Hot Tapping a Cooling Water Tank During Operation Without a Shutdown
How can a reinforced concrete wall of a cooling water tank be drilled while the facility remains fully operational, without the possibility of using divers and without the risk of cooling water leakage? For FASTRA, this meant developing and repeatedly testing a new technological procedure directly at the EVO Planá nad Lužnicí power plant. The intervention itself was then completed within a single day.
FASTRA, s.r.o. has long focused on the development and manufacture of shutdown-free technologies for the maintenance, repair and modification of piping systems and product pipelines. These technologies make it possible to carry out specialized service work while systems remain in operation, without the need to shut down the entire system.
One example is an intervention carried out at the EVO Planá nad Lužnicí power and heating plant, where openings DN 150 and DN 250 had to be drilled through the reinforced concrete wall of a cooling water tank.
A Demanding Intervention During Full Operation
The project was commissioned from FASTRA by Metrostav a.s. The task was to drill openings through the reinforced concrete wall of the cooling water tank while the facility remained fully operational.
Several factors complicated the operation. Above all, divers could not be used, while at the same time any uncontrolled leakage of cooling water had to be prevented. The flowing water generated by powerful pumps also created conditions that had to be taken into account when designing the entire work procedure.
Any shutdown would have meant restricting the operation of the power plant, resulting in significant economic losses. It was therefore essential to create a safe and leak-tight system that would allow the drilling to be carried out without draining the tank or interrupting operation.
The Solution: A Special Flange and Sealing System
For this intervention, FASTRA prepared a special flange that was secured to the tank wall using high-strength chemical anchors. Each anchor had a declared load capacity of approximately six tonnes.
The assembly was sealed using three rows of robust O-rings made of special rubber, combined with a permanently flexible butadiene sealant.
During practical on-site tests, the concrete was also found to be highly porous. The designed system therefore had to cope with this additional complication while still allowing the planned intervention to proceed safely.
Drilling Reinforced Concrete During Operation
The drilling itself was carried out using an S180 hydraulic drilling machine. The equipment had to penetrate not only the concrete structure itself, but also two layers of steel reinforcement.
One of the most critical moments was the removal of the drilled core. Once separated from the structure, it could not be allowed to fall into the tank or otherwise jeopardize its operation.
Thanks to precise control of the drilling technology, the drilled section could be safely captured and removed directly using the core drill bit.
The Entire Intervention Completed in a Single Day
After the drilled cores had been removed, the installed gate valves were closed, their tightness was checked, the drilling chambers were drained and the equipment was subsequently dismantled.
The actual intervention was completed within a single day.
This result, however, was preceded by extensive preparation and repeated testing of the proposed technological procedure directly on site in the presence of the investor. Verifying the individual steps under real operating conditions was an important part of preparing the entire operation.
Further Shutdown-Free Projects
This intervention is one example of situations where the technological procedure must be adapted to the specific operating conditions.
In addition to similar specialized interventions, FASTRA also performs pipeline isolation under pressure and line stopping of pipeline networks without the need for a shutdown.
This year, for example, FASTRA carried out a demanding operation on a DN 350 high-pressure gas pipeline at an operating pressure of 23 bar. The intervention required the creation of four isolation points and the installation of a 50-metre bypass. This ensured that the supply of natural gas could continue while the necessary work was being carried out.
From Hot Tapping to Pipeline Isolation Under Pressure
FASTRA develops and manufactures its own shutdown-free technologies and uses them to perform specialized service operations. The aim is to enable the maintenance, repair and modification of piping systems without unnecessary operational shutdowns.
Every intervention requires an assessment of the specific conditions, the correct choice of technology and thorough preparation of the work procedure.