Energy chain system for sand trap basins in sewage treatment plants

Profile

• What was needed: basic flizz®" system, energy chain, chainflex® electrical cables, chainflex® special cables with TPE outer jacket, condition monitoring system
• Requirements: Energy supply system that can withstand continuous loads (365 days/year in operation) and severe weather conditions, rapid project realisation within a few months
• Industry: Sewage treatment plant
• Success for the customer: particularly low-maintenance energy chain, weatherproof solution that can withstand the elements, on-site installation and on-time completion within a very short period of time

The mechanical biological sewage treatment plant in Bamberg with nutrient elimination is designed for around 220,000 inhabitants. Between 95 and 99 per cent of the substances contained in the wastewater are removed here before being discharged into the Regnitz. The tasks are carried out by a total of 29 employees from the process engineering departments, an electrical and metalworking workshop and the wastewater laboratory.
In the area of the grit trap scraper, an outdated solution with an automatically winding and unwinding motorised cable drum for power and data supply needs to be replaced. This original design no longer met the increasing technical requirements in the area of complex data transmission. The new solution has to prove itself in the plant under continuous load, as the sand scraper is in operation around the clock, 365 days a year. At the same time, the old system has already been severely affected by the weather. As the motorised cable drum finally gave up the ghost during the project planning phase, the new energy supply solution also had to be implemented within just a few months.

Today, a standardised "basic flizz®" system is used to guide energy, data and air, which has been tried and tested in wastewater treatment plants throughout Europe for many years. The low-maintenance system covers travel distances of up to 100 metres and more. With its modular design, it combines the energy chain, chainflex® cablesand guide trough in a compact, weatherproof complete solution encased in stainless steel, which defies the effects of weather such as sun, wind, snow and ice and functions reliably under continuous load.
In addition to chainflex® electrical cables for the pumps and the motor, the energy chain also includes chainflex® special cables with a TPE outer jacket for outdoor use for data transmission. They are mainly installed on site by the specialists or inserted into the chain. A condition monitoring system for additional tension/push force monitoring also provides the necessary system protection in the system today. If the set value is exceeded or not reached, the system switches off automatically. This prevents costly malfunctions in advance. A floating moving end, attached to the moving arm, compensates for lateral movements or the lateral offset of the scraper and ensures that the chain runs smoothly in the guide trough.

An unprotected cable was automatically wound and unwound on the motorised drum, which previously supplied the grit trap scraper with energy, and was constantly kept live via a separate drive. The data and power lines were laid in a very confined space, which has always led to a certain susceptibility to faults. In addition to the traditional copper cables, network and fibre optic cables are also used today, which are difficult to implement in a motor drum due to the insufficient spatial separation.
Wear and economic efficiency also play an important role. All signals were transmitted and forwarded from the drum's rotary movement via slip ring contacts. The contact points were subject to moisture and therefore corrosion and had to be replaced regularly. System downtime is pre-programmed. Frost also plays a role in winter. The cable gets wet quickly, freezes and therefore has to be heated during the cold season, which results in additional costs. The separate drive, the power consumption due to the separate heating, the maintenance effort and the insufficient yield in data transmission are all arguments in favour of using more powerful components with increasing efficiency.