One of the most common lashing systems is friction lashing. In the friction or friction system, the lashing belt must be placed so that it presses against the load and the load presses against the surface. Depending on the type of load, a certain number of tensioners or lashing belts will be used. This varies depending on the friction force Fr, the type of tensioner and the tensioning force Ft of the tensioner.
To determine the number of belts to be used to develop the ideal restraint and securing system, the following factors must be taken into account:
- The load situation in order to obtain a good distribution of the masses.
- The degree of integration of the restraint devices on the vehicle structure.
- If it is a work equipment, if it has wheels, chains, tracks, etc....
- The weight of the work equipment or load to be transported.
- The availability of at least four anchorage points.
- The fastening devices, lashing belts.
The number of tensioners is calculated by the following formula : n ≥ [(cx,y - μ-cz)-m-g/k-μ-senα-Ft]-fs
where:
cx,y and cz = coefficients of longitudinal, transverse and vertical acceleration of the forceFp.
μ = coefficient of friction. g = acceleration of gravity (9.81 m/s2).
k = coefficient of loss of the tensioning force (1.5).
Ft = tensioning force of the tensioner.
fs = safety factor (in land transport1.25).
α = vertical angle of lashing between the lashing device and the horizontal plane of the vehicle surface
(depending on the working angle α the STF acting on the load will vary).
INSHT, nº1.038 2015 Fastening devices for work equipment and miscellaneous loads on transport vehicles: Safety.
