Hermes Technologie, based in Schwerte, Germany, has been successfully developing coating procedures using ERGELIT dry mortars for over 20 years, launching the KS-ASS (M-Coating) process on the market in the late 1990s, and very quickly complementing it with an automated shaft cleaning rig. Named the TSSR, this is an array of high pressure cleaning nozzles which form part of the M-Coating equipment and are raised and lowered in the shaft mechanically, to achieve thorough preparation of the substrate.

Continuous market observation and monitoring of client reaction led to a ‘high speed’ version of the TSSR at the end of 2006. The company said that at 380 bar and 24 litres per minute and with a completely new design of rotary nozzles, shaft cleaning equipment was now developed almost to perfection. Almost – there were still some questions to answer.

How to treat hard clinker brick surfaces, new concrete shafts or synthetic coatings before coating with ERGELIT? Intensive research and experimentation finally led to the conclusion that only sand-blasting could provide a satisfactory solution. But how? By exposing operatives to conditions in the shaft?

Anyone who has ever seen such an operating procedure can understand this would ran counter to the thinking behind the M-Coating process of which the TSSR was an integral part. When developing the M-Coating process, the Hermes team has given the same priority to protecting the workforce as to improving performance when it came to shaft rehabilitation. The M-Coating name became virtually synonymous with fast, effective and top quality shaft coating with ERGELIT. This was and still is the reason why this, and only this, process has received the Berlin DiBT’s certificate for coating wastewater collectors and inspection shafts.

In the autumn of 2009, the Hermes team’s technicians and engineers found the solution to the sand-blasting problem: developing the TSSR into the HDS jet equipped with a combination of water- and sand-blasting technology. The new process amazed the professionals at the ENTSORGA show in 2009.

This apparatus, registered with the German patent office under the name HDS-jet, is equipped with two water/sand blasting nozzles. Operation is as the TSSR. The array rotates through 360 degrees on its own axis and is raised and lowered by winch. Working on the venturi principle, the high pressure water pump creates a strong vacuum which in turn draws the blasting sand out of the container.

The sand is then accelerated so powerfully through the nozzle that it keys or prepares tiles, new concrete surfaces or synthetic surfaces so that the new ERGELIT coating makes a permanent bond. Thanks to the short, uniform and easily adjustable distance between the nozzle and the shaft wall, the blasting sand, with carefully selected grain size, gives very even results.

The speed at which the HDS jet cleans is around 15 minutes per metre. That is, it normally takes one hour to complete the cleaning and preparation of a standard four metre deep shaft with these problematic shaft walls. In exceptional cases the procedure can be repeated several times, depending on the sandblasting finish required.

There is no need to send operatives into the shafts, which is particularly important where these are narrow or difficult. Often it is only the M-Coating procedure that can cope with major projects – for example, a 25 metre deep shaft in London could not have been renovated without this technique. As is the case with the usual TSSR cleaning, the specialist operatives stand at the top of the shaft and monitor the cleaning process or top up the blasting sand if required.

The new water/sandblasting equipment is proposed as a complete kit, or as an add-on to the M-Coating equipment. As usual, the HERMES Technologie team will demonstrate the HDS jet and explain the operational method and particular technical and economical features on the spot. Poorly cleaned substrates, however bad they originally were, should now be a thing of the past. The economic problems of coating breaking off because of inadequate substrate preparation can now be avoided. The technology is available and simply needs to be applied. For clients already using M-Coating, this is simply an important addition to existing technology. HERMES Technologie ensures a powerful bond and a highly durable coating.