Multi-Screw Jack System Load Calculation – How to Size Correctly

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Multi-Screw Jack System Load Calculation – How to Size Correctly

When multiple screw jacks support a single load, the system must be sized from the load at the most heavily loaded lifting point – not simply by dividing the total load by the number of jacks.

Step 1: Nominal Load per Jack

For a centered load:

Nominal load per jack = Total operating load / Number of jacks

Example: 20,000 kg platform with 4 jacks → 5,000 kg per jack

Step 2: Apply Uneven Load Factor

Manufacturing tolerances, frame deflection, and off-center gravity increase load on some jacks. Apply an

 uneven-load factor of 1.20 to 1.30 for a rigid, guided platform.

5,000 kg × 1.25 = 6,250 kg maximum expected load per jack

Step 3: Apply Safety Factor

Load Type	Minimum Safety Margin
Static Load	+30%
Dynamic Load	+10%

Static load: force at standstill; Dynamic load: force required to move the load – including friction and acceleration.

Static: 6,250 kg × 1.30 = 8,125 kg

Dynamic: 6,250 kg × 1.10 = 6,875 kg

Select a jack with rated capacity ≥ the higher of the two (static load).