Robit DTH Prime – solid success after teething troubles


The product development of drilled piles is constantly advancing. Stronger steel grades set ever higher demands on wear parts such as ring bits. What’s more, piling often has to be performed in densely built environments, which poses risks as pressurized air escapes from drilling holes, eroding the surrounding ground.

To answer these challenges, Robit started the development of the DTH Prime product family in 2015. Originally it included ring bits in six sizes (114.3–323.9 mm) and matching pilots. The ring bits were designed to be used with both welded and threaded tubes. The Flow Control method would prevent air from escaping into the surrounding ground.

The first tests proved the concept as workable. After some minor changes the next batch was delivered to selected customers – and in the field, teething troubles began to emerge. “A contractor tested the Prime at the Tampere Deck and Arena site and found the performance less than satisfactory. Another contractor had problems too: the Flow Control did not work as expected”, Robit’s Sales Manager Sami Paavola recounts.

So it was back to the drawing board. “We paid close attention to our customers’ experiences and produced new versions of the pilot at a rapid pace. Thanks to our manufacturing staff and subcontractors, we managed to deliver improved versions quickly to our customers. These new pilots proved much more durable and usable”, says R&D Engineer Pasi Korte.

The new development cycle was bearing fruit. In the difficult ground conditions of the Tampere Deck and Arena, where piles were drilled 40 m deep, DTH Prime finally defeated the competition. “At a high-rise construction site in Jätkäsaari, Helsinki, they drilled 250 piles into an extremely challenging ground where all sorts of debris such as iron rails, derelict cars and a shipwreck were buried. They drilled an amazing 3,600 metres on a single pilot. Half of that would be a good achievement in a broken ground”, Sami Paavola says.

In the course of 2018, DTH Prime has shown its competitive edge on several construction sites. A drill-through model is also available; it speeds up work as the entire rock socket can be drilled in a single run. The size range has also grown wider, the largest ring bit now being 1,220 mm. In these large-size systems with integrated ring bits, the Robit DTH Prime has no noteworthy competition in the market.

Please watch the Tampere City Centre Development Programme 2015-2030 video.