Design and Assessment of Hydrometric Cableway Systems
Whether under the Provision and Use of Work Equipment Regulations (PUWER) or the Lifting Operations and Lifting Equipment Regulations (LOLER) it is necessary to ensure that stream gauging cableways are fit for purpose and safe to use.
Because a load is involved in the form of the sinker weight, some are of the opinion that the lifting regulations apply. Others believe that, as the sinker is ballast and part of the installation, PUWER is appropriate. Whilst the administration and compliance requirements are different, from a practical point of view there is little difference. Accidental overloading is a risk during flood gauging, when floating debris can become attached to the sounding cable. It is important, regardless of the regulation that the cableway can cope with this in a predictable manner.
However, it is important to remember that the purpose of an installation is to deploy a current meter or ADCP rather than to lift ad hoc loads. For this reason, the criteria for specifying the working sag are different from those that may be applied to a cableway designed for transporting material.
For “normal working” it is appropriate that the factors of safety and coefficients of utilisation required for lifting equipment apply to ropes and fittings. It is also important to protect against conditions, which can arise during river gauging but are not “normal working”. General design guidance, including factors of safety for the various components is provided by BS EN ISO 4375:2014, “Hydrometry–Cableway systems for stream gauging”.
Our equipment design and inspection procedures are based on ISO 4375:2014, the Code of Practice for the Safe Use of Lifting Equipment (COPSULE) and the requirements of LOLER and PUWER.
Many existing cableways installed 30 or 40 years ago were poorly designed or have no records showing their construction. When commissioned to carry out a thorough examination of these, in the absence of a technical file, we carry out a design check against BS EN ISO 4375:2014. To deal with the uncertainty surrounding undocumented foundations we have developed load limiting devices to protect the bank-side structures.