Sling Leg Tension
Calculate the tension in each leg of a multi-leg inclined sling, T = W ÷ (n·cos α), from the load weight W (N), the number of legs n and the angle of each leg from vertical α (degrees). When a load is lifted by a multi-leg sling (ropes or chains from the hook spreading to the attachment points on the load), the tension in each leg is NOT simply the weight divided by the number of legs — because the legs are INCLINED. The more OPEN the angle (more horizontal legs), the HIGHER the tension in each leg, possibly MULTIPLYING the load several times! This happens because, with inclined legs, part of each leg's force is 'spent' on the horizontal component (which cancels between opposite legs, compressing the load), and only the vertical component supports the weight — so the total tension must be higher for the vertical components to sum to the weight. This is one of the most dangerous and common rigging errors: using slings with very open angles overloads the legs, possibly breaking them even with a load 'apparently' within capacity. So codes LIMIT the leg angle (typically 60° max from vertical, ideally less) and sling WLL tables give the REDUCED capacity per angle. Enter the load weight, the number of legs and the angle.
Result
—
Tensão por perna de lingada
A tração em cada perna de uma lingada (linga) com múltiplas pernas inclinadas é T = W ÷ (n·cos α), a partir do peso da carga W, do número de pernas n e do ângulo de cada perna em relação à vertical α. Quando uma carga é içada por uma linga de várias pernas (cabos ou correntes que partem do gancho e se abrem até os pontos de fixação na carga), a tração em cada perna não é simplesmente o peso dividido pelo número de pernas — porque as pernas são inclinadas. Quanto mais aberto o ângulo (pernas mais horizontais), maior a tração em cada perna, podendo multiplicar a carga várias vezes! Isso ocorre porque, com pernas inclinadas, parte da força de cada perna é 'gasta' na componente horizontal (que se cancela entre as pernas opostas, comprimindo a carga), e só a componente vertical sustenta o peso — então a tração total precisa ser maior para que as componentes verticais somem o peso. Esse é um dos erros mais perigosos e comuns no içamento: usar lingas com ângulos muito abertos sobrecarrega as pernas além da conta, podendo rompê-las mesmo com carga 'aparentemente' dentro da capacidade. Por isso as normas limitam o ângulo das pernas (tipicamente máximo 60° da vertical) e as tabelas de WLL de lingas trazem a capacidade reduzida conforme o ângulo. Informe o peso da carga, o número de pernas e o ângulo.
Related Tools
Sling Tension Factor
Calculate the tension (load) factor of a sling leg, k = 1 ÷ cos α, from the leg angle from vertical α (degrees). The tension factor is the MULTIPLIER showing how much a sling leg's inclination INCREASES its tension versus a vertical leg. For a vertical leg (α = 0°), the factor is 1 (the leg supports exactly its share of the weight); as the angle opens, the factor grows: 1.04 at 15°, 1.15 at 30°, 1.41 at 45°, 2.0 at 60°, and shoots to infinity approaching 90° (horizontal legs, physically impossible to support). This factor is the quick, standardized way to assess the angle 'penalty' in lifting: just multiply the load per leg (weight ÷ number of legs) by the tension factor to get the real tension. Rigging tables and sling safety labels carry these factors precisely for the operator to adjust capacity. The golden rule of safe rigging is to keep leg angles CLOSED (near vertical, below 45° from vertical whenever possible) — very open legs are a frequent cause of overload accidents. Knowing the tension factor is essential for any lift with inclined sling legs. Enter the leg angle from vertical.
Cable Tension in Accelerated Lift
Calculate the dynamic tension in a cable while lifting a load with acceleration, T = W·(1 + a/g), from the load weight W (N), the vertical lift acceleration a (m/s²) and gravity g. When a load is lifted with ACCELERATION (at lift start, when accelerating the rise), the cable must provide not only the force to support the weight (W) but ALSO the force to accelerate the mass upward — by Newton's second law, the total tension is the weight times the factor (1 + a/g). This means the DYNAMIC tension is GREATER than the static weight: an acceleration of g/2 (5 m/s²) raises the tension by 50%! That is why ABRUPT lifts (fast start, or worse, lifting an already-moving load or stopping abruptly) generate dangerous dynamic OVERLOADS in the cable, which can break it even with the static load within capacity. The effect is worse in abrupt STOPS and in loads 'snatching off the ground' (cable slack suddenly removed, generating an impact). So experienced operators lift SMOOTHLY (low acceleration), and the cable safety factors (5 or more) exist precisely to cover these inevitable dynamic overloads. This calculation quantifies the tension increase due to acceleration, essential in the safety analysis of dynamic lifts. Enter the load weight and the lift acceleration.
Wire Rope Working Load Limit (WLL)
Calculate a wire rope's allowable working load, WLL = MBL ÷ SF, from the minimum breaking load (MBL, N) and the required safety factor. The working load (WLL — Working Load Limit, or SWL — Safe Working Load) is the MAXIMUM load that can be safely applied to a rope, fitting or lifting equipment — the information STAMPED on slings, shackles, hooks and equipment plates, and what the operator uses to decide whether a given load can be lifted. It is obtained by dividing the breaking load (the real strength that would break the component) by the code safety factor (5 for general lifting, more for special situations). Respecting the WLL is an absolute safety rule in lifting and material-handling: exceeding the working load dangerously approaches the component to rupture, eliminating the safety margin covering dynamic effects, wear and uncertainties. The WLL is not the rope's strength — it is the SAFE fraction of it. Every rigging operation starts by checking that the load to lift is below the WLL of each component in the load line (rope, slings, shackles, hook, eye), since the chain is only as strong as its weakest link. Enter the breaking load and the safety factor.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.