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The ratio between the calculated bearable and the actually occurring load. It covers what the calculation does not know: material scatter, wear, dynamic allowances and operator error. For friction-based attachments it is markedly higher than for positive ones, because there the friction coefficient varies as well – oily, dusty or damp surfaces hold worse than the data sheet assumes.
The safety factor is the ratio between the load at which a component fails and the maximum load it may carry in service. A factor of 4 means that the minimum breaking force is four times the permitted load.
The EU Machinery Directive calls this quantity the working coefficient. It specifies values for hoisting media and slings that are to be met as a general rule and leaves the details to the harmonised standards.
The permitted load applies to the new component under static loading. Reality deviates from this, and the factor covers those deviations.
The factors are not graded arbitrarily. A steel chain shows wear visibly and measurably and deforms before breaking. A wire rope consists of many wires that can break individually before the rope fails – but internal damage is harder to detect. Textile webbing and ropes age through light, chemicals and cuts, and their condition is the hardest to judge from outside.
The less reliably the condition of an element can be established, the greater the distance between permitted load and failure.
If a gripper holds the load by positive locking, safety depends on the strength of the components. If it holds by friction – clamping, vacuum or magnet – a second uncertainty is added: the holding force itself. It depends on the friction coefficient, the surface and the seal, and it varies in operation.
For this reason EN 13155 requires vacuum lifters to hold at least twice the working load limit. On clamping grippers the clamping force is sized with a friction coefficient for the least favourable surface – oily, wet or dusty, not clean and dry.
It is not a reserve at the operator’s disposal. A chain with a factor of four must not be loaded with twice its rated load: the reserve is already allocated to dynamics, wear and scatter. Nor is it the test load – that lies above the rated load but far below the breaking load, and serves as proof, not for operation.
What Entracon offers here is on the matching page.
See what we offer| Component | Working coefficient as a general rule | Reason for the level |
|---|---|---|
| Chains | 4 | Wear visible and measurable |
| Wire ropes | 5 | Internal damage harder to detect |
| Textile ropes and slings | 7 | Ageing and sensitivity to cuts |
| Vacuum lifters (EN 13155) | Holding force at least 2 times | Holding force varies with surface and seal |
No. The rated capacity is the limit. The safety factor is already allocated to dynamic forces, wear and scatter and is not available.
Not necessarily. It makes components heavier and, on grippers, increases the dead weight. The specified factors are matched to each type of element; going beyond them makes sense for particular risks, not across the board.
Only if the component is within its discard criteria. Wear eats into the margin to failure. That is why discard limits and periodic inspections exist.
One short conversation usually settles more than three quotations. Call or write — you will reach an engineer directly.
Start typing – for example “balancer”, “SAP” or “pipe stress”.
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