixtures fixed.' Present the near face at 30 cm and the LI drops to 0.90 at essentially no operating cost. Worth challenging the constraint before accepting it - the constraint is often a maintenance preference rather than a physical impossibility.
3. Two-person lift. Halves the per-person load to 7.5 kg, LI = 0.75. Cheap and immediately available. Its real weaknesses are coordination, uneven load sharing, and the fact that the second person is now taken off productive work - so it is a containment measure, not a fix, and it should be time-limited.
4. Re-specify the incoming tote. The product weight is fixed but the tote is a purchasing decision. A 10 kg fill in a smaller tote, accepting 50% more tote handlings, gives LI = 1.00 at the cost of higher frequency (which pushes FM down, so realistically about 20% more totes at 1.2 lifts/min drops FM to ~0.91 and LI to ~1.05 - still marginal). Treat this as a supply-chain negotiation, not an ergonomics fix.

On rotation as a control: rotation does not reduce the LI of a lift. It redistributes exposure across muscles and joints, which is genuinely valuable for reducing fatigue and repetitive-strain injury, but the spine of the operator lifting 15 kg at 50 cm still sees 15 kg at 50 cm for every tote they lift. If the rotation swaps this task for another task of equal spinal loading, nothing improves. Rotation is a valid supplementary control and a reasonable bridge while a lifter is procured - but presenting it as the solution to an LI of 1.50 would be a defensible-looking answer that leaves the hazard in place. Document the interim control, set a date for the engineering fix, and re-measure the LI after installation rather than assuming the calculated value holds in the field.