A day in the working life of a construction diver15. November 2018
Have you ever tried to install something with your eyes closed? No? For construction divers, “blind” installations or working in zero visibility is part of their everyday work. Read on to find out how this works, what the daily work of a construction diver involves and what challenges they face.
Close your eyes and go for it?
Working in sub-zero temperatures and in total darkness over several hours is unimaginable for most people, even more so when it comes to having to do all this under water. This is precisely what construction divers do. Placing drill holes in zero visibility, inserting injection mortar and rod anchors – all no problem for them, even if they must also overcome other complicating circumstances such as high pressure ratios. “Over 90 per cent of our work is carried out in zero visibility, which we refer to as black water”, says Karl Kerlen from the Kerlen Taucher GmbH company from Hanau near Frankfurt am Main. “In these cases, we can only feel out our work”.
But these skills have to be learnt. Construction divers go through special training. They have to have completed a manual work apprenticeship, while the subsequent training to become a certified diver in a diving school takes at least two years and is completed through an examination with the Chamber of Industry and Commerce. But the job still isn’t a walk in the park once the qualification has been completed. “Divers must be physically and mentally fit in order to work under pressure and without visibility and most undergo an extensive annual health check”, Kerlen emphasises. Good improvisational skills and a diverse technical understanding are just as important. Construction divers get around a lot on a daily basis and travel to the most diverse projects: new constructions, maintenance, inspecting and renovating harbour facilities, ships and excavations as well as hydro and nuclear power stations and many other projects.
Combining a hobby and a profession?
Perhaps. Summer is the ideal “construction diver season” and provides a welcome opportunity to cool down in hot temperatures. Dives tend to become more of an ice-cold challenge in winter, however. Construction divers can stay under water for a maximum of two to three hours in sub-zero temperatures. While the helmet and diving suit provide good protection for the divers’ heads and bodies, their hands can only be kept warm to a certain degree. “We need our hands to work with and are therefore only insulated to a limited extent”, the expert explains. Hands are the most important tool under water, because using mechanical tools and materials under water is substantially more difficult.
Using the right products
The expert considers neither the limited visibility nor the temperature to be the greatest difficulty under water, however. “Materials and tools cannot be used under water in the same manner as on land”, Kerlen emphasises. “We must therefore carefully consider a selection and we often use specialist solutions. It also requires careful planning and coordinated work with the team”. The fixing products must therefore be chosen with equal precision. The fischer epoxy mortar FIS EM Plus with a threaded rod is an ideal system for underwater applications: FIS EM Plus is a powerful injection mortar for rebar connections and anchors for cracked concrete. It is approved for anchors in water-filled drill holes and is therefore especially suitable for underwater rebar connections, providing high load values.
Working on the restoration of a hydropower station
The restoration of the VWEW-energie hydroelectric power station in Biessenhofen in the Allgau region is a recent example. The facility came into operation in 1962 and is currently being refurbished which involved the construction of an underwater reinforced concrete wall. The wall was connected to the current dam wall which was damaged by high water levels. Together with a needle valve it separates the Wertach river from the working areas.
The construction divers of the Kerlen Taucher GmbH company attached B 500B reinforced concrete with the fischer injection mortar FIS EM 1500 S in combination with connection sleeves to an existing ground plate. Our FIS EM is approved for water-filled boreholes according to anchor theory and is especially suitable for rebar connections in concrete alongside other system components, all while providing high load values. The system temperature of up to five degrees Celsius is also suitable for underwater installation. The subsurface did not consist of standard concrete. The experts examined the load-bearing capacity of the system through tests and pull-out tests using a rock anchor testing device set at a tensile force of 200 kN.
The FIS EM was heated before its installation in order to prevent the risk of it becoming viscous through the low water temperate. The construction divers created the boreholes underwater before informing our Application Engineer Bernd Wetzel by radio when they required any further mortar. fischer’s expert then responded by injecting the mortar through a tube, enabling the construction divers to fill the boreholes. The weir facility was successfully drained and reinforced using this procedure.
“In general, we only use fischer products for underwater installations”, Karl Kerlen emphasises. “By using the fischer injection mortar system in order to strengthen the reinforced concrete wall in the Wertach river we can be absolutely certain that it will withstand the extreme conditions”.